Bilstein B6 HD absorber - anyone tried?

[pupjoint]

http://www.truckspring.com/products/Bilstein-B6-Heavy-Duty-Shock-Absorber__24-006200.aspx

anyone tried these? currently on stock ones, stock beam no adjusters.

how do they compare to the red konis?

[ibg]

good for road race, they lift the front maybe an inch and are very firm. I prefer my Konis I have now. though the billies were good on the back, it was like stiffer torsions.

[Torben Alstrup]

good for road race, they lift the front maybe an inch and are very firm. I prefer my Konis I have now. though the billies were good on the back, it was like stiffer torsions.

X2
For the street Koni´s are better.

T

[hotrodsurplus]

If you go Bilstein then don't buy them from a catalog. Call Bilstein in Poway, CA and have a set valved for your specs. When Bilstein simplified the catalog it kept the most popular part numbers and the only people buying for years were off roaders. The remaining part numbers are a touch too stiff for most street cars and that's a shame because the harsher ride turns off so many people. The cost to re-valve is $60 per damper but I think if you buy them and have them re-valved at the same time the cost is lower.

It will cost more in the long run but the results are worth it. The Konis are simply twin-tube dampers with crude orifice metering and check valves whereas the Bilsteins are monotubes with deflective-disc valves. Once you ride in a car with properly valved Bilsteins you'll never ever consider any other damper than a monotube. 

[Torben Alstrup]

I disagree on that last point. I still say Koni shocks are better for the street in general. They "pick up" bumps better. But Bilstein is very good for the track. If I was to choose something else it would most likely be AVO.

T

[hotrodsurplus]

I disagree on that last point. I still say Koni shocks are better for the street in general. They "pick up" bumps better. But Bilstein is very good for the track. If I was to choose something else it would most likely be AVO.

T

If you don't intend to tune a damper for an application then a twin-tube Koni may in fact be a better damper for the application. However, if tuned properly a quality monotube damper (like a Bilstein) will out perform any twin tube damper.

The lack of 'pick up' that you observe is usually a consequence of excessive low-speed damping force. And you're right; the off-the-shelf Bilstein part numbers have excessive damping force for most street applications. That is why I recommend having them tuned to your operation. To say that the design is not capable of offering good ride quality and handling properties is like saying a Mallory or MSD distributor will not perform properly because it comes with a poor advance curve. Like every other part that you expect to perform well you have to tune them.

The twin-tube design as the Koni uses for our application does not offer as much tuning latitude as a large-piston monotube design that Bilstein (and Fox and King and Öhlins) use. Because of the limited working area most twin-tube designs are limited to a fairly progressive damping curve. A monotube can be more precisely tuned to specific applications.

I have worked a lot with Bilstein and RCD (third-party damper tuner). I know from experience that you can tune a monotube damper like a Bilstein to ride very soft over small road inconsistencies yet control the suspension when the wheel hits very rough terrain. An extreme example is a Mercedes Benz. MB started using the DeCarbon monotube design in 1957. The only people who complain about Mercedes Benz ride quality are Cadillac drivers.

So if you intend to simply bolt on a set of dampers and are willing to live with some compromises, yes the Koni might be the better choice. But if you want the very best of ride quality and handling then a custom-tuned monotube damper cannot be beat. It will cost more but it will also perform better. 

[Torben Alstrup]

So if you intend to simply bolt on a set of dampers and are willing to live with some compromises, yes the Koni might be the better choice. But if you want the very best of ride quality and handling then a custom-tuned monotube damper cannot be beat. It will cost more but it will also perform better. 

That was almost exactly my point. ;--)
T

[hotrodsurplus]

So if you intend to simply bolt on a set of dampers and are willing to live with some compromises, yes the Koni might be the better choice. But if you want the very best of ride quality and handling then a custom-tuned monotube damper cannot be beat. It will cost more but it will also perform better. 

That was almost exactly my point. ;--)
T

As they say, almost only counts in horseshoes and hand grenades.

I understand where you're coming from. It irritates me that Bilstein ignores our market. We tried like hell for Bilstein to embrace the hot rod market but it would never advertise. People don't understand what they're missing until they ride in a car with well-tuned springs and damper rates. Then everything else feels mushy or harsh.

[danny gabbard]

So when you order a set of Bilstein shocks, What do you tell them when ordering for a VW on the street ?

[hotrodsurplus]

So when you order a set of Bilstein shocks, What do you tell them when ordering for a VW on the street ?

You'll call the Poway office and ask to speak with a tech. I don't know Juan's last name but he's a good contact. Joel Ward and Shane Casad are head techs in the off-road department and you'd be stoked to talk to either one. Mike Ritchey is a rep and he'd be a good starting point to get things done. You will have to explain that the production damper's damping force is way too strong for a lightweight street-driven car. More than likely they'll want to know the axle weight and so forth but hopefully they still have the pertinent specs on hand.

If they don't want to play ball then call RCD (Race Car Dynamics) www.racecardynamics.com. Steve Duck used to be the contact there but he's gone now. I'm sure you can find a sympathetic ear there though. And RCD is a retailer so chances are you can talk them into a deal if you buy a set. 

Bear in mind that Bilstein dampers, like our cars, are infinitely rebuildable. The cost to rebuild and re-valve is the same (about $60 per last I checked). So you can save serious money by buying used ones and having them rebuilt. They might even send you the bare bodies so you can have them powder coated to match your suspension.

[danny gabbard]

Good Idea ! So match stock length ? On a lower beam with lower'd spindles.

[pupjoint]

very nice info. those who order kindly feedback here.

over here in this part of the world, asia, i can order as per catalogue, but no service to valve or whatsoever. this includes Konis.

currently using stock Mexican shocks, stock beam, dropped spindles.

[hotrodsurplus]

Good Idea ! So match stock length ? On a lower beam with lower'd spindles.

Dropped spindles alone won't affect the damper length. The arms' position determines that. Regardless, stock-length dampers usually collapse enough to allow full travel for suspensions that have been lowered only by adjusters or pulled leaves. I run stock spindles and stock-length dampers on a kingpin beam and the front will get so low that 145s will hit the headlight buckets before the dampers bottom out. The key is modifying or eliminating the snubber. I modify mine to stop the damper about 1/4-inch from fully compressing or extending. That works out to almost 9 inches of suspension travel!

The ball-joint Bilstein dampers use the OEM screw-on upper damper mounts. You have to either trim or eliminate the snubbers if you intend to use adjusters or pull leaves to lower the front. If I remember correctly the ball joints will bind before the dampers fully collapse. So short dampers offer no more compression travel and limit rebound travel.

Pupjoint, you could probably have someone close to RCD or Bilstein ship the dampers to you for less than what those companies would charge to ship them. The stock replacement dampers ride uncannily well. The best-riding lowered car I ever owned was a '65 with pulled leaves and non-pressurized
replacement dampers.

Finally, you can rebuild and revalve Bilstein dampers yourself. You release the pressure by drilling the base, disassembling the damper, brazing or welding a tab over the hole, and drilling/tapping the tab for a Schrader valve. This requires a nitrogen bottle and a high-pressure regulator but a lot of cycle shops have those and will recharge the dampers for you.

Bilstein will not service a modified damper but it will sell you the parts you need to service yours. The valves consist of Belleville washers and those will fit in an envelope (cheap shipping).

[65bug]

Chris,
    Very informative! Thank you. I run the bilsteins on the back of my 65 and love them. When I used to use them for off-road was when I really fell in love with them. They are amazing shocks. I will be ordering
the dialed in ones for the front as you suggested.
    I have dropped spindles and it rides pretty good with the G2 gas charged shocks on it now. I know the difference though, and will be switching soon.

[deano]

I just removed a full set of almost new Bilstein shocks on my '67 convertible (ball-joint/swingaxle). This is a real low mileage original car, so there can't be much times on these. I took them off, since I wanted a full set of Boge OEM shocks. I have no use for the Bilsteins, as they look new on the outside. They are in southern California.... Make me an offer... Dean

[hotrodsurplus]

Make me an offer... Dean

Sent you a PM, Dean. Thanks.

[deano]

Sold to Chris... Thanks, Dean

[pupjoint]

Make me an offer... Dean

Sent you a PM, Dean. Thanks.

wow, thats fast....chris, care to share some pics and what are your plans on these shocks, tuning wise?  revalve?

[mg]

Good idea on the revalve, had Bilstein do a set for my track 911 years ago.
They worked very well with the stiffer torsion bars sizes and R rated tires on that car.
The trick is knowing what compression and rebound to specify.
If you miss the ideal set up you can always send it back if you want to adjust one or both.
Bilstein might have had the Koni shocks on a shock dyno already have those specs.
So from there they can match or improve them based on your torsion bar sizes.
On a VW I'd like a little more rear rebound to jack the back of the car down.
Just to help stop the rear of the car from unloaded too quick..
Seems you don't need much compression on the front either.
A drag car likes very little front rebound for quick wieght transfer, but thats not going to help it corner well.
Worst shocks I ever had on the front of a bug were old KYB gas shocks, way to stiff for the light car.

On my road race cars I like (Penske) double adjustable shocks.
Nice but overkill for most VWs.
http://www.resuspension.com/

[hotrodsurplus]

wow, thats fast....chris, care to share some pics and what are your plans on these shocks, tuning wise?  revalve?

No definite plans yet. They might go to Javabug so he can try them out on his car but only if he plays nice. I have a '68 pan that might get a Thing beam and a reduction-box transaxle mounted with an NOS Johnson no-hop kit that would go under my wife's Baja. But I'll stop talking about that so heads don't explode. 

The trick is knowing what compression and rebound to specify.

Damper tuning is sort of a mysterious thing because the techs understand how the things really work. To us it's usually just, "It rides like sh!t on the street" but they usually can teach you how to analyze the ride quality so you can express it more accurately. 

Bilstein might have had the Koni shocks on a shock dyno already have those specs.
So from there they can match or improve them based on your torsion bar sizes.

That's exactly what led to the custom damper valving for Bilstein's hot-rod market. For a little background on me, I work in that world. I came from the VW side so I was familiar with what Bilsteins are/what they do/what they're capable of. Steve Duck was at Bilstein in Poway at the time so when he heard about that he latched right on to me. I did some tech pieces with Bilstein of North America when Duck was pushing the company to break into that market.

The tech center worked up a few part numbers for live-axle hot rod applications based loosely on the chintzy Pete & Jake's dampers. So when my dad was building his roadster in the late '90s and early '00s I got him together with Duck and they started testing those new part numbers. They discovered that the rates were too aggressive (surprise!) so they pulled a ton of compression damping out and added some more rebound. They also softened up the low-speed valving until the ride quality improved. Bear in mind that my pop lives in Las Vegas. So it's true that this can be done remotely.

The valve rates that Bilstein Poway established for my pop's car became the production valving for the hot-rod dampers that it sells today.

There's something else that most people don't realize and it goes a long way in suspension tuning: spring rates. At the risk of making a book out of this, the twin-tube design limits valve capacity. Most manufacturers adopt a really rudimentary network of metered orifices (holes with balls and springs to control flow). In fact the metering area is so small that twin-tube manufacturers divorce the compression valve from the piston and attach it to the end of the working cylinder (called a base valve). The problem with a metered orifice is that it can flow only a certain rate until it hydrostatically locks, at which point it gets as rigid as a solid rod. You know that "BANG" that you get when you hit a huge bump or pothole at speed? That's probably not the suspension collapsing; it's usually hydrostatic lock transmitting all that force to the chassis. So when you adjust a Koni, all you're doing is covering and uncovering these orifices. When tight, they hydrostatic lock really easily.

Don't take my word for it. Koni itself will show you explicitly how the designs differ (Koni also sells a monotube but not for our cars). Note how teensy the valve networks look on the twin-tube designs. The Konis at least use a belleville spring to bypass under heavy hits but it's nothing like the one in a true monotube.

http://www.koni-na.com/pdfcatalogs/KONIMotosportCatalog.pdf

To prevent that hydrostatic lock the OEM suspension designers specify very loose damping force (large orifices). That of course makes the car mushy on compression so they increase the spring rate to compensate (the spring serves a lot of damping purpose). Of course to control the increased rebound from the stiffer spring the designers throw in more rebound damping.

But because a monotube damper has a larger working piston it uses a larger, more sophisticated valve network that isn't vulnerable to hydrostatic lock. Because of that, a vehicle equipped with a properly tuned monotube damper can run less spring rate. At that point the damper can adequately control the motion without hydrostatically locking. That translates to improved ride quality and usually handling. That's precisely what my dad did to his car: he pulled plates (the technical name for individual leaf springs) and played with damper rates until the car rode and handled right. To paraphrase a Bilstein tech, when using a properly tuned monotube the spring only holds the car up at a given height and the damper controls the motion. Of course we had to shim the spring to make the car ride at the right height with the lesser spring rate but it doesn't impair with the car's capacity. My dad loads that thing to the gills with luggage and takes passengers with him across the country. No joke.

The results are positively staggering on my dad's car. In 2006 he got invited to participate with his '32 Ford roadster in Rod & Custom's Asphalt Ego Rama, a dynamic thousand-mile program that rates cars based on various performance parameters. He won the entire event. Among the categories he outright won were ride and drive quality. On Bilsteins. And live axles. And buggy springs. On bias-ply tires. Bear in mind that he was up against cars with four-wheel independent suspension and radial tires. 

http://www.rodandcustommagazine.com/eventcoverage/0603rc_asphalt_ego_rama_v/viewall.html

The point of that long-winded piece was to illustrate that Bilstein will indeed work with you and that mere mortals like us can actually achieve really positive results if we take the time to tune the system.

Incidentally I did the same thing as my dad did but on the front suspension in the '62 that I will eventually build.  I pulled plates until the car rode right with Bilsteins. That of course lowered the car. So I installed my torsion adjusters to go down a little bit lower the car further up a whole bunch so I can go back up to stock height if need be. It rides like a magic carpet even when low. And before someone says that a spring pack like that won't last, I've driven tens of thousands of miles on two other cars with pulled leaves and stock dampers and they never gave me a moment's trouble.

Damn. I should do this for a living!

On a VW I'd like a little more rear rebound to jack the back of the car down.
Just to help stop the rear of the car from unloaded too quick..
Seems you don't need much compression on the front either.

It's my experience that the dampers Bilstein currently makes for Volkswagens have vastly excessive compression damping. That could be because most people who buy them intend to use them on off-road cars. But also based on my experience I got great ride quality once I reduced the front spring rate. Now the damper is controlling more of the compression force. The ones on the rear of my Thing right now are waaay too stiff and it's going to be tough to reduce spring rate on that end. I've also noticed that the rear could use some additional rebound damping. I can hear the spring plates clunk on the stops when I drop off a curb in that car. Of course it's lifted a little bit so that preloads the spring and screws with the tuning.

A drag car likes very little front rebound for quick wieght transfer, but thats not going to help it corner well.

Yeah, and that's an application that probably won't benefit from a monotube. Weight transfer is so slow that the cheapest damper can keep up. The tracks are so smooth that the damper really won't do much work once the car launches.

Worst shocks I ever had on the front of a bug were old KYB gas shocks, way to stiff for the light car.

I have a pair of ball-joint Gas-A-Justs in the garage. They're positively awful. I'm a big boy and when I had them on my Thing I could stand on the bumper and it would hardly move. I gave them a week and it was one of the worst seven days I've spent behind the wheel.

In case you don't want to sift through the Rod & Custom article, here's a picture of my pop's roadster. It clicked 95,000 miles when he returned from his most recent trip last summer. That's 10,000 miles a year. What do you do with YOUR car?

[ Attachment: You are not allowed to view attachments ]

[mg]

Jim enjoyed your reply, thank you. 
Your dad’s 32 must ride as nice as it looks.
I’m sure he put a lot of thought to spring rates before custom valving his shocks.

In road racing my experience has been to find the optimal set up first determine the spring rates, then the dampner rates and lastly reconnect the sway bars.

My 2 cents.
I would prefer to balance the Cal Look with spring rates first.
Rear torsion bars come in various sizes, not sure about the fronts.
You could pull leaves to tune or soften the front spring rates.
The trick would be to determine the correct spring package for the Cal Look VW.
The custom valved dampners would be next imho.

What are the best spring rates for a lowered Cal Look with big and little (harder 300 treadware) tires?
It would be a little to fortunate to expect stock worn torsion bars front and rear to provide the best ride or handling.
How can you tell?
Without the shocks installed is the front spring too stiff and is the rear too soft?
Does it under or over steer?
Controlling weight transfer and trailing throttle oversteer common to rear engine cars should considered too.
With 150hp are the rear springs too soft, does the rear collapse to the bump stop on acceleration?

It may help but is it optimal to custom valve shocks to optimize the random spring rates of 50 year old stock torsion bars.
So what is the optimal spring rates of the lowered Cal Look?
 

[pupjoint]

that will be hard to determine because the front spring leaves would be old and also differs from vehicle to vehicle, some are chopped, some with adjusters fitted etc....

i am finding it hard to order custom valve shocks without testing on the real car itself...

[Jeff68]

This is one of the best posts / topics that I've read in a while! I always wanted to find the best suspension set up, or how to set the suspension up best for hot street use and freeway driving. I don't drive a drag only car on the street. I had no idea that a company like bilstein would work with you to valve a damper for a specific application. Maybe once the valving for our cars was developed they would keep this application available. Even though each car differs at least you would have a good starting point. I always thought our cars were capable of riding and handling better. Thanks for the information on this!

[hotrodsurplus]

Thanks for the props, guys. Whenever I recommend things I try to justify them for a reason. All too often in the aftermarket world we change things without fully understanding the implications much less the reason why we spend the dough (and some parts ain't cheap and a bunch don't do what people expect them to). I just happen to go a little overboard with explaining sometimes. 

I’m sure he put a lot of thought to spring rates before custom valving his shocks.

In road racing my experience has been to find the optimal set up first determine the spring rates, then the dampner rates and lastly reconnect the sway bars.

My 2 cents.
I would prefer to balance the Cal Look with spring rates first.
Rear torsion bars come in various sizes, not sure about the fronts.
You could pull leaves to tune or soften the front spring rates.
The trick would be to determine the correct spring package for the Cal Look VW.
The custom valved dampners would be next imho.

What are the best spring rates for a lowered Cal Look with big and little (harder 300 treadware) tires?
It would be a little to fortunate to expect stock worn torsion bars front and rear to provide the best ride or handling.
How can you tell?
Without the shocks installed is the front spring too stiff and is the rear too soft?
Does it under or over steer?
Controlling weight transfer and trailing throttle oversteer common to rear engine cars should considered too.
With 150hp are the rear springs too soft, does the rear collapse to the bump stop on acceleration?

It may help but is it optimal to custom valve shocks to optimize the random spring rates of 50 year old stock torsion bars.
So what is the optimal spring rates of the lowered Cal Look?
 

What you described is basically what he did to tune his car although your method is a little more precise as he doesn't quite have the same latitude in tuning options. His car has an almost perfect 50/50 weight distribution with bias to the nose which should induce a little oversteer. The smaller front tires naturally induce a little understeer so things sort of balance out. The front suspension has hairpins on a forged I-beam axle so it naturally acts like a bit of an anti-roll bar. The rear has ladder bars which is usually a really bad idea because a tubular axle housing will not readily twist and that would make it the anti-roll-bar from hell; however, the pickup points come pretty close to touching so the bushings end up yielding and letting the rear suspension articulate pretty freely. So in the end the car has a slight understeer bias. But that's just luck.

Actually the extent of thinking about spring rate was thinking about having to jack up the car and having to release the damn spring pack (it's not fun). I put him together with Mike Eaton at Eaton Detroit Spring (OEM supplier and aftermarket mfgr.) so he actually does know the spring rate but that's sort of after the fact.
 
I don't know the front spring rate and as pupjoint observed it would differ so greatly among cars that I don't think you could rely on any number as a baseline. Going by the book you'd have to determine it on a case-by-case basis but I don't think our application even warrants that. These cars have a bunch going against them handling-wise: engine out back where it can do the most damage to the handling, zero front roll center, and a very high rear roll center and extreme roll couple. Then we go and lower the nose and run skinny tires up there.

By the way, there's really no need to run a front anti-roll bar on most air-cooled Volkswagens and even less reason to run one on a cal-look car. They induce some understeer so Frau Ursula wouldn't get too confident and put the car into a corner too fast and lift when she got scared (rollover recipe). The skinny front tires have the same basic consequence: they induce understeer. So a front anti-roll bar AND skinny front tires is a good way to make a car plow into a corner and generally handle like poo. If you REALLY want to make a car understeer then install a camber compensator (basically a pro-roll device). Sure you could run a rear anti-roll bar (even with swingaxle--people just don't think you can or should) to restore some balance but then you're right back to where you started, the car is more complex, and the suspension loses a lot of its independence, so to speak. The nice thing about a well-tuned damper is that it will kill almost if not all body roll anyway.

About rear torsion bars, we're sort of limited but some of us have options. The aftermarket offers only larger bars and probably won't make lighter ones. Luckily we swingaxle owners (almost all of us) can reduce our spring rate easily by just using '69-'72 IRS bars and pre-'60 spring plates. Bear in mind that would probably hurt your launch but that applies largely to drag-only cars. You could REALLY soften things with '73-and-later IRS bars with custom spring plates but I think that's overkill and would almost definitely hurt launch. Here's the breakdown for bar dimensions (I don't go out and search this stuff on a case-by-case basis; I have copious cheat sheets. I'm a kook, not a fool!).

Car   Years        Length             dia (mm)
TI   49-59   24 11/16”    24   Intermediate early Beetle
TI   60-68   21 3/4”            22   Short Beetle
TI   69-72   24 11/16”    22   Intermediate late Beetle
TI   73-79   26 9/16”           23.5   Long late Beetle

i am finding it hard to order custom valve shocks without testing on the real car itself...

Yeah, someone is going to have to tune a set and report the findings so others can copy it. There's no reason that we should have to tune each set independently. Good enough for one street car like ours should be good for all of the others, including stock-suspension cars. Actually I could probably just send in one of my 'vintage' ones to have the valving tested. Those ride great because they're valved looser than the modern ones. They were made when Bilstein offered a regular valving and 'sport' valving.

This is one of the best posts / topics that I've read in a while! I always wanted to find the best suspension set up, or how to set the suspension up best for hot street use and freeway driving. I don't drive a drag only car on the street. I had no idea that a company like bilstein would work with you to valve a damper for a specific application. Maybe once the valving for our cars was developed they would keep this application available. Even though each car differs at least you would have a good starting point. I always thought our cars were capable of riding and handling better. Thanks for the information on this!

Yeah, we have a lot more options than people think. For some reason the road-going Volkswagen crowd is very self limiting nowadays. Once upon a time it was really innovative but for some reason it got into a really narrow mindset about 25 to 30 years ago and since then people have just copied each other. Our cars will never handle *great* but they can certainly handle better than most do.

The only reason Bilstein will work with us is largely because of the off-road racing market. The Poway tech center is almost exclusively off-road stuff. That market won't tolerate off-the-shelf limitations. It demands custom valving. So we're the beneficiaries of their insistence. If Bilstein WON'T work with us then we can try RCD. I'm almost positive that it will.

Now if you'll excuse me I have to take a rabbit to an animal hospital 50 miles away, a bunch of cloth to a place for flame resistance coating, and money to a materials shop for a slab of acrylic sheet. It never gets boring at the Shelton household...

[mg]

Good stuff Chris!

Bummer there are no spring choices for street VWs.
Agree from the factory all cars are made to push/understeer.
The large front sway takes away front grip and creates understeer.
A stiffer rear sway would take away rear grip.
As it is my Thunder roadster has no sway bars, the chassis has been tuned with springs and shocks.
I only miss the sway bars during higher speed left/right transitions, just have to be smooth.

here is my concerns with old springs.
I wonder if it’s time for someone to make a new spring/torsion bar package for VWs?
Should you be concerned when one rear torsion bar on the car drops?
It’s easy to re-index rear torsion bars to set the ride height or stance correct.
But what has really happened is that the torsion bar on one side has weakened and has less spring so it has collapsed.
For years the fix has been just to re-index the low side and give the weak torsion bar more preload.
The car sits level again but are the spring rates the same on both rear bars?
Is there an easy way to check or match rear torsion bars spring rates, like they do with coil springs.
If not starting with a new set of rear torsion bars might at least ensure you have the same spring rates in the rear right to left.

Are there replacement torsion bars for the front?
I expect many of those have old stock bars have gone dead and now have little spring at all.
That creates the illusion of needing little front shock rebound to control the weak spring.
When in fact the 50 year old front torsion bars may have got tired and now have too little front spring?

[hotrodsurplus]

I wonder if it’s time for someone to make a new spring/torsion bar package for VWs?

Technically? Probably. Reality? Won't happen. Just because a spring loses a little rate doesn't doom it. It just won't perform at 100 percent rate. People (including me) still flog 40- and 50-year-old springs on Bajas and buggies and Things and they hold up alarmingly well. Sure they fatigue eventually but they did that in the late '60s and early '70s when the cars were only half a dozen years old.

Should you be concerned when one rear torsion bar on the car drops?
It’s easy to re-index rear torsion bars to set the ride height or stance correct.
But what has really happened is that the torsion bar on one side has weakened and has less spring so it has collapsed.
For years the fix has been just to re-index the low side and give the weak torsion bar more preload.
The car sits level again but are the spring rates the same on both rear bars?

I think it's relevant to be concerned if a bar fatigues more than another. I've never had that happen to me though. Every car that sat funny that I've ever owned did so because the prior owner started playing around with the suspension and didn't understand how it worked.

Is there an easy way to check or match rear torsion bars spring rates, like they do with coil springs.

If you lived around sprint-car racers you'd probably find one pretty easily. Otherwise you'd have to make your own fixture. And if you made long trailing arms you could use a floor jack, tape measure, and bathroom scale to measure the rate. But in the end would it be worth it? I really doubt it. I doubt that you'd even feel a side-to-side difference.

I'd say that spring failure isn't as bad on an air-cooled Volkswagen as it is on a conventional car exposed springs. Volkswagen bars operate in a pretty well protected environment. That's not to say they won't fatigue at one point but they're not as vulnerable as they are on a car with exposed springs. I have 390K on an '86  T0y0ta pickup and the springs are fine on it. And I have literally abused that truck off road.

I expect many of those have old stock bars have gone dead and now have little spring at all.
That creates the illusion of needing little front shock rebound to control the weak spring.
When in fact the 50 year old front torsion bars may have got tired and now have too little front spring?

I'd say that most of those springs have held up really well. Consider this. The front of an air-cooled Volkswagen is notoriously over-sprung. As a Baja owner I can vouch that they're up for the task in most play-car applications. The cars wouldn't perform well off road if they weren't over sprung to a degree. Furthermore, the stock snubbers limit them the springs to a really narrow operating range. Those springs have about the cushiest life on earth. Case in point, my wife drives a car that was turned into a Baja in the '70s. According to the damage since then, it was beaten like a rented mule. The springs are great in that car. Are they as good as they were when new? Probably not. But they're certainly up to logging roads and small jumps.

If you play with a stock Volkswagen front damper you'll notice that it has practically zero compression damping. Consequently they have quite a bit of rebound damping. Both of those indicate a stiff spring rate relative to the axle weight. I might be underestimating things but I don't know if there is any reason to replace springs that haven't outright failed.

The other reason is the general Volkswagen owner. Most are tighter than two coats of paint. Unless it makes a car 'cool' or shiny or go fast or make lots of noise, most VW people aren't interested. I know; I sold parts to them when I were in kollidge. 

[mg]

Hey Chris again thoughtful reply and all makes sense.
When I wanted to soften the ride on my street cars I would remove rebound from the rear and let them float more down the freeway.
A lot of rebound gives me confidence on high speed sweepers but it also tramits a lot of the freeway chop on the long boring straights.
I was trying to relate the 911 tuning where front and rear torsion bars are available and improved spring set ups are common.
Custom valved shocks from Bilstein to match the new stiffer torsion bars are common for 911 drivers as well.
Normally shops are very protective of their custom valveing and Bilstein will not share them either.
Although if you call Bilstein they will take the best of all these and offer a solution. 
Certainly an area that has been over looked too long in the VW world.
You are on the right track no doubt.

I have double adjustable JRZ remote reseviour on the 911 track car.
Bilstein 911 sport shocks on the daily drive 911.
Penske double adjustable remote resivior on the IMSA GTO race car.
Happy with all of them.
cheers.

[pupjoint]

ok, dropped by at a local Bilstein dealer yesterday, showed hims some number i got from the net and he told me it wasnt Bilstein number. then he showed me his catalogue








there are 2 types of B6 apparently....for the rear they are 2 numbers

i narrowed down to BJ front and Swingaxle rear








i cant figure what is 280/100 and 330/130...

Rennen means sport, race, etc from google translation


dealer said i am the first person who asks for this and will get back to me the differences between the 2.

[hotrodsurplus]

My apologies for not responding to your PM yesterday. I was out on a quest to buy a car that never came through. Long story...

Okay, Bilstein changed its numbering system a few years back. The old alphanumeric numbers are gone, in their place a new 'logic' so to speak. By the way, the term B46 in the old Bilstein numbering referred to 46mm piston diameter; B36 referred to 36mm piston diameter. Note that all of our Volkswagens got the 'manly' 46mm pistons. It's because we rock.

The figures 280/100 and 330/130 are damping forces in kilograms but I can't remember the rate. The first figure is rebound (extension) and the second figure is compression. A damper usually needs more rebound damping than compression damping as the spring itself serves as a compression damper. The rebound damping controls the rate that the spring releases its energy after being compressed. So increasing spring rate requires more rebound damping and less compression damping; reducing spring rate requires less rebound damping and more compression damping. Make sense?

Rennen is racing auf deutsch.

Here's a cross reference of old numbers and the new numbers with application. The online format screws up the tab spacing so you'll have to copy-paste-edit it in a word processor.

App         Old #         New #      damp      length
Typ I ball      F4-B46-0620-H0   24-006200   185/75   16.12/10.31
Typ I ball Cut/turn   B46-0493VW    265/70    18.6/11.7
Cut/turn w/reservoir   B46-1085R

Typ I kingpin      F4-B46-0032-H1   24-000321   255/108   15.25/10.24


Typ I swing      F4-B46-0040-H1   24-181488   330/130   15.25/10.24
Typ I rear      F4-B46-0033-H0   24-000338   330/130   15.43/10.41
Class 11 rear      F4-B46-0930          345/135    16.22/10.86
Typ I IRS      F4-B46-0034-H0   None (NLA)    360/160   16.22/10.71
Thing/Super IRS   F4-B46-0634-H0   24-006347   
Typ I IRS      F4-B46-0034-H1   24-000345   

Split bus front   F4-B46-0032-H1   24-000321   255/108   15.25/10.24   
Split bus rear      F4-B46-0040-H1   24-181488   330/130   15.25/10.24

Bay bus front (orig)   F4-B46-0828      NLA
Bay bus front      F4-B46-0032-H1   24-000321   255/108   15.25/10.24
Bay bus rear      F4-B46-0032-H0   NLA       
Bay bus option   F4-B46-638-HA         NLA      178/71   22.05/13.62
VW 221 513 031   bay bus rear,             22.2/13.74
Bay bus opt II   F4-B46-1047-H0   24-010474   (from Bilstein off road; same as Astro/Safari van)   
Bay Bus opt II   1989 GMC Safari van, rear; (Rancho RS5147)   22.98/14.03
89 GMC Safari rear

Typ III front      F4-B46-0032-H1   24-000321   255/108   15.25/10.24
Typ III rear (all)   F4-B46-0040-H1   24-181488   330/130   15.25/10.24
      
Here are the listings from the old Bilstein racing catalog. These are all Volkswagen applications for primarily off-road racing. Ball is ball joint.

Part Number      Application    Length      Valving
B46-0032-H1      Kingpin          10.25 to 15.25   289/104
B46-0033        king or swing   10.41 to 15.43  330/130     
B46-0034-H0      IRS                    10.86 to 16.13   358/166
B46-0040-H1      BJ or swing   10.25 to 15.25   337/136
B46-0930              Class 11 front    10.86 to 16.22  345/135        
B46-0493VW      turned BJ           11.70  to 18.60     265/70 

[pupjoint]

great stuff Chris. thanks. I know which one to order.