SD bilsteins ride quality
 

I have had my SD revalves for over a year now. The car has been in the paint shop for 8 weeks now and after only 3 days of driving it to work (70 miles a day) my lower back cannot take it any more. Honeymoon is over! I cannot convince myself anymore that awesome handling is worth the unacceptable ride. The whole point of getting these was to get an acceptable street ride with crisp handling for my 1-2 track days a year.

What are the long term reviews for ride comfort from the guys that have SD revalves? Especially with setups similar to mine at 400lb/in 7" fronts, 300lb/in 9" rears, factory ride height (high as hell), FCM NB tophats, brand new poly suspension bushings.

I have had 4 different suspension setups on my 91 and this one is the harshest on my back, its not a rough ride, just the constant vertical accelerations are killing me, especially on the less than perfect roads on my drive to work. Even my first upgrade to AGX's with RB springs and cut down factory bump stops did not do this to my back. Sure it sucked when the suspension would crash over bumps and stuff, but I did not have all the vertical accelerations that are killing my back. I ran Ricelands for a year at similar spring rates to what I run now (425f/350r) and the ride was actually much better. I think the main improvement over the AGX setup was the fact that the Ricelands came with descent bumpstops (compared to OEM NA stops). Nothing performed like the Bilsteins do, thats for sure, especialy in the "confidence" department.

I am debating on going to softer springs to see if it will improve the ride quality, but am not sure if this will help at all. I have already tried all different ride heights, ended up going to 9" spring in the rear because I was having coil binding on the 7" 250lb original spring. I sent the shocks back the first time to be adjusted due to the ride quality being worse than expected. The final result is shown on the attached plot.


Please no discussions about Bernie being an a-hole or the fact that my dumbass just should have gotten Xida's! I know and I know, wish I had Xida's too, especially when spending just as much to end up with a setup that does not work for me.

There is a strong correlation between ride quality and tire grip on uneven surfaces. Damping that's optimal for grip will be very close to optimal for comfort. A little extra damping over that will give you the feeling of more "control", "confidence", and precision, but at the expense of some actual grip. There is no reason why a damping setup should be very uncomfortable for a given spring rate.

Looking at your damping curves, the fronts appear underdamped in rebound and both are underdamped in bump. (I can't remember offhand what the proper low speed slope should be for your spring rates). It may very well be that the rears are overdamped too. The fronts are supposed to be stiffer due to the higher spring rates which is a consequence of the higher motion ratio in front. It's not correct to have the same low speed damping front and rear. The damping mismatch will cause uncomfortable pitching motions.

My direct experience is limited to FCM's, Tein Flex, and a bunch of lower end shocks. The FCM's ride remarkably well and have the most predictable handling at autox, compared to all the rest, despite having the highest spring rates, with no apparent downsides.

The whole basis for me going with a Bilstein re-valve is the fact that a properly tuned suspension should exhibit good manners on the street as well. With the selected spring rates it should definitely be tolerable.

The attached plot is what the original curve looked like for my shocks. After my initial complaints of excessive vertical accelerations, Bernie took them back stating that the tune might be a little aggressive for my original spec of a nice grippy street car, perfect for mountain roads and acceptable on the occasional track day (I know, wonderfully vague on my part). He re-valved the shocks as shown in the first plot above (current configuration). While packaging the shocks up to send back to me he noticed that the bushings had been damaged on the shocks . This he claimed was due to me torqueing the suspension bolts without the car being at ride height and running at too low a ride height. The blown bushings were blamed for all the symptoms I was experiencing. These symptoms were there from the first day I installed the brand new re-valved shocks so I do not understand why gradually damaged bushings would cause the large amplitude vertical motions that are bothering me. At this point he wanted me to pay for the 2nd re-valve that was originally going to be done for free (oh at a 60% markup from original rates). I had to pay to get my shocks back. This meant that if the correct re-valve was done originally, I now had a re-valve that would not be correct and any additional changes would require me to pay an additional re-valve fee. See where this is going?

I got the shocks back, installed them, with minor improvements, still not 100% happy. When I challenged Bernie for info in order to educate my dumb@ss and in the quest to understand why the car is feeling like it does, the dialog deteriorated to the point that I will never be able to trust him with my shocks. I now have a set of shocks that I am not happy with that cost $1300 just for the shocks and no way of sending them back to get fixed properly.

Ok, sorry I’m getting bitter again. On topic.

Since sending the shocks back clearly is not an option. Is there anything I can do to make this more streetable? Would changing to lower spring rates improve anything? Is there anything else that can be adjusted/changed? It would be nice not to have my lower back on fire after my 35mile drive to/from work!
I wish I knew more about reading the plots to know what I need. That is what I get for “thinking” I knew what I wanted.

I have similar rates. 450/300 QA1, nb top hats, poly bushings, and fcm bumpstops. I think I'm running 5.5/5.75 at pinch welds.

My ride improved when switching from FM springs to the 450/300. My ride was much more harsh with the lighter springs. Iirc my shocks were tuned for the current rates because I figured one day I would upgrade from the FM springs. I believe I was riding on the bumpstops a lot with FM springs. What bumpstops are you running?


My only comfort comparison:

FM springs AGX shocks < SD shocks FM springs < SD shocks 450/300

Shaikh at FCM does Bilstein revalves. Maybe he can help you out.

djp0623 could you possibly post a plot of your shocks for comparison?

I am running FCM 36mm bumpstops, NB tophats with all the FCM bushings. I am running a ton of ride height (close to 97 OEM ride height) on order to get all the ride height possible and stay off the bumpstops.

I would hate to bother Shaikh, especially since I should have just spent the extra $100 or so and gone with him to begin with. Thats what I get for being cheap! I am debating on bugging Shiakh to at least get an expert opinion on whether the shocks are in fact tuned correctly or if I am just an idiot that did not know what I wanted to begin with.

Does Shaikh still revalve used shocks? I was under the impression he no longer does revalves on customer-supplied shocks.

I don't know. I bought new from him. Still, couldn't hurt to call.

I'll have to see if I still have the graphs. I know I do, but it's a matter of finding them in my junk.

My FM springs were better than the AGX shocks,so I don't think I realized I was hitting the bumpstops so much on the SD revalves. When I upgraded to the stiffer springs I was wondering how the hell the ride could be softer with stiffer springs over speedbumps, etc. That's when it hit me that I was hitting the bumpstops.


I want to say that my lower curves are much steeper (whatever that would mean)

Any chance you experienced the same thing, thought it was too stiff, then revalved softer? Which would only amplify the situation.

Shaike mentioned in a thread over on m.net that they sometimes cut the 36mm stops to 18mm (in the rear iirc) with the softer spring rates. I believe your/my spring rates are on the border of when to use cut down bumpstops to increase travel. He also mentions which portion of the bumpstop to use since they are progressive.

djp, what length are the 450 and 300 springs you used?

I rode in an autox devoted miata with FCM suspension (back when bearnie did the valving IIRC) he was on 700/400 and it felt great on the street, comprible to my teins. Which still isn't soft by any means, but is worlds above my Konis with anything but stock springs...hell even then the konis were awful.

I reviewed my old calcs and your current rear damping rates are about right for your rear spring rate. The front is a bit underdamped.

This was partially a coil bind situation with the OP. in my case with 550# front springs jumping from 300# to 350# in the rear improved ride quality.

I believe the are 7" QA1 front and rear. I can't find my shock dyno plots. if I come across them, I'll post them up.

Jason, "a bit underdamped" in the front, does that mean ok? At this point I will take "OK" over "screwed".

Our setups are nearly identical, except I don't have the polly bushings yet, and I'm on 400/300 FCMs in an NB. I have no complaints about my suspension whatsoever. I can get spring lengths, ride heights and bumpstop lengths if its helpful, but I'd imagine you would have plenty of travel if you aren't in the weeds already.

I had lunch with Shaikh @ MRLS back in April and had a great conversation regarding my suspension. I "erred of the side of caution" and went with 400/300 (maybe 275? derp) for dual use but I now see that I could go A LOT higher and still be comfortable on the street. We discussed this and he was willing to do a revalve for me on my current shocks, but that may be because I'm a current customer. He's a nice guy, but super busy. It can't hurt to ask.

What are you using for a seat? My Sparco makes the car feel a lot different than the foamectomied seat I was using before

Seems like you realistically have 3 options if you want to be happy.

1. Convince Shaikh to revalve your shocks. I have yet to read a bad review of his work.

2. Sell the SD shocks and purchase new FCM revalved shocks.

3. Sell the entire setup and purchase Xidas.

Otherwise, you're still going to have the bad taste of the SD interaction lingering.

#1 is to fix the coil bind issue-revalving from FCM isn't going to solve that issue.

#2 underdamped in the front isn't necessarily a horrible thing. That does allow for tuning without the rear bar for autocross.

It sounded like he had the coil bind issue taken care of... fix that first

True, but I'm not really talking about diagnosing what's wrong with the current setup. It just seems like OP has some lingering resentment over the SD situation. In my experience, even when a product is satisfactory, if the transaction and experience sucked, I'm never going to be happy with it.