I have been searching and reading for many, many hours to understand the S2000 suspension geometry situation.

The most relevant thread I have found to this question is here:

https://www.s2ki.com/forums/index.ph...=218984&st=125

But that's an old thread about a (then) new product announcement, not my question, so I'm asking the question separately.

Here it is:
Can you update an '00-03 car with a limited number of parts from an '04+ and fix the rear bump steer? The thread above seems to suggest you might be able to "just" change the upright/knuckle and have the problem solved. Not exactly a small task, but not insurmountable for those of us with access to lifts, air tools and hydraulic presses. And possibly doable for the cost of a J's Racing BSK.

I think I have a pretty clear understanding of J's Racing, TCD/GFL, and Megan rear BSKs and their subtleties. I'm not asking this question to start a thread about those parts, because they're already well-discussed elsewhere.

I am also pretty capable of deciding whether it would make more sense just to buy a BSK. My question is about what stock parts would be needed, not whether it's a better solution.

This is my first post here. If my pretty much all-day searching didn't reveal an answer that's well-known in the community, sorry, and please point me to it. Thanks!

 

bump for the evening

 

I believe we have at least one member who has installed a complete AP2 rear subframe, suspension, etc., in his AP1. I suspect you could do the same at the front of the car, but I'm not really sure.

I'm sure that you realize that the bump steer is just a byproduct of roll understeer, and doesn't necessarily mean that anything needs to be "fixed."

 

The complete subframe, etc. is more than I was hoping to have to do. At that point, a BSK looks really good.

I've been involved with a lot of cars, and have learned that when there's as much activity as there is around a "feature" like the S2000's bump steer, there's something going on. It doesn't mean the car is a bad car, just that it could perhaps be improved significantly, maybe even made great.

My BMW is my standard because it's what I flog now. It is fairly stiff for a street car and has lots of travel and good damping. There is very little bump steer/roll steer at either end. As a result, I can rail through a corner over massive pavement undulations with little disruption of the car's heading or grip. I don't bottom out. Handling comes down to classic theory about response to weight transfer. The car is completely intuitive, and does exactly what you want it to, exactly the way you want it to. I think that's a good thing. It's the drivetrain, electrical system and interior that are all clap. On the S2000, it seems Honda got those right. Plus, I have more friends who are Honda guys than BMW club guys.

The summary of my understanding about the AP1 is that the front toes out significantly under bump, and the rear toes in significantly under bump. So you have a car that has lively turn-in but naturally stabilizes as it rolls through the middle of the turn and may seem to loosen up as it comes out of the turn, which is fun. It will also respond agressively to lifting the throttle due to the rear toeing out as the suspension lifts, which lets a skilled driver cure understeer at will. This is carefully tuned to work well with the mu/slip-angle response of the custom-engineered stock tires on stock wheel widths, at the stock ride height, and on a perfectly smooth race track. Throw in more grip, different tire response characteristics, a change in ride height, a change in roll stiffness, or bumps the wheel must travel over in the turn, and you've got all kinds of issues. And that's leaving out damper tuning.

My experience leads me to believe that if you could dial out the toe changes with bump, you would eliminate the change in slip angle and thus lateral load that is able to be supported as the car rolls and responds to bumps in a turn, throttle inputs, etc. The ability to carry lateral load consistently would make the handling much smoother and more predictable. Because you wouldn't be trying to lock out suspension movement, you could have a car that worked decently with softer spring rates, and thus maintained more even contact pressure as the tires moved up and down over bumps, increasing the number of corners it's naturally fast through. Braking on bumpy surfaces would also be improved. Then you could spend your setup time on getting the tires to really work.

At least that's what I'm hoping is possible with this car. I know, it's a lot to ask and might be a lot of work.

We pretty much all know the '04 reduced the toe curve in the rear significantly. The thread I linked above said there were changes to the subframe itself relative to the mounting of the upper control arm, but the Honda engineer writing didn't know whether they were only for strength or for geometry as well. In either case, I can't imagine there would be any meaningful effect on the toe curve. The UCA was changed, but only to reinforce the bushing installation. There were changes to the knuckle for geometry. The toe control link and LCA are the same parts. So it looks like you might be able to get it all just by changing the knuckles.

I'm just wondering whether I'm the first guy to think of this. Guess I'm like everyone else, want to be the second person to do the mod... I want it now, but pleeeez someone else go first and tell me it works.

Actually I have to sell a bunch of RSX and BMW parts first. Anyone here got FWD?