Rear drag race suspension

[Eric Justus]

Id like to get a general consensus on a good rear suspension drag set up? And I am talking the whole shuh-bang, not just shocks. Use for example....say a type 1 running a high compression 2 litre, with a set up for competitive 11.90's. Any and all comments and opinions greatly appreciated! 

Cheers,

Eric J

[Ohio Tom (DdK)]

Assuming you are talking about a stock configuration rear suspension.
For 11.90's, you can do alot for a little.
 
The low-buck approach can be just a set of bus sunbbers, eurathane bushings. A set of coil over shocks help to stiffen things up too.
If the car is light weighted, that helps as well.

The "right way" is to purchase a set of larger diameter rear springs (choosen carefully based on car weight) and some adjustable shocks.


My personal race car has is 1,500lbs. Runs 11.70's to 11.80's on any given day.  I'm using stock rear spring with eurathane bushings and snubbers.
It pretty much uses up the suspension and plants on the limiters on launch (and pulles a good wheelie). This isn't such a bad deal with IRS rear suspension.
However, it's time for me to upgrade to some larger rear springs. Sometimes she drags my deep Berg sump...

[Jonny Grigg]

Id like to get a general consensus on a good rear suspension drag set up? And I am talking the whole shuh-bang, not just shocks. Use for example....say a type 1 running a high compression 2 litre, with a set up for competitive 11.90's. Any and all comments and opinions greatly appreciated! 

Cheers,

Eric J

You haven't said what car, what weight, whether it is IRS, swing axle or ladder bar, whether you have rasied the torsion housing, whyether you are using wheelie bars and whether you are also going to use it on the street.

The set up I am currently working with on my race car (which I am still building) is:

Swing axle, 30mm torsion bars with adjustable spring plates, a T1 trans on RLR raised mounts, AVO adjustable dampers and JayCee spring plate retainers. I will use limit straps once I have worked out what length I need.

I pondered the whole set up at length and considered raising the whole torsion bar housing, but I had already got so far with the car and the engine position was 'fixed' by the parachute mount and various brace bars and the wheelie bar mounting position. I also considered 'back halfing' it like Dave Dinnings' set up (which is awesome)- Dave's was made by Jim Smith here in the UK, but I suspect it is very similar to what Ron Lummus sells (check his website out).

I went to Ron's shop when I was out in California this year and discussed the whole set up and my concerns. He made it quite clear to me that approach I was taking (if it was set up right) would be good for 'high 9s'. As I am shooting for the mid-10 bracket, this was good advice.

You can't look at the rear end set up in isolation either- you need to get the front end right too.

Not wishing to confuse matters and contradict Ohio Tom, but my experience of mixing coil springs and torsion bars is not a great one (certainly with swing axle)- I think you have to go with one or the other as they have different spring rates and can make the car unpredictable.That said, I'd imagine there are alot of people who would disagree and would say it did not detrimentally affect the high speed stability.

[Eric Justus]

The car is a an all metal 55 sedan, swing axle rear end. Front end is going to run 90/10 shocks on a 2" narrowed front beam. I am going to run the RLR adjustable rear shocks, no wheelie bar and no tranny raise. Along with that is bus snubbers and urethane bushings. i guess the big question is the size torsion bar, i was thinking about 30mm, but I need to get a little more educated on the whole size vs set up ratio. For a guesstime on weight, the 55 is only missing the bumpers and seats, everything else is there. t-bars and an aluminum racing seat to replace, but it does have the nhra spec 11.90 cage in it.

[vwxtc4free]

I  would use the 30mm bars on a full weight car.I have the 29mm on mine with solid sping plate bushings , 90/10 fronts and 12 way adjust QA1's on the back.It's full weight and still squats a lil on launch.

[Mike Lawless]

The car is a an all metal 55 sedan, swing axle rear end. Front end is going to run 90/10 shocks on a 2" narrowed front beam. I am going to run the RLR adjustable rear shocks, no wheelie bar and no tranny raise. Along with that is bus snubbers and urethane bushings. i guess the big question is the size torsion bar, i was thinking about 30mm, but I need to get a little more educated on the whole size vs set up ratio. For a guesstime on weight, the 55 is only missing the bumpers and seats, everything else is there. t-bars and an aluminum racing seat to replace, but it does have the nhra spec 11.90 cage in it.

Eric
If you run the bus snubbers, don't bother with the adjustable shocks and big torsions. If you set bus snubbers like they need to be on a drag car, in contact with the snubber stop, it renders all the high tech stuff ineffective. In that case, all you need is a set of $40 apiece KYBs.
If you're gonna go with big torsions and adjustable shocks, run the whole package with no snubbers at all. 28 to 30mm torsions are pretty much standard equipment for an 11.90 car. You don't need to bother with 90/10 shocks in the front either. The front wheels are gonna be high in the air if you make enough power to run the number. Look at the Palmers and Bakkens car, and you will see what I mean. Should weigh in the neighborhood of 1800 to 1850 lbs with driver installed.

[kev d]

Hi Mike,

Would you still advise the same for a lightened car with irs?
I`ve got type 3 torsion bars & was considering fitting coilovers with maybe 150lb springs.
Would bigger torsion bars be better?
I`m aiming for @225bhp in a lightened oval, track fun only

Sorry for the hi-jack Eric

[Mike Lawless]

IRS cars are a little more forgiving as they don't go thru the severe alignment changes with suspension travel. With a swing axle, not only does camber change dramatically, but also toe. Most guys recommend a little toe-in at ride height. However, I set mine up with a little toe out because at ANY suspension location other than ride height, you will have a large amount of toe -in as the axles swing forward thru the arc of their travel. On an IRAS car, you don't have that. The wheel stays pretty much in alingment throughout it's travel. All you really need are springs and shocks stout enough to keep the sump from smacking the ground. In either case, 90/10 shocks are not needed for a car with enough beans to yank the front end end up. A shock light enough to promote weight transfer, then let the front settle without bouncing is all that's necessary. Well worn stock shocks are almost perfect.

[Eric Justus]

Can i wear well worn gym socks to match my well worn stock shocks when i race too? I heard they promote quicker foot speed

[NoBars]

I am in this same boat right now.

check out this thread http://www.cal-look.com/forum/index.php?topic=22616.0