Spring Rates

I am running 450# front 550# rear with deleted torsion bars and Weltmeister rear adjustable sway bar, I am also using Aldan double adjustable coilover shocks. The setup runs quite well but I have a pair to 600# springs for the rear to eliminate a little oversteer, I don't find this setup too harsh for the road.

pormgb wrote:I am running 450# front 550# rear with deleted torsion bars and Weltmeister rear adjustable sway bar, I am also using Aldan double adjustable coilover shocks. The setup runs quite well but I have a pair to 600# springs for the rear to eliminate a little oversteer, I don't find this setup too harsh for the road.

Thanks for the input! Wouldn't stiffer rear springs generally INCREASE oversteer?

Anyone else want to share?

Luke714 wrote:

pormgb wrote:I am running 450# front 550# rear with deleted torsion bars and Weltmeister rear adjustable sway bar, I am also using Aldan double adjustable coilover shocks. The setup runs quite well but I have a pair to 600# springs for the rear to eliminate a little oversteer, I don't find this setup too harsh for the road.

Thanks for the input!  Wouldn't stiffer rear springs generally INCREASE oversteer?

Anyone else want to share?

From what I understand, oversteer caused by spring rates is related to front spring rate vs rear spring rate. 450# front and rear will cause oversteer, I would like to have a 200# spread between front and rear.

I'll share my setup if it helps. I have JRZ shocks with 450/600 springs. Mine is a track car but I've run 350/500 on the street without issues. Yeah, you'll feel every pot hole but I still enjoy it.

General rule for spring rates vs grip - the stiffer the spring the less grip the tire has. So if you want to induce some oversteer, you can bump up the rear spring rates.

Thank you!  Sorry for the dumb question, but to clarify, you are running the 600 (or 500) on the rear?  I wonder why Jay got me to go softer in the rear than front.  I think we were worried about getting enough traction, but it ended up giving me too much rear grip and now I understeer.  I do like how well it comes out of the hole though.

I think I might try upping my rear spring rate a little bit and putting the rear sway bar back on (although I need to modify my exhaust or lengthen my drop links to do that   )

Cheers,

Luke

Yes, 500 or 600 in the rear. I have no torsion bars in the car, so if you're doing torsion bars and springs you'll want make sure you're adding things. As others have said, a 200lb split front/back has been the general rule for 944's for some time, though I think it's changing with setups and tire tech.

From some of your other threads, it's hard to gauge what you're planning to do with the car. AutoX, DE/track car, driver? You won't want a full track setup for the street and the reverse.

Haha, yeah it's been evolving. I live in Maine, so getting to a good track is a bit of a slog, but I do a lot of auto X. I plan on doing more and more DE and track days with it though, I want to improve my driving if I can (but I don't plan on doing actual racing for the foreseeable future). I drive it on the street, but is isn't my daily driver (although I do drive it a lot of the time during the summer). Performance is what I'm stressing in the car for sure, but I don't want to go quite as firm as your track setup. I'm thinking the 350/500 you use sounds about right for me. Thanks for all your input! What do you use for sway bars?

I'm thinking:
-Up the rear to 450# from 300#
-Hook up the stock turbo rear sway bar
-Drop the front to 400# from 440#
-Keep the front turbo sway bar

If I need to soften the front/stiffen the rear to increase the split to the recommended 200# I can, but springs are cheap and I think I want to feel the dynamic change incrementally so I can better understand the effects its having. Anyway, I think the front is definitely too stiff as it is because of the understeer problem and I think the 440# springs are a bit much for my dampers as I get a bit of jitter over bumps. They are adjustable though, so maybe I increase the damping a bit and see if that helps the jitter problems first.

Cheers,

Luke

Don't forget, tires also affect under/oversteer. In the tire thread you state that you are running 255F/295R, this will induce understeer as well and is one reason why you will need a greater spring differential front to rear. Some of us are running square setups (275 on all corners), and in that case, I don't think you need as much difference between front and rear spring rates (I run 650 on all four corners).

Yep, 275's all round for me. Rear torsion bar delete, 450# up front, 700# in the rear, 968 M030 swaybars front and rear.

Car is very neutral with this setup and points easily with the throttle.

Lemming wrote:Don't forget, tires also affect under/oversteer.  In the tire thread you state that you are running 255F/295R, this will induce understeer as well and is one reason why you will need a greater spring differential front to rear.  Some of us are running square setups (275 on all corners), and in that case, I don't think you need as much difference between front and rear spring rates (I run 650 on all four corners).  

A really good point, thank you.  I think I'll still make the changes I mentioned above, but with the knowledge that I might have to increase the differential front to back even more because of my large tire width difference.

I'll keep the thread updated with the changes I make!

Cheers

Much easier to just get rid of your staggered setup and run a 275 square setup...

Go have fun and test and play. What feels great for one person will feel terrible to another. No disrespect to anyone who's posted, but driving style is being left out of this. I was driving the Praga R1 this summer and loved it while the next guy thought it was horrible... As you said, springs are cheap and you'll get good at changing out the rears quickly and readjusting the ride height. Fronts take a little more work..

As for sways, I'd suggest MO30 or larger. The turbo stocks are still a little too small IMO. I had 968 M030's in my 951 but have tarett sways in the 948 and have been really happy with them.

I'm assuming you have an LSD trans? If not, I'd start there before thinking about some serious track time

If you make it down to Lime Rock or the Glen, let me know and maybe I'll join you for a day.

docwyte wrote:Much easier to just get rid of your staggered setup and run a 275 square setup...

Not after all the research I did to find the right offset with the ZR1 wheels! That was too much work to throw away.... ah, you're probably right   

The C-clip holding 3rd gear in place on it's shaft wasn't put on correctly in my transaxle so it decided to wander into the neighboring gears. A shop is freshening up the box now and I'm having them put in an OS Giken super lock. I'll definitely drive with that for a little bit before I make any final decisions.

Thanks all for the great continuing comments!

Cheers,

Luke

I just ordered 4 new 900 lbs springs (6" length), upping it from 650 all around. My car runs 275's on all four corners and is pretty much 50/50 weight front to back. I went with a short spring because with the 650 x 8" coils, I was already at the bottom of the perch. Plan is to lower the car a bit more with the new springs. Will post up my thoughts once installed and tested.

wow! That's serious!   Have you removed the torsion bars in the rear, or do you now have 900 lbf/in springs plus the torsion bar spring rate?

Also, does anyone know what the stock front rate is for a 951?  

according to this: http://www.clarks-garage.com/shop-manual/susp-15.htm the front rates are 3286N.  Just "Newtons" isn't the right unit for a spring rate, so are we assuming N/m?  3286 N/m=739 lbf/m=225 lbf/ft.  Does that sound right?  According to the same source the rear rates for a 951 are 126 lbf/ft.  If we aren't screwing up the weight balance with the LS1 very much I think it would make sense to maintain this same front to rear ratio of spring rates while stiffening the suspension overall. I.e going to something like 440/246 f/r since 440/246=1.79 and 225/126=1.79.  Doing otherwise would change the handling characteristics and balance of the car, which is something that some might want to do, but that is a whole other debate.

Thanks,

Luke

No torsion bars. Some racers are running 900F/1300R but that's with staggered wheel/tire sizes. Not sure how I will like it but will give it a try

Yeah, I guess it all depends on what you do with the car.

Can you explain why the car comes from the factory with stiffer front springs, but so many people seem to end up going stiffer rear than front?

Because most of us with track cars and deleting the rear torsion bars.

Luke714 wrote:Can you explain why the car comes from the factory with stiffer front springs, but so many people seem to end up going stiffer rear than front?

Most cars are setup from the factory to understeer. This so people put them straight into whatever they hit and the safety systems of the car are most effective, like airbags and crumple zones. Hitting something sideways is almost always worse for the occupants of the car.

But us track hounds hate understeer. Stiffening the rear suspension relative to the front reduces understeer making the car more neutral. Going too far introduces oversteer. This is super basic, there is way more to it all of course.

Rich

Max Energy wrote:Luke,
Contact Jason at Paragon Products they work alot with Koni shocks and 944 suspension
Max

Jason at Paragon was great. He got me set up right. It's been like 10 years of tracking the car, it his spring rates for front and rear were spot on (is the sig coming through?)

Not sure if he's at Paragon anymore though.