Snrub

Hi,

I'm getting what I believe is excessive wheel hop in my car. I'm looking for some advice. I know there have been other threads on the topic, but I'm not satisfied with the information they contain.

Symptoms:
If the roads are wet I experience wheel hop accelerating from a stop with medium throttle. It will also do it from a roll if I floor it in first once it the engine is higher in the rev range. If I am turning it seems to happen very easily. For instance, I experienced it today turning right onto a road from a stop, applying medium throttle around 3-4000 rpm (I didn't rev above 4k). I had someone else who owned a RX-8 in my car and they felt my car had more wheel hop than normal.

Troubleshooting Thoughts/Info:
* Shocks - I find shocks are very difficult to diagnose unless they're completely shot. I don't think mine are completely shot. Supposedly softer shocks can actually help wheel hop. Is it possible the different shocks in a Shinka contribute to the problem?
* Engine mounts - The mounts look okay to me, no obvious tears or leaking. In a previous car I resolved a wheel hop issue by replacing the mounts.
*Sway bars - Supposedly has next to no affect on this issue.
* Other mounts? It doesn't seem to me like the diff mount or the tranny mount would affect this issue as much.
* Bushings - I have a lot of trouble believing I have catastrophic bushing failure (haven't seen anything obvious with a superficial check)

I'd rather not start dropping money with random part replacement. For engine mount options it seems the Mazdaspeed Japan or Megan Racing units are the best option. I'm not certain which might be a better option.

Any thoughts/ideas?

Thanks!

Charles R. Hill

iTrader: (7)

Stiffer swaybars and springs usuall help with wheelhop. No need to be extreme with either component, either. You do want to make sure your suspension bushings are not shot, first.

TheWulf

iTrader: (4)

I've been having that problem for a long time. New sway bars and bushings, new shocks and springs, still happens.

I'm considering a diff brace but I'm not optimistic. I'm thinking my new springs just aren't stiff enough.

Charles R. Hill

iTrader: (7)

What worked for me was Racing Beat springs, Racing Beat swaybars, and a set of Nitto NT-555s in 245/40-18 on the factory wheels. The rear squats, I get some wheelspin (even with nitrous use) and the car steers straight and true.

TheWulf

iTrader: (4)

I considered going over to RB springs, but remember the problem I had with one of my struts where the inner hex cavity was missing from one of tips on the back passenger strut? I have some hesitation about pulling that strut off as I'm not sure I'll ever be able to put it back on.

Tires may be a contributing factor here too. I'm running Star Specs which may stick a bit too much and refuse to spin.

Snrub

I'll check the bushings. RX-8's don't come from the factory with this level of wheel hop do they? I can't imagine stuff is worn out after so little millage (I've had the car since 13k miles and it's now at just under 30k).

monchie

So little mileage on the car, why is it happening? I don't know exactly and i don't know your driving habits. For my opinion, i think it's your shocks, have it checked.

40w8

Are you sure it's wheel hop?

I've got a 07 gt 6spd auto so I'd be hard for me to get wheel hop, but when I'd turn right and jump on it, the DSC would go off pulsing the brakes to stop the slip.

So, after a few years of track days, and alignments, I straightened up the rear wheels to a -1.65 camber instead of the -2.1 they had, and now it handles like a champ, and the DSC only goes off if it's wet or I provoke it.

CRO8TIA

Why would a Diff brace help, the 3rd member is solid mounted ?

Charles R. Hill

iTrader: (7)

No, it is not..... it "floats" with the help of the motor mounts, the PPF, and the rear suspension bushings.

CRO8TIA

Ok, what Im saying is, the 3rd member is "mounted" to the chassis via bushing's, it doesnt "hop" like a live axle . So, please tell me, how a diff brace would help ? And, when it "floats", it moves millimeters,until it torque's up .

Snrub

I'm pretty sure it's wheel hop because I don't usually have the DSC/TCS on. Also, I experienced wheel hop years ago in my TII FC.

Regarding a diff brace - I could theorize it would help because there is some movement which could potentially negatively affect the suspension.

Charles R. Hill

iTrader: (7)

Not that I am a big believer in differential braces but here goes;
Since the entire driveline is isolated from the chassis (by Mazda's intentional design) there is plenty of opportunity for the driveline to induce wheelhop from the varying forces and flexions upon acceleration and the varying surface changes on the roadway. Plus, the bushings throughout the entire isolation system (motor mounts and suspension bushings) are rather soft because that is what the average driver prefers. Not to mention that the PPF, itself, is prone to a bit of flexing under torque. Hell, they are prone to breaking at around 420 h.p. or so.

Brettus

iTrader: (2)

Just some of my thoughts - don't claim to know the answers .

Sway bars : Can't see how they would make any difference as they do nothing unless one wheel is higher than the other . I imagine wheel hop as both wheels up and down in unison - could be wrong .
Springs : stiffer springs might help but can't see them curing it altogether as they will still be prone to resonance
Shocks : The shocks have to make a big difference if they can slow down the resonance of the springs sufficiently
Wheel/tyre combo : must make a difference
Bushings and diff brace : no idea how much this would help
Weight : i know this has a big effect on my car . Big fan of battery relocation to rear and anything else you can do to get more weight over the rear .

would be great if someone were to do some tests on this to see specifically what had the most effect .

Charles R. Hill

iTrader: (7)

1) Wheelhop rarely (if ever) happens with both wheels moving in unison so swaybars can directly help as they did with my own car.
2) Springs help because they cause more force to be exerted before uncontrolled suspension action to happen.
3) Yes, exactly, and for the same reason as #2.
4) Tires more than wheels, fershure, but wheels often influence the tire dimensions so they kinda go hand-in-hand.
5) They matter for the same reasons as the dampers.
6) This is not nearly as important as all the other points we are discussing, although rear weight does help in a drag-racing context.

Your request was granted back in 2005 when I was street-racing with nitrous and blowing away GTOs, Evo8s, STis, and the like and I wrote about all this way back then, too.

Brettus

iTrader: (2)

Thanks for the reply - good info .

As far as the testing - did you ever like have wheelhop on stock setup - change one thing and eliminate it ?
I think most people would like to know what one change would have the most effect - seeing as how costly it is to change everything

Snrub

To update this thread:
I tried installing new Megan racing engine mounts (rubber). The wheel hop was the same, but the weirdness I was feeling when corning (eg. turning left at a light from a stop and accelerating medium+) went away.
Next I installed Mazdaspeed shocks and new stock rear springs. The wheel hop is pretty improved, but still more than I think should occur (ie. very little). The car use to bound over certain types of bumps and the rear end felt a little lose when going through a tight corner quickly. It's improved things. One of the rear shocks was leaking.

TeamRX8

iTrader: (25)

you are on the right path. It is a compliance damping issue; the shocks/valving, suspension bushing compliance, engine/differential mount compliance, tire sidewall design and air pressure setting compliance, etc.

Snrub

I think I'm perhaps now at the point where my car is like other RX-8s. It seems ridiculous that I should need to go any further. I'm glad I have done what I've done, most of it was needed, but not in a state of critical failure.

I can believe the tires are a contributing factor, but I don't think that explains the issues in slippery conditions.

I have a really hard time believing that bushings are the problem, the car simply isn't old enough to have ruined bushings that aren't simply a visible failure (ie. I can't see anything obvious). Additionally, aftermarket bushings for this car are expensive for some reason. Energy suspension makes a kit for almost every bushing on the FC RX-7s for like $80. Single bushings for this car go for that price.

REDRX3RX8

You never did tell us your alignment settings.

I had to align twice to get it where I wanted it, and after the first alignment with the rear camber at -1.9, it would still lose rear traction even with my "weak auto trans".

I could only turn it down to -1.65, but that worked.

Snrub

I'm going to get one done soon, but I'll put it to stock.

Snrub

The alignment really did the trick. There is a big difference. I think the problem is now completely resolved.

40w8

Great!

I'm the guy that told you that would fix it twice.
It would have with no other parts, since my car did it new.

Brettus

iTrader: (2)

Recently did a bit more work to try eliminate my so-called 'wheel hop' . This was happening under wheelspin on anything but a dry road and smooth tarmac.

Fitted HKS hypermax coilovers with adjustable dampers to rear - small improvement but still there .

Fitted near solid (nylon) diff mounts . Problem GONE !

It seems the issue I've had all these years was not wheel hop at all but the diff bouncing around the extremely soft stock diff mount rubbers.

However - a major drawback from fitting these has been the increase resonant vibration and noise into the cab . Definitely would not recommend it in a daily driver. Thinking I might try machining my own out of something a little more forgiving than Nylon - Delrin perhaps .

HiFlite999

iTrader: (2)

Did you solve this problem? I was wondering if this SuperPro Differential Center Support Bushing Kit - 70K Durometer for RX8 with durometer 70, or its companion of durometer 80, would be a good compromise?

Any guess as to which one to choose?