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Old 11-11-2017, 01:21 PM   #1
stewmagoo73
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Center boring a GM transport wheel

I have a small dilemma. I have a 67 c10 typical 6 lug drum brake set up. I recently acquired a complete set and they just will not fit the hub. The center hub on drum in a conical shape and it doesn't like much to fit flush.

I thought about a spacer kit and bought one but it just doesn't fit flush over the lugs either.

Does anyone know what diameter I need to have my wheels bored to?

Thanks in advance
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Old 11-11-2017, 10:15 PM   #2
stewmagoo73
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Re: Center boring a GM transport wheel

Surely somebody has performed this. I can't be the only one struggling with this.
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Old 11-11-2017, 10:57 PM   #3
bigrigpardo
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Re: Center boring a GM transport wheel

Best way is to pull your brake drum off and measure the center hole in it. I am pretty sure it's 3.5 inches. You should be able to take them to a machine shop and have them opened up. But measure your back spacing. Most say you need 2 inch spacers to have the wheels fit in the wheel wells in the back without hitting.
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Old 11-12-2017, 11:17 AM   #4
jerry moss
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Re: Center boring a GM transport wheel

i would not recommend boring out the center hole, it will weaken the wheel. when i was a kid my dad had a 72 scout which has the 5 on 5 1/2 bolt pattern, same as older ford trucks. the center hole of ford truck wheel is smaller so he had our local machine shop bore them out. the wheels ended up cracking between the lug hole and the center hole because the center hole lip was bored out which took away the strength mounting area.
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Old 11-12-2017, 11:30 AM   #5
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Re: Center boring a GM transport wheel

x's 2 on what Mr. Moss stated.
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Old 11-12-2017, 12:48 PM   #6
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Re: Center boring a GM transport wheel

Check out @themaintenancedepartment or @dillman1977 on Instagram.
They have been modifying these transit wheels for a long time.
They also do 5-lug and 8-lug conversions for these wheels.
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Old 11-12-2017, 02:20 PM   #7
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Re: Center boring a GM transport wheel

Thank you guys. There is a lot of meat left in these centers for safety sake. It really don't need about a quarter inch to clear. I want a true ride on hub wheel vs riding on spacers. My reputable machine shop asked me to pull my drum and hub for a proper fit. Just don't want to cripple my vehicle while I'm getting them machined out.
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Old 11-12-2017, 03:14 PM   #8
garyd1961
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Re: Center boring a GM transport wheel

I don't think the amount of material you take off is the problem. If you look at the picture is post #6 you see that they took out the crease around the middle hole. The crease is what gives it strength/rigidity.
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Old 11-12-2017, 05:08 PM   #9
stewmagoo73
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Re: Center boring a GM transport wheel

Thank you guys. So do you feel riding on aluminum spacers is a safer bet?

Let me ask this senerio? So let's say I trim out enough to fit snug and flush on the hub, and have full length studs for tightness, even though it may be weaker, how is that any worse than aftermarket wheels that have huge center hubs, and only riding basically on the wheel studs?

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Old 11-12-2017, 05:53 PM   #10
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Re: Center boring a GM transport wheel

FWIW, I had the centers of the stock steelies on my 67 opened up to fit center caps and havent had any problems in the past 5 years. Part of the center rib is still there but its extremely thin, and the lug nuts are what is centering the wheels now.
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Old 11-12-2017, 07:03 PM   #11
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Re: Center boring a GM transport wheel

its never a good idea to rely on the tapered surface of a lug nut to maintain the wheel on center.

also, the center portion of the wheel, and the area of it that interfaces with the hub are hardened by working the metal when it is pressed to that shape and by the heattreatment of the sheetmetal when it is actually manufactured.

among safety inspectors in the dragracing community it is not allowed. I had a ford 9 inch rear modified to install under a 50 pontiac, it used the 50 pontiac rims wich had a different inside diameter.. the wheels kept comming loose. I took it to a shop that installed my tires and their solution was to put the lug nuts on with so much force that I could not remove the lugnuts with a wrench. I took it back to them and when the attempted to remove the lug nuts they stripped the studs out of the axle flange.

when in doubt, consider this. the engineeres did things for a reason, and the accountants did too.
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Old 11-12-2017, 07:21 PM   #12
stewmagoo73
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Re: Center boring a GM transport wheel

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Originally Posted by mike16 View Post
its never a good idea to rely on the tapered surface of a lug nut to maintain the wheel on center.

also, the center portion of the wheel, and the area of it that interfaces with the hub are hardened by working the metal when it is pressed to that shape and by the heattreatment of the sheetmetal when it is actually manufactured.

among safety inspectors in the dragracing community it is not allowed. I had a ford 9 inch rear modified to install under a 50 pontiac, it used the 50 pontiac rims wich had a different inside diameter.. the wheels kept comming loose. I took it to a shop that installed my tires and their solution was to put the lug nuts on with so much force that I could not remove the lugnuts with a wrench. I took it back to them and when the attempted to remove the lug nuts they stripped the studs out of the axle flange.

when in doubt, consider this. the engineeres did things for a reason, and the accountants did too.
You are correct sir. I also guess that's why the transport wheels really weren't DOT certified wheel anyways.
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Old 11-12-2017, 08:35 PM   #13
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Re: Center boring a GM transport wheel

I dont know transit, transport or DOT approved wheels.

an apples and oranges comparison but with unsafe consequences

some safety organisations do not approve them and for good reason.

I know that the fasteners that hold the wheels on huge trucks are themselves different and function specifically to fasten the wheel on and center the wheel. automotive lug nuts dont do that, or rather are not designed to do that.

maybe theres a good reason or two not to do it.

BY all means justify doing it but also accept the consequences.

Last edited by mike16; 11-12-2017 at 08:52 PM.
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Old 11-12-2017, 09:42 PM   #14
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Re: Center boring a GM transport wheel

I had the centers bored out on my transits. The axle hub specs at 3.5” but my center bore is about 3.6”. It definitely doesn’t center the wheel like the stock setup does, so it’s all up to the studs/lugnuts to center the wheel. That being said, I haven’t had any issues with vibrations or loose wheels. I have upgraded to longer Moser studs as well. If I were to do it again, I definitely would have pulled the axles and had the hub turned down to fit snug in the transit wheel center bore instead. As was mentioned above, these wheels won’t fit on the back with the 6” of backspacing. I flipped the centers on mine to give me 4”BS and they fit perfectly now. Oh, and these wheels are DOT approved, it’s stamped right on them.
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Old 11-13-2017, 06:44 PM   #15
Bagd72Chevy
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Re: Center boring a GM transport wheel

Easiest way to fit the front is 1/2" wheel spacer and longer studs. Then the wheel will sit flat. I ran like this for over a year.

On the rear you can use a 1.25" spacer or I did as the guy above and flipped my rears.
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Old 12-10-2017, 06:26 PM   #16
stewmagoo73
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Re: Center boring a GM transport wheel

So my question is this. Can you not run these wheels without a spacer due to backspacing ?
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Old 12-10-2017, 09:04 PM   #17
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Re: Center boring a GM transport wheel

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Originally Posted by stewmagoo73 View Post
So my question is this. Can you not run these wheels without a spacer due to backspacing ?
In the front, you CAN run these without a spacer as long as you do one of two things: 1) bore the centers if you're running drum brakes, or 2) run a disk brake conversion.

In the rear, you CANNOT run these without a spacer in the stock size (22x9 w/ 6" BS). The wheel will interfere with the edge of the bed floor. You basically have two options here as well: 1) flip the center and do a custom backspace between 3.5" - 4.5", or 2) run at least a 1.25" spacer. How much depends on which rear end you have (earlier pre 69 rear, or 1.5" wider 69-up rear).
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Old 12-11-2017, 10:43 AM   #18
stewmagoo73
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Re: Center boring a GM transport wheel

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In the front, you CAN run these without a spacer as long as you do one of two things: 1) bore the centers if you're running drum brakes, or 2) run a disk brake conversion.

In the rear, you CANNOT run these without a spacer in the stock size (22x9 w/ 6" BS). The wheel will interfere with the edge of the bed floor. You basically have two options here as well: 1) flip the center and do a custom backspace between 3.5" - 4.5", or 2) run at least a 1.25" spacer. How much depends on which rear end you have (earlier pre 69 rear, or 1.5" wider 69-up rear).
I appreciate this info. I have a machine shop that said if I bring them my hub they will measure it and center bore my wheels. I have a spacer kit, that I can use for the rear if need be. Or may just sale my set and run my stock steelies that i have and not have any issues.
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Old 12-11-2017, 11:44 AM   #19
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Re: Center boring a GM transport wheel

The other option is machine down the center of the rotor or hub to fit the wheels, I changed to 5 x 4 3/4 pattern once and had the rotor machined to fit he wheel. Check it to see if the hub or rotor has enough meat to machine it down.
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Old 12-11-2017, 03:32 PM   #20
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Re: Center boring a GM transport wheel

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The other option is machine down the center of the rotor or hub to fit the wheels, I changed to 5 x 4 3/4 pattern once and had the rotor machined to fit he wheel. Check it to see if the hub or rotor has enough meat to machine it down.
This is definitely a good idea too, and actually the way I would have gone if I were to do it again. The rear axles can easily be pulled out and machined down to match the center bore size on the transit wheel. The only thing you'll have to figure out then is backspacing (either run a spacer or change the backspace on the wheel). For the front, if you do a disk brake swap then the transit will fit without issue.
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Old 12-11-2017, 03:48 PM   #21
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Re: Center boring a GM transport wheel

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This is definitely a good idea too, and actually the way I would have gone if I were to do it again. The rear axles can easily be pulled out and machined down to match the center bore size on the transit wheel. The only thing you'll have to figure out then is backspacing (either run a spacer or change the backspace on the wheel). For the front, if you do a disk brake swap then the transit will fit without issue.
Sure the rear axle hub can be machined down, but it still needs to fit the brake drum bore.
What is everyone doing here?
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Old 12-11-2017, 04:08 PM   #22
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Re: Center boring a GM transport wheel

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Originally Posted by lolife99 View Post
Sure the rear axle hub can be machined down, but it still needs to fit the brake drum bore.
What is everyone doing here?
Have the machinist put a step for the brake register then the remainder for the wheel
Or re-drill 5 lug drums to 6 lug
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