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Installing New Drive Flanges & Rotors
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Author:  junior [ Tue Jan 07, 2014 4:29 pm ]
Post subject:  Installing New Drive Flanges & Rotors

I recently purchased a new set of rotors & drive flanges (for 7.5” brakes), I have tapped the drive flanges on lightly but they won’t seat nicely on the face of the rotor.
It would appear that the base of the wheel stud (ie the non-threaded section) has an interference fit with the holes in the drive flange preventing the drive flange from seating parallel, is this normal & do you need to seat these with a heavy tap into place or do you think I might have to relieve the holes in the back of the drive flange?

Author:  drmini in aust [ Tue Jan 07, 2014 9:07 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

Sounds dodgy, I've never seen this problem in the past. Got a pic?

Author:  simon k [ Tue Jan 07, 2014 9:31 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

does sound weird, they're normally a nice neat drop on fit - how do they compare with your old ones?

are the old rotors and flanges a neat fit?
do the old flanges sit nicely over the new rotors?
do the new flanges sit nicely over the old rotors?

Author:  mini_mad_matt [ Tue Jan 07, 2014 10:09 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

In the last 12 months or so i have put together a few disc brake kits for people and all of them have had this problem.

I don't really like it, but with some persuasion, tightening the screws, some more persuasion etc you should be able to get it all seated. You can tell as soon as you place the flange on the top of the wheel studs that they don't line up very well.

Author:  junior [ Wed Jan 08, 2014 7:23 am ]
Post subject:  Re: Installing New Drive Flanges & Rotors

simon k wrote:
does sound weird, they're normally a nice neat drop on fit - how do they compare with your old ones?

are the old rotors and flanges a neat fit?
do the old flanges sit nicely over the new rotors?
do the new flanges sit nicely over the old rotors?


I have changed from 8.4's to 7.5's so can't make the comparision

Author:  junior [ Wed Jan 08, 2014 7:32 am ]
Post subject:  Re: Installing New Drive Flanges & Rotors

As mini_mad_matt mentions, it's obvious that something is not right when the flange first goes on over the wheels studs, it's as if all the studs have a slighty smaller PCD that the holes on the drive flange.

Problem slightly exagerated, ie the drive flange is only just pressed on. It will go on further with a light tap, but still sits 1-2mm off the face on a similar angle

Image

Image

Author:  Mick [ Wed Jan 08, 2014 8:52 am ]
Post subject:  Re: Installing New Drive Flanges & Rotors

That's pretty ordinary. The load from the drive train and from the disc is transmitted through the interference fit of the studs onto the disc. If the holes are oversized it will start to flog, and it will also transmit load unequally onto the studs.

Author:  Davo111 [ Wed Jan 08, 2014 12:08 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

yeah, what mick said, if the head of the wheel nut is tapered, it will sit the stud in the centre of the hole, so there is some play if the nuts are not tensioned evenly and tight.

Author:  drmini in aust [ Wed Jan 08, 2014 6:27 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

I'd be getting a vernier caliper and measuring the PCD of those studs. They should be 101.6mm (4"). If much more or less, they can break in service as the nuts will force them to 4" PCD at the wheel.
Also, measure the PCD of the holes in the drive flange.
Where did you buy them? It is unusual for the rotors to be dodgy (even Chinese made RDA ones I once had were OK).

Author:  junior [ Wed Jan 08, 2014 8:39 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

PCD of the drive flange measures 101.6, & between 101.2 & 101.4 for the studs on the rotor.
Looks like the issue is the base of the studs, the non threaded section measures 9.9mm & the tread at 9.44mm causing the interference.

Doc, they came with a job lot of new & used parts I bought recently, they did however MiniS..... part number stickers on the wrapping. The edge of the rotor is stamped BDC.

Author:  drmini in aust [ Wed Jan 08, 2014 9:51 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

That PCD is not far out enough to cause any problems except fitment, I would drill the drive flanges just enough to clear.
Can do them accurately here on the mill for nix if you care to drop in.

[edit] Or you can spend 5 mins with a round file, there is hardly anything to come out.

Author:  Davo111 [ Thu Jan 09, 2014 11:53 am ]
Post subject:  Re: Installing New Drive Flanges & Rotors

Doc, we need someone exactly like you down here in Mexico, have you considered moving down here, please, :-/ :-/ :-/

Author:  junior [ Thu Jan 09, 2014 12:51 pm ]
Post subject:  Re: Installing New Drive Flanges & Rotors

drmini in aust wrote:
That PCD is not far out enough to cause any problems except fitment, I would drill the drive flanges just enough to clear.
Can do them accurately here on the mill for nix if you care to drop in.

[edit] Or you can spend 5 mins with a round file, there is hardly anything to come out.


Doc, thanks for the offer, will try the file first.
cheers, josh

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