Lots of Bump Steer and Road surface Feedback

[rioyellows2k]

I'm thinking it's because of my 19" wheels any ideas?

I run 225/35-19 and 255/30-19 on 19X8, and 19X8.5 Air pressure is set to OEM spec.

USDM OEM alignment spec, Tein H-Tech springs OEM, dampers

I get lots of bump steer, and road feedback, it's unsettling.

I never had problems when I ran 18"s, but that was on stock suspension.

This was on a country road run. I can only imagine how much worse it would be on a track day.


help?

[repiv]

IMO, as we stiffen up the ride one mod at a time, we reach a point where that last alteration is the one that produces the most noticable change in the way the car works. Road imperfections have a higher tendency to unsettle the car's orientation while going down the road, the less compliant the ride quality becomes. The low aspect ratio of the tires needed to ride on 19 inchers likely took the car beyond the threshold of blatant bump steer. All else remaining unchanged, the remedy would be to reduce speed over these road surfaces or to alter one of the existing parameters, be it alignment, springs, tire pressure, etc. However, changing something may very possibly negate the benefits of the other components. For example, lowering tire pressure will increase the risk of rim and/or tire damage. Altering alignment may give you tire wear that you can't live with. Such things are always a give and take situation.

[WillErickson]

I'd think it would be less of an issue at the track, most tracks have a relatively smooth surface.

[drobbins]

You also switched to different tires when you switched to 19" wheels. Tires can have a huge impact on ride quality. I have OEM wheels with Michelin Pilot Exalto PE2 at 40PSI, and they feel a ton nicer that my old Goodyear F1 All-Seasons at 32 PSI. The Michelins even feel better at 43 PSI than the goodyears at 30 PSI. I recommend Michelins. It could improve the road feedback issues quite a bit.

When the tires are giving you a good ride, it can dramatically reduce other harshness issues. Before these Michelins, I felt the need to add bracing to the rear of the vehicle to reduce harshness. Now I don't. The ride is great. Bracing the rear might be an improvement but I don't feel an imminent need for it.

[JonBoy]

Have you checked your alignment recently? I'm getting similar issues to what you're getting and I'm on the stock 17s. I'm thinking I need to have my alignment redone...

[drobbins]

To follow up on this, I just got some Bilstein PSS9's installed on my '05 and in re-reading your original post, I blame your OEM dampers. I had harshness issues and they disappeared when I got rid of the OEM shocks. Harshness from the rear of the car is gone. The car used to feel unsettled except on pristine roads -- now it is relaxing and confidence-inspiring to drive. The car actually feels quite a bit slower because it is so much more controlled. It you crank up the PSS9's to full stiff, this feeling goes away and the car feels fast again. And I still think it feels better than stock on full stiff.

My OEM dampers were very harsh, resisted rapid compression, and thus bounced a lot (rather than properly absorbing bumps). Fixed with the PSS9's. Rear wheels used to bounce off the pavement regularly when encountering road irregularities during turning. This appears to be fixed. This is my first day but they are an obvious HUGE improvement over OEM.

People say that the S2000 OEM suspension is great. Eh. Not so on my car. I have been in S2000's where the suspension has felt a lot better than mine, so this tells me that OEM shocks can go out of spec for some people and not for others. Based on what you are saying, it really sounds like the shocks/springs combo. My '05 has 20,000 miles on it (purchased with 10,000) and had OEM springs and shocks until today. The shocks didn't feel wonderful at 10,000 and got worse from there.

[Chris S]

19's are too big for the S2000 IMO (actually, I feel the same about 18's). Too much unsprung weight, not enough tire sidewall.

[gomarlins3]

I would suggest trying the UK alignments specs. They helped my car when I went to 18" wheels. However, as Dave said, your tire wear will increase. It's a matter of give some to get some.

[Coop]

I have found that in the CR vis my 02 with stock and Koni/GC, I feel, more Bump Steer and Road surface Feedback. I don't seem to notice it as much on the road, but have at the track

[drobbins]

19's are too big for the S2000 IMO (actually, I feel the same about 18's). Too much unsprung weight, not enough tire sidewall.

I think that problem could be addressed just fine with a good set of coilovers like some Bilstein PSS9's. PSS9's can be set up to feel downright luxurious in the softer settings, and can neutralize "too much feedback" coming from the road and make everything feel planted again. I think the key is a quality adjustable shock with a track record of delivering comfort and performance, and that's what PSS9's are known for. Then you tune the damping for the new wheel weight.

His 19" wheels may weigh the same or even less than OEM. Aftermarket can be quite a bit lighter. Odds are they are a bit heavier but probably not by much. In any case, an adjustable shock will allow you to tune your suspension to compensate.

People successfully put 18's on MX-5's and get good results with proper damping so I think that 19's on an S2000 would be do-able.

-Daniel

[Chris S]

Heck, I think 18's are overkill on the NC, and thought that 19's were too big for the Cayman. It's just my opinion, influenced by performance being much higher priority to me than bling...

Yes, PSS9's would be a good choice to improve the ride, but that's a lot of money on trying to get "good" and "bad" mods to offset each other.

[drobbins]

I tend to agree with you because I don't like the extra rotational mass, but in this particular case it sounds like his dampers do not have the proper damping for his wheels.

This isn't the fault of the wheels but due to the fact that the OEM shocks are tuned for OEM wheels. Any change in unsprung weight (up or down) could throw this damping balance off. If the unsprung weight is going to change significantly -- up or down -- I think it's a good general advice to get a set of quality coilovers.

Otherwise, odds are there will be a significant compromise in ride quality. It's not that the changes are "bad" but that you have no way to correctly compensate for them. So the overall effect can be bad.

[wildncrazy]

I'm betting it's the weight of the rims and tires. A friend of mine put some 20" on an Isuzu and afterward the car would change lanes on you if you encountered some irregularities in the road.

He wasn't careful of the weight. We could change the tires/wheels back and the probs would disappear. Why don't you try that. Switch the rims back to stock or even your 18' that worked and if the problem disappears then it's the tire/wheel combo.