RGM Front Brake Disc Issue

Long for detail. Qualifier: I have been a mechanic for over 50 years on Euro and Road Race Cars, the last 20 of which have been focused on BMW's. I have owned, ridden, raced countless bikes over all of those years. I have experience with Brembo and Stop Tech.

Coming towards the end of a restoration/upgrade on my '74 Commando as the original owner, I decided to upgrade the front brake disc to compliment the 13mm MC, braided SS line, and Grimeca caliper after seeing the exact same components on another '74 Commando that also had the RGM drilled/floating front brake disc.

In May of 2022, I received the RGM caliper adapter mount and brake disc. I removed the wheel, inspected the new sealed wheel bearings, the tubular internal spacer, and the fit of the external factory spacers. All good there. I removed the caliper and hung it knowing that I would have to fit/adjust it at the end after the new mounting bracket was installed as well as the wheel with the new disc. I installed the wheel and Axel and started tightening the large nut by hand when I saw that the rivets were making contact with the inside of the right side slider. Hmm....I released the nut until I saw some clearance, and took a rough measurement of .004". With this clearance, I guessed I needed about a .035" additional wheel spacer.

I contacted RGM and after a couple of days received an email reply to my findings from Amanda (?) where I requested what the specified clearance spec should be to the slider and what size shim. She told me that the last batch of these parts "were not the norm" and Roger said I should increase the size of the additional spacer. WTH????
I replied to her again requesting the specs and suggested that if they were going to sell a known problem product, they should include an extra set of instructions and provide a spacer assortment as not everyone has the experience and resources that I have who are working on their Nortons.

I never heard from her again. I wondered why first, there wasn't an apology. Second, why they didn't offer to send me a proper disc with a PPD return label to send back this disc, or send me a PPD label to send this kit back and credit my debit card.

I looked at the other Commando's brake disc, and noticed that the offset of the center section/hub was visibly different as was the way the rivets were attached. I measured the clearance of the rivets to the slider and it was .043".

I contacted my NASCAR buddy who has been building tube cars from the plate up for at least 50 years and asked if he could work his usual magic. I took the wheel with disc, Axel and nut and the 2 factory spacers to him. 2 hours later, he called me to say he was done. He fabbed up a spacer out of steel where the ID matched the OD of the Axel and the OD of the spacer matched the OD of the factory spacer on the right side. He said he made the spacer .0875".

I installed the wheel and the 3 spacers, and really didn't notice much of an external spreading of the forks with the new spacer. I measured the clearance of the rivets to the RS slider and it was now .095", but the wheel rotated nicely after the nut was torqued. Knowing I was going to have to shim the caliper inboard and that the nylons would not make contact with a shorter bolt, I installed the caliper with regular nuts and blue lactate (uh, auto spell). I shimmed the caliper inboard with 3/8" flat washers and now the brake disc was perfectly centered in the caliper. I adjusted the caliper so the outer surface of the pads rested just below the outer beveled edge of the disc.

The bike should make it's maiden ride sometime next week and I'll check everything out after a complete, no money spared, bare frame restoration over the last 2+years.

Not a chance in hell would I ever buy another product from RGM after this experience. I am personally and professionally insulted by their lack of taking care of their issue.

I have been buying from them for maybe 20 years. And yes it has been a bit up and down.

I have had quality items from them I could not find anywhere else so that was good.

But on the other hand an Engineer friend of mine says that sometimes you can end up being Roger's beta tester.

I can see your from the USA. It's an English thing. They have good ideas but execution can be a bit marginal sometimes. Remember the English invented the trade called fitter. I doubt that trade is necessary in an American context.

My same friend considers it almost miraculous when any slightly unusual part made in the UK fits straight up. In fact for a number of years he was employed by a bike dealer in NZ basically reworking British supplied parts so they could onsell the parts to customers with a reasonable chance of those parts fitting and working as designed.

It's kind of frustrating because these guys still build most of the F1 cars, designed Concorde and other world class machines. But their normal manufacturing capability reached a peak around WW2 and has been crashing ever since.

I buy a fair amount of kit from RGM & in the main it's good. Having said that, I've also had a few problem parts over the years. I've just fitted another of these discs to a friends 850 Commando I'm rebuilding & set the disc to clear the slider then pulled the rim back to centre. The thing with fitting parts from different sources is you really do need a certain amount of mechanical expertise. I know we all moan about parts that don't fit, but at least we can still buy some decent quality stuff for our long obsolete clunkers.

Martyn.

This problem has existed for a long time. Not just a batch "out of the norm". Spreading the fork legs with a spacer seems questionable, since the legs wouldn't be parallel anymore.

batrider said:

This problem has existed for a long time. Not just a batch "out of the norm". Spreading the fork legs with a spacer seems questionable, since the legs wouldn't be parallel anymore.

Click to expand...

Spreading the forks is more than questionable!
Forks have to be perfectly aligned to work

Just over 12 years ago my stock Commando brake nearly killed me throwing me over the handle bars, lucky for me was a slow speed accident but fractured my left arm and broken thumb, while recovering I upgraded to a full Grimeca front brake system from RGM, M/C, longer brake lever, SS brake line Grimeca caliper with mounting bracket and 12" floating disc, all mounting was straight forward without any mods at all with the full kit, one of the best upgrades to my brakes, have had no problems at all with this set up, I have also bought other parts for my Dommie project bike from RGM and so far no problems at all with quick service and delivery to AUS.

Ashley

74 Cafe' said:

I installed the wheel and the 3 spacers, and really didn't notice much of an external spreading of the forks with the new spacer.

Click to expand...

If spacers are added to the disc side of the hub assembly then (up to a certain point) there should be no spreading of the fork legs because the non-disc side slider has a "self-aligning" pinch-bolt clamp onto the axle. The axle would be displaced further toward the non-disc side by the spacers as it is the shoulder of the axle (visible in the gap) that locates the hub assembly on the non-disc side and not the slider.