Wheel hop

JP MEIER · #1 (**permalink**) 02-17-2005, 05:14 PM

I have Venom Performance standard with BMW suspension. Problem is; When I get on the gas, mostly after I shift to second, the rear end goes bumpety bump for as long as I stay on it. Any solutions for this problem??????? A friend of mind (back yard mechanic) had no slution but classified it as wheel hop. Sounds like the thing is coming apart to me! Ideas and solutions needed!
Thanks for all the help!!!!

Dennis Kelley · #2 (**permalink**) 02-17-2005, 07:18 PM

I'm no expert but what is the ride height in the rear? Wheel hop is usually associated with flex. Check and make sure that all the rear suspension bolts are tight. If the ride height is normal I would say that there is something loose. Has it just started the wheel hop? I'd do a bolt check. There are two bolts on the back of the differential and one on the front (19mm I think) I would start there.

Good luck

relaxinrob · #3 (**permalink**) 02-17-2005, 07:29 PM

Preload the passenger side rear coilover a little heavier and that should help.

JP MEIER · #4 (**permalink**) 02-18-2005, 08:27 PM

I have checked the rear suspension and everything is tight!
What is preloading the passenger side this is not a familiar term.
The springs are adjustable, I measured and adjusted them, they are the same now. I will mention when I bought her their was a 1 1/4" diffrence, the passenger was adjusted higher thus lighter, I am only pretending to know what I am doing here honestly. The two mechanics I brought her to in the last couple of days don't want to touch her. They recomended I talk to other Owners of the same vehicle. so I here I am! More info. please.
Jp

Edley Rondinone · #5 (**permalink**) 02-18-2005, 08:46 PM

How much air are you running in the tires?

xlr8or · #6 (**permalink**) 02-18-2005, 09:36 PM

Have someone watch you getting on it and see if the wheel is actually hopping. If not maybe it's your drive shaft binding under load.

relaxinrob · #7 (**permalink**) 02-19-2005, 05:34 PM

Adjust your rear passenger side spring higher to preload that sode of the car and your wheel hop should go away.

JP MEIER · #8 (**permalink**) 02-20-2005, 11:50 PM

Sounds good. I will try these ideas, can't hurt.

Edley,
I am running about 30 psi in all 4 tires. I have a smooth ride once you get going or if you take it easy on the take off, but who wants to take it easy. We have Cobras for Goodness sake, I say use 'em as they were meant to be used.

Dennis Kelley · #9 (**permalink**) 02-21-2005, 08:05 PM

I would check the drive shaft also. when I can't find the problem I just beat on it til the damn thing breaks. You may have to do this. Do you have a rev limiter on the motor. Get one and launch the piss out of it. Just a thought.

later Dennis

decooney · #10 (**permalink**) 02-21-2005, 08:23 PM

xlr8or,

Your post got my attention and I've been thinking about it quite a bit since. I developed a wheel-hop dampner kit for ERA 427 Cobras. It helped a lot, but it may be helping to remedy the situation, but not to cure the root cause. Masking it that is.

Candidly, what experience do you have with driveline binding being a possibile cause of wheel hop? If true, your analysis may tie together something else I was wondering about during my own wheel-hop testing on my ERA, and why I developed the ERA Wheel-Hop-Absorber Kit in the first place. There are some adjustments that relate to what you stated here and I want to tie up one loose end I'm still wondering about.

Can you ellaborate a bit more on your comment and direct experiene with drive line bind creating wheel hop and what was done to resolve it?

Thanks ahead of time for your response.

relaxinrob · #11 (**permalink**) 02-21-2005, 08:23 PM

Dennis,
Now that you mention it, my dad's cobra shook and vibrated heavily on a hard launch when he first got it and we discovered that the pinion angle was not correct. Instead of pointing down slightly and coming up straight under power, it was straight at rest and was lifting. He may not have wheel hop, but a really bad shudder from the drive shaft clunking. If this is the case, adjust the pinion angle and replace the u-joints.

JAM1775 · #12 (**permalink**) 02-22-2005, 06:27 AM

What type of rear do you have ?
My understanding of wheel hop is the tires grab and "wind up" the suspension to it's limits, like a coiled spring. This happens if the rear is not geometrically angled correctly and the car's weight transfers too far ahead OR behind the wound up rear suspension. The springs snap back causing the violent wheel bounce or hop. As you stay on the throttle the hop gets more violent and can do damage . When mine hopped I could never drive through it...it just hopped harder until all was a blur. Once your suspension transfers the car's weight over the center, while under load, it will hook much harder as the energy is transferred to plant the tires not allowing them to spring up. You will of course always eventually slip when over powered but can stop hopping. The day I corrected my live axle wheel hop I was so excited about the new found traction I left the chassis shop, jumped on it hard hit second, then third and BOOM....kissed my little T5Z goodbye !!! All I had left was Gravel in the box.
Oh well....that's why they created Tremecs . If you want to know exactly what is happening have a friend video your rear wheels as you jump on it. A race chassis shop in your area should be able to tune your rear suspension to address the problem before something lets go.