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Machining the rear hub flange

7 Oct 2007, 8:37pm
I noticed yesterday, when my car was up in the air, that my rear discs had some scratch marks on them, but not the whole way around.....

On investigation, I discovered my rear discs had quite an alarming amount (if it's visible, it's pretty bad!) of runout. On closer inspection, although I thought my discs were mounted properly on the hub flange, it transpired that the discs weren't making contact with the flange face, instead the radius of centering spiggot was making contact with the disc, causing the disc to sit approx 0.5mm from the face of the flange. Thus when bolting a wheel on, depending on which wheel nut was pinched first, the disc was pulled against the flange in the area of that nut, ONLY! The effect is that of a buckled disc, and as the wheel sits against the disc, the wheel also wobbles.

I ignorantly previously thought I didn't have a problem with my rear hubs, despite reading that others had machined their rear hubs.

Luckily I know someone who will turn the hub face to match the disc, but the experience has made me wonder how many other people have made the same mistake I have.

I've now stripped my rear uprights, and all I need to do before presenting my hub centres for machining, is remove the inner bearing shell, which unfortunately has come away from the bearing (it's faily typical, but still annoying!).

While my rear suspension is in bits, I think it's time to opt for the phase 2 setup.......
7 Oct 2007, 8:56pm
Yeah I had this problem. Marlin machined mine while getting body fitted. They machined the discs though. Though not a problem for me now as I have changed the rear suspension and uses different discs.

But builders should be made aware of it.
7 Oct 2007, 9:01pm
John,

Do you know what disc the new kit uses, and did you opt for the standard caliper mount, or the post mount?

So far as I could tell, the disc being used on the standard caliper style hubs, is the 260mm Rover item, as fitted to the ZR 160s.
7 Oct 2007, 9:44pm
John, I had my hubs machined last year and glad I did it this way now (instead of disc) as I have changed rear discs twice!

Mine were machined with bearings in, just took thw whole thing along to them and they did it in no time at all for I think £10.

Thought the rear discs on mk 2 setup were 240mm?
7 Oct 2007, 10:27pm
Yeah, I'm now wishing I'd got mine machined when I had the hub in pieces. Oh well, after feeling the rear end of Rich's car go rather floaty, when switching from acc' to braking, I'm going for the mk2 setup, for the extra toe stiffness anyhow.

The mk2 setup definitely doesn't use the 240mm disc. Exactly which disc it uses I'm not sure, but I know the disc used on Dylan's car (with the post mount Willwood caliper) is different to the disc used on the OEM sliding caliper cars.
8 Oct 2007, 6:14am
Hi guys.

Unfortunaty, having a play the week end with the suspension but got wrong discs. Got the fronts delivered so can't comment. They should be from a Nissan Almera GTI or Pulsar GTI rear. Hopefully check with Nissan today.

Interesting you mention the mounts. Did not know there was a choice. But did a quick check offering up the caliper, and it seemed to interfere with the lower wishbone. Thought I was going crazy! I'll speak with Marlin today.
8 Oct 2007, 6:48am
John

You are already gathering that you are not alone here, I was absolutely appalled that this was not put in the manual because it is a very easy mistake to make. I fortunately did not make it, but only because of sheer fortune I was with Trevor one of the early builders the day he uncovered this, and Merlin man (AKA Ian) kindly turned the disks down on his lathe.

I put this to Mark Mathews that I felt this information should be in the manual (or the new one I was told was under production eighteen months ago), his response was somewhat dismissive, by saying surly it’s obvious. Well actually no its not as many builders have fell into that trap as I pointed out, the apology has been slow in coming.

Steve

P S David H worth getting your flanges machined down, rather than the disks, as Craig pointed out you only have this done once then.
8 Oct 2007, 12:27pm
John,

The link below, is handy for checking brake specifications:

http://www.conti-online.com/generator/www/com/en/ate/ate/general/home/index_en.html

Go to 'catalogues', then 'replacement parts online'

You can browse the specifications of most cars, including disc diameter, centre bore, thickness, offset, caliper piston size, etc...

Having just had a very quick look, the PCD of almera discs is quite different to a Rover.......

Regards,

John.
8 Oct 2007, 1:20pm
SDMC001 wrote:
P S David H worth getting your flanges machined down, rather than the disks, as Craig pointed out you only have this done once then.


Steve,

Yeah, am always of the mind to do things once, have already stuck a postit note in that section of the build manual to remind me when I get to that stage.

Cheers

David.
8 Oct 2007, 4:59pm
Hi guys.

I'm going to start a new thread about new setup. Saves mixing this thread.

BTW anyone needing a set of rear discs alread machined, I have a couple that is no use to me. They are grooved and drilled. But again, once they wear out, the new ones will need machining so on a long run, hubs are a better choice to get machined.
9 Oct 2007, 11:43pm
Luckily I picked up the disc issue from this forum. I got the hubs machined at work before fitting them. I still found I needed to grind off the outer corner of the hub as well so it fitted properly into the disc bell. Otherwise I found it still didn't pull down properly flat onto the hub.