Rear wheel hop under heavy braking, HELP!

[TheJDMan]

Guys, I have started encountering a new problem since installing new track brake pads. The new pads produce so much stopping force that I have now started to experience rear wheel hop under hard braking. This is a new problem that I have never had before and I have no idea why or how to stop this. Just to refresh I'm running a Moser 9" floater with the Chassisworks G-link. What causes rear wheel hop under braking and how does one stop it? Any help will be greatly appreciated!

[dhutton]

Curious if your lower rear bars are level with the ground.

Don

[CSG]

Is that the Torque arm or 4-link chassiswork kit?

[oleyeller]

Did you readjust the brake bias after changing the pads?

[dontlifttoshift]

Go back to the other pads or at least go to a pad with less bite.

Adjust brake bias like mentioned above.

More front spring.

Less rear rebound.

If you are standing the car on it's nose with the new front pads, the rear tires are loaded very lightly, it doesn't take much to get them hopping. The rear geometry goes wonky, too, and you end up with a very short side view swing arm.

Violent downshifts can induce wheel hop as well.

[SSLance]

I'm with Donny... Reduce rear shock rebound and\or rear brake bias. You can sneak up on it, little changes make a big difference here.

[79T/Aman]

as others have said check your brake bias sounds like too much rear brake.

[TheJDMan]

Lower bars are parallel with the ground, brake bias is currently non-adjustable but that will be changing soon. I have the proportioning valve, I just need to get off my butt and install it. I recently upped the spring rates 600lb to 800lb front and 200lb to 300lb rear. My only adjustment for now will be to reduce the amount of rebound in the rear shocks and/or to reinstall my old rear pads. I have to tell you that it gets your attention when you are hard on the brakes approaching a 90deg turn from near 100mph and the rear wheels start hopping. Thanks guys!

[MonzaRacer]

First of all readjust brakes. Are you using an adjustable proportioning valve? If so, reduce pressure.

[krom]

forgive the ignorance.. but if you aren't locking the rears first why would you want to reduce brake pressure instead of fixing the hop with suspension changes/adjustments.

[rocketrod]

What pads are you running front & rear. Are rear pads the only change you made, or did you change the front's at the same time?

[David Pozzi]

If you install an adjustable proportioning valve, remove or bypass any existing non-adjust prop valve. The adjustable valves will reduce rear braking by 10% even when turned up all the way.

[Ron Sutton]

What is your rear spring rate?

[y5e06]

also, under what conditions are you getting the hop? Is it just over a crest/rise while heavy on the brakes? is the backend unusually light under braking? only over rough surfaces?
Reduce rear braking either by rear bias (prop valve) or brake pad compound is the most immediate way to fix, at least to me. Shock tuning may help.
Its basically like dragging a rock using a string, as you may have done as a kid.

[David Pozzi]

What is your rear spring rate?

Ron, see post #8 above

[Ron Sutton]

Ron, see post #8 above

Thanks Dave. I missed that.

Steve,

300# rear spring rate is plenty. So it's not a spring issue. Believe it or not the shock valving can be too soft or too stiff ... and "allow" rear wheel hop under hard braking. But it's not the cause. Since your spring rates are fine. I suspect you have too much anti-dive in the 4-link. Do you have a way to measure where the instant center is, so we can figure out your anti-squat percentage?

[TheJDMan]

I changed to Hawk HP+ pads front and rear that is when the problem started. Last week I changed to Hawk Ceramic pads in the rear. So far so good. Funny, I was watching the NASCAR race at Watkins Glen this past weekend and I was surprised at how many drivers were reporting wheel hop under braking. You would think those teams would have this issue figured out by now.