Drum to Disk Conversion Help - Team Camaro Tech
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post #1 of 11 (permalink) Old Sep 13th, 10, 01:48 PM Thread Starter
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Erik
 
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Drum to Disk Conversion Help

Hello I recently purchased a set of Hopster 17" rims for my 4 wheel drum brake 1969 Camaro. I was hoping to upgrade to disk brakes at a later date so i got 5.5" offset in the rear and 4.75" offset in the front. The problem is the rear tires hit on the rear when executing most any turn. The tires I have in the rear are 275/40R17. Having looked at disk brakes I really like the Track4 front/ SS4 rear brake kit. I emailed them and they say that it will offset the tire .90" more than my drums will. I am now worried about hitting on the outside in the rear. Does anyone have experience with this set up? Would 5.5" offset and another .90" out work with a 275 tire? Do you know any good way to check this ahead of time, I was thinking spacers but that would be a large spacer. Is rolling a fender a very big deal? Thanks so much for any help you can provide!
Erik
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post #2 of 11 (permalink) Old Sep 13th, 10, 01:57 PM
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Re: Drum to Disk Conversion Help

I can't believe any rear discs will offset your wheel by 0.90" or 9/10 of an inch. Are you sure he didn't say 0.090"? 0.090" is a good bit less than 1/8" and a relatively small distance when you consider tire clearance.

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post #3 of 11 (permalink) Old Sep 13th, 10, 02:15 PM Thread Starter
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Re: Drum to Disk Conversion Help

"Hey Erik,
On the stock drum cars the conversion would add .900 a side.
It will push the wheel out almost an inch per side.
Thx!"
That is the reply from Baer's representative. I believe the offset comes from the difference between the Rotor of the new setup and the thickness of the existing drum hat which i have not measured but is pretty thin. I was also surprised that it was that much, I would have guessed a half inch.
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post #4 of 11 (permalink) Old Sep 13th, 10, 02:40 PM
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Re: Drum to Disk Conversion Help

Erik -

I think you got some bad info from Baer. There is no way in heck that the rotor flange is .90 thicker than the drum. Maybe on a 767 or some other large jet, but not on a passenger car. The stock drum should measure ~ .125" at the flange and the rotor should be around .250 - a difference of 1/8" per side.


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post #5 of 11 (permalink) Old Sep 13th, 10, 03:35 PM Thread Starter
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Re: Drum to Disk Conversion Help

I just wrote another email to Baer about the offset because I agree it does sound like a lot. What he said is that the offset comes from not only the rotor thickness but the hub face. He seems quite sure about the .90" figure and has asked other people at Baer. He also said the rotor hat is .3" so clearly thats not where the offset is at. In any case, do you think there is enough room to move a 275 tire out .9" if its farther in than is should be, or would this be too much? Are spacers a good way to test this?
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post #6 of 11 (permalink) Old Sep 13th, 10, 04:40 PM
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Re: Drum to Disk Conversion Help

Your wheel and tire are absolutely not going to move out 0.900" on each side. If the rotor face is .300 thick and the brake drum face measures .187" then your wheel extends out the difference of .113" (and I just made those numbers up). The thickness of the rotor disc has absolutely no bearing in the position of the wheel and tire. Your axle hub is not repositioned either.
I think the Baer Brake guy is trying to say .090 but somehow it is coming across as 0.900.

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post #7 of 11 (permalink) Old Sep 13th, 10, 09:50 PM
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Re: Drum to Disk Conversion Help

Quote:
Originally Posted by X33D80 View Post
Your wheel and tire are absolutely not going to move out 0.900" on each side. If the rotor face is .300 thick and the brake drum face measures .187" then your wheel extends out the difference of .113" (and I just made those numbers up). The thickness of the rotor disc has absolutely no bearing in the position of the wheel and tire. Your axle hub is not repositioned either.
I think the Baer Brake guy is trying to say .090 but somehow it is coming across as 0.900.
Andrew is correct. I've measured a drum at the hub flange, they're ~ .125" (1/8"). If your Baer rotors are .300 at the hub flange, then the difference is .175" That is the ONLY thing that will affect your wheel spacing, and from the sound of your original post, you could use it if your tires are rubbing on the inner wheel housing.

Sounds like the Bear guy has been smoking' some Wilweed. Or drinkin' a few PBRs.


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post #8 of 11 (permalink) Old Sep 13th, 10, 09:56 PM Thread Starter
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Re: Drum to Disk Conversion Help

Haha I guess so, I was already confused by the whole thing and now even more so. I figured out tonight that my rear end is sagging though. The left side is at 25.25" and the right is at 26.25 or so. I think getting new leafs would help my clearance a ton! I talked to prodigy customs today and he said that the wilwood kits went from 1/8 to 3/16"... i just don't know if it will be enough.
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post #9 of 11 (permalink) Old Sep 14th, 10, 02:57 AM
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Re: Drum to Disk Conversion Help

Good talking to you last night. As i was telling you the only difference in the rear is the difference in the thickness of the rotor hat and the drum hat. The Wilwood is only going to be about 1/8. Some other rotors like factory repro style and some after market disc conversions can change it up to 3/16.

As i mentioned, replacing you sagging mono leafs with firm multileaf will help a lot in the side to side movement of the rear, and then possibly a small wheel spacer will push the wheels out a bit to gain some clearance on the inside.
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post #10 of 11 (permalink) Old Sep 22nd, 10, 12:08 PM
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Re: Drum to Disk Conversion Help

Quote:
Originally Posted by lantis View Post
Haha I guess so, I was already confused by the whole thing and now even more so. I figured out tonight that my rear end is sagging though. The left side is at 25.25" and the right is at 26.25 or so. I think getting new leafs would help my clearance a ton! I talked to prodigy customs today and he said that the wilwood kits went from 1/8 to 3/16"... i just don't know if it will be enough.
I have a set of Global West muli leafs and shackle kit for sale. If you are interested pm me.
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post #11 of 11 (permalink) Old Sep 29th, 10, 12:54 PM
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Re: Drum to Disk Conversion Help

The Baer rear kit will push you out just over 1/8" per side.
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