Bumpsteer

[Cliff Beer]

Many of you might have already seen the excellent acticle by Dean Lampe on bumpsteer adjustment in the current Kit Car Magazine. Obviously, a lot of thought and precision engineering went into the testing, adjustment, and final set up on Dean's RCR40 with regard to bump steer. Ultimately, bump steer was adjusted to optimal (for mostly track settings) by adjusting the angle of the steering rod relative to the wishbones by moving the outboard end up and down on an adjustable post fitted to the steering arm attached to the hub (there are great pics in the mag which make my clumsy description here understandable). The outboard end looks to have been shimmed up by about 3/4 inch or so for the final setting.

A question came to mind after reading the article - why not shim/adjust the whole rack rather than the outboard end of the steering rod? Doing so advoids the torsional loads and any flexing that may occur related to the extensive shimming (of the peg) on the steering arm.

Whenever I've messed with the ride height of my cars for track purposes I've always adjusted for bump steer by moving the rack - either shimming or machining off material off the rack mounts, or the rack itself. Maybe my approach has been kind of hack in so doing but I've always had good results. Appreciate any comments/thoughts.

 

[Bob Putnam]

You're right. Moving the rack would be much preferable to extending the tie-rod. Which is why, in the ERA, the steering gear can be shimmed up and down for a final adjustment.

Maybe it's not practical to move the rack up or down in the RCR?

 

[Clayton]

Hi Cliff
With adjustable tie rod ends you can adjust one side at a time without changing the settings on the opposite side (fixed rack).
I’m using shims under my rack because of std tie rod ends (rego purposes).

Clayton

 

[Fran Hall RCR]

The rack can be shimmed just as easily as the outboard tie rod.....we have waterjet shims in various thickness available FOC for the rack mounting surface.

 

[Cliff Beer]

Thanks, got it. Makes sense. Was just really wanting to make sure my approach wasn't totally hack or hairbrained.

Great article with super good information and pics. Really shows off the nicely machined and well engineered suspension parts of the RCR 40! I'm sure Dean's car is one fast GT40.

 

[Dean Lampe]

Thanks guys, I have learned a lot writing this series of articles for Kit Car mag. The rack is usually the rough adjustment and the hiem shims are for the final adjustments left and right. They are usually slightly different. I thought the rack on the RCR was already close enough for street use so I didn't think I needed to shim. In hind sight the rack could have been shimmed a little. The Load on the hiem is nothing compared to the mass of the steering arm, the huge bolt and the hiem that hold it all together. I would really like to see the bump steer numbers on some of the other cars. The short arms on the front can make it difficult to get right. The fact that the RCR is so adjustable makes a big difference.

 

[Jason Ferraro]

RCR Bumpsteer Kit

There is some talk from other RCR40 kit owners of a bump steer kit (they are apparently waiting for it to arrive). Does anyone know what it consists of?

 

[Fran Hall RCR]

It is a QA1 standard off the shelf kit, also available from Steeda....used on Ford Mustangs to dial out OEM bumpsteer when being set up for the track....

Jason,
I am not aware of anyone waiting for one....as they are in stock here..drop me a pm if you know different.

As a sidebar...when's the baby due??

 

[Jason Ferraro]

Fran is the Steeda or QA1 kit in stock?

Steeda (good explanation of purpose here)
http://www.steeda.com/news/tech_articles/instructions_bumpsteer.php

QA1 is a little hard to find info on.
Can you recommend the better one?

Also which Steeda kit should be used if that is chosen?

555-8106 Steeda Bumpsteer Kit: '05-'09 - Blue
555-8104 Steeda Bumpsteer Kit: '94-'04 - Blue<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com<img src=" /><o></o>
555-8103 Steeda Bumpsteer Kit: '79-'93 - Gold <o></o>
555-8105 Steeda Bumpsteer Kit: '79-'04 – Red (with manual steering rack)

 

[Fran Hall RCR]

QA1 in stock