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Re: First start up (disasterous) t500

Posted: Fri Jan 04, 2019 10:39 am
by tricky1962
Splant wrote:What is the radiusing you do to them ?can't see any make on the shoes I've got on at the moment
When you apply the brakes, certainly when new, only bits of the shoes will contact the drum. To get more area of shoe in contact with the drum, machine shops can stick the shoes on a lathe and remove the high spots etc

This rather chirpy bloke calls it re-arcing (which I think is a better description) and has a mate who has a machine that does it

https://www.youtube.com/watch?v=T0sdYjuyIYQ" onclick="window.open(this.href);return false;

It is a bit tedious, but you can do it yourself.

What I did was buy some chalk, and rub it on the brake shoes. Reassemble the wheel and brake (remembering to pull on the brake before tightening the axle as this allegedly centres the shoes in the drum). Release the brake, the wheel and slowly apply the brakes for at least one full revolution of the wheel, preferably several.

Disassemble and you will see the chalk has been removed from some areas of the shoes but not others. The clean areas are the high spots on the shoes, the chalky areas the low spots. The aim is to have most of the chalk removed so maximum contact area.

Using sandpaper (not coarse from memory but not emery either) sand the clean areas a bit to remove the high spots, rechalk, reassemble, retest and repeat. This is tedious but within 6 or so goes you should have 80-90% of the shoes clean after a brake application - shoes radiussed.

I found out this process by googling. I think the old fellas on BSAs and wotnot used to do this all the time and was led to it from the classic motorbike websites.

I would suggest getting some EBC shoes first though - night and day in my case

Best of luck

Re: First start up (disasterous) t500

Posted: Fri Jan 04, 2019 1:59 pm
by dollydog
what d'yer mean 'old fellas'? :D
i'd also suggest WEARING A MASK WHILST SANDING BRAKE SHOES!
i don't know what the new material is made from, or whether it's aggressive to the lungs, but the old type contained asbestos. still better to be safe :D
cheers, dd. [ex bsa rider]
p.s. i think you'll find to radius a shoe is to chamfer the leading edge down slightly, all the way across.

Re: First start up (disasterous) t500

Posted: Fri Jan 04, 2019 5:18 pm
by tricky1962
Sorry Sir!!
A mask is a good idea, but when I was sanding the shoes down, it was a few rubs over a couple of sq inches so not a lot of dust

"Radiusing" was how I found it, but as I said I though re-arc was a better description
and these guys may beg to differ with your description

http://www.autoandindustrial.co.uk/inde ... s-grinding" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Anyway, we know what we mean Image

Re: First start up (disasterous) t500

Posted: Sat Jan 05, 2019 2:56 am
by Splant
So what grade sandpaper are you thinking 80? I think that re,arcing on YouTube (like the second comment on there) needed to be done with brake shoes expanded to be any good, not in the rest position. I'm trying understand how the tightening axle while holding brake on works!

Re: First start up (disasterous) t500

Posted: Sat Jan 05, 2019 4:04 am
by tricky1962
I think I'd start with something finer. You wouldn't want to remove too much in one go. Also I seem to remember that it sanded more easily than I expected.

As to the axle tightening procedure, no I'm not sure either, but I thought it won't hurt will it

Re: First start up (disasterous) t500

Posted: Sat Jan 12, 2019 3:43 pm
by dorT500
Remember, drums do have wear/diameter limits....and limit shown inside the drum as you have probably seen. I recently had to replace my original rear drum but I had well over 100,000 miles on it

Back in the early '70's I worked part time for an independent auto supply store while in High School and we measured drums and arched shoes with the exact equipment shown below and of course it was not until years later we started hearing about the danger of the asbestos used in brake shoes then as 'dollydog' alluded to.

Image

Image

https://forums.aaca.org/topic/242058-ar ... ake-shoes/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;



I imagine you might still find an old independent auto supply house that still may have this machine or one like it bolted down to a bench collecting dust (regular dust) or a big truck (commercial) repair shop.

General consensus over the years were that the front brakes on the T500 series were not that great even when the bikes were brand new. I don't think I have ever adjusted the dual leading front brake linkage exactly right but Alan H. gave a description on how to do it in a thread somewhere around here....that and an occasional cleaning of the drums,cams and cleaning and or replacing the brake cable helps of course. I use EBC and they also sell the type with angled slots to help displace water, dust, etc or you can cut slots in the brake shoes your self. You might have noticed the picture of this in one of the links member 'jabcb' posted.

link to your other post on the subject.. viewtopic.php?f=2&t=13819" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;