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#1 |
Registered User
Join Date: Jul 2018
Location: Ripon, WI
Posts: 12
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I have a 1970 GMC C2500 (2WD) that I have bought aftermarket wheels and tires for. The wheels are 8 X 6.5 bolt pattern. The center hole in the wheel is just under 131mm. If I bolt a wheel onto the hub of the Dana 60 full-floating rear axle, the wheel has a significant gap between the center hole of the wheel and the hub of the axle. The axle hub is difficult for me to measure despite having a digital caliper and 4-5" micrometer. The studs get in the way of my making an accurate measurement. Does anyone know the diameter of the hub at the wheel mounting surface? (I will need to order some rings to fill the gap between the hub and the inside of the rims center hole if I want my rims to be hub-centric.)
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#2 |
Born Psycho
![]() Join Date: Feb 2001
Location: brentwood,cal,usa
Posts: 4,888
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your tapered lug nuts center the wheel to the mounting flange of the hub. you must be thinking of a Ford truck that uses hub centric wheels.
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jerry moss 72 cheyenne super K20- tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,tow hooks,bumper guards,toolbox,aux. fuel tank,posi front and rear,plus other goodies!!! SOLD 69 suburban K20-tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,4 inch all spring lift,4 speed, 14 bolt full floater, dana 44 HD,warn winch,posi front and rear,tow hooks,plus other goodies. 73/80 chevy/gmc K20 SB400,turbo 400,205,tilt,a-c,gas hog. 77 K/5 cheyenne blazer-daily driver/beater. SON HAS IT NOW BRENTWOOD,CALIFORNIA |
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#3 |
Registered User
Join Date: Jul 2018
Location: Ripon, WI
Posts: 12
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Re: 1970 GMC C2500 rear axle hub diameter?
Nearly all factory installed wheels are hub-centric. The 1970 GMC had steel wheels that mated tightly to the hub. I know that many aftermarket wheels are designed to be more universal, and center off of the lugs, in order to have a single wheel casting be useable with several applications. My opinion is that lug centering wheels may be less than ideal, especially for a HD truck that will be carrying heavy loads, driven in rough terrain, abused with dragstrip launches, and/or towing a trailer. Anyway, it looks like my question is turning into something that I haven't asked. Are hub-centric rings needed for aftermarket wheels?(This is a simple google search that I have already done. The jury seems to be about evenly divided on the subject.) Thank you for sharing your experience.
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#4 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,651
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Re: 1970 GMC C2500 rear axle hub diameter?
FWIW, I have owned my K20 for 47 years and during that time it has had four different sets of wheels.
1) The stock 16" lock-ring wheels. 2) Aftermarket 15x8" white wagon spokes. 3) Aftermarket 16.5x9.75" chrome wagon spokes. 4) Ford (Accuride?) 16x7" steelies. I couldn't say if the stock wheels were hub-centric, but none of the others were. The truck has been heavily loaded more times than I can count (up to a verified 3 tons in the bed), with no wheel-related problems ever. I agree with Jerry Moss, hub-centric rings are absolutely not needed in your configuration.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#5 |
Registered User
Join Date: Jul 2018
Location: Ripon, WI
Posts: 12
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Re: 1970 GMC C2500 rear axle hub diameter?
Thank you for weighing in, Mike. You and Jerry supplied just the kind of advice/reassurance that I was needing. I will install the wheels without hub-centric rings and feel confident that there won't be any wheel related issues. I came to the right place.
Thanks Again Brad |
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#6 |
Senior Member
![]() Join Date: Feb 2022
Location: Ca
Posts: 520
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Re: 1970 GMC C2500 rear axle hub diameter?
Just one thing to consider when not using the hub to center a wheel. It will be all the more important to sneak up on tightening those lug nuts allowing the wheel to slip some as the nuts center the wheel before too tight for movement. Rotating the wheel when doing so may also be advisable, in a way centering the weight during the tightening process. This might be overkill, but I've had wheels bind up at the track while mounting. You think everything is fine till that 165MPH section of track comes up. It about blinds you.
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#7 | |
Registered User
![]() Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,532
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Re: 1970 GMC C2500 rear axle hub diameter?
Quote:
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Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. |
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#8 |
Senior Member
![]() Join Date: Nov 2018
Location: Waterford California
Posts: 2,539
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Re: 1970 GMC C2500 rear axle hub diameter?
In this era GM rear hubs are 4.56"+/- Ford rear hubs are 4.77"+/-
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#9 |
Senior Member
![]() Join Date: Aug 2005
Location: Los Angeles
Posts: 1,334
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Re: 1970 GMC C2500 rear axle hub diameter?
Rule of thumb is if the aftermarket wheels use a tapered lug nut, then they center off the lugs. If the wheels use a flanged nut that is flat on the bottom, the wheels center off the hubs (hub-centric). If you have any doubts, call the wheel manufacturer. If your wheels center off the lugs I would not be too concerned as for many years heavy trucks and buses used 'Budd' wheels which used tapered lug nuts (and studs for the inner wheels). They never came loose if properly torqued! Here is a picture of my '67, tapered nuts and a little gap around the hub:
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1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90. |
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#10 |
Senior Member
![]() Join Date: Dec 1999
Location: Southern California
Posts: 2,817
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Re: 1970 GMC C2500 rear axle hub diameter?
In my experience I have not recall having seen 8 lug hub centric wheels. The older stuff was not AFAIK. Honestly, in the newer vehicles I have worked on I never even thought about it. The temp wheels on my 72 truck are not hub centric as well as the final US Mags wheels I am using. Have used wheel spacers on the rear of my 94 1/2 ton for many years, not hub centric. I have worked on semi trucks and the Alcoa wheels were not hub centric. Nothing to worry about IMO.
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Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746 |
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