$64 toe-steer question

Ralphy

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Dec 12, 2009
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If you build a suspension with toe-steer, Can you alter rear toe and camber settings to zero? What I have seen, typical IRS settings include negative camber and toe-in. If you were able to compensate the negative effects in cornering with toe-steer, allowing the rear wheels to track dead straight and flat would increase speed performance in straight line driving, no?:bs:????

Stroker?
TT?
 
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One thing you might consider is that you will get toe steer -- both wheels -- with squat on acceleration and during "dive" conditions during braking (toe steer induced as a function of suspension travel). Your rear wheels could be set up to track flat and straight in constant speed, steady state conditions, but you might get unwanted toe during hard acceleration. Also, most IRS's are set up with a slight amount of toe-in to aid in braking where any slop in suspension components translates to toe-out during hard braking. I personally eliminated all toe steer (5-link ala C-4 geometry) because it is hard to set up for all dynamic situations (sometimes works great to tighten a circle track car making only left turns) -- I did not want the car to "tighten up" and start to push under hard cornering due to toe-in roll steer.

Cheers
 
Pappy,
Damn if you don't learn something every day. I wondered about that, with the C4 design. I have a couple of suspension books plus going online. I see contradictions in so many areas. Recently I have been searching the term roll steer and I see several explanations as far as what causes roll steer. I figure they all equal the same.

As far as toe steer, I have read recommendations to not have toe-steer. Same with anti-squat.

Anyhow I need to compare settings, C3 vs. C4. I think the C4 IRS can be set more neutral.

Thanks Pappy!
 
I totally agree with Pappy!
Rear bump steer can be very usefull is specific conditions... even at the beginning or at the end of the corner.... but is very critical to be adjusted.
Furthermore any different track or condition needs a specific design.

For example I did a test with my car setting a good quantity of bump toe-in and rebound toe-out. This was helping a lot in a very tight autocross.... braking the toe-out helps the insetion in the corner and toe-in during acceleretion coming out from the corner was avoiding oversteer.

Anyway was very difficult to set the proper amount of toe changing.

A neutral condition is the best compromize for predictability!
 
Thanks for the honest reply Stroker. Another question have you tried setting your IRS neutral?
 
Pappy,
Damn if you don't learn something every day. I wondered about that, with the C4 design. I have a couple of suspension books plus going online. I see contradictions in so many areas. Recently I have been searching the term roll steer and I see several explanations as far as what causes roll steer. I figure they all equal the same.

As far as toe steer, I have read recommendations to not have toe-steer. Same with anti-squat.

Anyhow I need to compare settings, C3 vs. C4. I think the C4 IRS can be set more neutral.

Thanks Pappy!

Ralphy,

You can adjust the toe steer of a C-4 style IRS by changing the length and pick-up locations of the toe link, just like you do in adjusting bump steer on the front suspension. On a C-3 suspension with the standard trailing arm, you will get toe-out with both bump and rebound. The front pivot point of the trailing arm is at a fixed distance from the vehicle centerline. The wheel flange, on the other hand, swings in an arc as the axle shaft moves up and down. The flange is at it's greatest distance from the vehicle centerline when the axle shaft is parallel with the ground. As the suspension travels up or down, the flange is pulled closer to the centerline. Since the flange remains rigidly parallel with the trailing arm, it will point the tire out (toe out) with any suspension travel. I don't know of any way to adjust that toe-out issue. Most good C-3 drivers simply recognize the potentially "loose" condition on corner exit and are judious with the throttle when it counts.

Pappy
 
Pappy,
Thanks again I do understand the toe differences. I found settings at Guldstrand's site, I was more curious about camber. And I do see toe and camber are running closer to zero with the C4.

http://www.guldstrand.com/alignment.asp

I was researching roll steer, particularly roll over steer. What I have read is that two things can cause this, first is toeing out from suspension movement such as the C3. And also the coning of the rear outside tire in a turn. I find this interesting, that if the rear outer tire goes positive camber it wants to travel in the opposite direction as the chassis causing over steer. It would seem to me if you reduce toe out you would need less negative camber also. Looking at the numbers at Guldstrand's site this holds true. Then because you need less toe and camber, when driving in a straight line you should be scrubbing off less HP. And have a more even contact patch, plus less wear. More negative camber can reduce over steer, hmmm... Being able to adjust camber gives an IRS a big advantage over solid axle guys. NASCAR actually toes and cambers their housings and have splines that are radius-ed.

I am still learning ideas, I have started removal of my suspension mounts. In fact I'm pretty well done. If I were to keep the C3 design I would have to shorten my trailing arms 3" to 4". That is not a direction I want to go. This would only give me more toe out. OUCH!
 
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