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[PSA/WARNING] - Centerbores out of spec on new Bendix PRT1132 11.75" disc brake rotors

cudak888

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Note: Seeing as rotors are primarily Chinese junk rebadged and sold in everybody's box under different names, there is a possibility that this issue exists with other brands other than Bendix.

Last night, I ran out of daylight working on my '68 Satellite's disc brake conversion (all factory parts) and had to button up the left side as quick as possible - and so I quickly installed one of my new Bendix 11.75" rotors that I had bought from Rock Auto almost half a year ago. No caliper or anything; just a rotor so I could get the car on the ground.

As I tightened the wheel to the rim, I was rather surprised that it seemed as if the lug studs on the disc hadn't been pressed into the drum correctly. Each bolt was loosening up as I went through the torque sequence, as if I were pulling the studs onto their seats as I torqued the nuts. Eventually, all of the nuts seated tightly, and I called it a night.

Enter next morning. I loosened the lug nuts, jacked the car back up so I could start installing the caliper - and the wheel won't come off. PERIOD. One might as well have welded it to the rotor.

Centerbores out of spec on new Bendix PRT1132 11.75" disc brake rotors by cudak888, on Flickr

That rim is lying face up on the ground. Gravity should have made quick work of putting the rotor in its place.

Centerbores out of spec on new Bendix PRT1132 11.75" disc brake rotors by cudak888, on Flickr

Centerbores out of spec on new Bendix PRT1132 11.75" disc brake rotors by cudak888, on Flickr

Centerbores out of spec on new Bendix PRT1132 11.75" disc brake rotors by cudak888, on Flickr

Eventually, it came to light that what my tired-as-heck self didn't notice that evening was that I wasn't seating the studs onto the rotor. I was seating the rotor to the wheel - more permanently than I care for.

And by that, I mean that the centerbores of the Bendix rotor measure out to 71.64mm (and I'm still not 100% sure I had the caliper jaws on the center - the variance may be more!), while the factory centerbore specification is 71.1mm (2.8"). That was just enough for the rim to slide on with the careful application of a 5-lug tightening sequence...and stay there without the assistance of a hydraulic press to get 'em out.

Centerbores out of spec on new Bendix PRT1132 11.75" disc brake rotors by cudak888, on Flickr

BendixPRT1132-rotor-sm.jpg


That's all ~225lbs of me or so standing on the rotor's hub in this picture; barely putting weight on the rim. You could hold a squaredance on that rotor; it's not coming out.

Needless to say, my mid-1970's Mopar slotted police rims proved the variation difference, and I also verified the fitment issue by checking my second rotor on an early-1980s 15x7" standard Mopar rim (off a B150). Same tolerance problem.

I have a couple of ideas of getting them back apart, but in the meantime, I'm going to email Rock Auto (where I got these from) and Bendix and see what they're going to do about this problem.

Also - in the meantime - I ordered one of Centric's 121.63009 rotors and the (sinfully ugly) drilled/slotted Power Stop AR8309XPR rotors. Though I realize the source of these rotors may be the same place in China, the Bendix parts are starting to look more and more like they bought up some factory seconds and shoved them in a box (with balsa wood to protect the hub area, no less).

So with this said, I warn everyone doing a 11.75" disc conversion: MEASURE your rotors' centerbores before installing. THEY MAY BE OUT OF SPEC. Fact is, it's very easy not to realize something is going VERY wrong when you're installing your rims on these hubs. And if you are lucky enough not to damage your rim on install, there remains the question of safe removal (and I can only imagine how this might damage a restored rim's paint job).

I can only hope that the bulky police rims will do their job and hold up when I finally get this thing removed.

Will report on March 1st or 2nd when the alternate rotors arrive. (And because I'm proud of the unreasonable difficulty it took to get this far - long story - here's a self-propagandizing picture of the front end conversion):

Centerbores out of spec on new Bendix PRT1132 11.75" disc brake rotors by cudak888, on Flickr
 
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Time to put a piece of wood where dust cap goes and a 5 lbs persuader to it, yuck. Did my conversion 16 years ago no problem like that. Pisser is you'll have to remove and then machine it. Then put studs back in, auh so. PS that's Chinese for I understand.
 
Time to put a piece of wood where dust cap goes and a 5 lbs persuader to it, yuck. Did my conversion 16 years ago no problem like that. Pisser is you'll have to remove and then machine it. Then put studs back in, auh so. PS that's Chinese for I understand.

I'm not machining ANYTHING. I paid good money for these things to be the way they're supposed to be, and unless there's NO other option, I'm going to wait until the pair I get are CORRECT out of the box.

Not sledging them either. Great way to damage the rim. Going to go for lots of oil around the bore and even hydraulic pressure.

-Kurt
 
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I agree a press makes more sense, hammering bad idea. I've never dealt with Rock Auto, they're mail order?
 
I agree a press makes more sense, hammering bad idea. I've never dealt with Rock Auto, they're mail order?

Mail order. Very good, and they've handled special issues like this very well in the past. I hope they will do so this time as well, even though the item is well past the 30 day return period - though it is still under manufacturer warranty.

I did just finish emailing them though and pointed out that if I'm to return these things, I'm NOT going to sacrifice my rim for that rotor - it's going to be the other way around if it has to be.

-Kurt
 
You should have done that barefoot...too much recoil in those shoes...lol!

Kurt, How is it you have a clean white shirt and your pants are all greased up......Are you staging us into thinking you actually work on your cars? lol jk

Man that blows....sorry to hear that happened and the hassle to come...
 
It's going to be a crappy deal to get it off. Wonder if you have access to anything like a 12" id pipe. Where I work they had all kind of stuff hanging around. Good thing you didn't have caliper on.
 
You should have done that barefoot...too much recoil in those shoes...lol!

Kurt, How is it you have a clean white shirt and your pants are all greased up......Are you staging us into thinking you actually work on your cars? lol jk

Man that blows....sorry to hear that happened and the hassle to come...

Is it wrong that I actually did think that a wooden heel would have helped my case? Wasn't really trying to get it off then though; I knew I had to put the car down, and I also knew that none of the parts stores in town had a replacement rotor in stock.

That's Sunday's shirt. All I did was the tie rod end, grease the ball joint ends, and put the dust plate on. This is Saturday's shirt:

9899i1.jpg


And don't you forget it :p

Could have been a lot worse. But what really pisses me off is that it was a triple whammy: My tie rod end remover gacked up the tie rod threads, so I had to rush today to get a pair of overpriced MOOGs at an Advance Auto an hour's drive away. And not only was the service at AA terrible, one of the castle nuts came PRE-STRIPPED. How the hell does all this happen on one project?

-Kurt
 
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Is it wrong that I actually did think that a wooden heel would have helped my case? Wasn't really trying to get it off then though; I knew I had to put the car down, and I also knew that none of the parts stores in town had a replacement rotor in stock.

That's Sunday's shirt. All I did was the tie rod end and some grease. This is Saturday's shirt. And don't you forget it :p

(Pic in 5)

Could have been a lot worse. But what really pisses me off is that it was a triple whammy: My tie rod end remover gacked up my tie rod threads, so I had to rush today to get a pair of MOOGs at an Advance Auto an hour's drive away. And not only was the service at AA terrible and the Moog tie rod ends expensive, one of the castle nuts came PRE-STRIPPED. How the hell does that happen?

-Kurt
Saturday's shirt...Love it! Great humor my friend!

Ohh those wonderful parts stores.....makes you want to go postal sometimes.....

Pre stripped or a stripped return.....rains it pours....sucks and I feel for ya!
 
Saturday's shirt...Love it! Great humor my friend!

Ohh those wonderful parts stores.....makes you want to go postal sometimes.....

Pre stripped or a stripped return.....rains it pours....sucks and I feel for ya!

Take a look at the pic that I just posted for you. It'll be a bit funnier...

Eh, I don't mind the parts stores. If you want to get things done or get a deal, you have to swim in the **** with hustlers and ********. And parts stores are just one of those places to swim.

Pre-stripped, stripped returns... Must...resist...obvious...joke...

-Kurt
 
I've been working on things for a long time and have realized things come in threes. You should be good to go now :thumbsup:

They come in fours. I forgot to mention that the strut rod's roll pin would NOT come out. Another hour wasted.

-Kurt
 
FWIW, I recently bought a couple of those things off eBay and they were good to go using cop car wheels. My wheels are not repops , if it matters.
I absolutely refuse to buy so much as a roll of tape from Rock auto, because they would probably send me a pencil eraser instead
 
FWIW, I recently bought a couple of those things off eBay and they were good to go using cop car wheels. My wheels are not repops , if it matters.
I absolutely refuse to buy so much as a roll of tape from Rock auto, because they would probably send me a pencil eraser instead

Bendix as well? Part number the same? Any pictures of the box?

Mine are originals too.

-Kurt
 
Bendix as well? Part number the same? Any pictures of the box?


Mine are originals too.

-Kurt
I'll see if I can find the info on them again. They are already on the car with my cop car wheels. I should have the part numbers.
 
Wonder if you put dry ice inside where bearings and spindle shaft go. Then let sit a half an hour before you try to press rotor out. The dry ice would shrink the diameter 4 or 5 thousandths?
 
Wonder if you put dry ice inside where bearings and spindle shaft go. Then let sit a half an hour before you try to press rotor out. The dry ice would shrink the diameter 4 or 5 thousandths?

Interesting thought - if putting it inside the spindle/hub shaft would prevent the rim from shrinking at the same rate. This would be ideal if the hub were aluminum due to the faster shrinkage rate.

Might have to try it at any rate. That, or shoot a couple of CO2 bottles straight at the shaft on the outside...

-Kurt
 
Here it is Kurt
They came from summit racing

  • Part#: BEN-PRT1132
  • Item: ROTOR
  • Status: Shipped on
    6/17/2016
  • Price: $36.97
  • Quantity: 2
 
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