Sponsored

Understanding Wheel Hop And Soultions.

Mikeiscoo2

Well-Known Member
Joined
Aug 19, 2014
Threads
44
Messages
910
Reaction score
161
Location
Fort Myers Fl.
First Name
mike
Vehicle(s)
2015 Mustang GT
Credit from this article goes to "MC2RACING" for their amazing write up.
Link: http://www.mc2racing.com/tech/20061012a/



What is wheel hop?
Wheel hop is a nasty action whereby the driven wheels of a car violently 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 wheel spin 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.
Sponsored

 

BMR Tech

Well-Known Member
Joined
Sep 4, 2014
Threads
168
Messages
5,141
Reaction score
3,691
Location
Tampa, FL
Website
www.bmrsuspension.com
First Name
Dion
Vehicle(s)
2018 GT, 2010 GT500, 2019 F-150 5.0
Simply put, wheel-hop is caused from a lack of traction AND lack of rear axle assembly stabilization.

If a car does not have traction issues, and has a rear axle assembly that is stabilized as much as possible, then the car will not "hop" or shake the rear wheels.

There are a few things I would like to add / correct about the above writing.

Springs: Stiffer spring rates WILL help with wheel hop, as they help stabilize the wheel vertically.

Camber/Toe: This is a tough one, and typically they do not help with wheel hop characteristics. That said, going back to the causes of wheel hop, traction is a major factor. On the S550, under acceleration the rear camber is very far from optimal. The more negative or positive camber you have (away from zero) - the less contact patch the tire has to the surface = more tire spin.

Excessive Toe changes can also cause tire chatter. The force of the engine torque pushes the chassis forward, fighting the directional design of the tires.

At the end of the day, the best way to start reducing wheel hop on the S550 is to:

-Stabilize the cradle with solid style bushings (cradle bushings)
-Stabilize the Differential with solid style bushings (diff bushings)
-Stabilize the RLCA and Upper Camber Link with bearings/Delrin (remove rubber)
-Stabilize the Vertical Link with bearings/Delrin (remove rubber)
-Run a stiffer rear spring
-Use a better rear shock

And of course, all of the above combined with a softer compound rear tire that promotes traction, should seal the deal.
 

smokinzx14r

Well-Known Member
Joined
Mar 2, 2015
Threads
64
Messages
1,591
Reaction score
355
Location
ST Petersburg FL
First Name
Lee
Vehicle(s)
2015 GT A6 3.55 Gears ..
The problem is pretty clear from what you guy have posted .. After changing my axles and spending time under the car I can see the weak points pretty clearly .. Toe bars stock are very wimpy and the bushing are so darn soft .. In fact all the bushings feel real soft ..Top that off the bushing are hollow in spots making them even weaker ..I can wait to see what the complete BMR package looks like ..You guys are pretty close to offering a full package ?
 

smokinzx14r

Well-Known Member
Joined
Mar 2, 2015
Threads
64
Messages
1,591
Reaction score
355
Location
ST Petersburg FL
First Name
Lee
Vehicle(s)
2015 GT A6 3.55 Gears ..
Simply put, wheel-hop is caused from a lack of traction AND lack of rear axle assembly stabilization.

If a car does not have traction issues, and has a rear axle assembly that is stabilized as much as possible, then the car will not "hop" or shake the rear wheels.

There are a few things I would like to add / correct about the above writing.

Springs: Stiffer spring rates WILL help with wheel hop, as they help stabilize the wheel vertically.

Camber/Toe: This is a tough one, and typically they do not help with wheel hop characteristics. That said, going back to the causes of wheel hop, traction is a major factor. On the S550, under acceleration the rear camber is very far from optimal. The more negative or positive camber you have (away from zero) - the less contact patch the tire has to the surface = more tire spin.

Excessive Toe changes can also cause tire chatter. The force of the engine torque pushes the chassis forward, fighting the directional design of the tires.

At the end of the day, the best way to start reducing wheel hop on the S550 is to:

-Stabilize the cradle with solid style bushings (cradle bushings)
-Stabilize the Differential with solid style bushings (diff bushings)
-Stabilize the RLCA and Upper Camber Link with bearings/Delrin (remove rubber)
-Stabilize the Vertical Link with bearings/Delrin (remove rubber)
-Run a stiffer rear spring
-Use a better rear shock

And of course, all of the above combined with a softer compound rear tire that promotes traction, should seal the deal.
Kelly seeing that you are in Tampa and i'm in St Pete I have to ask ... Does your shop do the install of the parts you sell ? If so I would rather just have you do it and do a alignment when done..
 
OP
OP

Mikeiscoo2

Well-Known Member
Joined
Aug 19, 2014
Threads
44
Messages
910
Reaction score
161
Location
Fort Myers Fl.
First Name
mike
Vehicle(s)
2015 Mustang GT
Kelly seeing that you are in Tampa and i'm in St Pete I have to ask ... Does your shop do the install of the parts you sell ? If so I would rather just have you do it and do a alignment when done..
Yes im in Fort Myers as well only about 2 hours from you guys. I wouldn't mind this either.. looks like ill be buying the half shafts along with my NT05R's.
Sponsored

 
 




Top