Wheel Hop


Fonzu

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May 31, 2007
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Well, I've searched this forum and found no information on Wheel hop. I moved on to search on the web and found some useful information that I wish to add;

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.

What doesn't get rid of wheel hop?
As mentioned earlier, a lot of people throw the wrong parts at the car in an effort to eliminate wheel hop. First, springs and sway bars will generally not do anything to promote or prevent wheel hop. Additionally, suspension settings, such as camber and toe, will generally not help the issue. It is the change in toe that leads to wheel hop, not the static setting. Tires do not cause wheel hop, though they do determine the grip level at which wheel hop occurs. For example, race tires, with their increased grip over street tires, will not break traction until you reach a higher level of acceleration. Some people might think that race tires solved their wheel hop problems, but in truth they merely changed their "wheel hop acceleration threshold" from a level below their launch acceleration to a level above their launch acceleration. Once they increase their horsepower to the point where they can accelerate enough to once again reach that threshold, their wheel hop will return.

Limited-slip differentials will also not prevent wheel hop. They may increase the acceleration threshold at which wheel hop occurs (much like installing race tires), but once again an increase in horsepower will eventually reintroduce the problem.

Check your shocks. If they are not malfunctioning, then you need to increase your bushing stiffness.

Just thought it could help anyone on researching the subject :nice:

Source:mc²racing
 



Fonzu

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May 31, 2007
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That means a lot coming from someone like you blinx :)

Was discussing this issue with a friend of mine (tuner) and he also suggested that soft-rated springs may also cause wheel hop.

I'll try to find some upgraded bushes to replace the oem on my car. Have looked at Energy and Hardrace but the price difference is wow!

Any opinions Blinx and all the rest? :nice:
 


stevenEK9

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Mar 11, 2007
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Stiffer engine mounts get rid of wheel hop, less energy is absorbed by the engine mounts especially with billet ones like hasport/innovative so more power is transmitted throught eh axles to the wheels

Weight distribution is key too, with a raked stance more weight is thrown over the front wheels

Idealy if you want to go rosejoints, you don't want to be rosejointing EVERYTHING, the front inner wishbone bush is a good place though since it controls the toe on the front, spherical bushes at this point will maintain the toe alot better
 


SPek9

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I had bad wheel hop going hard from 1st to 2nd gear, fitted energy engine mount inserts to the lower torque positions and it helped but did not cure the problem. Only after fitting the energy inserts to the awkward rear engine mount attached to the subframe did the wheel hop dissappear completely, made a big difference:nice:
 



blinx9900

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That means a lot coming from someone like you blinx :)

Was discussing this issue with a friend of mine (tuner) and he also suggested that soft-rated springs may also cause wheel hop.

I'll try to find some upgraded bushes to replace the oem on my car. Have looked at Energy and Hardrace but the price difference is wow!

Any opinions Blinx and all the rest? :nice:

On what? Bushings?

Stiffer engine mounts get rid of wheel hop, less energy is absorbed by the engine mounts especially with billet ones like hasport/innovative so more power is transmitted throught eh axles to the wheels

Weight distribution is key too, with a raked stance more weight is thrown over the front wheels

Idealy if you want to go rosejoints, you don't want to be rosejointing EVERYTHING, the front inner wishbone bush is a good place though since it controls the toe on the front, spherical bushes at this point will maintain the toe alot better
Agreed, i ditched the torque mounts and just filled the remaining 3 with urethane and i have zero wheel hop even when i use the launch control, i also have R comp tires so that helps...
 


Fonzu

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May 31, 2007
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@blinx9900 - Yep, I've read that the HardRace are the closest you can get to "Rosejoint" stiffness but keeps the car bearable on the road.

I'll take a look at the engine mounts as well. They shouldn't be the cause though, as I've put inserts in about 4 years ago. Is that enough time for them (the inserts) to need replacing?
 


stevenEK9

trackattack
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Inserts I always see as a temporary repair if you are fitting them to worn OEM mounts

New mounts will always make a substantial difference, I would always reccomend billet ones now that I run them, get the power down SO well

Although my 75A innovatives give off mega vibrations, on idle you can even see the front bumper vibrating if you look closely on the outside :lol:
 


R883

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Good read !!! cheers

Just what i was looking for after getting loads of wheel hop at Crail yesterday
 


Banzai43

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Jun 27, 2008
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I had wheel hop on my car...

I found that if i fiddled around with the tyre pressures it made a huge difference...

I also hav energy torque mount inserts..

but to be honest the tyre pressures made the most difference..
 


SPek9

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Did you need to lower or raise the pressures to reduce wheel hop? What pressure was best?
 


Banzai43

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I got them at 30psi front and 28psi rear right now..

So thats down on what they should be if i remember right...

Im running 17"s that the moment... so it might vary on different sizes..
 



Fonzu

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May 31, 2007
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I appreciate your gratitude for this post.

I have been looking around and I think that the only way that I can totally eliminate wheel hop is by getting these:

Full-Race Motorsports

The only problem is that they are currently out of stock and will have to wait another 40-50 days:((

Until then, I'll try to raise the tyre pressure to stay safe.

Oh, btw, I will still probably replace all the bushes of the car's underside. The car will certainly improve as a result.
 


blinx9900

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Just went from 100 treadware NT01 to 200 treadware RT615's and this is totally true!! my wheel hop is back :(
 




J700OCK

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Jan 22, 2008
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tiger seal . i done it but ideally you need to fill them and leave them to dry in warm atmosphere for around 3 days
 


R883

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perfect cheers lads

Ive got a couple of tubes lying about :)
 


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