harrjar

I replaced the stock wheels and tires on my 6MT Enthu. I went with 18" 5Zigens with Nitto NT555 tires. All of the specs are in my block at the bottom but for convenience:

F: 18x8.5 245/40/18
R: 18x9.5 275/40/18

I don't think the offsets that were advertised by the place I got them from (the numbers in my block) were actually what I ended up with. I'll have to check the tags on these wheels to see exactly what they are.


The bottom line is, I'm pretty sure that I went with a commonly chosen wheel size/tire size combo. But immediately after having them mounted I noticed that once I hit about 70mph I start to feel a vibration in the car. It's like a cyclical shuddering. This shudder surges though my butt, the stearing wheel, the pedals, even the shift ****. As I accelerate to 90 mph it only gets worse and more noticeable.

I have had two alignments as well as a tire swap from side to side (in the front, trying to slow feathering?), and a four-wheel computer balance. The vibration is still there. The dealership is telling me that they don't know how to fix it and their techs drove the car on the highway but didn't notice anything. I don't think they drove fast enough because I don't know how you could miss it.

Does anyone know if I made a mistake with the tire/wheel sizing, could the wrong offsets cause this problem? Could the wheels themselves somehow be out of round? What else could cause the problem, assuming my balancing and alignment were correct?

This problem is really bothering me, I can't drive the car very fast and I'm curious if whatever is causing the vibration is affecting tire wear also.

Thanks for the help.

RacerX

Are your wheels hubcentric? If they are not, did they come with hubcentric rings?

If your wheels did not come with rings to match your hubs, this could be causing the vibration you are talking about.

jckolnturn

iTrader: (1)

The place you bought them from doesn't know what's wrong? How much experience do they have with z's?

harrjar

Well, I've been talking to the vendor and they have sold this wheel/tire combo to a ton of people. Actually, the vendor himself has this setup with no problem. So, we're still trying to chase it down.

The wheels are lug centric but that doesn't mean that hub rings wouldn't help. It's possible that Big O just doesn't have the experience with these kinds of wheels and they aren't getting it right.

I'm going to call a contact at 5Zigen to see what they suggest and probably give Discount Tire a crack at the balancing.

If that doesn't work, I guess I'll put my old wheels back on to see if it goes away (I know it wasn't there before). If not, then it could be the alignment and I'll go yell at the dealership again, maybe they'll pay an outside place to align my car...wishfull thinking...

Thanks for the replies!

MonkeyBoy

I have this problem as well and found out it is due to not having the correct hub-centric ring for the rims that I bought. I would look at the ebay autions online from discount tire direct and get the appropriate hub-centric rings for the 5Zigen rims.

EddieJr

First, get the hub-centric rings from Big-O. They should have been included with the rims. Second...If they have a Hunter 9700 RoadForce balancer pay the extra to get them MATCH balanced.

If that store doesn't have one, find a place that does it will solve your problem. Also the alignment will have no effect on wheel vibration.

havabooz

and if all that doesnt help it then one of your wheels might be bent

one of mine is bent..but i dont even feel the vibration..so yours must be reaaaaaly wobbling

good luck with everything..

D'oh

If you want to do a quick check, just loosen your lug nuts, and jack up the car.

Then, gradualy tighten each wheel in a star pattern (tighten every other nut until it just touches the wheel, then go back and tighten each one a bit more, and then a bit more, etc) Finally, when you have the nuts as tight as you can get them with the tire off the ground, lower the car until the tire is touching the ground and fully tighten the nuts. This process will be sure to center the wheel on the hub (since the nuts are cone shaped). If the tire place mounted the wheels with an impact wrench and fully tightened one nut before installing the others, it is possible for the wheel to be shifted a bit.

When I first got my race wheels I forgot to get the hub rings and had to run a couple AutoX's using the lug centric approach. It worked fine (no probs @ the races or on the highway to and from) but is was a pain. I therefore went back to Discount Tire and they gave me the rings for free (should come with the tires to match the Z's hub size).

Good luck!

-D'oh!

harrjar

Hey guys, thanks for all of the responses. I called the US 5Zigen office today and they were very concerned. The said an extremely small percentage of wheels could possibly be out-of-round and if they couldn't find a solution for me, they would replace the wheels so that they can analyze mine. I can't believe the service I got from them! They told me that the rims are specifically designed to not require hub rings. Nevertheless, they feel that it's probably easier to get a good mount of the wheel (for inexperienced people) with the hub rings. So they put the proper rings in the mail this afternoon (about 30min after I called them), free of charge.

I'll see if Big O has the machine that EddieJr talked about, have them match balanced, and then put the wheels on the car using the rings.

I'll let you guys know, thanks again!

dbasteve

I friend of mine had a vibration problem like this and couldn't work it out until he organised an on car balance test.

The lock nut (lug nut) was a different weight to the rest of the nuts and this was the reason for the prroblem. They even moved the lock nuts to another stud to prove this theory.
He went out and bought another set of lock nuts and it went away.

Sounds a bit far fetched but it was proven to be true.....