Best spring plates for coilovers - advice please

[SoCal70RSR]

My front suspension appears to be sorted out but I'm having second thoughts about the springs plates for my rear suspension.

The car is going to be 60% street and 40% PCA events. I've read several threads about 935 type spring plates and statements such as "bone jaring" or "rattling teeth" have steered me back into OEM type spring plates.

I bought a set of 935 type spring plates from fellow pelican beepbeep some time ago and also have a set of OEM spring plates with new neatrix bushings. I can go either way. Which setup do you guys recommend? Will a 935 type spring plate make it too unconfortable/noisy for street use?

[SoCal70RSR]

Anybody??

[Chuck Moreland]

The 935 plates should not make a significant change to the ride quality.

Most people who put on coilovers and 935 plates have stiff springs and stiff shocks. It is no surprise some of these cars can be called "bone jarring" but it's not from the 935 plates.

That said, if you decide to go with the factory spring plate - get a set of early non-adjustable plates. They can be had nearly free because everyone wants to upgrade to adjustables, as they should.

Sell that adjustable set you have there, they offer no benefit with coilovers.

[cashflyer]

Forgive me for hijacking this thread, but I have to expand my knowledge by asking.... why use coilovers?

Seriously... I don't know.

Does it allow you to eliminate the torsion rods?
Is it just for extra rigidity?
Do I need these?

Enquiring minds want to know.

[SoCal70RSR]

Hmm.... The rear springs are 500 and the fronts are 300. If I remember correctly (it's written down somewhere) the valving on the rear RSR shocks is 325/125. With the 935 type spring plates, all the rubber is basically eliminated on the rear suspension. I have ERP trailing arm monoballs, SRP shock clevis (no rubber), RSR type bilstein shocks (no rubber anywhere either) and the 935 plates with a metal donut to grab onto the torsion tube. It should make for a stiff suspension... Just not sure what this combination will be like on the street ie, noisy, harsh, etc... It's the situation most of us have to compromise on, what's good for the track is probably not good for the street. I'm at the point where I need to bolt something up to my rear suspension.

cashflyer, you probably don't need coilovers, I probably could've stuck with torsion bars myself but looking at the high end spring plates and torsion bars, the coilovers were a comparable expense if not lower. A few benefits are, ease of ride height adjustment and ease of changing springs... changing torsion bars and re-indexing spring plates/torsion bars is no fun. The 935 spring plates gives you additional flexibility as well.

[cashflyer]

Originally posted by SoCal70RSR
cashflyer, you probably don't need coilovers, I probably could've stuck with torsion bars myself but looking at the high end spring plates and torsion bars, the coilovers were a comparable expense if not lower. A few benefits are, ease of ride height adjustment and ease of changing springs... changing torsion bars and re-indexing spring plates/torsion bars is no fun. The 935 spring plates gives you additional flexibility as well.

Whew... I thought I was missing out on something!
So I probably don't need to consider it unless my "racing" ever gets more serious than just DE runs.

Does this setup completely eliminate the use of the torsion rods?

[Steve@Rennsport]

Fernando:

Bilstein's 911 RSR shocks come valved at 180/170 unless they have been redone and thats FAR from ideal,......

[don911]

I don't know if this compares but I recently installed 30mm tbars, elephant polybronze spring plate bushing along with trailing arm monoballs so all rubber is gone as well. I have rear RSR shocks that are valved for 30mm tbars (from Steve@rennsport - thank you).

I don't feel the ride is bone jarring or teeth rattling by any means. It's stiff but very compliant if that makes any sense. Don't know how 30mm tbars compare to your spings but I don't see how your choice of 935 spring plates vs OEM will have much, if any effect on ride quality.

[SoCal70RSR]

cashflyer: Yes, the coil-overs eliminate the torsion bars.

Wow, I didn't know the stock RSR shock was 180/170. I had mine revalved by Bilstein.

Don... The main difference between your setup and mine will be the torsion bars. A lot of the twisting/spring compression is inside your torsion tube. Where as mine will be distributed a bit different. If you have your stock shocks, there's probably a bit of rubber left at top and bottom (not sure how much this affects ride quality). Good info though and good to know you still have a confortable ride with your setup.

[don911]

the shocks are RSRs valved by Steve@rennsport.

ah, now I understand your question about ride quality with all the load now going into the top of the shock tower. I'm no help at all on this one.

Do you have a cage tied into the shock towers to help distribute the change in load path? nevermind...just went thru your pics and anwered my own question. Awesome job btw. Your car looks amazing. Your attention to detail looks borderline crazy. You might want to see someone about that.

[SoCal70RSR]

This is all that was done to the shock towers... hope it's enough

[don911]

I just edited my post after looking at your pics.

[SoCal70RSR]

Originally posted by don911
Your attention to detail looks borderline crazy. You might want to see someone about that.

Oh no... I'm not crazy!... Just most of the time I find myself confined to small room with four walls and an automatic door aparatus which can be open just enough to get a plate of food and fresh air once in a while

[Jack Olsen]

A side note on jarring the bones: an often-ignored component to ride quality is sound. In the same way that a car seems to have a lot more power when you switch to a louder muffler, driving in a 1900-pound, stripped-to-the-bones race car, the cacophonous assault on your ears actually plays a pretty big role in your sense of how smooth the ride is. In street driving, passengers often comment on how comfortable my car rides -- this with 600# rear springs, monoballs and 935 spring plates. A big part of their reaction is the full carpet, leather and additional sound deadening pads I run in the back for street driving. Your brain puts together a package of perceptions and 'reads' it as rough (or fast) -- but a lot more than just the suspension (or the actual horsepower) contributes to that final reading.

Also, tires make a huge difference in ride feel. And the cars stripped down for racing are often running on stiff (and loud) R Compound tires -- you drive over a dime and you can tell if it's heads or tails.

[SoCal70RSR]

Very good point... and now I have to worry about tire compound!

I added dynamat-like material throughout inside the car and a pretty good sound pad in the engine bay. This should eliminate some vibration and some sound transmited through the body.

For what I understand, the 935 type spring plates can be harsh/noisy at take-off and stopping. At takeoff, there's a pull on the spring plate towards the back of the car, and at stopping there'll be a push. All this will be going against the torsion tube. Up and down motion should be OK at the spring plate since the monoball will give easily for this type of movement. The up and down harshness will be based on the shock and spring used.

To go back to my original question, after this thread, I'm now leaning towards the 935 type plates... Any other opinions or experiences?

[Jeff Alton]

I have not experienced any increase in noise starting and stopping like you mention. There is no play in the system so those forces do not generate noise.

Cheers

[klaucke]

935 spring plates have the added benefit of raising the pivot point of the spring plate, which is good for preserving suspension geometry in lowered cars. It looks as though your 935 plates have two different choices regarding height.