bad vibes

[KennyG]

I am experiencing some bad vibrations while driving my 88 Targa. My 1st thought was tire balancing, but no such luck. It's most noteable at about 35 mph & 75 mph. Could this be a motor mount issue?

[IROC]

I'd still suspect tire balance. 35 and 75 are really close to the "typical" speeds at which tire balance issues are apparent. I'm assuming that you're already had them balanced? I once had to go to three stores to find a place to balance my tires correctly. Mostly it's a problem with the "I don't really care" techs working the machine.

If your tires are in good shape (worn tires can also cause problems), then I wouldn't rule out balancing just yet.

Mike

[subdewd]

if the balancing was don correctly, big if, might be atire that's
got a belt seperating. How old are the skins your rolling?

[Lothar]

Try playing some Beach Boys music while in the car. You might get some "Good Vibrations" to cancel out the bad ones.

Sorry, it just popped into my head when I read your post and I couldn't helpo myself.

[john walker's workshop]

tire balancing machines are notoriously inaccurate. most are not calibrated regularly. you could balance a tire/wheel perfectly, according to the machine, take it off, remount it to the machine, and it would show an out of balance situation again.

[RickM]

Over the years I've had my share of front end vibration woes.

Repeated balancing and suggestions to replace from control arms to ball joints....most times (not all) the problem vanished when I replaced the tires.

[RallyJon]

Go here and find the nearest shop with a GSP9700:
http://128.242.141.111/pub/search/FindGSP9700.cfm

Then pay them to do a "road force balancing". It usually costs extra, plus even more if they have to remount the tires a lot, but it really is worth it.

[RoninLB]

Originally posted by RallyJon
[BThen pay them to do a "road force balancing". [/B]

is that balancing on the car by spinning the wheel & tire?

[RallyJon]

They actually apply "road force" to the spinning wheel/tire with a roller and measure for slight out-of-round conditions, which translate into more pressure on the roller in certain spots. I think it's all about matching construction tolerances--if one wheel has a low spot, match it with a highest/heaviest spot on the tire.

It minimizes weights needed to balance, and can solve out of round problems that normal balancing doesn't touch. I think there's a FAQ on their web site with more detail.

[Embs]

Originally posted by RallyJon
Go here and find the nearest shop with a GSP9700:
http://128.242.141.111/pub/search/FindGSP9700.cfm

Then pay them to do a "road force balancing". It usually costs extra, plus even more if they have to remount the tires a lot, but it really is worth it.

RallyJon is correct, the GSP9700 machine simulates the road with a pressurized roller system. A shop down the street has one. A huge difference was noticed on my large truck tires and on the 911. Normal spin balancing is very subjective.

[RoninLB]

Originally posted by RallyJon
They actually apply "road force" to the spinning wheel/tire with a roller and measure for slight out-of-round conditions, which translate into more pressure on the roller in certain spots. .

wow, never knew about that.. thanks.............Ron

[Superman]

Let me get this straight. KennyG is publicly complaining about his own vibes? 'bout time. I think that sax you play is just too small. Pink Floyd and Bob Seger both bring someone who can play one of those HUGS baritone saxes, and it sounds GREAT. There's your answer. Size matters.

Now, where's that guy who wants two more inches......

[KennyG]

Thanks everybody. I've had a lot of trouble with balanced tires in the past. It seems the larger the wheel, the more magnified the problem. These are 17's, and I had them rebalanced by the only shop I've found to be able to always provide a good balance. But maybe they had an off day.
But not one of you mentioned a broken motor mount, so that makes me happy.
I guess it's off to another tire shop.

[Harlan Chinn]

Kenny, Which shop have you been taking your tires and wheels to?

[KennyG]

Originally posted by Harlan Chinn
Kenny, Which shop have you been taking your tires and wheels to?

Speedware is the shop that normally does what others can't when it comes to my balancing. Usually.