Eliminating wheel hop at the strip

[psulja]

So for those of you who take your car to the drag strip, what are some of the things you're doing to eliminate wheel hop?

Going to the drag strip next month and would like to take care of the inevitable wheel hop as much as I can so I don't explode my diff right away.

[DK Wolf]

Most people that experience "wheel hop" don't really know what it is. So just for redunancies sake... I'll cover all the bases.


Wheel hop generally relates to your tire jumping around when trying to accelerate as the grip snaps on and off. Most people get rid of those with control arm bushings being replaced with tougher material to avoid any overly "liberal" movement with gives way and the tires momentarily loses traction causing it to jump. If you have decent control arm bushings, I wouldn't be too worried.

However, many people confuse wheel hop with just a general lack of grip. And that requires a different criteria, taller springs with significantly lower spring rates and a higher rear ride height, larger diameter tires (obviously slightly deflated), and just trying to get your car to squat as much as possible (which really isn't a Miata strength).



If you do get wheel hop, and find a way to get rid of it eventually, I'd love to know. I never really considered making a Drag Miata, but I feel like the bug will eventually bite down the road.

[miata2fast]

I think one of the things that makes a Miata not as fun at the drag strip is that damn wheel hop.

Wheel hop is usually created when the front of the diff moves up for a moment and then bounces back down from the force of the ppf. The diff starts to bounce up and down which translates to the axle speeding up and slowing down. This movement is exaggerated by the wheel and tire which causes the wheel hop.

So, you want to eliminate the diff from moving up and down. One way to help is to install stiff bushings at the diff. Another way is to beef up the ppf or brace it somehow. How much this helps wheel hop, I personally do not know. I have purchased stiff bushings, but have not tested them yet since my car is down.

However, what really worked best for me to eliminate wheel hop was to use a set of biased ply tires for drag racing. I have used both 20x8x14 and 22x8x15 tires with very good results. The wheel hop went away almost completely. A word of caution when using drag slicks; the car does not handle the same, and tends to sway a bit on the track. I think that was one of the reasons the 20" was eliminated. It was pretty scary. The taller tire is not as bad, but is still there.

I still want to solve the wheel hop issue with radial tires, but that will take time.

[SM16RMSM]

Time for a Ford 9" solid axle swap.

[miata2fast]

9334

[SM16RMSM]

I bet those weight the same as our little cars do, truck axles. :lol:

[wannafbody]

If you have adjustable shocks trying cranking up the rebound.

[Hyper]

you guys need to brake a few factory diff in order to understand why i upgraded mine. The real problem with miata diff and excessive power, less say with race tires is that excessive vibration due to wheel hop will actually brake something. inside your factory diff.

In attempt to resolve the issue

you can beef up the diff by putting stronger diff mounts
you can brace the diff with PPF and chassis to reduce vibration
If you have adjustable shocks trying cranking up the rebound.
you can install stronger rear springs to reduce the car from squatting as well as install a beefier rear swaybar

the last thing you can do without getting things complicated is to keep the car balanced, for a drag car you want the weight to the rear tires. and pay attention to weight on driver's to passenger side. ... now..

to get your miata to another lever and have the ultimate launch, there are other things you can do.
the first thing that comes to mind is the OEM differential caps will not take the abuse for a long time, excessive wheel hop will disintegrate them completely, they are miata achilles hill in my point of view. pay attention to this part, open the diff remove one and understand what they are made off, do your search on them to prevent your expensive LSD or Torsen from failure

Last one of the things you can do aside for getting rid off the stupid IRS suspension is buy an electronic boost controller. The one I am talking about is expensive indeedbut will increase 1/4 times period. I know is cool to show off. show everybody how your miata smoke the tires but the real racer is not concerned about this, he only cares about doing a fast pass period. With an electronic boost controller specifically one that is controlled with CO2 you can do a lot of things to increase speed and reduce 1/4 miles times. This stuff is expensive indeed but in the real world of drag racing is what big dogs have in their cars.

Google search , Read about AMS - 1000

[DK Wolf]

this is like wheelhop... but backwards

http://www.youtube.com/watch?feature=player_embedded&v=cWBBnpwqsR0

[tsingson]

Holy Sh!t! I was not expecting that to happen.

[miata2fast]

Did you see how bad the drive shaft was shaking on both runs? Ouch.

[psulja]

So after a day at the track, as expected I had issues with wheel hop. I started the day with my coils on full soft in the rear and the wheel hop was terrible at the top of first, causing me to shift early into second, resulting in a mid-13's run.

I stiffened up the rear a little bit and tried to bring the power on a little more smoothly in attempts to reduce wheel hop and by the end of the day I had almost eliminated it just by controlling throttle inputs. My final and fastest run of the day I had pretty well no wheel hop at all, I smoothly got on the throttle, once I felt like I was about to hop I let off for a split second and got back on it.

I already have poly diff bushings.

Over the winter I will be replacing all the remaining bushings on the car, getting new coilovers and swaybars, and will see how much that helps. Biggest thing is I'll be picking up a set of slicks simply because I really want to cut down my times. But I will likely do a few runs on street tires at the first event next spring to see how all the suspension work helped out.

I was having issues with wheel hop on the street as well, so if I can eliminate it with new bushings that'll be a good thing.

[miata2fast]

I pulled the rear sub-frame to clean and paint, and am in the process of installing delrin bushings on my diff mounts. In doing so I observed a few things.

First of all, even with the new bushings, the diff will float up and down the retaining shaft on the sub-frame. Also, the hole drilled into the delrin bushing is not a tight fit on the shaft. This allows the diff to pivot changing the pinion angle drastically when not attached to the PPF. I know there has to be a reason for this built in play, but I think it is contributing to the wheel hop substantially.

The delrin bushing kit has two pieces. One presses into the diff wings, and the other fits over a modified retaining plate that fits over the shaft on the sub-frame, and is secured in three places. When everything is tightened down, the diff is not sandwiched tight between the sub-frame and retaining plate. I am thinking of placing a rubber shim between the two delrin pieces or between the sub-frame and the top of the diff mounting wings to keep the diff from moving up and down, and to lessen the amount of pinion the diff can freely move up and down when not attached to the PPF. My thinking is that the PPF will no longer be the only thing keeping the diff from moving.

Discuss.

[Hyper]

I pulled the rear sub-frame to clean and paint, and am in the process of installing delrin bushings on my diff mounts. In doing so I observed a few things.

First of all, even with the new bushings, the diff will float up and down the retaining shaft on the sub-frame. Also, the hole drilled into the delrin bushing is not a tight fit on the shaft. This allows the diff to pivot changing the pinion angle drastically when not attached to the PPF. I know there has to be a reason for this built in play, but I think it is contributing to the wheel hop substantially.

The delrin bushing kit has two pieces. One presses into the diff wings, and the other fits over a modified retaining plate that fits over the shaft on the sub-frame, and is secured in three places. When everything is tightened down, the diff is not sandwiched tight between the sub-frame and retaining plate. I am thinking of placing a rubber shim between the two delrin pieces or between the sub-frame and the top of the diff mounting wings to keep the diff from moving up and down, and to lessen the amount of pinion the diff can freely move up and down when not attached to the PPF. My thinking is that the PPF will no longer be the only thing keeping the diff from moving.

Discuss.

you can eliminate half of the problem by bracing the tranny and engine with the chassis. Okuyama or Carbing used to sell a kit also moss used to sell a kit. Remember that all factory miata have a PPF so any movement coming front the motor will transfer everywhere in the driveline. The transmission brace was great for drag racing as it allowed you to shift gears without any issue. Unfortunately they also vibrated enough to drive you insane after an hour of so driving but it was good preventive insurance for those seeking to protect the 5speed tranny. These part was discontinued by all vendors, perhaps with enough interest someone can design one again.

[psulja]

Diff braces seem like a really good idea to help the problem.

Also, one thing to note from my last track day; stiffer dampening on the rear coils helped reduce some of the wheel hop. I think overall just stiffening things up back there to reduce movement should help.

I currently am considering a RX7 TII Transmission swap, meaning I would have hard mounts for the trans and need to fab up hard mounts for the diff instead of using the PPF. I think this might help out with the wheel hop situation as well. Correct me if I'm wrong, but that's how I understood it, the PPF is allowing some of that movement of the diff, creating wheel hop?