[QUOTE=dhean,Mar 14 2008, 01:37 AM]My car was very sensitive over road imperfections; everything was stock for AP2.

 

REVIVING my old thread.

Okay, So i'm pretty much convinced that my car has bumpsteer and after reading through various threads I conclude that it has to do with the drop. I'm almost certain that an alignment won't fix it either and I'd hate to waste my money on it. So I have a few questions before I resort to a solution.

1) Does every S2000 that's dropped on springs suffer from Bumpsteer? Or any other cars for that matter? The reason I ask this is because Ive never really had this problem with any other import that was dropped on springs.

2) How much am I looking at for a bumpsteer kit installation?

3) Do my 18" rims make the bumpsteer worse?

It's really annoying. Today I was driving home to Houston and there was tons of uneven pavement and my car just seemed like it had a mind of its own and wanted to steer every which way!!

 

Cars that aren't lowered have less bumpsteer at the front. All AP1's have roll understeer designed into their rear suspension, and lowering, *up to a point*, doesn't alter the roll understeer (or corrosponding rear bumpsteer profile). Up to an inch or a little more and you're not changing the rear roll steer profile enough for anyone to notice. At some point beyond that (and I'm not exactly sure how far beyond) the picture starts to change.

Going back to stock ride height will give you more suspension travel, which can improve grip (front and rear) over rough/bumpy surfaces. On softer stock springs (assuming that's the case) toe at the back will change even more with the increased travel, but again, if the change is an inch or less, you won't notice.

All of the above is of course highly dependent on getting the car aligned after the ride height is changed.

If you go back to stock ride height you are still going to have to get the car aligned. There is just no way around it.

Front, or rear?

Yes. They also change the way the car responds to camber changes when cornering or traveling over bumps. IMO it is more likely that your wheels are what is actually causing the problem (IOW, the problem would go away if you went back to OEM tires and wheels), but since/if you want to keep the big wheels and tires, both front and rear bumpsteer kits *might* help. To get the handling back to where it was with the OEM tires, you'd have to do a significant amount of suspension tuning.

OK, let's think about what might be causing this, OK? Let's take a look at how my car has been modified, and how it handles at speed over roads that are so bumpy that they're scary.

First, the car. My car is lowered 1", on an Eibach Pro Kit, with Honda Spec non adjustable Showa coil overs ( IOW, OEM shocks), and very close to UK spec alignment.

Second, the road. I live in an area where the primary industries are logging and strip mining. We have lots of secondary back roads that are used almost exclusively for hauling kaolin (the stuff that is strip mined here). The mining companies maintain these roads, becuase their heavy trucks tear them up so quickly that the county can't keep up. They tend to patch for years before repaving, and over time the roads get downright nasty.

Third, the "test." Because of this very thread, I took my car out on one of our well worn secondary roads, because I wanted to see how much it would take to induce any kind of bump related steering. The road I selected is just one dip or bump after another, with every possible combination; There are bumps that all four wheels hit at the same time; There are bumps that only affect the wheels on the left or right side of the car, and there are places where the road bumps upward on one side, while dipping on the other. The road is STRAIGHT, and the reason I picked a straight road was because if there was any self steering or instability caused by the bumps, it would not be confused with the constantly changing tire loading. Always best to test one thing at a time, and if the back or front of the car self steers, and I hit the variety of bumps and dips fast enough and hard enough, I'll surely see any instability. Cornering stability is another matter and would require a different set of tests.

Fourth, the results. I kept picking up speed, trying to get the car to exhibith some kind of instability, until I was traveling so fast, and hitting the bumps and dips so hard, that I was on the very verge of getting airborn at the one extreme, and I'm almost positive that the car was sitting all the way down on the bump stops at the other extreme. I reached the point where I was afraid to go any faster, because I was using up all the available suspension travel, and if I went any faster things were apt to break from the resulting impacts. According to my GPS, this was at a speed of 124 MPH. The car was as stable as an arrow, so bumps, whether they hit one wheel at a time or two at a time, don't cause any kind of self steering or instability when you're traveling in a straight line. When cornering, other factors have a bigger play in the equation, but the car simply does not steer itself enough over even the worst bumps, even when lowered up to an inch, for the driver to be able to feel it.

At 10/10ths on the track things are different, and the roll understeer designed into the AP1's rear suspension *can* become an issue, but that's not what I think you're talking about here.

With OEM tires and wheels, a 1" or less drop, and UK alignment, your car should be as stable at speed as mine is. If it isn't, then either your wheels or tires, or alignment, is causing problems.

I'm not sure what a BSK cost "installed," but it's going to cost more than an alignment.

If it were me, I'd dump the 18's and get the car aligned.

 

Wow, that was a very VERY informative post; I really do appreciate your time answering my post. Thank you very much!!!

But just a couple quick questions, and please do pardon my ignorance but even though my car's steering wheel stays pretty straight when driving, does that mean I don't need alignment? Traditionally, I've always thought that you don't need an alignment until you're car doesn't drive straight anymore. In other words do people with bumpsteer symptoms actually go in for alignments to get alleviated? (I guess bumpsteer IS an alignment issue.) But the reason I ask is because the wheels have only been on the car for about 5 months so I doubt it would need an alignment so soon. Thats why I was concluding that I'd probably need a bumpsteer kit and that an alignment would probably do nothing. But then again, I'm not anywhere close to being an expert.

Perhaps I'm just being way too picky and noticing the bumpsteer a little too much but theres no doubt it's there and it's annoying me. I'd really like to keep the wheels and the drop. I might try to the bumper kit for the front and rear to see if that helps which takes me the my second question.

To elaborate on the question I asked on my previous post, Yes, how much would I be looking at for labor and parts for a front and rear bumpsteer kit?

 

Well, I'd feel better if I knew for sure exactly what you are feeling and/or exactly what's causing your problem.

Alignment, or misalignment, can cause all sorts of problems, so in some cases the steering won't be straight, but that's not always the case. For example, if the rear of the S2000 has too little toe-in, the steering will be fine, but the car will tend to dart around a lot at speed. This could in fact be what you are experiencing. Too little toe-in, or worse, toe-out, at the back of the car, makes for very nasty handling.

Bumpsteer (and roll steer) is a function of the suspension geometry, and can be viewed as a part of the cars dynamic alignment. Dynamic alignment changes as the suspension moves up and down. Static alignment, the kind of alignment you get on an alignment machine, is what you want to adjust *first*, because if the static alignment is off, then the dynamic alignment will be off too.

Without knowing your cars current alignment, there is no way to know what you need to do to solve your problem. Odds are it's either your tires and wheels, or your alignment.

With a stock or modestly lowered S2000, any steering at the back over bumps is due to the toe adjustment, not bumpsteer, but the 18" wheels confuse the issue. I'm suspicious of the wheels, if only because they *might* be an issue, and I have no experience with 18's on the S2000. So, I'm sorry, but the best I can do is to tell you how I'd approach the problem.

Actually, your questions may well help us find an answer. When did you first notice the problem? Did you notice it right after the wheels were installed, five months ago, or is it something that has developed slowly over time, since the wheels were installed?

Was the car aligned after the new wheels were installed? Do you have a copy of the alignment specs after the alignment?

I'm sorry I'm asking so many questions, but I'm trying to get a better understanding of your situation. I am assuming that your car's handling changed at some point (Is that correct?), and I'm trying to figure out exactly WHEN it changed. Knowing that may help us figure out WHY it changed.
Does that make sense?

How much are you dropped? (If you said earlier, I forgot. )

Bumpsteer, at the front of the car, can be felt when braking and one wheel hits a bump. The wheel that hits the bump will steer, and you will feel the pull on the steering wheel. Bad alignment can cause exactly the same thing, so if I were having that kind of problem, the first thing I'd do is get the alignment checked.

The normal "bumpsteer" at the back of an AP1 is actually a side effect of the rear suspensions roll understeer characteristics. It seems (to me, at least) that a lot of S2000 owners think that roll understeer and the corrosponding bump steering at the back, are unique to the S2000, but in fact, it is a characteristic of all cars with conventional leaf spring suspensions, as well as most street oriented IRS designs, and you shouldn't feel it any more on an S2000 than you do on a leaf spring Mustang or Camaro. On a race car it is not universally agreed that a little roll understeer is a good thing, becaue like just about everything else, it's a tradeoff. On a street car with leaf springs it's essential for safety. Anyway, roll understeer is achieved by turning the rear wheels *ever so slightly* into the turn as the car rolls. This results in either increasing understeer (most cars) or decreasing oversteer (AP1's), as the car rolls into a turn. All else being equal, a car with roll understeer will produce slightly more cornering grip than a car without roll understeer. One of the downsides of roll understeer is that when a tire hits a bump, the suspension can't know that it's not body roll, so that wheel steers, *ever so slightly*. If both rear wheels hit the bump, they both steer in, or out, by exactly the same amount, so there is just a small change in the car's toe setting. If only one wheel hits a bump, it steers slightly, with nothing to offset that steering, so we have a little bumpsteer. In normal street driving, with stock wheels and tires, you will *NEVER* feel the rear wheels steer, and if you do, it means that either the rear suspension is out of alignment, or something in the suspension is broken or damaged.

The bumpsteer at the back of the car (again, with OEM wheels and tires, lowered an inch or less and properly aligned, won't be felt in normal driving, but there are situations on the track (or when pushing the car's performance envelope anywhere, track or not) where it has the potential to cause problems. If you are experiencing problems in driving well below the limit (on OEM tires and wheels), then it's not bumpsteer that's the problem, it's alignment. When cornering near the car's limits, over bumps, the picture gets a lot more complex. When a tire hits a bump, the load on the tire changes, so the available grip changes. The wheel moves upward, so the alignment of the wheel (including toe and camber) changes. If you're already using all the tires grip, and have it fully loaded, then increasing the load or changing the camber or toe, is going to result in exceeding the tires available grip. On the track this can mean that you have to take a bump section of a corner at a lower speed, so you have some grip left over after you hit the bump. A dip does the opposite, unloadiung the tire, but the result is the same. A bump or dip, mid turn, will upset the car, and if you've used all the grip up before the upset, there is none left to deal with the upset, so the back end slides (and this can be quite unsettling at speed). Every track (and every driver) is different, but when you have a problem like a bump in one turn upsetting the car, there are lots of possible solutions, all of which involve tradeoffs. Eleminating a car's rear roll steer (to get rid of the associated bump steer) may or may not help, depending on the particulars. Shock valving and spring rate adjustments are apt to be at least as effective, if not more so.

BUT, very few people race (or even autocross) on OEM tires and wheels, and you yourself aren't on OEM tires and wheels. Wheels and tires open up more than one can of worms. If you put R compound tires on your S2000 for autocrossing, the inside rear tire will unload and spin on corner exit; Fixes include a stiffer FSB, removing the RSB, right through complete suspension retuning (where class rules permit). Wheels and tires potentially change EVERYTHING.

Hahaha, I know you've heard this too many times already in this thread, from me and others, but I have to say it again; Alignment, alignment, alignment.

Maybe my "bad alignment" story will help convince you. I have my alignment done by a guy who align's cars at a Ford dealership all week, and then align's race cars on the weekends. The guy's name is Mark Odom, and he's one of the best alignment men I've ever encountered. He does all the alignment work on all the CCR cars, and I have complete trust in him. However, everyone makes mistakes. Time before last when we replaced the tires on my car (I always have the alignment done after getting new tires) Mark made a mistake when doing my alignment, and because I have complete trust in him, I never even looked at the alignment sheet that he gave me. I just assumed that he's set the alignment to the values I'd specified. A week or so later I was over on one of the Huber roads (privately owned and very well maintained) doing some testing, and during a "speed run" I discovered that *something* BAD was wrong with my car. At 120 MPH the car felt unstable. At 130, the car was terrifying, darting all over the road. I never even though of the alignment, taking Mark's work as a given, and ended up posting a question in R&C to see if anyone could help me figure out what was wrong. Of course, everyone wanted to see my alignment specs, so I posted them, and I was so sure that Mark had gotten them right that I posted them without even reading them. Then, to my surprise (lol, shock and awe) everyone else saw my problem immediately. Mark had misread the numbers I gave him, and had set my rear toe at almost zero.

Now the reason I'm telling you this story ^^^^ is because it illustrates something important. Just because you had your car aligned doesn't mean that it is aligned properly. Anyone who does not have a printout of the alignment values achieved after their last alignment doesn't really know how well the car was aligned, no matter how good the guy was who did the alignment.

Maybe the answer to your next question will convince you.

I'm sorry, but I don't know what labor will cost, but I'm sure that you are looking at over $1000.00. Alignment cost $60.00. If you have your OEM wheels and tires, putting them back on the car cost nothing.

Really, 2KS2000, it's your car, your money, and your call, but if it were me, I'd spend $60.00 on alignment to make sure that wasn't the problem before spending over a grand on aftermarket parts and the labor to have them installed. If that didn't solve the problem, I'd try a set of OEM wheels and tires. After changing back to the stock wheels and tires I'd have the car realigned. Odds are that at this point the problem will be gone, and if it isn't, then it's something worse than bumpsteer.

Anyway, if you'll answer the questions I asked earlier in this long winded post, maybe we can figure out whether this is mostly alignment or mostly your wheels and tires. Odds are it's a combination of the two.

 

Well, I did an alignment and sure enough, the setting were WAY Screwed up! Now theres barely any bumpsteer on the road. They used some custom settings and they recommeneded me to get a camber kit. Thanks MX5 for all your help. I figured I owe this thread a response so heres the results of the before and after:

 

Thanks for the update.

I'm not an alignment expert, and don't want to discourage you, but if my alignment specs came back looking like your's, I'd be taking the car back and making them re-do it. But since your guy recommended a camber kit, I wouldn't take the car back to him at all. Your camber isn't far off, and a good alignment man should be able to get it spot on. Same for the other specs. A good alignment tech can get the car dead on the UK specs, even if the car has been dropped an inch.

I guess (and I am *just* guessing) that if the car feels OK and is driving well, then it's not an issue, but I expect more precise results when I have my cars aligned.

Anyway, glad to hear that you're happy with the car now. I think the car could be even better if you could find a better alignment shop, but at least it's not scaring you now.

 

I have to agree, your new specs don't look good. Your rear has almost one full degree difference in camber and it appears the rears are toed out now. Also, a lot of alignment shops may recommend a camber kit since pretty much all Hondas require them, however, the S2000 has adjustable camber from the factory. If it drives well, then forget about the numbers. Personally, I'd be looking for more uniform numbers from left to right. There shouldn't be that much difference in the specs.

 

[QUOTE=RED MX5,Apr 13 2008, 02:12 PM] Thanks for the update.

 

I don't know how far your car is dropped, and don't have any first hand experinece with drops much over an inch, but at the very least I'd expect to be able to get equal camber (and other) settings on both sides of the car. I'm not an alignment expert, and I don't want to freak you out, but I'd be unhappy if my alignment looked like yours. Your wheels and tires might also be throwing a wrench into the works, but I still don't see why the alignment should have to be different side to side.

If you can't get a better alignment than this with the drop/tires/wheels you're running, you'd probably be way better off going back to the stock configuration.