High-Speed Vibration

tsupranami · 02-12-2009, 05:35 PM

I've had more issues with tires and tire shops than I can remember. I'm 41 years old, and through my many years of tire-buying experience I have found a lot of shops don't have folks that can truly identify (or are willing to identify) tire/wheel problems.

It has usually been up to me to carefully watch them spin the tire on the machine and watch for runout.

Remember, you can balance an absolutely square tire on a spin balancer by simply adding the right amount of weight to the center of the sides, but it won't roll smooth across the ground.

Don't rely on the "tire guy" to tell you everything. If it is their tire(s), they have a vested interest in NOT telling you about what they might consider acceptable tire runout. They lose money on warranty exchanges.

I have contacted several tire manufacturers in the past for their runout specs, and they are usually in the >.05" lateral and radial range. This is almost visually imperceptible. Only a runout gauge (a dial indicator mounted to the balance machine that rests against the tire) can usually detect small but warrantable runout.

The home version is jack stands and a heavy block of wood/metal. While the tires are lifted a few inches from the ground, place the block of wood next to the tire, close enough to barely scrape it. Check for lateral runout at the sidewall and especially the bead area of the tire and rim.

Next, place the block under the tread section of the tire (be sure the wood is 'behind' the tire so it doesn't get grabbed and shot out from under the tire). Check for radial runout by watching the gap between the tread and the block. Anything more than about 1/8" will be noticible in a tightly suspended sports car such as the Supra. Old pickups wont care about 1/2'" of runout, but our cars do!

Dragging brakes, either the disks or the internal drum parking brake, can also cause vibrations at the rear.

Worn suspension components can do the same. Check the struts, linkage bushings, and wheel bearings for excessive play by prying under the lifted tire with a long pry bar.

I'll be posting a video of me checking my tires for runout. I'll post a link when I get it done.

Hope this helps.

02-12-2009, 05:35 PM	#6
tsupranami Intake Join Date: Jun 2008 Location: Washington Posts: 32	I've had more issues with tires and tire shops than I can remember. I'm 41 years old, and through my many years of tire-buying experience I have found a lot of shops don't have folks that can truly identify (or are willing to identify) tire/wheel problems. It has usually been up to me to carefully watch them spin the tire on the machine and watch for runout. Remember, you can balance an absolutely square tire on a spin balancer by simply adding the right amount of weight to the center of the sides, but it won't roll smooth across the ground. Don't rely on the "tire guy" to tell you everything. If it is their tire(s), they have a vested interest in NOT telling you about what they might consider acceptable tire runout. They lose money on warranty exchanges. I have contacted several tire manufacturers in the past for their runout specs, and they are usually in the >.05" lateral and radial range. This is almost visually imperceptible. Only a runout gauge (a dial indicator mounted to the balance machine that rests against the tire) can usually detect small but warrantable runout. The home version is jack stands and a heavy block of wood/metal. While the tires are lifted a few inches from the ground, place the block of wood next to the tire, close enough to barely scrape it. Check for lateral runout at the sidewall and especially the bead area of the tire and rim. Next, place the block under the tread section of the tire (be sure the wood is 'behind' the tire so it doesn't get grabbed and shot out from under the tire). Check for radial runout by watching the gap between the tread and the block. Anything more than about 1/8" will be noticible in a tightly suspended sports car such as the Supra. Old pickups wont care about 1/2'" of runout, but our cars do! Dragging brakes, either the disks or the internal drum parking brake, can also cause vibrations at the rear. Worn suspension components can do the same. Check the struts, linkage bushings, and wheel bearings for excessive play by prying under the lifted tire with a long pry bar. I'll be posting a video of me checking my tires for runout. I'll post a link when I get it done. Hope this helps. __________________ 89 Turbo Targa 5spd, 18x10 w/275/35/18, 18x9 w/245/40/18, Brembo CD rotors, Hawk pads, SS lines, HKS coilovers, ST sways, 1 pc. AL DS, V3 shifter, RPSmax PP w/HPF ferramic disk, custom crank, Eagle Rods, JE pistons, Ferrea valves, BC 264 cams, Fidanza cam gears, Walbro FP, AFPR, RC660 inj., Blitz SUS, Lexus AFM, SP 47trim CT26, HKS SSQ BOV, 2.5" AL IC pipes/FMIC, Lipp turbo elbow, RT DP, Greddy SP catback, HKS FCD, AEM Uego WB, Apex'i SAFC, Apex'i AVCR, EGT, Fluidyne AL rad, Flexalite fans.