SpecRacer.com

What is everyone using for measuring bump steer?

I spent most of the night trying to use a new Longacre bump steer gauge. It's the one with one analog gauge.

The main problem was it doesn't seem to be capable of measuring accurately. I could make a measurement 10 times and come up with 10 different measurements. Anywhere from .025 to .085. Also if I bump to 1" and then return to 0 the gauge never returns to 0. It's always .010 to .025 off?

Nothing on the car seems to be moving however I'm seriously doubting the construction of the gauge. The frame is really flimsy.

Make sure you that all the knobs are tightened down on the frame and that you're using the minimum amount of extension and that the dial indicator and roller are level and at 90 degrees to the plate. Keep sufficient angle in the frame to maintain pressure on the roller and the dial indicator against the plate. Check that you're not too close to the extremes of the dial indicator as well (I generally try to "zero" the gauge about 1/3 - 1/2" in. Finally, watch the level on the frame as any movement off-level will throw off the measurements. I assume you're pulling the brake calipers off when mounting the plate to the hub.

Thanks for the reply, I've checked most of this but will check it again tonight.

After thinking about it a little more today I wonder if I didn't miss a lose component in the front end. The hub bolt also hits the plate so I snugged up the lug nuts to make sure it wouldn't rock on the bolt head. Made sure I didn't tighten so much that I bent the plate as well. Just wonder if the plate isn't still moving on the bolt head as the washers do have a rubber back to them. Going to make a hole for the bolt head to clear.

Really hope I don't have another bad rack.

Your plate shouldn't touch the center bolt. I use 4 large hex nuts, 1 over each of the 4 studs to space the plate away from the center nut and brake rotor. I use the longacre gauge, have for years. Do you have some heavy weight on the base plate to keep it from moving?

Robert thanks for the advice. Looks like I had a couple of things going on. Once I installed a stack of washers over the two studs so the plate wasn't touching the hub bolt things started working better. Not perfect though. Looks like the frame hinge was too tight as well. Once I loosened up those two bolts things started working as I would expect them to. The tight frame bolts were causing insufficient pressure for the roller to track the plate correctly. I also made sure the dial indicator was reading around the middle of it's range.

I can get repeatable measurements now and the indicator goes back to roughly zero so it looks like I'm in business.

Thanks for the advice guys and we'll see you next weekend or the Black Hawk Major Robert?

Martin

trakmnky wrote:
Thanks for the advice guys and we'll see you next weekend or the Black Hawk Major Robert?

Martin

I plan on running this Friday @BHF and maybe the Sat race plus the Majors at BHF the following weekend.

See you there!