Bump Steer

[magicianJ]

I just put on new wheels and I noticed that there is ALOT more bump steer. The tires are pretty worn (new ones are comming in for the rear on the 25th). My question is... Will having my alignment re-adjusted reduce the bump steer? Should I get new fronts as well? both? if neither of these will help what will?

thanks for the input!

[cwestinap1]

Aftermarket front and rear tie rods will help reduce the bumpsteer. They are fitted with pillowball/monoball ends, which are stiffer then stock, and absorb bumps better. I have the j's racing front and rear tie rods on my car and there is a big improvement.

[alvanderp]

Is your car lowered?

The aftermarket toe links are of alternate length(longer) than the OE arms, which changes the toe geometry of the car, and has significantly more to do with the elimination of the bump steer than the change from rubber bushings to sphericals.

Alignment can help with the feel of bumpsteer but it doesnt really remove it. It just will give you some static toe-in so when the suspension compresses and the wheel begins to toe-out, it actually just goes back to zero or stays slightly toed-in. The only to actually "fix" the bumpsteer is to look for alternate toe links that specifically change the toe geometry of the car.

That said, you are just looking to optimize the bump-steer curve for the area of suspension travel that you use. The car will always have some kind of bump-steer, and as you move the suspension through its area of travel, it will affect certain load points more than others, depending on the length of the toe arm.

[repiv]

I just put on new wheels and I noticed that there is ALOT more bump steer.
Were you OK with it before? Since the only thing you changed were the wheels, were the specs on the rims vastly different than what was on there before? Width, diameter, offset, weight? Sadly, to get back what was acceptable to you before while keeping the new wheels, drastic changes elsewhere may be required. Others have already given their ideas on what those may be.

[hecash]

That said, you are just looking to optimize the bump-steer curve for the area of suspension travel that you use. The car will always have some kind of bump-steer, and as you move the suspension through its area of travel, it will affect certain load points more than others, depending on the length of the toe arm.


I'm getting ready to purchase a set of rear arms. I'm assumng that there is a solid process for tuning them. Are you able to point me to a reference on that method like a web site or handbook?

Thanks

[alvanderp]

I'm getting ready to purchase a set of rear arms. I'm assumng that there is a solid process for tuning them. Are you able to point me to a reference on that method like a web site or handbook?

Thanks

Ideally, you would really need to model the suspension to get an accurate optimal length for your toe arm at a given ride height and expected range of travel.

That said, the aftermarket kits(like the TC Design stuff SoS has) have been adequate for track S2k's that I have seen/spoken to the drivers of. Have you figured out your static ride height and expected range of travel yet?

Tune to Win by Carroll Smith is a good book to read when it comes to building/tuning a race/track car, and it goes through tuning suspension components for your application. How to Make Your Car Handle by Fred Puhn is also a good read. It will help you define the variables that you need to set to get your setup right for your application. You can figure out your expected range of travel once you have defined your spring rate, and by figuring out the motion ratio of the suspension. IIRC, the rear suspension on the S2k has a MR of approximately .75, but I would have to measure the arms myself to be sure, and I dont plan on taking out my springs and shocks any time soon to do so. You can figure it out yourself by taking some simple measurements, but you need to be able to move the suspension through its entire range of travel to get the best average for the MR, so the coilover assembly has to come out.

[magicianJ]

well the front tires were changed today and that more or less removed all the extra bump steer i was feeling. Of course, now I know for sure that I need a re-alignment. Anyway! Thanks for the all the helpful info guys!

[hecash]

Ideally, you would really need to model the suspension to get an accurate optimal length for your toe arm at a given ride height and expected range of travel.

That said, the aftermarket kits(like the TC Design stuff SoS has) have been adequate for track S2k's that I have seen/spoken to the drivers of. Have you figured out your static ride height and expected range of travel yet?

Tune to Win by Carroll Smith is a good book to read when it comes to building/tuning a race/track car, and it goes through tuning suspension components for your application. How to Make Your Car Handle by Fred Puhn is also a good read. It will help you define the variables that you need to set to get your setup right for your application. You can figure out your expected range of travel once you have defined your spring rate, and by figuring out the motion ratio of the suspension. IIRC, the rear suspension on the S2k has a MR of approximately .75, but I would have to measure the arms myself to be sure, and I dont plan on taking out my springs and shocks any time soon to do so. You can figure it out yourself by taking some simple measurements, but you need to be able to move the suspension through its entire range of travel to get the best average for the MR, so the coilover assembly has to come out.

I have no idea how I missed this response. Belated thank you :o

It's too bad that I did miss it. A week later I did have the coilovers pulled and could have made the measurements at that time. I just put a task into my Outlook to do it when as soon as I have the opportunity.