My car hops really bad when i floor it off the line.
Same as in this movie:
http://www.youtube.com/watch?v=35yhGrStX3s

I have a 400hp 350 engine, with t56 transmission. 12 bolt chevy 33 spline spool rear with 4:88 gears (yeah! ).
The problem is.. when i floor it, i get really bad wheel hop like in the movie (it's not my car in the movie) I have UMI rear control arms and a thick aftermarket sway bar..

The shocks i have are gas shocks... but they have coilover springs on them.. and my springs are the original 1970 springs.. could those be cousing this???

I litterly broke a rim once.. i messed up all the stud holes in the rims for the bolts and the rim was inches from coming completly off the car.. (that bad!) luckly it was a 10 inch wide rim and the drum dropped on the backspace area as i was pulling over..

help....

 

Is your car raised up really high in the rear?
Lower your rear end and the problem will go away.

Don't want to lower it? Get edelbrock or lakewood no-hop bars, or UMI lower control arm relocation brackets (can't use your rear swaybar if you get those though).

It has to do with the driveline angle & some rear suspension geometry and i barely understood when it was explained to me.

In short- look at your lower rear control arms. stock rear lower arms "SHOULD" be perfectly level to the ground. If due to raising the rear of the car, or lowering the rear of the car they are not level- then you need to fix this, either by adding adjustable upper control arms, or by adding the no-hop bars i mentioned above.

if you HAVE no-hop bars or lower relocation bars, then the lower control arms will NOT be level with the ground (due to the relocation) but they will still solve the geometry issue.

clear as mud? i just wrote it and am doubting any of that made sense....

 

you'll notice in the movie, the rear end of his car is raised up quite a bit over stock.

 

The car is jacked up to high, and as stated above you need some assistance in getting the unsprung weight toward the rear wheels. Traction bars, ladder bars, etc....

 

If you want to go tall in the back, the springs and shocks have to be mushy.

 

My car is not jacked up in the rear like this one in the movie...

here is my car:

 

You have to find a way to transfer weight to the rear of the car. You can run a drag shock on front, that allows for the front to raise. As stated earlier, traction bar setups, etc.... You can also play with air pressure in your rear tires.

 

No hop bars and air bags will stop it and plant the tires for you reducing wheel spin.

 

with aftermarket control arms, i am assuming the bushings are good? my Rallye 350 had a bad case of wheel hop till i replaced the control arm bushings. the old ones were shot and caused it. with the new bushings it completly went away. in high school i chucked a M-21 4 speed out of a car from wheel hop. wheel hop can cause all kinds of damage.

 

Yeah.. everything is brand new..

Here is a picture of the frame before i put the body on it..
It is still with the 12 bolt "o" type rear in this picture.. now it's the same, only with the new 12 bolt 33 spline chevy rear i got..

Maybe it's those coilover springs??
Here are some pics:

 

Had a '65 Chevelle 2-dr wagon with a big block and never got wheel hop until I tried a 'burnout' without the rear tailgate on - was probably a weight transfer issue.
Might try air shocks with individual valves, and pre-load the right side a bit.

 

I'd ditch the coilshocks and put in regulars.
Judging your rear springs by eye, they're pretty wimpy and squishy.....Which is decent for heaving the weight down on the rear axle.
The coilovers are probably stiffer than your rear springs, so you are basically using the coilovers as 2 pogo sticks instead of bearing the weight on the big rear springs.

You could spend $350 for a pair of double adjustable shocks and have any setting you want....but I'd just throw some regular old monroe sensatracs back there and you'll probably be fine.

 

p.s. Nice ride!!

 

w31cutlass,
Wheel hop can be caused by a few different things. The suspensions ability (inability) to hold the wheels from any lateral movement during hard acceleration has a direct effect on hop. In theory the wheels need to be rigidly fixed in the chassis. On a race car the suspension bushings would be solid or spherical bearings. But on a street car this is not a good solution as ride quality would be greatly compromised. Try putting an air bag in one or both of the rear springs. The passenger side first, then the other side, then both. Then play with the pressure in both bags. They might like different psi verses inflating both to the same psi?
Have you played around with tire pressure and contact patterns?


Wheel hop is very dynamic. Everything from road surface, tire compound, tire wall design, wrong spring rates for the application and worn suspension to thermal dynamics can contribute to it. Basically it’s the grip, no grip, grip cycle that your experiencing. This will cause the axle to "wrap" by way of shifting the wheels back in forth in the wheel well (the caster is moving back-n-forth). If the axle can be held from any lateral movement (caster) in theory it should eliminate the hop (that’s primarily what ladder bars are designed for but don’t jump to that solution yet).
So if everything is up to snuff in the suspension then you've covered the basics. Now try the other things I mentioned, beginning with the simple one, tire psi/contact pattern. From there add a bag in one or both rear springs and play with its inflation psi. The bags usually do the trick. A stiffer higher quality gas filled shock such as KYB or Edelbrock would be next, (IMO) not coil-overs, though some have had favorable results using them. Then possibly springs? Yours look a little light?
Have you tried playing with the pinion angle at all? Try a few degrees either way from where it is now.
From the pictures the springs look a little light weight? Moog or Eaton should be able help you dial in a spring rate for your application.

Caution: Use the “smart approach” to trouble-shooting a problem. Change one thing at a time and keep tract of those changes until the problem is solved. That way if you need to go back to where you started you’ll know exactly where that was. This also helps pin-point the root cause of the problem.

IMO I’d do it in this order (cheap & easy to expensive)
1. Tire psi
2. Pinion angle (cuz you already have adjustables)
3. Bags
4. Shocks
5. Springs
6. Ladder bars
7. Different tires
8. Spherical control arm bearings
9. Sell the car and buy one with out wheel hop (kidding ha-ha)

Get back to us and let us know what solved this for you.

 

looking at the photo, he doesn't have adjustable control arms, just the aftermarket tubular ones.

I would proceed directly to getting airlift 1000 inserts for the rear coil springs.

Valve them separately and put about 10lbs in each back.That will stiffen up the rear suspension w/o lifting it.

If that doesn't fix it, then i'd consider the edelbrock or lakewood nohop bars.

I realize in israel its tougher to get this stuff, so trying to keep your "try this" list as short as possible.

whatever happened to your 4 door chevelle? did you sell it to finish the olds?
This one looks like turned out real nice- heh, i remember back when you first showed up on team chevelle with the 4 door,back before you had even painted it! You've definitely come a long way with these cars!

 

I don't have adjustable control arm as stated..
being overseas, airbags are not something i can come by here..
so i am gonig to go with changing the shocks and springs first.. and see if it solves it..
I am thinking shocks first.. didn't like those coilovers to begin with.. this is what monroe had off the shelf here for the car.. they have regular gas shocks now.. i'll try them..

and the springs too. i can get a pair easly here.. i've got a few friends with Abodys here that have a spare set of rear springs..

will update.
thanks for the kind words about the car worked hard to get it the way it is.. being overseas.. it's not as easy for you guys

P.S.
Yes i did sell my 72 Chevelle.. what was your handle on TC? I am ChaosMalibu as you know
i still hold my shai@chevelles.com E-mail

 

i was ahsom69 back around '99, then switched to AHSOM70 in 2002 then switched to RAMBO around 08

gotta keep everyone guessing you know.