Do torsion bars get tired over time? Do they lose their ability to keep a car level in turns? Or is this more of a sway bar issue?

I can't say that I've noticed it while driving on the track, but some photos from last weekend show it leaning pretty good. In fact a lot more than I would have thought.

I have 23 and 30 mm bars with urethane bushings, 22 mm sway bars, Bilstein HDs up front and Koni sports in the rear, camber plates, strut tower brace, 18 BBS wheels with Dunlop slicks, etc.

Jim

 

Looks more like chassis flex to me.



No really, this is one of the reasons why whenever possible, racing Porsches change over from torsion bars to coil springs. You just cannot get stiff enough torsion bars for the track, and the cars lean too much on the really grippy tires. If it were my car, I'd at least go for the 34 mm rear bars, revalved Bilstein Sports, and a larger front sway bar (I do not think that you can get larger torsion bars for the front). For the record, I ran 23s & 30s on my Carrera at 2700 lbs on R tires and I felt that it could have been stiffer.

 

Assuming they are not damaged (cracked) torsion bars (and coil springs) will never lose their rate. They may lose ride height, but not rate.

 

Unfortunately...

The pre-964 911 chassis is about as stiff as a wet noodle. At a fairly early point, adding stiff springs doesn't do anything anymore. You reach a point where linearity dissappears, in setup, tuning, response... everything. Coilovers are also not a no brainer, because the rear upper mounts are not designed to handle much of a load, and indeed WILL NOT.

At least T-bars are easy to deal with in a 911... relatively.

Does it look like a lot of decamber in the front too?

 

Thanks Guys.

This picture is the worse case scenerio of all that I saw from that weekend. I'm going to try a few suspension changes and see what happens.

Where can I get larger sway bars?

 

I run 23/33 Sander Engineering torsion bars. The Bilstein sports are not up to the task with this setup so JRZ's are coming my way. You can get all of your suspension goodies and a bunch of advice from Steve Weiner at Rennsport Systems.

http://rennsportsystems.com/

 

Hey;

Sways work well on street cars with soft springs and no other adjustability. It is not widely accepted, or known anyway, but sways don't play the role that most people think when you get into track cars. You find that springs are what control roll, and sways are there for basic balance tuning. Beyond that, shock damping control is for fine tuning.

I don't think you would find sways having a large effect on your situation. I don't know what the pound rates of the 911 t-bars is, off hand, but I'd guess you are still pretty soft. With the grip levels generated by 18" slicks, I'd say you are asking a lot from those bars and shocks. Here's that slippery slope!

 

I'm running 23/31 bars from Sander's Engineering. I was going to change to the 33 rear bars but decided to go with 200lbs helper springs with a little bit of pre-load. This gives a nice balance to the f/r wheel rates.

Lyall

 

John has a very good point about the stiffness of torsion bars versus springs. With my 23/33 combination, I still deal with a fair amount of lean on corners. A full coil over suspension is out of the question for me, but it is something that you may consider if you're running slicks and an enhanced engine. I'm going for better shocks to better manage the suspension movement that I have.

 

OK. Bigger sway bars are out. Bigger torsion bars and better shocks are in. 30mm solid is the biggest I have seen. Are there any hollow bars that have a higher rating?

John, Would the torsion bar and coil over with helper spring combo be acceptable compared to a full coil over in the rear or all around, as it's only a helper?

 

I think a bigger wing would help............ according to TD......

 

Hey;

The tops have been known to pop off the rear shock mounts even with only stiffer shocks present. The helper coilover idea may be a good compromise since you could probably get away with minimal reinforcement -vs- a more extensive full coilover stiff spring job.

Next time the engine is out, plan on doing some shock mount mods. Or... plan on dropping the engine now. The simple method is to just weld up the cap, or add some plate on top of the mount to keep the cap from blowing through. More extensive mods begin with plating the top cap and tieing it into the pedestal or crossmember itself, and end at REPLACING the crossmember completely.

I'm away from home, or I'd post some pics for you. I'll post next week.

----------------------------------------------
Reporting Live from Brockville, Ont.

 

Well, you know what they say. Bigger is better...

 

Hey;

Home again. Here are the pics. I did this in a 930. You can see the stock top cap. You can gain a lot of strength by simply welding up what is there. I plated the top with 1/2" steel to do full coilovers. The side pedestal was added as a tube perch.




Then there is the more extreme example.




These should give you some ideas.

 

Thanks John.

To be clear, did you cut off the old top that looks spot welded on and then cap with the 1/2 plate?

From the picture, it looks like it would be easier from the passenger compartment due to the angle?