Hi,
I’m posting this for a new member who can’t post here yet.
by SimonD » Tue Dec 03, 2019 8:25 am
I have a query. I don’t seem to be able to post a question in the technical bit. Is this ‘cos I’m new?
Here’s the question, anyway.
1977 LM1. Horrid brake judder on front brake. Linked brakes are fine, as are pads, bearings, wheel, etc. Suggestions very welcome. Have not yet clocked disc.
Thanks in advance
Simon
Are you just having the judders on the front brake opperated by the handlebar lever? Is the disk true and not warped? Has this just started or is it an ongoing problem? My guess would be a warped disk, if it is you can get them skimmed depending on the thickness.
Brake judder is usually down to a warped disc, easily seen by spinning the front wheel and looking head on.(easiest place to see it is on roller brake tester where dial oscillates, MOT failure!!)
Is it definitely brake judder and not suspension chatter?
Skimming a warped disc may not be possible as just getting the disc true again might involve removing too much metal
CHRIS
My Spada had a lot of run-out on the right-hand disc, but when I clocked the mounting surface on the wheel some of it was there. I was able to more-or-less eliminate it by trying the disc in each of the 6 positions until I found the least total run-out.
Ian
My Spada does it when heavy sustained braking on the right front disc. I just put it down to a scar on the disc from where the pads have sat for a while leaving a mark.
Thanks to Uki for moving my question to the forum, Jennet for changing my status to member, and those who posted replies:
The judder is only on the hand-brake, it doesn’t appear on the linked brakes. I think it started when I went over a hideous pothole some years back, but I wouldn’t swear to it.
It feels like a once-per-rev pulse on the lever, the actual braking doesn’t seem to vary.
I did try to clock the disc a week or so back but need to sort out a better way of setting up the dti. Will report back when done. The disc does not appear to wander visually side-to-side in the calliper, I’m guessing I’d be able to see 10 or 20 thou. run out. When I measure the run out, I’ll measure for eccentricity too. And check the disc thickness.
Callipers & pads all good.
Cheers
Simon
If you got a micrometer, you can go around the disc measuring the thickness at various points. I remember doing this on my Spada’s discs and was surprised how much variation there was. Altho there wasn’t any problems in use. When I got my LM the rear was junked almost straightaway, looked like it had been scraping on something metal never mind just wear!
Thanks Mike,
I have a digital vernier (well, you know what I mean) and will do so.
My micrometers are 1-2” and 2-3”, so not exactly ideal, still they were free.
Atb
Simon
Well, I changed the fork stanchions last week, and took the old girl for a ride this afternoon. At this point I discovered that something was wrong. It appears that when I thought I had drained the fork oil, I didn’t do a good job of draining it - it didn’t drain with the screw removed, and needed to be pumped out by stroking the fork leg - so when refilling rather overfilled it. Sorted that this afternoon, I hope that it was the reason for the strange noises and clunks up front. We shall see.
Whilst I had the callipers off, I checked the runout. The right hand disc has a very distinct wobble. Need to get that sorted.
More soon
Atb
Simon
I did this with the Spada. Tried draining the forks, hardly anything came out so I thought oh no nothing in there! I knew it wouldn’t affect damping so assumed just no oil. Couldn’t get the tops off so injected fresh oil into the drain screw holes, I had measured how many pumps of the oiling can produced the correct number of cc’s. Next ride out (to work), forks were solid. Pumped them out in the works car park by diving the front end with the screws removed. Lesson learned, must get the fork caps off (somehow) to let the air in when draining, and to refill. Can’t remember how I did it but doubtless involved a big spanner and probably a hammer.
The right hand disc has a very distinct wobble
A-ha! 
Mike,
I’m glad it wasn’t only me!
I got the caps loosened whilst the forks were still in the bike, and I had the fork upright in the vice (with soft jaws!) with the tube removed, but I didn’t remove the springs or dampers. It wasn’t air-locked.
My guess is that a coil of the spring effectively blocked the drain hole, as it was only one side.
And a thought for anyone who thinks that filling the forks from the top is a good idea. It takes a very long time fo4 the oil to run down between the stanchion and the damper. And if it hasn’t all run down, it sprays everywhere when you press the stanchion down onto the damper…
Took her for a run on Monday and all was well. Lesson learned!
Merry Christmas
Simon
Super.
Don’t remember having a problem doing that, but you might be right.
My guess is that a coil of the spring effectively blocked the drain hole, as it was only one side.
I once had to poke a thin Allen key up the hole because it was blocked with crud. I thought, again, appears to be empty, but let’s try shoving something up there