R80ST MOT

MOT test yesterday.

I have not used this particular test station before, but was in a town on my route home yesterday, so booked in.

The tester made an advisory:

Brake indicates slight fluctuation of brake effort Front, 1.2.1 e
Brake indicates slight fluctuation of brake effort Rear, 1.2.1 e

He showed me the needles in the brake tester fluctuating when a steady pressure was applied to brake lever.

He did record a pass.

Is he expecting the brake performance of a 35 year old bike to be the same as a brand new bike?

How to resolve?

Front.
Looking at the disc itself it is pretty ridged across the area in contact with the pads.
Its easy enough to replace the disc and pads.
Is there likely to be anything wrong with the caliper or master cylinder leading to allowing this fluctuation to occur?

Rear.
Probably not quite so easy. Sure, I could fit new shoes, but is it possible that the drum is not truly round anymore. ie Ovality.

Can these drums be skimmed round?

Anybody shrinking in new steel liners?

Thoughts?

My St drum went oval - like yer foot would bounce while depressing the pedal. Got a newer wheel as I dont think they can be re-lined (well at that time 10 year ago).
I told the tester the pedal was only there to make the rear light work = he smiled but failed it
I just replaced the pads on front with new uns that could make the wheel lock up in second.
Good luck

If there is plenty of meat left in the drum it might be possible to give it a light skim, but after 35 years it might be a little worn.
Max OD is usually on the drum somewhere.

Might be worth giving a wheel builder a look first, as at some point the wheel may need truing and he might know if it is best done before or after skimming. Or instead of!

The drum lining is cast in into the alloy and is an integral part of the wheel, usually using the Alfin process, which is why at one time no one would touch them.
But imbecility seems to be prevailing these days, CV Boris and Donald, and there are now some guys advertising that they can do it for sports car wheels.
Might work on a trailer queen which at best might do a parade lap at a show, but it would take either a very, very brave man to ride a bike with one. Or a complete effing idiot!

Always true up the wheel first before skimming the drum.

Every bike I've ever seen tested fluctuates the meter.

Edit: There is definitely a tendency for MOT testers to plaster Passes with Advisories these days. Whether it's arse covering or just to show they actually did something, I couldn't say, but I would ignore it.

Having used the ST again today, 75 mile round trip, I am now looking for this brake fluctuation.

Rear brake, could not feel a thing.

Front brake, when braking hard, not a thing, but when feathering the brake very gently I could just sense 'something' coming down to low (< 30) speeds.

The needle indicators on the rolling road must magnify the brake result 100's of times, making it look worse than it really is.

@cookie. I think you are right, ever since they changed the MOT form (last year?), I think that I have had an 'advisory' for every vehicle presented. My son even had the manufacturing date code of the two rear tyres recorded as 'advisories'

Arse covering. Don't the DVSA trust the testers any more?

dr nosh said:

Having used the ST again today, 75 mile round trip, I am now looking for this brake fluctuation.

Rear brake, could not feel a thing.

Front brake, when braking hard, not a thing, but when feathering the brake very gently I could just sense 'something' coming down to low (< 30) speeds.

The needle indicators on the rolling road must magnify the brake result 100's of times, making it look worse than it really is.

@cookie. I think you are right, ever since they changed the MOT form (last year?), I think that I have had an 'advisory' for every vehicle presented. My son even had the manufacturing date code of the two rear tyres recorded as 'advisories'

Arse covering. Don't the DVSA trust the testers any more?

Click to expand...

The way I see it, is that the DVSA are using the computers to produce statistics, to tell them which stations to randomly inspect, and the testers are countering this with producing the right statistics, so that they fly under the radar.

My lemans always has brake flunctuation when it’s tested, but it goes after about 10 miles.

This cropped up a few year back on my 2006 Electraglide. Barely noticeable in normal riding, but I knew I had overheated the fronts a tad on the Manghen Pass (Dolomites). Having decided to replace with HD discs & EBC pads I have to admit the brakes, such as they are on a Harley, were vastly improved - seemingly, although the run-out appeared minimal on the brake tester, it must have been knocking back the pads slightly. The trouble is, if you carry on, they only seem to get worse progressively; highly undesirable on a heavyweight bike.

Then your rear drum. My neighbour used Villiers Services. He had a local engineering shop skim the drum & then VS relined the shoes with oversize brake linings which are an essential element for good performance. They specialise in Classic bikes, but well worth a chat as they seem very versatile & say they can handle virtually anything.
........... https://villiersservices.co.uk/index.php?main_page=page&id=9&chapter=4