PorscheG96

I did my first DE of the season yesterday and noticed a rumbling/vibration from the back of the car under hard cornering that became more noticeable throughout the day. Doesn't happen when driving at speed down the straights and seems about the same on both left and right hand corners. I checked wheel and hub nut torques then got under the car and checked all shock, sway bar, and rear suspension bolts that I could see or get a wrench on but didn't find anything. One thing I did notice was more and more rubber build-up on my rear tires - has anyone experienced this and think it could cause the symptoms above? Otherwise, I'm not sure if my CV joints are toast? There are zero symptoms on the street, only at the track. Thanks.

FrenchToast

CV joints usually will rumble no matter how the suspension is loaded, and you can typically hear them just driving around at paddock speed.

What size tires are you running? If you're running 275 or wider or your wheels are spaced out check for tire rub. Look on the tire sidewall/shoulder for evidence of this, also on the inner fender wells.

Does it make noise under hard acceleration too, or just cornering? Is the vibration car speed dependent? Engine speed dependent? Or neither?

Get under the car again and firmly wiggle all suspension components to check for play. Just with your hands, no wrench. Shocks, sway bars, etc. Couldn't hurt to remove the wheels and put them back on, they may not be seated correctly. Although that problem would rear its hear in the paddock too.

Also check the brake disc shields, exhaust shields, hangars, anything really, for any play.

I would recommend posting this in the main 924/944/968 section, it gets more traffic.

If you have a DE tomorrow too I would recommend sitting it out until you solve this.

Good luck!

PorscheG96

265 width tires with factory offsets and -2 deg camber so I'm pretty sure they aren't rubbing but I'll check the inner wheel wells anyway. Outer walls of tires and fender lips don't show any rubbing. Vibration is car speed dependent, not related to engine speed. I checked the exhaust hangers, shocks, and axles by hand...should there be ANY axial play on the axle or is a tiny bit OK? I firmly shook each of the mounted wheels and they feel solid.

No more DE for about 6 weeks. Thanks.

FrenchToast

Any play in the axle should be longitudinal (parallel to the axle lengthwise). There shouldn't be anything other than that. You would hear a rumbling driving around at street speed if its the CV joints.

If you have a local shop maybe take off your rear wheels/tires and have them re-balanced. Also look at your tires. You may have flatspotted tires, or may have blown a cord. All of these three things would cause a vibration. I think that should be the next thing to check is balance and tire condition.