MBC Racing

iTrader: (3)

I did a parking lot autocross on Sunday and noticed that I would get some nasty wheel hop from the right rear when braking hard. I have HAL shocks front and rear, BMR track pack, hotchkis springs and sway bars. What could be causing this? I softened up the rear shocks and it still did it. Anybody else having this problem? <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
Thanks
Brad

jimmyblue

iTrader: (11)

If you have put LCA relocation brackets on,
try backing off one hole. There's a "sweet spot"
between acceleration wheelhop and braking
wheelhop as you keep on lowering the rear LCA
mount point against the axle. This is my guess.

You may be forced to compromise between drag
launch and braking manners. It's an age-old
problem, I have seen many articles over the
years, even people using dual torque arms of
strange configuration, one of them active at
acceleration and free on deceleration, the
other opposite. With a single torque arm and
LCA angle you have a single instant center
that is probably not the ultimate best for either
launch or stop. How you bias it is your thang.

MBC Racing

iTrader: (3)

What will have more effect, pinion angle or angle of the control arm in the relocation bracket. I am in the lowest hole right now. How about shock stiffness?
Thanks.

trackbird

iTrader: (4)

Are you using a shorter than stock torque arm (I think that is a "short one")? The shorter torque arm will "lift the tires" under braking which can lead to wheel hop (brake hop). Brake hop is uncontrolled (undampened) vibration, you may try stiffening the rear shocks and see if it is better. I don't suspect that pinion angle will have much effect on it, that short arm will act as a lever and still try to lift the rear. I ran an autocross on race rubber this weekend and had "0" wheel hop or brake hop, but I have a stock torque arm (I'll list my sig, with the suspension mods). My main problem was spinning the inside wheel (car wouldn't throttle steer much, and didn't put power down very well either....on race tires), Torsen diffs don't seem to like autocrossing much (after taking the Koni rebound settings to full soft it was somewhat better).

MBC Racing

iTrader: (3)

I have no problem with the posi. Strange 12 bolt with eaton pro. I will try to soften the shock some more. I was told that too stiff will make it hop. I guess I will try going real soft and real stiff and see what happens. I am running a shorter torque arm. Mounts to the bottom of the car instead of the trans. I may even call QA1/HAL and see what they recommend.
Thanks
Brad

trackbird

iTrader: (4)

Wish I had an Eaton.....(or anything more positive....Torsen T2R, etc).

I suspect that your torque arm is a large part of the problem. I think you will want to use more bump (compression) stiffness, and slightly less rebound (for starters....) and adjust fron there. I'm running my koni's at 6 clicks from soft on compression and full soft on rebound (to hook the rear up, it tracks better with 1/2 turn of rebound in the rear, but I was lifting the inside tire and spinning real bad in the tight stuff). Let us know what you find out.