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-   -   Wheel hop! (http://www.ramforumz.com/showthread.php?t=73134)

sprintertech 02-01-2011 01:56 PM

Wheel hop!
 
so i swapped out the 3.21 gears for some 3.92's......i wanted to do this in steps to see the difference for myself.....eventually ill wind up with 4.56 gears.....anyways with the 3.92 gears and trac loc i now have wheel hop if it spins......what suspension mods have you guys done to cure this (i havent even looked).........

chithead 02-01-2011 02:14 PM

Hmmm... my cure was hacking 1 1/4 coils off the rear springs. It was mainly to level the stance of the truck by bringing down the rear. But an unexpected side effect was my wheel hop disappeared.

TheSatinPumpkin 02-01-2011 04:00 PM

Yep. I had bad wheel hop when i first got the truck and it would be a joy on the washboard dirt roads we have here.
A little went away went when putting rear 2" drop shackles on.
A lot went away when going down to 4/6 drop.
Caltracs took care care of the rest.

erm 02-01-2011 04:27 PM

Here's some interesting insight from MC2racing:

What is wheel hop?
Wheel hop is a nasty action whereby the driven wheels of a car voilently shake, vibrate, hop, grab, and/or thump upon acceleration. It's usually quite obvious when your car suffers from this condition, for it sounds and feels like your car fell off a garage lift three times every second. Wheel hop doesn't just feel bad - it's bad for your car, too. For reasons that will be explained below, wheel hop can lead to broken drivetrain parts, including axles and rear differentials on a rear-wheel-drive car, and axles and transmissions on a front-wheel-drive car. If your car wheel hops - get it fixed!

What causes wheel hop?
A lot of people don't know why wheel hop occurs, which often leads to them throwing the incorrect parts at the car in an effort to eliminate the issue. Fortunately understanding (and correcting) wheel hop is not difficult. Here is what happens. When a car accelerates, you can picture the forces involved as something (the ground) pushing the driven wheels of the car forward. Obviously if you push the wheels forward, the car is going to move forward also. However, the wheels are not rigidly fixed to the chassis, so when the ground pushes on the wheels, they move forward a bit in the wheel well. Normally a car's acceleration is so small that this motion is negligible, but when a car accelerates quickly, especially during a launch, the wheels can move forward quite a bit in the wheel wells. As the wheels move forward, significant toe changes occur. Now, everybody knows that a tire can provide the most grip when it is perpendicular to the ground, parallel with the acceleration, and pressurized to provide the optimal contact patch. That being said, if the toe of the driven wheels changes during acceleration, the grip of the tire must be changing. Wheel hop is a result of this change in grip. Here is the sequence of events:

1.) Acceleration begins with good grip.
2.) The wheels move forward, toe changes, and available grip is reduced. Wheelspin occurs.
3.) During wheelspin, acceleration is very small. The wheels move back again, toe changes back, and the tire regains grip.
4.) Acceleration begins again, and the process repeats itself.

This rapid switching between grippy acceleration and wheelspin is wheel hop. My above description of the wheel hop process sounds tame, but the frequency of the grip changes and the magnitude of the forces involved is what makes wheel hop so violent. Race tires can prevent wheel hop since they have more grip (i.e., they don't lose grip even with the toe change), but cars that wheel hop with race tires will do so in a much more violent fashion.

How do I get rid of wheel hop?
Getting rid of wheel hop really isn't difficult. If you can limit the motion of the wheel with respect to the chassis, then the toe changes during acceleration will be small and the tire will not suddenly lose grip. If the tire does lose grip (common on a high-HP car of course), then it won't suddenly regain grip due to the wheel moving back to it's static position. How do you keep the wheel from moving with respect to the chassis? Well, assuming your car has reasonably rigid suspension arms, then all you need to look at are the suspension bushings! The wheel can move with respect to the chassis because the bushings flex...especially old, stock rubber bushings. Sometimes simply replacing old rubber bushings with new rubber bushings is all that is required. However, on a modified car that posesses more horsepower than the designer's intended, upgrading to stiffer materials like nylon or polyurethane may be required. The ultimate solution is to use rod ends or spherical bearings at every suspension joint, but that is unreasonable unless your car will never again see public roadways. Anyway, by simply upgrading your bushings, the suspension bushings will not flex as much under strong acceleration, the wheel will not move far forward in the wheel well, the toe of the car will not appreciably change, and your tires will not lose grip. Wheel hop will have been eliminated.

In some cases weak shocks can allow a perturbed wheel to continue hopping up and down since the motion is not damped. This is a less likely scenario, but shocks should not be ruled out as a potential culprit.

The easiest (and cheapest) method to stop wheel hop is to get a ladder bar, sometimes called a slapper, and attach it to the bottom of the rear springs under the axle. The axle tends to rock back and forth (as viewed from the rear) when heavy torque is applied. In some old drag strip photos, you can actually see the whole frame of the vehicle twist when launching off of the start line. As the tire on one end gains traction it pushes the car forward, then the other side can gain traction by the axle rotating in the other direction. Slappers got rid of this by stopping the axle from torquing over too much. As the axle rotated, the slapper hit the springs with a rubber bumper, stopping the rotation and keeping the tire on the pavement. This was not completely efficient, but it did stop the average peel out from the stoplight wheel hop.

chithead 02-01-2011 04:31 PM

Oooooh that's good info.

erm 02-01-2011 04:46 PM

Google is our friend... ;)

sprintertech 02-01-2011 09:05 PM

thanks for the replies.....cant lower cause i got a heavy ass boat.....and i planned on finding some poly bushings for the rear control arms....but never in my life have i seen a four or five link hop like this.....those bushings must really be soft....

erm 02-01-2011 09:20 PM

They are pretty soft. That's why it rides so good! ;)

HoustonHemi 02-02-2011 02:30 PM

Hmm, back in the day, going to a 4/5 link was the 'upscale cure' for wheel hop,,,
Gots to be some soooooft bushings in our 4th gens,,,

dustin72 02-02-2011 11:14 PM

Anybody making some good urethane bushings for the 4th gens yet? I have terrible wheel hop every time I leave the burnout box at the track. Launching is no better.


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