back of car jumping

[dmitrikinaev]

Hey guys, i bought a silvia recently
It has a ca18det with a t28 of a 200sx, 3" all-the-way-thru exhaust, lsd and cusco suspension (i think the suspension on the back is stock though)

anyway when the wheels spin, in first or second, sometimes the whole car jumps up and down, you can see the gear knob moving erratically. This only happends at high revs though. I think it could be juist because of the combination of grippy tires (just 195 with good tread) and lsd. I don't think silvias have traction constrol but this one acts as if it does. Does anyone have any ideas? Thanx - Dmitri.

[AKADriver]

Wheelhop. It goes something like this...

The tires grip, which loads the suspension. Because of the suspension design of these cars, when the suspension is loaded by acceleration you lose grip and the tires break loose. The tires breaking loose unloads the suspension and by doing so you regain grip. Repeat until the car starts moving.

The loading/unloading motion of the rear suspension is what you're feeling.

[mrdirty]

AKA: Is that a design flaw, or does it have some benefit?

[AKADriver]

Flaw? not really...

Remember that the car WAS NOT designed to drag race.

It's due to two contributing factors... compliant stock bushings and the "anti squat" layout of the suspension arms.

You can eliminate the bushing issue using subframe spacers. There's a configuration of subframe spacer placement that keeps the rear subframe from contributing to wheelhop.

[Zemus]

I have that same problem with my stock car and wider tires, its very annoying, my car wont burn out, it just freaking hops, so your saying all i need is new bushings, or is it just those subframe one

[nismofeind]

yea I got wheel hop too.

my s13 is pretty old with no lsd. I had always thought if i replaced the shox and springs that it would stop it. is this true.

[GlacierFreeze]

I think you could soften or harden (one or the other) your shocks (spring rate?) and that might do something, right? I know different shocks are good for different things, just don't know which ones with what.

[weirdstyles.net]

I think we all have wheel hop, its just never bothered me. What does bother me is the fact that after hitting a bump, my rear feels like theres a 400lb gorilla on the back jumping up and down...


freakin shocks...

[N1ceDrgn]

I 'had' the same problem with the 180 I had. I am thinking about doing the same thing with my 240. What I did to correct it is I completely eliminated the bushings all together. It's A LOT rougher on the frame but it does take care of a lot of the hop, almost to nothing. I had a problem with bushings going bad and versus dropping the money to replace them at the time, I simply got a hold of an impact gun and locked them down. Either eliminating them altogether or wrenching them out as the locking nut got railed by the impact gun. The end result was a grunt, the a$$ end would kick to the side and I would launch. One thing to keep in mind, once you get to a point where you're putting out a helluva lot more power than you are now, at that time you might start to have some problems again. Like I said, this is a temp fix, can be a permanent one if you want it to be though...