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Brake Rotors
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Picture of Spud
posted
The front rotors on my 1972 22' Barth have deep grooves in them, so I decided to replace them. I took the one-piece rotor-hub assembly to NAPA and they ordered new ones. The new ones (NB 4885740) are too thick. The old ones had an initial thickness of, I'm guessing, 1.29, and have a min. thickness (cast on rotor) of 1.21. The new ones that NAPA gave me are 1.54 inches in thickness. The thicker rotor cannot be accommodated by the calipers. Wider calipers (jb8) won't fit the mount. I have spent about 20 hours online trying to locate an off the shelf rotor that fits with no success. So, two questions: 1) Does someone know of a rotor that will fit? (The one recommended in an earlier post on BarthMobile for a 1971 does not look anything like what I have) 2) Is there any reason I cannot have my new rotors machined down to fit?
 
Posts: 24 | Location: New York | Member Since: 03-10-2017Reply With QuoteReport This Post
Picture of Spud
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Thanks for your help!
 
Posts: 24 | Location: New York | Member Since: 03-10-2017Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 8/16
Picture of Kevin
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quote:
Originally posted by Spud:
2) Is there any reason I cannot have my new rotors machined down to fit?
Only reason not to machine them down, is if you would go lower than the limit stamped on the new rotors.
 
Posts: 2586 | Location: Northeast , Ohio | Member Since: 07-29-2012Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 2/16
Captain Doom
Picture of Rusty
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If they're vented rotors, turning past the limit isn't a good idea.


Rusty


MilSpec AMG 6.5L TD 230HP; built-to-order by Peninsular Engines:  Hi-pop injectors, gear-driven camshaft, non-waste-gated, high-output turbo, 18:1 pistons.  Fuel economy increased by 15-20%, power, WOW!"StaRV II"

'94 28' Breakaway: MilSpec AMG 6.5L TD 230HP

Nelson and Chester, not-spoiled Golden Retrievers

Sometimes I think we're alone in the universe, and sometimes I think we're not.
In either case the idea is quite staggering.
- Arthur C. Clarke

It was a woman who drove me to drink, and I've been searching thirty years to find her and thank her - W. C. Fields
 
Posts: 8201 | Location: Brooker, FL, USA | Member Since: 09-08-2005Reply With QuoteReport This Post
Picture of L78steve
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Depends where the extra meat is. If the vents are wider than stock than that's not good.
If the extra meat is on the outer width (swept area)then they can be cut.


1990 34 Regency WB
3208 300HP

1993 34 Regency WB
8.3 Cummins 300HP
 
Posts: 133 | Location: Hendersonville NC | Member Since: 02-02-2016Reply With QuoteReport This Post
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I went through the same thing with my 73'. The rotors are non-existent. Don't turn the new ones down. I was able to turn my worn ones myself and massage them without getting out of spec. The local brake shops wouldn't touch them.


There are two solutions that I found. The rotors from a C2500 , 90's vintage I think, have the correct thickness and fit perfectly. The catch is you have to run single axle front rims or space the offset dually wheel out. I don't like the idea of spacers especially on the front. The other solution is change out the spindles to late model.
 
Posts: 18 | Location: tennessee | Member Since: 09-23-2015Reply With QuoteReport This Post
Picture of Spud
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So, there are a handful of solutions:
1) replace the drop spindle with one that has a different caliper mounting bracket that will accommodate the jb8 (wider) caliper.
This could totally work, but seems like a pain in the ass.


2) get the other rotor, the one that is not nearly as wide as the one we have. But if we do this, the wheels won't fit back on. So we'd have to get different wheels and/or spacers that would fit on differently so the wheels don't rub up on or hit anything.
Sounds crazy, but props for the creativity.

3) take the old rotor and make it work by turning it or leaving it in its current condition.
This is dull, but I think it will work for a while.

I propose a 4th solution. Which is to do solution 3 for now. But then try to shave the new rotors to fit and then put them on at a later date. The meat added thickness of the new rotor, relative to the old one, is entirely in the "meat" of it. The vent size is identical. It seems to me that the minimum thickness, in this case, is not to ensure the structural stability of the rotor, but to ensure the fitment. These new rotors are 1.54 inches, as opposed to old 1.29, and the vent is identical. Why not shave the new ones like Steve says? I don't think the composition of the metal varies considerably before you hit the vent...

Again, thanks everyone!!! Great information here. Special thanks to Flathead.
 
Posts: 24 | Location: New York | Member Since: 03-10-2017Reply With QuoteReport This Post
Picture of Spud
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I've got a brake mechanic who says he'll do it. He seems to think it's alright. We'll take a look at the old ones too. They're pretty close to being resurface-able. Thanks again for the input everyone. I'll update after the weekend if I don't forget. You gals and guys are lifesavers.
 
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Captain Doom
Picture of Rusty
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If the vents are the same width on both the old and the new, the new can be turned down. If the vent width on the new is wider, turning down to the "right" thickness would leave less metal, and make the rotors prone to warping or failure.


Rusty


MilSpec AMG 6.5L TD 230HP; built-to-order by Peninsular Engines:  Hi-pop injectors, gear-driven camshaft, non-waste-gated, high-output turbo, 18:1 pistons.  Fuel economy increased by 15-20%, power, WOW!"StaRV II"

'94 28' Breakaway: MilSpec AMG 6.5L TD 230HP

Nelson and Chester, not-spoiled Golden Retrievers

Sometimes I think we're alone in the universe, and sometimes I think we're not.
In either case the idea is quite staggering.
- Arthur C. Clarke

It was a woman who drove me to drink, and I've been searching thirty years to find her and thank her - W. C. Fields
 
Posts: 8201 | Location: Brooker, FL, USA | Member Since: 09-08-2005Reply With QuoteReport This Post
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Check the offset first.
If I remember correctly I considered turning the new "thick" rotors but after measuring I determined that most, if not all, of the meat would have to come off of one side for the calipers to work. Please post what you find. I may have had a different rotor than the one that you have.
 
Posts: 18 | Location: tennessee | Member Since: 09-23-2015Reply With QuoteReport This Post
Picture of Spud
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That's a great point Flathead. I had considered that, but hadn't measured it precisely. I resolved part of the fitment issue by doing away with the dust/splash guard, but you're right, if the offset is too much, I still won't be able to fit the rotor inside the caliper with new pads.

After looking at the old rotors, I think they are about 1.25, but turning them is going to bring them awfully close to the minimum because of the depth of the grooving. I think I'll try that first though.

As it concerns the new rotor, what do folks think about cutting more meat off one side than the other? Seems like it would lead to warping because of heat distribution differences.
 
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Picture of Spud
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Does anyone have any experience with a rotor coating of some kind that will extend its life?
 
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Supporting Member of Barthmobile.com 8/16
Picture of Kevin
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Never wore out any rotors except when the pads were gone. Nothing will save your rotors if you have no pads. Change the pads Before the pads get too thin.
Do not ride your brakes on hills. It could overheat the glue and the pad will separate from the metal. Anticipate traffic lights, curves, and hills, so you do not need your brakes.
 
Posts: 2586 | Location: Northeast , Ohio | Member Since: 07-29-2012Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 7/17
Picture of Doorman
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quote:
Originally posted by Spud:
Does anyone have any experience with a rotor coating of some kind that will extend its life?


Good coat of grease. Sorry


1986 31' Regal -1976 Class C
454/T400 P30 -350/T400 G30
twin cntr beds - 21' rear bath
 
Posts: 779 | Location: Dayton, Ohio | Member Since: 09-27-2009Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 6/12
Formally known as "Humbojb"
Picture of Jim and Tere
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Amen to that, Kevin. That's how I drive my '06 Mercury. Had to change the pads on the front for the first time at 199000 miles. The back are still good.
Jim


Jim and TereJim and Tere

1985 Regal
29' Chevy 454 P32
8411 3172 29FP3B
Gear Vendor 6 Speed Tranny
 
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