Competitive spring rates/ suspension for the RX8

Maybe I am spoiled. I've been playing with Miatas and other cars with good online support and an extensive racing pedigree and history of swaps, etc. Now I'm getting into an RX8, and I realize the online support is just not as good. There are a lot of fanbois out there, with very little real knowledge.

So, I am looking for a starting point to begin building a competitive low budget setup for the Challenge. Looking for something just short of full race, and getting pretty close to harsh on the street. Gonna buy all the pieces on Ebay.

The car will be about 500 lbs under stock, and will perform double duty- street and Challenge. However, I will have a 2nd street suspension setup. I will replace all the rubber with polyurethane or equal.

With a Miata, we found spring rates in the 5X stock range to be about right.

The best info I seem to be able to find is that the available quality setups for the RX8 seem to have spring rate increase in the range of 130%- 180% over stock. That doesn't seem like anywhere near enough. I did notice that the Ohlin full race set up is more like 400-500%.

I am also noticing that every online comment about the RX8 OEM suspension seems to feel it is "nearly perfect", and every online comment I can find about the Miata NC suspension calls it a disaster. Aren't these the same platform?

So, give me some ideas for a starting point. In a racing environment (without rules), does the RX8 respond well to stiff spring rates? Mild drop in height? Anti-roll bars? Other?

Stock spring rates for the RX8 are 156/113, so I am thinking my starting point is about 400%- that's 650/450 (11.6kg / 8kg for you metric guys), with drop limited to keeping the lower A-arms level.

Thoughts?

http://www.rx8club.com/rx-8-racing-25/whats-your-stx-set-up-2010-edition-193171/

look into what the ST and SP level autocross people are doing to use as a starting point. probably lean one way or another depending on your tire choices.

If you're looking at piecing together an inexpensive RX8 suspension, shoot me a PM. I have some bilsteins and Tein coilover shocks for the RX8 that I was just thinking about tossing on ebay.

No comment on the spring rates, since we raced ours in stock class. The suspension design is very very very similar to the NC miata. If you're having trouble finding advice, you might start there.

AIUI, the problem with the early NC suspension is not the geometry, it's the rates & damper curves (the later NCs are supposed to be much better).

I'll bet our Fox suspension will fit the RX8 platform. But it'll blow a Challenge budget immediately. We run 550/400 on them for track use, IIRC.

The stock NC suspension (specifically 2006-12) is a disaster due to poor damping choices. There's nothing wrong with the geometry. If different decisions were made for the RX8, that would explain why you see differing opinion.

Keith Tanner wrote: If different decisions were made for the RX8, that would explain why you see differing opinion.

My opinion is that:

• You are right. Different decisions= differing opinion.

• Car is heavier, and therefore acts different.

• Different use means different audience. If the goal is a bolt on name brand sport street suspension, you get one answer. If the goal is a entire racing class built around 1 car that perform well at national levels in virtually every class, you have a different audience, and therefore a different answer.

Apexcarver wrote: http://www.rx8club.com/rx-8-racing-25/whats-your-stx-set-up-2010-edition-193171/ look into what the ST and SP level autocross people are doing to use as a starting point. probably lean one way or another depending on your tire choices.

That is a great link- thanks. But there is still a great deal more mention of name brands in that thread than of specifications.

It's a different audience.

I can match a 10Kg spec to some circle track crap I bought off Ebay for $20. It's a lot harder match something to a name brand off-the-shelf package.

SVreX wrote:

Keith Tanner wrote: If different decisions were made for the RX8, that would explain why you see differing opinion.

My opinion is that: - You are right. Different decisions= differing opinion. - Car is heavier, and therefore acts different. - Different use means different audience. If the goal is a bolt on name brand sport street suspension, you get one answer. If the goal is a entire racing class built around 1 car that perform well at national levels in virtually every class, you have a different audience, and therefore a different answer.

Plus the NC choice was just plain crap in every possible way Seriously, it rode poorly, flopped around like a dying fish and had no redeeming qualities. But you could get Bilsteins!

Willing to do your own revalving? I know the stock NC Bilsteins had crimped tops, but if the aftermarket ones can be disassembled that might be a way to get where you need.

In reply to Keith Tanner:

BTW, of COURSE I've already been to your site!!

It's both a good place to buy, and a good place to learn!

Keith Tanner wrote: Willing to do your own revalving? I know the stock NC Bilsteins had crimped tops, but if the aftermarket ones can be disassembled that might be a way to get where you need.

Come on- it's the $20XX Challenge. I'm willing to TRY to do just about anything!

SVreX wrote:

Apexcarver wrote: http://www.rx8club.com/rx-8-racing-25/whats-your-stx-set-up-2010-edition-193171/ look into what the ST and SP level autocross people are doing to use as a starting point. probably lean one way or another depending on your tire choices.

That is a great link- thanks. But there is still a great deal more mention of name brands in that thread than of specifications. It's a different audience. I can match a 10Kg spec to some circle track crap I bought off Ebay for $20. It's a lot harder match something to a name brand off-the-shelf package.

True, but I saw something in the link where someone listed 11kg/mm front springs and 6kg/mm rear. throw that into the google converter and you get 615lb/in front and 336lb/in rear. If you then get the measurements you need for stock fit (or cheap coilover fit) in diameter and length, you could dive into the roundy round (or summit/jegs) ether and find your prize. Being that I dont know an instant cheap coilover setup with specs or the stock size for the car, I cant really take it further than that.

I also saw 450lb/inF and 280lb/inR mentioned by someone who had 2nd and 3rd at a national tour, so thats food for thought.

Figured I would give you the source data so you could crunch it and determine your best path.

I also see much mention of a racing beat front swaybar, so you could research that part and see if you can find one used for cheap, or the diameter to see if you can find a cheaper solution with the same relative stiffness. If there is no budget way of getting that diameter bar, there is always something I saw mentioned on a challenge car at some point about doubling up a bar.

Aparrently the MX-5 may have had a larger rear bar that bolts in? I dont really know, but they mention an MX-5 rear bar.

SVreX wrote:

Keith Tanner wrote: Willing to do your own revalving? I know the stock NC Bilsteins had crimped tops, but if the aftermarket ones can be disassembled that might be a way to get where you need.

Come on- it's the $20XX Challenge. I'm willing to TRY to do just about anything!

http://www.roadraceautox.com/showthread.php?49818-Bilsteins-Does-anyone-service-revalve-their-own&highlight=revalve

might help you on your way

In reply to Apexcarver:

Thanks Apex.

I didn't take any of that the wrong way. It's just info, and helpful info. I will be digging through the details as you suggested.

FYI, we got our best results out of the NC chassis when we ran a surprisingly high rear spring rate relative to the front (550/450, I checked) and valving that was relatively low on compression. I can shoot you dyno charts.

Oooh- that would be exciting!

Not that it's 100% applicable, but I'm quite happy with my KW V3 rates at about 450 front, 280 rear (I think), but it's a full weight street car. Still rides pretty well on the street and handles track use with 255 wide R's quite well. I do have Hotchkis sway bars though, which are some of the stiffest one can get for this car. Its very neutral, giving nice, safe understeer normally, but in the tighter corners I can easily get it to rotate with power.

As you know I've got the street/track Öhlins setup on mine. The stiffer springs are a noticeable improvement over the stock springs (which actually don't feel that soft), but I attribute that to the quality of the dampers that allow you to get away with the spring rates (does that make sense?).

I wouldn't go too stiff, my impression after the Öhlins is that the car for a dual-use car that's about where you want to be, and then you really want to address the sway bars. With the suspension now properly set up on mine, there is still a noticeable amount of understeer. My preference is for more neutral cars so it's probably time to play with the bars.

In reply to BoxheadTim:

Aren't the Ohlins 13k/ 8k?

I've got the Road & Track from Goodwin, those are 458/229lbs/in. Or 8k/4k if I deciphered the conversion correctly. Those still feel good on the road but I haven't ventured out potholing over in CA yet.

Keep in mind I'm a member of the softer springs and beefier swaybars school, not the "I'll stop the suspension from moving and then don't need swaybars" approach.

Subbed just for as much info as possible, sorry I can't offer any info aside from get new coils/plugs/wires and a test pipe.

I am interested in this. As an aside. My current build has just made the suspension free. So hmmm.... can I make this thing fit the budget.