How much caster need a fast drag VW Beetle?

[ROJO]

I am interested what other cars have at the front. My car has serious problems to stay in lane at the end of the track.
The body is now lifted from the pan and i want to make the front 10cm longer. In this situation i can weld the front in any direction i want.
Bumpsteer is also a problem. A Porsche rack and pinion is on my mind to overcome this problem.

I hope i get some input on this.

Robert

[Bruce]

7-12º should keep you straight.

Beware, your idea of using a R&P may actually make bump steer worse.  All you need to know is short tie rods = bad bump steer, long tie rods = minimal bump steer.  Most R&P installations I have seen in Beetles are worse than stock for bump steer.  Their left tie rod is just as short as stock, and their right tie rod is the same, eliminating the good (long) stock tie rod.

[bang]

drop ron lummus or jimmy larsen (jcl) a mail.

[Fiatdude]

A lot of fast pan dudes put the notch in the pan to really lay the front back -- (recommend by me) -- If your only going straight -- you almost cannot have to much caster

[ROJO]

drop ron lummus or jimmy larsen (jcl) a mail.

Has Jimmy Larsen (JCL) a website?

[ROJO]

7-12º should keep you straight.

Beware, your idea of using a R&P may actually make bump steer worse.  All you need to know is short tie rods = bad bump steer, long tie rods = minimal bump steer.  Most R&P installations I have seen in Beetles are worse than stock for bump steer.  Their left tie rod is just as short as stock, and their right tie rod is the same, eliminating the good (long) stock tie rod.

I know that longer rods are better but finding the right R&P is not so easy. I found a smal one from BRT. But is this tried on a Beetle with stock spindels. I saw at Bitburg that silver colored new Beetle with that R&P but they hat struts and that's not what i want.

[Neil Davies]

I tried rack and pinion and it didn't work at all. In fact, I would go as far as to say that it was dangerous, so dangerous in fact that after one run I went to see the scrutineer of the meeting and the race director and pulled out of the event. It's just not worth the hassle. I took the R&P off, put on a stock steering box and no problems after that at all.

I wouldn't lengthen the car at all - I used two pairs of caster shims under the bottom beam, and as Bruce says, you should be aiming for between 7 and 12 degrees - the more the better. You could cut off the framehead and reweld it in whatever position you like, like Harold (Fiatdude) said.

To eliminate bump steer, you could use the JCL method (well, I've seen it on a couple of JCL cars!) of using the longer of the two stock track rods from the steering box to its spindle and one long tie rod between the two spindles.

There are other reasons whey the car is having a wander at the top of the track. Rear toe-out, rear camber, air building up under the panels, even driving technique can all have an effect. Post some more detail on your set up and I'm sure people more knowledgeable than me will chip in too.

[Peter Shattock]

I can agree with a lot of what has been said here as I changed from a regular steering box and tie rod arrangement this year to a “JCL” set up and found the car to be significantly better. If you need convincing that there is an issue with this set your car up with your preferred toe in at ride height, then jack the car up an inch and see what your tracking looks like! Needless to say ride height changes through out the run as the car loads up and unloads and perhaps most importantly when you shut down at the top of the track. The amount of toe in and out movement is dependant on several things (tracking arm length, angle arc of movement and suspension movement are the main ones). Some of the variations can be reduced by reducing suspension travel, although this does potentially have other consequences, but it can help. Look at some of the DVD’s and you will see a lot of the fast cars do have relatively limited suspension travel at the front.

Even with the “JCL” setup, I was very surprised to see how sensitive the toe in and out variations were with ride height and the stock steering box and track end locations, even on the long arm. I ended up using rose joints and spacers to find the optimum angle for the steering arm for my cars ride height. After a lot of messing around I eventually ended up with a dead vertical plot within my known suspension travel. To plot the amount of change in toe in and out I took the front wheels off, removed the short steering arm and set the car at ride height with the tracking set and the steering pointing straight ahead. I then supported the trailing arm on a jack and took out the two centre beam adjusters so that the stub axels could free swing but well still be held firmly in place. I then fitted a laser light to the hub and plotted a line on the wall (about 1.5m in front of the hub) of my garage. I put a dot on the wall in 25mm increments and covered the full range of suspension travel. The first time in the stock arrangement was terrible but with some fiddling around with spacers and moving the steering box I soon found the right spot and the car has been significantly better to drive ever since. I then marked everything for future reference and made up some proper spacers (I used washers to check and adjust the required heights at each end). So if you are experiencing handling problems this is definitely an area worth considering, it takes a little while to get right but its not expensive when you consider what you have to loose!

As others have suggested there are other issues to consider at the back end including movement front and back affecting toe in and out when you come on and off the gas as the bushes in the torsion housing take quite a beating, and they play a critical part in controlling the movement to reduce the effect. I did once drive my car (before I know better) with unchecked toe out at the back, and I can tell you that is not something I will ever do again! 

If you really want to use a rack (I understand the potential benefits) you certainly want to consider a long arm arrangement and or restrict suspension travel as the shorter your arms and more suspension travel you have the bigger the problem. It’s tricky business altering steering geometry as there are things moving in inconsistent multiple planes so there is a lot going on. For instance you will loose the effect of the arc the pitman arm travels in when you use a rack. I’m not saying its significant as I don’t know, (I decided not to use a rack and consequently did not get to the bottom of the issue) but it is something worth researching, before throwing your steering box in the bin.

Don’t compromise on safety! We are all pushing to go faster and it’s easy to loose sight of safety, as it’s not as exciting to talk about as most of the other stuff, but I think we are closer to the edge more times than we realise.

I think it’s a good subject to discuss and perhaps some of the more experienced racers will be able to add some good comment. I’m sure some people will want to keep there performance tricks to themselves, but there is no excuse for not sharing safety tips.

Hope this helps

Peter
 

[dangerous]

I think you will find that JCL uses the short arm.
It tends to folow the arc of the trailing arms better than the long one.

[danny gabbard]

Great subject!!

[Bruce]

I think you will find that JCL uses the short arm.
It tends to folow the arc of the trailing arms better than the long one.

Short tie rods are never better than long ones.

[Bruce]

... I used two pairs of caster shims under the bottom beam,....

I was over at a buddy's house checking out his street car.  When I looked under the front, I saw he had FOUR pairs of caster shims under the bottom tube!  He said he was shooting for over 10º.  Now you might think it would be almost impossible to steer in a parking lot.  Nope.  Even with a smaller than stock steering wheel, I couldn't tell the difference.  It almost seems to me that you can't have too much caster.

[Peter Shattock]

After all that I forgot to mention the castor shims I use 3 with the back of the car just below stock height and the front slightly nose down. As others have suggested there are not many problems with more beam castor other than the wheel being further forward in the arch (you can scrub the headlamp bucket depending on wheel and tire combo) and it raises the front of the car. In a stock framehead car this can mean that you have the trailing arms at quite an extreame angle relative to the beam if you want the car very low. That said I've seen several cars run like this with no problems.

One other thing don't forget that static castor you measure on the car is not representative of the cars castor when you shut off at the end of the track and the nose of the car drops and the back comes up and the rear tires at there largest diameter. Needless to say this all happens at your highest speed when you need castor more than ever. Next time your at the track have a look at a few cars go through the top end, some do it more than others but there is a fair bit going on. Better still get someone to film your car so you can see what's going on.

I would say a little more rather than less static castor would better. 

Back to the JCL issue. It would be interesting to hear from someone running the short rod set up. When I did mine I checked the short rod side out of interest, and the run out was much worse than with the long rod.

Peter

[Woodentop]

I agree Bruce

I tried the short tie rod route first, i just couldn't get anywhere near enough bump steer out, made me realise that the longer the rod the better, swapped to a "long" tie-rod over the frame head as such and got the bump steer down to almost zero. i did at the time manipulate the frame head a tiny bit by grinding slightly and bashing where the tie rod passes over it to give me a little more downward wheel travel.
The other advantage of this particular set-up is that tracking is set perminantly and will not be changing to toe-out as the nose of the car lifts up and down maybe when shifting gear etc. As Peter mentioned, just check and see what your front wheels do with the front end jacked up just 1", mine used to go to 1/8" toe-out with a stock set-up if i did this.

What Peter is essentially describing is the long process of adjusting things, ie the angle / postion of the steering box, shimming etc (i even ended up machining a bit off the underside of the spindle where the tie rod fixes) and then its checking and re-checking to eventually reduce bump steer to minimal amounts. i also found that tie rod at "level" when the car is sat is a close starting point and fine tune from there.

Not sure this setup can actually be done by the way with dropped spindles on the car, doubt you will clear the frame head.

Because i have balljoint car I will add that since then i asked Jim @ Cotsweld to cut the frame head and raise it 1 1/2" and he also put me some extra caster in there while he was at it, the tie rod misses the frame head easy now. (he did do an incredibly accurate job) i also get my suspension back after my balljoints ran out of travel.

[Martin]

Ive got 7 deg in mine. and i converted the tie rods as per woodentops car. Ive got one tie rod between the sub axles and i connect the long tie rod to the steering box.  I made my tie rods from cromolly.


its all fine and dandy at 148 mph, and very smooth and predictable during the launch.

mines a king and link pin front end with dropped spindles

hope this helps

[ROJO]

Thanks for all the input.

The front of my pan is not perfectly in line (right and left wheelbase are different) I want to correct this is and take the opportunity to make the wheelbase also longer. I heard that lengtening the wheelbase makes a lot of difference. I am going for 10 cm but optical i only want to move my flipfront about 5 cm. The JCL way is maybe a good option. Martin have you a picture frome the steering rods setup of youre car? I have included pictures from my current front and rear situation.
The rear is te first thing i am going to change. On the inside i throw out the urethane and go for a monoball. You see that often in Porsche on the track. Then on the outside a M18 uniball setup must do the trick.

[Martin]

Sorry ive not got a picture of my setup, but ive drawn the tie rods on your picture for you. i had to clearance the frame head to allow the wheels to drop on the launch.

Oh and i dont use a steering damper.

[Fiatdude]

If you would like a very old drag racing secret -- -- the old dudes -- -- myself include use to stagger our front ends -- different wheel base on each side -- from 1 to 2" -- -- this added to having the largest diameter tire we could get on the front end would increase the roll out at the starting line -- -- could mean that we would be moving 3 to 5 mph before we broke the starting beam

[Bruce]

The rear is te first thing i am going to change.

What kind of gearbox is that?

[ROJO]

The rear is te first thing i am going to change.

What kind of gearbox is that?

It's a 4 speed Porsche 930 housing with all special internals. Straight gears with a sequential mechanism. On the gearbox i mounted a actuator (hydraulic 100Bar) and thats controlled with a lot of electronics. I this way i can shift from my steering wheel with the pusch of a button. By the way the clutch is also electronicly controlled.

@ Fiatdude I'am also a old dude my self. I race almost 20 years on the strip. I'am competing (driving half on the trottle) in SuperGas and want to go to SuperComp or Super pro ET wenn the car is stable. That wheelbase thing is familiar to me but i don't know of it get me in troubels with speeds above 150mph.

[Fiatdude]

The red Austin is mine -- here is a video of it running a 11 sec pass -- lost high gear in the glide -- it had a 2" stagger

<a href="http://www.youtube.com/v/Pgt4ziwljzw" target="_blank">http://www.youtube.com/v/Pgt4ziwljzw</a>

[Frallan]

The rear is te first thing i am going to change.

What kind of gearbox is that?

It's a 4 speed Porsche 930 housing with all special internals. Straight gears with a sequential mechanism. On the gearbox i mounted a actuator (hydraulic 100Bar) and thats controlled with a lot of electronics. I this way i can shift from my steering wheel with the pusch of a button. By the way the clutch is also electronicly controlled.

@ Fiatdude I'am also a old dude my self. I race almost 20 years on the strip. I'am competing (driving half on the trottle) in SuperGas and want to go to SuperComp or Super pro ET wenn the car is stable. That wheelbase thing is familiar to me but i don't know of it get me in troubels with speeds above 150mph.

Mighty impressed with your 930 box.
I know of a guy (RIP in VW heaven Klasse Ebbenäs) in Sweden who did something similar with a 4 speed 915. He did his own Liberty dog gears and built a 300M spool. Very nice stuff and he shifted it clutchless....like a swiss watch.
Now you have taken it many steps further. Well done!
Keep sharing with us. You have a lot we wish to hear and see pictures on.
Were are you located?

[ROJO]

The red Austin is mine -- here is a video of it running a 11 sec pass -- lost high gear in the glide -- it had a 2" stagger

That's an old video. You did a 11,96. That's a huge difference between a low 9 second run. My car comes in throubles above 130 mph. Than it's a handfull to stay on the track.

I found some nice info about stagger R.T, E.T, Deepstage etc.
http://www.wediditforlove.com/techtalk3.html
http://www.nhra.net/dragster/1999/issue21/racing_technology.html

That's wy i want to go back to an equal wheelbase. The reactiontime from my car is a little bit slow due to the electronics. I have to work that out also (it's not that i am sleeping at the startline LoL).

@Frallan I live in the south of Holland.

[fahrvergnugen]

Hey Robert,

Nice to see you here as well.
So you finally started on the front setup, hope you'll find the wright solution. Ron told me about your 911 rearsuspension plans and you loaning one of my eccentric bolts.

Keep those updates coming, talk to you soon.

Paul.

[Ole]

... I used two pairs of caster shims under the bottom beam,....

...When I looked under the front, I saw he had FOUR pairs of caster shims under the bottom tube!...

When I took the Pink Panther's front beam out of the car a lot of dirt/stuff fell to the ground. The car must have been stored in a meadow for some time...
I inspected what fell down and I found a pair of the usual caster shims. But then there was a split Type1 main bearing... It didn't take long to find the other half.
I removed the dirt from the bearings and realized somebody grinded off both ends of every single half What the... I checked the marks on the beam and the frame just to find out they used the bearings as a second pair of caster shims, mexican style ...

I put it back together the way it was and all I can tell is that it works perfect. The car runs straight like an arrow, even when it unloads at the end of the track.

I wouldn't recommend to do so again, but it shows that the search for the right caster was an issue back then.

[ESH]

... I checked the marks on the beam and the frame just to find out they used the bearings as a second pair of caster shims ... all I can tell is that it works perfect. The car runs straight like an arrow ...

I think Sal's car needs shims and I have some old bearings I can send over to Dean so thanks for the info, that's a good tip.

[fahrvergnugen]

Found an old movie
http://home.kpn.nl/jongenrobert/video/9_629%20Run%20Bitburg%202007.wmv

[ROJO]

Ive got 7 deg in mine. and i converted the tie rods as per woodentops car. Ive got one tie rod between the sub axles and i connect the long tie rod to the steering box.  I made my tie rods from cromolly.


its all fine and dandy at 148 mph, and very smooth and predictable during the launch.

mines a king and link pin front end with dropped spindles

hope this helps

Martin,

What is the diameter and thickness of youre cromolly tie rods and wy did you remove the steeringdamper?

[Martin]

Can't remember the Diameter, i'll measure it when i service the front end for you. I used rose joints instead of the usual track rod ends. I know there 3/8" .


I removed the steering damper, due to the amount of castor i have in it. you get a better 'feel' for whats happening to the road wheels. it comes from experiments i did years and years ago with one of my cars. I wanted to make the car handle and i used the route to work to test this out, some of the things i did didn't work well!! but increasing the castor and removing the steering damper really helped predict the way to car slid. you could poke the rear out and the steering would always want to go in the direction of the slide, all you had to do adjust via throttle and a little steering input. it was a great driving car.

on the track i have also found this to be true. if my car gets a little 'wayward!' then i have a much better feel for what the front end is doing and i can correct to suit. I suppose its for people who like to drive by the seat of there pants.

the damper has always clouded the information i felt.


Regards



Martin.

[ROJO]

Can't remember the Diameter, i'll measure it when i service the front end for you. I used rose joints instead of the usual track rod ends. I know there 3/8" .


I removed the steering damper, due to the amount of castor i have in it. you get a better 'feel' for whats happening to the road wheels. it comes from experiments i did years and years ago with one of my cars. I wanted to make the car handle and i used the route to work to test this out, some of the things i did didn't work well!! but increasing the castor and removing the steering damper really helped predict the way to car slid. you could poke the rear out and the steering would always want to go in the direction of the slide, all you had to do adjust via throttle and a little steering input. it was a great driving car.

on the track i have also found this to be true. if my car gets a little 'wayward!' then i have a much better feel for what the front end is doing and i can correct to suit. I suppose its for people who like to drive by the seat of there pants.

the damper has always clouded the information i felt.


Regards



Martin.

Martin,

I almost ready with the rear of the car en want to go to the front. Did you already looked at the steering rod diameter? I am also interested in how you mounted the two rods on one side.
That 3/8" rose joint is that strong enough? Standard the ends have 14mm thread.

Regards

Robert