Hub Centric Adapters

[SH69Z28]

I read the earlier thread about mounting Torque Thrust II's on a 67 z/28 but no source for adapters was given. I my case I have a 69 Z with TTII's made in the mid 90's. I've tried the use of conical lug nuts to achieve a better concentric fit and then switch over to the long necked lug nuts but it's quite hard to repeat that successfully. I've contacted numerous Wheel/Tire stores but no one (not even American Racing) offers concentric adapters for my wheels and car. My measurements indicate a 70.5mm ID with a 85.5mm OD and .25inch thick would be good. It seems that I'll have to have custom ones made, but before I do that I thought I'd ask this august body for any other suggestions. BTW, the tires and wheels have been professionally balanced and checked for roundness and that helped but just not enough. Up to 60 mph all is ok, but after that the vibration get's obnoxious. I also tried original YH wheels that when installed work perfectly. Thanks. 

[JohnZ]

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I read the earlier thread about mounting Torque Thrust II's on a 67 z/28 but no source for adapters was given. I my case I have a 69 Z with TTII's made in the mid 90's. I've tried the use of conical lug nuts to achieve a better concentric fit and then switch over to the long necked lug nuts but it's quite hard to repeat that successfully. I've contacted numerous Wheel/Tire stores but no one (not even American Racing) offers concentric adapters for my wheels and car. My measurements indicate a 70.5mm ID with a 85.5mm OD and .25inch thick would be good. It seems that I'll have to have custom ones made, but before I do that I thought I'd ask this august body for any other suggestions. BTW, the tires and wheels have been professionally balanced and checked for roundness and that helped but just not enough. Up to 60 mph all is ok, but after that the vibration get's obnoxious. I also tried original YH wheels that when installed work perfectly. Thanks. 

Tires can be perfectly balanced and still cause vibration, also known as "smooth road shake" due to tire construction variables that don't show until the tire is loaded with vehicle weight.

Find a shop/dealer with a Hunter GSP-9700 Road Force Balancer (go to www.gsp9700.com and use the locator feature - there's one near you) and have them check out your wheels/tires - it checks both lateral and radial runout, balance, and response to full road force load at speed, and its diagnostics show the operator how to optimize it by moving the tire on the rim.

Use of adapters/spacers is a BAD idea. Use the lug nuts the wheels were designed for.

[My68SS]

Hi John, OP has no doubt resolved his/her problem by now, but there might have been a slight mis-reading here of OP's problem.
He/she is looking for hub centric adapters to match the rim bore to the axle hub, so the rim will be 'hub centric', not 'lug centric' which should be avoided.

[JohnZ]

Hi John, OP has no doubt resolved his/her problem by now, but there might have been a slight mis-reading here of OP's problem.
He/she is looking for hub centric adapters to match the rim bore to the axle hub, so the rim will be 'hub centric', not 'lug centric' which should be avoided.

Almost ALL production wheels are designed as lug-centric; don't know about aftermarket wheels.

[My68SS]

Hi John, OP has no doubt resolved his/her problem by now, but there might have been a slight mis-reading here of OP's problem.
He/she is looking for hub centric adapters to match the rim bore to the axle hub, so the rim will be 'hub centric', not 'lug centric' which should be avoided.

Almost ALL production wheels are designed as lug-centric; don't know about aftermarket wheels.

?? I think you meant hub centric for oem wheels. Aftermarkets are made with an oversized bore so they will fit as wider range of vehicles as possible. The fitter should then press the correct ring into the wheel bore so the wheel is a snug fit on the axle/spindle hub of that vehicle.

[SH69Z28]

Just thought I'd close out this post. I had a set of hub centric adapters made per my own measurements after having a local tire shop balance my wheels/tires as John suggested. The balancing (road balancing as they called it) helped but not enough to satisfy me. The adapters worked wonderfully well. The adapters were made on a lathe from some heavy wall aluminum tubing I found at a local distributor.

[70L34]

Did they have a significant impact on the vibration? That would be interesting to know.

[My68SS]

We'll hope for OP to come back here and give a definitive answer, but the way I'm reading his last post is that he had the adapters made after extensive balancing efforts were tried without adapters, but to no avail.
Adapters were then fitted which fixed the vibration problem.

[SH69Z28]

Guess I'll try again to bring this to a concise close. The adapters I had made were successful at reducing the vibration issue to the point I have no remaining complaints (smooth up to 75 mph which is as fast as I've gone so far). I fought this issue for years and worked through bell housing alignment, harmonic damper, motor + transmission mounts, drive shaft, u-joint angle and probably more stuff than I can recall now. I discovered and fixed a bad rear bushing in the Muncie (thanks to 5speeds.com) a bad balance job from an engine shop now out of business, a misaligned bell housing (fixed with .007 inch offset dowels) and now the hub adapters. I undertook them because my alignment shop suggested them after rotating my wheels and finding that the vibration changed slightly with each wheel position but never went away. Then JohnZ suggested the road balance method used by shops with such balancers which helped a bit more. Now that the journey is over I just thought you all deserved a summary. CRG has been a simply awesome resource for me and my restoration of two 69Z's.