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Discussion Starter #1
My next project is to install a MM bumpsteer kit. I've been reading up on the science of optimum outer tierod end setup. All of the racing sites refer to an upper and lower A-arm suspension and not a strut/ lower arm setup.

I'm trying to simplify the setup of the adjustable MM outer tierods. Why can't I just set the tierod parallel with the A-arm? Wouldn't the outer tierod and lower A-arm travel in the same arc?

I'm running H&R race springs with poly spring dampers on all 4 corners so the car is lowered a bit. I'm not racing but building for a daily driver with great cornering. Currently; the car hits bumps and the steering wheel turns with no input.

Thanks.
 

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If the car hits the bumps its not lowered a bit, its lowered quite a bit. If you are hitting the bumps then you will never be able to sort the problem out. That is always going to cause a problem. But that said everyone has a different way of setting up the steering. Over the years I have come up with a way that works for me. I have it set to stock specifications then take it to local track days and start to make adjustments based on what it is doing.

I have a 98 and the only way I was able to get everything to work the way I wanted was to add drop spindles. Once I did that I was able to get the steering angle where I wanted for the car to drive how I wanted.

Also do you want the car to drive real well or do you want track steering? Which for me is not enjoyable on the street.

Jake
 

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Getting the tie rod and A-arm parallel will get you very close. I have a laser bumpsteer kit you can use to set it precisely when the time comes. But most often, if the steering changes noticeably when you hit bumps, it's "tramlining", or getting steered by the ruts in the road, more than it is bumpsteer.
 

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Currently; the car hits bumps and the steering wheel turns with no input.

Thanks.
Bumpsteer is most evident when you drive over smooth 'heaves' in a curve. Either the car steers slightly if you hold the steering wheel dead-steady (if you can keep yourself from trying to compensate) or you find yourself sawing away at the wheel in order to stay on the same curved path. It's caused by up/down suspension movement that doesn't need a sharp bump in order to happen.

When hitting bumps causes the steering wheel to move, that's more likely a scrub radius issue, where the rearward force from hitting the bump has greater leverage for steering that wheel.


Norm
 

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Discussion Starter #5
If the car hits the bumps its not lowered a bit, its lowered quite a bit. If you are hitting the bumps then you will never be able to sort the problem out. That is always going to cause a problem. But that said everyone has a different way of setting up the steering. Over the years I have come up with a way that works for me. I have it set to stock specifications then take it to local track days and start to make adjustments based on what it is doing.

I have a 98 and the only way I was able to get everything to work the way I wanted was to add drop spindles. Once I did that I was able to get the steering angle where I wanted for the car to drive how I wanted.

Also do you want the car to drive real well or do you want track steering? Which for me is not enjoyable on the street.

Jake
I think you took me literally. When the tires roll over dips or bumps in the road surface; my steering wheel gets yanked in both directions in one quick movement. Yesterday it did it while driving in a straight line. I haven't noticed it in curves yet.
I'm looking for a great handling and predictable car for every day driving and the occasional curvy mountain road.
 

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Discussion Starter #6
Getting the tie rod and A-arm parallel will get you very close. I have a laser bumpsteer kit you can use to set it precisely when the time comes. But most often, if the steering changes noticeably when you hit bumps, it's "tramlining", or getting steered by the ruts in the road, more than it is bumpsteer.
I will have to drive over that same area of road again and see if it is a bump or groove. It felt like a bump, but not positive. The car does tramline but this was different. The steering wheel was yanked back and forth quickly when it happened. Thanks for the kind offer. I may take you up on that depending on how close you think that I need to dial it in for my use.
I had thought about putting the car on a drive on alignment rack. I then would attach a large ratchet strap from the rack to the car. This way I can ratchet the front end down a couple of inches thus cycling the suspension and watching toe changes in real time. I would then adjust the spacers as needed to get the least amount of toe change when cycling the suspension.
 

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See the post linked below.

http://forums.corral.net/forums/8565296-post36.html

It has a drawing attached to it that shows the optimum geometry for minimum bumpsteer on a car with a strut. It is analyzed the same way as a car with an SLA, but the strut car has a virtual UCA, instead of a real one. To find the virtual UCA, you draw a line though the upper strut mount at right angles to the strut. This is what forms the upper line in the drawing.
 

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Discussion Starter #8
See the post linked below.

http://forums.corral.net/forums/8565296-post36.html

It has a drawing attached to it that shows the optimum geometry for minimum bumpsteer on a car with a strut. It is analyzed the same way as a car with an SLA, but the strut car has a virtual UCA, instead of a real one. To find the virtual UCA, you draw a line though the upper strut mount at right angles to the strut. This is what forms the upper line in the drawing.
Thank you Jack.
 
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