[C2] Wheel mounting surface...Drum vs. Disc
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 6,569
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From: Redacted
Wheel mounting surface...Drum vs. Disc
Does anyone know, when swapping a drum brake car over to discs, does the wheel mounting surface move inboard or outboard at all?
The reason I ask is because I'm looking at ordering a set of 15x7 wheels to replace the factory hub caps. At some point in the future, I will likely swap to disc brakes and just want to verify that in doing that swap, the wheel isn't going to move in or out in the wheel well and thus potentially affect clearance.
The wheels I'm looking at are 15x7 with 3 7/8" backspacing which I know others are currently running with no issues on drum brake cars. These particular wheels provide 5/8" clearance from the mounting surface to the back of the spokes at the closest point, so they will clear the calipers I intend to use in the future disc conversion. I'm just trying to verify that in going to discs, I'm not going to move the wheel inboard or outboard at all.
Thanks for the help.
The reason I ask is because I'm looking at ordering a set of 15x7 wheels to replace the factory hub caps. At some point in the future, I will likely swap to disc brakes and just want to verify that in doing that swap, the wheel isn't going to move in or out in the wheel well and thus potentially affect clearance.
The wheels I'm looking at are 15x7 with 3 7/8" backspacing which I know others are currently running with no issues on drum brake cars. These particular wheels provide 5/8" clearance from the mounting surface to the back of the spokes at the closest point, so they will clear the calipers I intend to use in the future disc conversion. I'm just trying to verify that in going to discs, I'm not going to move the wheel inboard or outboard at all.
Thanks for the help.
Race Director
Joined: Feb 2007
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From: northern california
C2 of Year Finalist (track prepared) 2019
The difference in wheel position between disc and drum will be very slight. Disc brake rotors, being cast metal, are slightly thicker in the mounting flange than are brake drums, the mounting flange of which are stamped steel. So with discs, the wheels might move outboard 1/8" or so. Shouldn't be a big deal.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
The track width on a '64 drum brake Corvette is 56.3 front and 57 rear.
The track width on a '65 disc brake Corvette is 57.0 and 57.6 rear.
These numbers are listed by GM using OEM parts.
The track width on a '65 disc brake Corvette is 57.0 and 57.6 rear.
These numbers are listed by GM using OEM parts.
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,407
From: Redacted
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,407
From: Redacted
Also interesting, if you go to American Racing's web site and look at the Torque Thrust D, they list the same part number for the 15x7 with 3.76 inch backspacing as fitting both the '64 and '66 Corvette. I imagine at the slight differences we're talking about here, tires selection has as much to do with what fits and what doesn't as minutia in tack width difference.
I agree that the smart thing to do would be to wait and do the brake swap and then measure before ordering wheels, but with that project at least 12-18 months down the road, and the summer driving season upon us, I may just risk the $98 per wheel and enjoy it this year and then sell them in a year or so if there are fitment issues to recoup at least some of the money.
I agree that the smart thing to do would be to wait and do the brake swap and then measure before ordering wheels, but with that project at least 12-18 months down the road, and the summer driving season upon us, I may just risk the $98 per wheel and enjoy it this year and then sell them in a year or so if there are fitment issues to recoup at least some of the money.
Drifting
Joined: May 2006
Posts: 1,469
Likes: 329
From: Southold New York
According to those specs, the difference in track width is 0.7" in front and 0.6" in the rear. Allowing that half that difference applies to each side, the wheels would be moved outward 0.35" at the front and 0.3"at the rear, which would be between 3/8" and 1/4". You should be good to go.
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 6,569
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From: Redacted
According to those specs, the difference in track width is 0.7" in front and 0.6" in the rear. Allowing that half that difference applies to each side, the wheels would be moved outward 0.35" at the front and 0.3"at the rear, which would be between 3/8" and 1/4". You should be good to go.
Team Owner
Joined: Apr 2008
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From: Middle TN by way of KY, OH, VA, IL, CA, FL, NY, SC, HI
Greg,
My '65 with original factory disc brakes is sitting in the garage (missing it engine), in the South Greenbrier area.
I can take a measurement if you can spec what it is you want measured, or you can drop by and see for yourself.
I'll be home most all of Friday and parts of Saturday, but am traveling Sunday.
Kevin
My '65 with original factory disc brakes is sitting in the garage (missing it engine), in the South Greenbrier area.
I can take a measurement if you can spec what it is you want measured, or you can drop by and see for yourself.
I'll be home most all of Friday and parts of Saturday, but am traveling Sunday.
Kevin
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Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,407
From: Redacted
Greg,
My '65 with original factory disc brakes is sitting in the garage (missing it engine), in the South Greenbrier area.
I can take a measurement if you can spec what it is you want measured, or you can drop by and see for yourself.
I'll be home most all of Friday and parts of Saturday, but am traveling Sunday.
Kevin
My '65 with original factory disc brakes is sitting in the garage (missing it engine), in the South Greenbrier area.
I can take a measurement if you can spec what it is you want measured, or you can drop by and see for yourself.
I'll be home most all of Friday and parts of Saturday, but am traveling Sunday.
Kevin
Kevin,
Much appreciated but I think I got what I needed. At the minutia of track width differences were talking about here, I think any slight increase in track width from drum to disc can be compensated for by a slightly different tire profile if need be....but at 15x7, I think I should have room to play with. Next task is to verify that the brake kit i have sitting on my shelf will in fact fit inside 15" wheels.
Instructor
Joined: Jul 2014
Posts: 135
Likes: 17
From: Punta Gorda, Florida
In the FWIW category, an aftermarket drum to disk conversion kit states "It moves the wheels out 1 1/4" on each side." That's a big difference if it's true.
I'm thinking along the same lines as you, wishing to go to the TT wheels too, but want to leave my options open for converting to disks at some time in the future. Let us know what you end up going with.
I'm thinking along the same lines as you, wishing to go to the TT wheels too, but want to leave my options open for converting to disks at some time in the future. Let us know what you end up going with.
Race Director
Joined: Jun 2006
Posts: 17,901
Likes: 751
From: Inverness FL
St. Jude Donor '07
In the FWIW category, an aftermarket drum to disk conversion kit states "It moves the wheels out 1 1/4" on each side." That's a big difference if it's true.
I'm thinking along the same lines as you, wishing to go to the TT wheels too, but want to leave my options open for converting to disks at some time in the future. Let us know what you end up going with.
I'm thinking along the same lines as you, wishing to go to the TT wheels too, but want to leave my options open for converting to disks at some time in the future. Let us know what you end up going with.
Bill
Race Director
Joined: Feb 2007
Posts: 15,479
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From: northern california
C2 of Year Finalist (track prepared) 2019
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,407
From: Redacted
In the FWIW category, an aftermarket drum to disk conversion kit states "It moves the wheels out 1 1/4" on each side." That's a big difference if it's true.
I'm thinking along the same lines as you, wishing to go to the TT wheels too, but want to leave my options open for converting to disks at some time in the future. Let us know what you end up going with.
I'm thinking along the same lines as you, wishing to go to the TT wheels too, but want to leave my options open for converting to disks at some time in the future. Let us know what you end up going with.
