Wheel skipping/hopping when traction lost

[TriggerFish]

Hi all,

Maybe this is something common, but I've not seen it discussed before, and I remember my old RX8 (on stock suspension and Pirelli tyres) used to do the same thing too.

Whenever the car looses traction, be it under power from a standstill, changing from 1st/2nd or 2nd/3rd quickly, or sliding the back end slightly in a corner (with or without power), it makes a horrific juddering noise/sensation that makes the whole car shake and trim rattle. Like wheel hop, but even when sliding too. I hate it, and it puts my partner going in the car in this weather as it will start to lock the rear diff (and therefore hop) very easily in this cold and greasy weather.

Now, my open diff 330d before it was written off didn't really do this (maybe in 5% of traction lost scenarios), and my E30 with an LSD definitely doesn't (that thing just slides seemlessly ).

Is this a common RX8 thing, or is this something specific to mine/indicative of something amiss? It's on PZ suspension (fitted by the PO) and has Dunlop SportMaxx tyres in whatever the standard size is (225/45?) at the factory pressures.

Cheers!

[mrspiller]

That’s traction control I think - does the dash light illuminate ?
Switch it off and try it , should do the trick
I’ve had both 330d and a 325 e30 and they were magnificent power sliding , probably die to the high torque
The 8 is hard to hold


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[Nickp47]

Do you have DSC turned on? I just ask because it kind of sounds like what happens when that kicks in

[TriggerFish]

The DSC light doesn't flash all of the time it happens. I turned it off yesterday and it still did it when pulling away from some lights, so I don't think it's DSC. I'll test again next time I drive it alone

[TriggerFish]

325 e30 and they were magnificent power sliding , probably die to the high torque
The 8 is hard to hold


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Especially when a stroked out 2.8l M20 The massively lower redline takes getting used too again when switching back from the '8 though!

[mrspiller]

The DSC light doesn't flash all of the time it happens. I turned it off yesterday and it still did it when pulling away from some lights, so I don't think it's DSC. I'll test again next time I drive it alone

You need to hold it in for 8 seconds at least ( I think ) for full disable . And some say it’s still on a bit
Easier just drop the fuse out


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[mrspiller]

325 e30 and they were magnificent power sliding , probably die to the high torque
The 8 is hard to hold


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Especially when a stroked out 2.8l M20 The massively lower redline takes getting used too again when switching back from the '8 though!

Oh my yes
Mine was standard
Owned 20 years ago


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[TriggerFish]

whilst echoing all the above, you still get a little wheel hop on the rx8 on launch with sticky tyres. its one of the only deficiency's of the rx8 chassis, and one i intend of spending some time getting rid of on mine.

[untakenname]

The design of the car with the PPF and driveline isolated from the chassis means wheelhop is one of the downsides.

On my old RX8 which was high mileage suffered from such bad wheelhop that it used to cause the radio to cut out due to the vibrations, changing to polyurethane filled engine mounts helped a little but the biggest gain was when I fitted a superpro performance diff bushing, the downside was increased noise but they now do softer version designed for road cars.

https://www.superproeurope.com/products ... cleid=6288

Screenshot_20210103-162759.png

[qwakers]

ill remember that. i also intend to machine up a set of solid steel bushes for the trailing arms

not recommended for a road car....

[warpc0il]

I think it's the trailing arm bushes that are designed to deflect slightly when cornering hard, to provide an element of rear-wheel-steer and are one of the secrets of the 8 handling ability.

I certainly recall someone on here reporting that polybushes (or was is Japspeed replacements?) caused the car to be much more unpredictable when close to the limit.

[mrspiller]

I think it's the trailing arm bushes that are designed to deflect slightly when cornering hard, to provide an element of rear-wheel-steer and are one of the secrets of the 8 handling ability.

I certainly recall someone on here reporting that polybushes (or was is Japspeed replacements?) caused the car to be much more unpredictable when close to the limit.

Japspeed replacements I’d say
My car’s much more stable to drive now I’ve put originals with polybush back on it
@ James
Yeah I’d check the bushes if get jumping , I don’t tend to get that even on half warm slicks
Just a slight pleasant slide on take off


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[Django91]

I've personally owned 3 different rx8s for different periods of time and the issue with axle hop when launching is something I've experienced with all three of them, especially if you launch at lower revs/closer to grip threshold.

When sideways if you are past the threshold and have wheels properly spinning seems like there is less hop. I'd never driven rwd before the 8 so I assumed it was how all cars behaved.

[TriggerFish]

The PPF is a good point. I wonder if that was alligned after the engine rebuild... Also a good point with the suspension bushes - although it got through an MOT fine, but maybe there's enough play to cause issues if not flag an advisory...

Anyway, I went out earlier and on the way home turned off DSC (as shown at the start of the videos) and got two different results. The first launch (the first I've done without DSC) I got the revs much higher than I usually would (by mistake), but it took off cleanly with just wheel spin, and then shifted into 2nd and 3rd cleanly. This was pulling out if a dusty(ish) layby.

The second attempt had wheel hop. You can see it when I first pull away, and again once on the dual carriageway when shifting into 2nd and again into 3rd. As DSC is off, it's ruled that out

Without wheel hop

https://youtu.be/0XJZ0oDLtu0

With wheel hop

https://youtu.be/kiUmxYgMn0U

[warpc0il]

So the answer is, if you want to avoid wheel hop, use more revs....

[Steve.82]

Anyone mind if I resurrect this one?

I did a driving school day at Prescott yesterday. I get a bit of a hop launching at around 3500 rpm which was good on dry rubbery tarmac. Any higher and too much spin. In the wet is horrible, really sets in until it gets traction. Sideways loss of traction in second is fine, wet or dry. Looking at the onboard, the lateral movement of the gear lever when cornering is mental.... Are 6 month old OEM engine mounts really up to that application or is it likely to be solvable elsewhere, like the diff bushes mentioned above? Or just something to live with for now...

[warpc0il]

The engine is mounted at three points; the engine itself either side plus the gearbox mount.
It might be worth checking the latter.

Excessive engine movement can also indicate a problem with the flexible joint between the cat & catback, as movement in the exhaust has a lot of leverage on the engine mounts. Sometimes, if the exhaust hanger mounts go soft, even a joint in good order can't isolate the movement.

"Tramping" can also be caused by poor rebound damping in the rear suspension, or just a harmonic that needs one element changed to avoid the frequency.

[Steve.82]

Ah yes missed the gearbox one... if it's as bad as the engine mounts were that may not be helping... will take a look.

The middle flex joint is ok, albeit with over compressed springs with the thicker aftermarket cat back flange. Might pop some nuts on the bolts to space it out a bit.

Damping is fairly firm already but will do some experimenting with settings and pressures at Shelsley in a few weeks. Nothing is quite like a super grippy rubbered in start line on a steep incline to set it off...