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maybe less even, OE shocks don’t hold capability as long as most people think, but most people likely may not know the difference.
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I was "most people" until I hit up the tail of the dragon recently. Stock 90k Bilsteins felt fine daily driving on 500TW tires on boring Florida roads; but stickies and twisties highlight your deficiencies real quick
Let the coilover search begin...
Similar Bilstein shocks on the Hard S Miata's I think can go 100K or more. Unless a failure mode can be observed, ie: leaking, scoring, other damage, and the driving experience remains good, personally, I'd leave them alone.
Similar Bilstein shocks on the Hard S Miata's I think can go 100K or more. Unless a failure mode can be observed, ie: leaking, scoring, other damage, and the driving experience remains good, personally, I'd leave them alone.
I'm creeping up on 100k and from what I'd read about Bilstein's elsewhere it lead me to believe that they could still be performing adequately. Before I hit the road I checked for leaks and damage and did the "push on the trunk" test, all seemed fine. After I stared pushing them however they seemed to become less and less responsive and eventually even small bumps at low speeds resulted in harsh contact with the bump stops.
Last edited by sharingan 19; 07-18-2021 at 05:45 PM.
Interesting. And they recovered back to feeling normal once back on regular roads (and cooled down?)
Normal flat roads they felt "normal" compared to the condition in which I started the trip (90k +) But on any kind of incline or bump they feel "soft" in the rear even compared to how they were before the dragon. It's not bouncy, it doesn't sag (any more than you would expect at almost 100k) it feels almost like someone swapped the springs and dampers from a lighter car into the rear, they just feel...overwhelmed.
I wonder if the stock Rx8 Bilsteins were a lesser spec than the aftermarket stuff. I have had Bilsteins with 200k miles plus on the street on BMWs. Not racing of course, but hard street driving at times, on a heavier chassis with more power and braking than the RX8. No noticeable loss of damping or ride quality difference, the mid-corner bump absorption and stability that makes them so nice in many applications was not noticeably changed over that mileage either. These were all aftermarket.
Certainly not crashing bump stops. Interesting.
I wonder if the stock Rx8 Bilsteins were a lesser spec than the aftermarket stuff. I have had Bilsteins with 200k miles plus on the street on BMWs. Not racing of course, but hard street driving at times, on a heavier chassis with more power and braking than the RX8. No noticeable loss of damping or ride quality difference, the mid-corner bump absorption and stability that makes them so nice in many applications was not noticeably changed over that mileage either. These were all aftermarket.
Certainly not crashing bump stops. Interesting.
#PlotTwist ....
So I've been doing some research, and apparently the way the RX-8 suspension is designed, the bump stops aren't a "air bag" that is only encountered in the case of misuse, but rather an integral part of normal suspension operation. Additionally the stock rear bump stops appear to be made of some very soft foam like material. So it seems possible that the hard dips on the dragon destroyed the stock bump stops and now the car is riding partially unsupported in the rear, so instead of the additional "spring rate" the bump stops provide there is free space and every time a bump is encountered there is nothing "stopping" it from bottoming out.
Of course this is just a theory, and as curious as I am to know the truth I don't see myself pulling the suspension apart just to find out without having some new parts to install.
#PlotTwist ....
So I've been doing some research, and apparently the way the RX-8 suspension is designed, the bump stops aren't a "air bag" that is only encountered in the case of misuse, but rather an integral part of normal suspension operation. Additionally the stock rear bump stops appear to be made of some very soft foam like material. So it seems possible that the hard dips on the dragon destroyed the stock bump stops and now the car is riding partially unsupported in the rear, so instead of the additional "spring rate" the bump stops provide there is free space and every time a bump is encountered there is nothing "stopping" it from bottoming out.
Of course this is just a theory, and as curious as I am to know the truth I don't see myself pulling the suspension apart just to find out without having some new parts to install.
Interesting. The BMW 3-Series from E9x on has a similar design. The E9x M3 front suspension has <1" of travel before engaging the bump stop, which makes the total effective spring rate progressive and reduces the severity of really big bump stop hits.
If that kind of bump stop got degraded or compacted or something, I can see how that'd make things pretty spicy.
Interesting. The BMW 3-Series from E9x on has a similar design. The E9x M3 front suspension has <1" of travel before engaging the bump stop, which makes the total effective spring rate progressive and reduces the severity of really big bump stop hits.
If that kind of bump stop got degraded or compacted or something, I can see how that'd make things pretty spicy.
Just disassembled a set of mazdaspeed shocks & springs (currently for sale ...) and now I KNOW that after the dragon my R3 has no rear bump stops left . The material is very weak and soft, think of a dish sponge you let soak in ATF overnight......a year ago. Both sides crumbled and fell out in 100 pieces upon disassembly leaving a nasty pink-ish residue on the top of the shock and substance the consistency and color of ahi tuna in the bump stop cup. The front bump stops were still in need of replacement but are made of a much denser foam and were still mostly in tact.
With the way the RX-8 / NC miata suspension is designed the stock bump stops absolutely need to be replaced before the shock wears out, the rears are probably trash by 20,000 miles maybe less. Makes me wonder how many shocks have been replaced prematurely due to bad bump stops or how many shocks have failed prematurely for the same reason
In any event my Bilsteins have 97k on them and I've owned the car for the last 40k so even if the shocks still have a little life left, I'm looking at upgraded bump stops + lowering springs + Sway bars + replacement shocks (sooner rather than later)......so for my future plans (auto X, track days, time attack etc) investing in coilovers still make the most sense for me. However if you replace the bump stops at least every 30k and do mainly street driving I can see the stock Bilsteins providing acceptable performance for 100k +
Last edited by sharingan 19; 07-18-2021 at 05:45 PM.
Probably a bit premature to start confidently estimating the lifespan of the OE rear bump stops.
I tracked my old R3 on its original suspension with >96k miles on it. Zero unusual behavior before, during, or after the event.
What was your baseline for "unusual" Have you owned the car since new? Did you disassemble your rear shocks and assess the condition of your bump stops? Just because you didn't notice it, doesn't mean the bump stops weren't degraded. You could have been on a mostly flat track with non sticky tires and mostly stayed off the bump stops..... ? Now that I'm back in flat Florida the issues I experienced on the tail of the dragon are mostly absent.
Regardless you won't find anyone knowledgeable advocating for trusting 100k stock bump stops so I stand by my assertation that they fail sooner than most people realize, maybe not 20k on a street cars, but they do not stand up to abuse well and are a wear item that need replacement.
In any event more to the point of this thread, the bump stops will fail before the stock Bilstein's, but running them with failed bump stops will cause them to fail faster than they otherwise would, however assuming everything is in good working order they should at least make it to 100k but I'd do a serious assessment at 50k.
Breathe easy, man. I agree with almost everything you've said here. You've done some good work with what you've had access to.
Only thing I'm taking issue with is the level of confidence on the service intervals:
Originally Posted by sharingan 19
the stock bump stops absolutely need to be replaced before the shock wears out, the rears are probably trash by 20,000 miles maybe less.
Originally Posted by sharingan 19
if you replace the bump stops at least every 30k and do mainly street driving I can see the stock Bilsteins providing acceptable performance for 100k +
If we want to start making blanket recommendations for what "absolutely" has to be done and at what mileage for all R3s, we need a lot more data points.
However, if all you wanted to do is diagnose your own problem and assess your own mod path, the rest of what you're saying makes sense.
Breathe easy, man. I agree with almost everything you've said here. You've done some good work with what you've had access to.
Only thing I'm taking issue with is the level of confidence on the service intervals:
If we want to start making blanket recommendations for what "absolutely" has to be done and at what mileage for all R3s, we need a lot more data points.
However, if all you wanted to do is diagnose your own problem and assess your own mod path, the rest of what you're saying makes sense.
This is all recreational, so no worries on this end (sorry if it came off otherwise). Regarding the service intervals I fully admit that I do not have hard data to back up those recommendations , my goal was to emphasize how shitty the stock bump stop material is and encourage people to check on them more often....fairly easy since most people have never even seen the rear bump stops lol. Many people make blanket suggestions to replace shocks before 50k and the bump stops are weaker, not very scientific , I know .
Changing your bump stops early has no negative impact and maybe they are still good at 20k? maybe 30k? Obviously YMMV based on usage and conditions. But at 100k they are certainly done and at that point how long has one been riding around with a suspension in sub par condition? Unfortunately the rear bump stops are so thoroughly hidden that it doesn't even make sense to "check" them since it requires disassembling the rear shock, hence the recommendation to simply replace them before they become a problem. It's like not changing your conventional oil at 3,000 miles because the car can still run at 10,000
Here's what 97k rear bump stops look like...
if you have sticky tires or do any kind of spirited driving chances are yours will meet this fate MUCH sooner. The rear spring rates are stupid soft, and the rear suspension relies heavily on these bump stops. They should be replaced sooner rather than later.
The last pic is a visual of what I was experiencing on the Dragon when I first thought I was hitting bump stops, just a metal cup smashing into the top of the shock!
That said, the shocks are not blown 😳, so if I didn't have Coilovers going on I'd invest in some of the upgraded bump stops from Goodwin or Fat cat.
Last edited by sharingan 19; 07-28-2021 at 06:04 PM.
07-12-2021, 01:25 AM
...) and now I KNOW that after the dragon my R3 has no rear bump stops left 
. 
