Ridetech bump steer

[bret]

Ok, I have tested my suspension for bump steer with everything in except the spring
Ride height toe +5mm (13/64)
Full extended toe +16mm (5/8)
Full compressed toe -13mm (33/64)

Complete ridetech with truturn.
Happy to answer any questions to hopefully help sort.
CheersAttachment 148447

just to clarify...the image you posted shows your bumpsteer measuring device? It appears that the measurements are taken some distance in front of the spindle. How far? That will certainly magnify the readings that are normally observed.
A couple more pieces of info .I'd like to see...
1. Caster setting
2. A general picture of the front suspension so I can see that the components are assembled appropriately. (Humor me...I've seen some strange stuff over the years )

when I return to the office tomorrow I'll dig up the bumpsteer graph that we observed and try to post it here.

cheers!

[Tweak]

just to clarify...the image you posted shows your bumpsteer measuring device? It appears that the measurements are taken some distance in front of the spindle. How far? That will certainly magnify the readings that are normally observed.
A couple more pieces of info .I'd like to see...
1. Caster setting
2. A general picture of the front suspension so I can see that the components are assembled appropriately. (Humor me...I've seen some strange stuff over the years )

when I return to the office tomorrow I'll dig up the bumpsteer graph that we observed and try to post it here.

cheers!

Hey Bret
I'm at work now, Monday morning here in NZ, will take images tonight.
No this system doesn't magnify results at all. Yes it will change overall widths, but the toe angles stay constant.
If It is 2 degs. at the rotor face, then its 2 degs further forward.
The two pieces of tape you can see indicate the diameter of the tire. Other wise my ride height toe angle would be off, which it isn't.
This jig allows you to get very accurate measurements when suspension is fully compressed as the chassis isn't in the way.

Cheers

[andrewb70]

Hey Bret
I'm at work now, Monday morning here in NZ, will take images tonight.
No this system doesn't magnify results at all. Yes it will change overall widths, but the toe angles stay constant.
If It is 2 degs. at the rotor face, then its 2 degs further forward.
The two pieces of tape you can see indicate the diameter of the tire. Other wise my ride height toe angle would be off, which it isn't.
This jig allows you to get very accurate measurements when suspension is fully compressed as the chassis isn't in the way.

Cheers

But you gave measurements in inches, not degrees. Those measurements will definitely change if you take them at different distances from the wheel centerline. I would take measurements at the tire radius distance.

Andrew

[Tweak]

But you gave measurements in inches, not degrees. Those measurements will definitely change if you take them at different distances from the wheel centerline. I would take measurements at the tire radius distance.

Andrew

Hey Andrew
I would suggest you do a simple chalk drawing on the ground of a triangle. Measure the distance of the third angle over a given distance (say 26") then move along the triangle and take the distance of the third angle over the same distance and the measurement will be the same.
You measure Toe by distance ie. 1/8+ toe, but this is define by the ANGLE of the rotor. Angles stay constant and relative to the other rotor.

Hope this helps

[Tweak]

Hey Andrew
I would suggest you do a simple chalk drawing on the ground of a triangle. Measure the distance of the third angle over a given distance (say 26") then move along the triangle and take the distance of the third angle over the same distance and the measurement will be the same.
You measure Toe by distance ie. 1/8+ toe, but this is define by the ANGLE of the rotor. Angles stay constant and relative to the other rotor.

Hope this helps

Hope this helps

[Tweak]

[Tweak]

Ok as installed and wheel alignment done
Toe measurements
Ride height +5mm. 13/64
Full bottom +16mm. 5/8
Full top. -13mm. 33/64

Best results so far with mods
Ride height +4mm. 5/16
Full bottom. +2mm. 5/64
Full top. -7mm. 9/32

So I’m getting close to realistic bumpsteer numbers that improve on existing

[Tweak]

Not sure why, but it appears ridetech have gone very quiet on this thread.
I have reached the limit of adjustment I'm prepared to go at the steering arms.
So new test equipment will determine design of drag link and dial out all bump steer.

[Mean 69]

For comparison, I bumped an Art Morrison frame last week, with their steering arms, etc. +/- 2" of wheel travel from the ride height position I had +0.10 to -0.08" which isn't perfect, but it's reasonable for a street car. Something definitely sounds strange here.

My compliments, you are a very crafty guy. Engineering background, I presume?
Mark

[onair]

Column B is the numbers we measured here at ridetech.
I'm curious in the length of your idler arm and pitman arm? The chart I posted is with the 5.8" on both the idler and pitman arm. There are 2 lengths that are common, 5.25" and 5.8".
When you are measuring full compressed and full extended, are you basing those off the shock travel? Dimensions of the shock for this setup is 10.48" compressed, 14.08" extended with 12.55" ride height.

Rodney Mason
ridetech
[email protected]

[nzcarguy]

Hi Damien,

That is not good, on the positive side, ridetech are engaged, I am going through the same process with the Roadster Shop and they wont even provide a response to emails simple details on the brake lines. Whilst our NZ compliance rules are somewhat bizarre some of the checks and balances are could be of benefit to all those building these cars.

[Tweak]

Column B is the numbers we measured here at ridetech.
I'm curious in the length of your idler arm and pitman arm? The chart I posted is with the 5.8" on both the idler and pitman arm. There are 2 lengths that are common, 5.25" and 5.8".
When you are measuring full compressed and full extended, are you basing those off the shock travel? Dimensions of the shock for this setup is 10.48" compressed, 14.08" extended with 12.55" ride height.

Rodney Mason
ridetech
[email protected]

Hey Rodney
Yes I have 5.8” on both and have shocks in with no springs
I am testing travel from bump stop to bump stop of shock travel and ride height is very similar to yours
I’m starting to think maybe ridetech doesn’t fully understand what bump steer is
Your chart you provide states at the top toe in is negative toe, when in fact toe in is positive toe
I’m sure your measurements are correct to your test method, problem is I’m pretty sure your method of testing is incorrect
The front end of a Camaro isn’t rocket science and I have fitted all components as designed
Cheers

[marolf101x]

You have yet to tell us your alignment settings. As more positive caster is added, the steering arm is lowered, which affects bumpsteer.
Just looking at your images the shims on the upper control arms appear to be about even (though difficult to tell). If correct, that means you don't have much caster in the alignment as it sits.
Let us know what you are running for alignment and we'll go from there.

We understand what bump steer is. You don't have championship winning cars without knowing a bit about basic suspension geometry.
I know that once you get under a certain number bumpsteer doesn't really matter as it doesn't really affect anything. This is determined in part by the tire you select.
I know the numbers you are stating are way off what we found during our testing and development of this product.
I also know the 1st Gen TruTurn was designed years ago before we started 3D scanning the cars and designing everything on the computer first. So data from that era is a bit difficult to come by. If we cannot find it in some notes somewhere it may not exist any longer. The newly developed parts have much better documentation and retention of those documents.
I know these cars are all a bit different. . .they were all slightly different the day they rolled off the assembly line, and in most cases haven't' gotten any better.

I also know we'll do about whatever it takes to get this figured out and make you happy. . .that's our job!
It is a little more difficult since you are not on the same continent as us, but we'll do what we can.

[David Pozzi]

Ok, I have tested my suspension for bump steer with everything in except the spring
Ride height toe +5mm (13/64)
Full extended toe +16mm (5/8)
Full compressed toe -13mm (33/64)

Complete ridetech with truturn.
Happy to answer any questions to hopefully help sort.
CheersAttachment 148447

You must keep the angle irons level in side view when jacking up your suspension. If you let them droop as you raise the suspension, any camber change will affect the toe angle of the irons IF they are not kept level.
As Brit said, your caster setting affects the height of the outer tie rod ends, & bump steer. More caster = less toe out in bump.
I do think trying to get perfect bump steer over the whole range of suspension travel is pointless. The car doesn't operate there. I would look at 2" of bump, and 1" of rebound, but it's your car.

[Tweak]

You have yet to tell us your alignment settings. As more positive caster is added, the steering arm is lowered, which affects bumpsteer.
Just looking at your images the shims on the upper control arms appear to be about even (though difficult to tell). If correct, that means you don't have much caster in the alignment as it sits.
Let us know what you are running for alignment and we'll go from there.

We understand what bump steer is. You don't have championship winning cars without knowing a bit about basic suspension geometry.
I know that once you get under a certain number bumpsteer doesn't really matter as it doesn't really affect anything. This is determined in part by the tire you select.
I know the numbers you are stating are way off what we found during our testing and development of this product.
I also know the 1st Gen TruTurn was designed years ago before we started 3D scanning the cars and designing everything on the computer first. So data from that era is a bit difficult to come by. If we cannot find it in some notes somewhere it may not exist any longer. The newly developed parts have much better documentation and retention of those documents.
I know these cars are all a bit different. . .they were all slightly different the day they rolled off the assembly line, and in most cases haven't' gotten any better.

I also know we'll do about whatever it takes to get this figured out and make you happy. . .that's our job!
It is a little more difficult since you are not on the same continent as us, but we'll do what we can.

Hey Brett
Cheers for your input
I still believe ridetech was the right choice for my car. Well made strong components
I have spent many hours fine tuning my front end and I have decided to make a new drag link similar to your version but have moved the tierod pick up points slightly
With them moved I ended up with
Ride height toe +5mm 13/64
Full up toe +5mm. 13/64 No change
Full down +6mm. 15/64
I reckon I’ve found the sweet spot

Attached image isn’t great but shows what I’ve done
Will build a more rigid test rig to lock in new dimensions before I cnc new drag link

[Tweak]

You must keep the angle irons level in side view when jacking up your suspension. If you let them droop as you raise the suspension, any camber change will affect the toe angle of the irons IF they are not kept level.
As Brit said, your caster setting affects the height of the outer tie rod ends, & bump steer. More caster = less toe out in bump.
I do think trying to get perfect bump steer over the whole range of suspension travel is pointless. The car dowesn't operate there. I would look at 2" of bump, and 1" of rebound, but it's your car.

Hey David
Thanks for your input
I was pretty happy how my car handled with as bought set up
Unfortunately it’s not my decision here in New Zealand
Our modified cars have to be certified by government appointed certifier and pass very strict testing to be allowed on nz roads
This is where it failed bump steer and this all began
Looks like I have sorted and will post images of new drag link
Cheers

[David Pozzi]

I like your tie rod test plates.
GM designed in some toe-out in bump to compensate for lower A arm bushing deflection which allows the spindle to move inward & rearward when cornering hard. The problem was, it had much more bump toe-out in production than was optimum. My point is, shooting for zero toe change is probably not ideal under real-world conditions. However, the Ride Tech components reduce deflection immensely, which reduces the need for compensation. If your inspectors require near zero bump steer, it will drive ok.

[Tweak]

I like your tie rod test plates.
GM designed in some toe-out in bump to compensate for lower A arm bushing deflection which allows the spindle to move inward & rearward when cornering hard. The problem was, it had much more bump toe-out in production than was optimum. My point is, shooting for zero toe change is probably not ideal under real-world conditions. However, the Ride Tech components reduce deflection immensely, which reduces the need for compensation. If your inspectors require near zero bump steer, it will drive ok.

That's great info David.
What would you recommend the best Toe-in bump to be for all round street performance. Not sure if you know much about nz roads, but our roads resemble canon roads and they are everywhere. Makes for fun driving. I plan to add a video to my build page soon, they are awesome.
Here is what I have proposed for certification. Not far from the ridetech part.
I haven't put the kink in it to match shape of GM draglink as I'm running LS7 oil pan and bottom of pan sits above drag link with no clearance issues.

[Tweak]

I like your tie rod test plates.
GM designed in some toe-out in bump to compensate for lower A arm bushing deflection which allows the spindle to move inward & rearward when cornering hard. The problem was, it had much more bump toe-out in production than was optimum. My point is, shooting for zero toe change is probably not ideal under real-world conditions. However, the Ride Tech components reduce deflection immensely, which reduces the need for compensation. If your inspectors require near zero bump steer, it will drive ok.

This is the early response from certifier, any help would be greatly appreciated.

"So you need to make the tapered holes the correct thickness material so theirs no welding etc , LVV (government agency) will want plans id say of the oe draglink and dimensions of your bolt on piece , id say what the question will be is raising the height of the inner pivots what extra leverage does that have on the oe draglink and connections to the pitman and idler ? id expect it to made out of steel.
I can do a stress analysis of new part, but really need to find OE steering loads?

Cheers

[David Pozzi]

Very nice! You did that very quickly!
Somewhere between zero and .125" toe-out per side in 4" travel is great. I was advised .080" out per side over a 4" travel by Dick Guldstrand on race cars with solid steel A arm bushings. The small amount of toe out will help offset any deflection. I have no way to predict deflection but there has to be some. A small amount of toe out in bump also helps assist Ackerman correction which isn't a bad thing at all.