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Trying to improve my front brake.
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Blue Heeler
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April 7, 2020 - 6:21 pm
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Grand job Nick and love your artistic "up the fork leg" photos too 🙂

Blue

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nickjaxe
Runcorn Cheshire UK
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April 7, 2020 - 7:33 pm
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Now you mention it Blue...yes looks good doesn't it...pure fluke. 

My Bantam video              https://www.you.....jpOFmzRZRI

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JackE
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April 26, 2020 - 4:33 am
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I've read this thread with interest, as one of the motorbike mags did a full article on a company up the road from me in Whaley Bridge (Classic Brake Services, between Buxton and Glossop, Derbyshire) which specialises in doing full brake overhauls.

In view of the comments about the 'brake linings feeling a bit hard', one of the comments the boss made in the article that he's come across a certain model of bike whose riders complain about the brakes lacking bite;  it turns out that particular model used exactly the same brake shoe as was used on the Mini - but the Mini brake shoes were a lot cheaper to buy, so many people fitted them instead of the proper shoe.  Trouble is that linings for cars are much, much harder than those meant for bikes, as the weight of a car is so much more - i.e., there's a LOT more kinetic energy to be turned into heat when they slow down.  So this bloke will ONLY use linings meant for bikes - and ensure that the grade matches the sort of use you'll give it.

Next point is that he says, especially with an old hub, which may have been re-spoked in the past, the drum (especially if it's pressed steel rather than cast iron) may have been pulled a tad out of true - so his first job is to make sure the rim is running true, then fit the wheel in a gap bed lathe, and skim just enough off the drum to make sure it's circular, and running true to the rim and spindle.  Finally, he measures the internal diameter of the drum.

Then he moves onto the shoes, fitting them with over-thickness linings of the right grade, then assembling them onto the backplate with two very thin shims in between the ends of the shoes and the operating cam - and finally turning the linings down to the exact diameter of the drum.

The result is that, when the shims are removed, there is just sufficient clearance between the linings and the drum that they won't touch, but you only have to pull the brake lever in slightly for the entire surface of the linings to be in full and even contact with the drum.  He says many of his customers are shocked at the difference it makes, as it's only then that they realise just how worn out the brakes were!

With regard to wear, bear in mind that a bit of wear on the pivoting ends of the shoes, on the pivot pin, and on the faces of the operating cam all add up, and all detract from the efficiency - see Picture 1.

Final point about maximum efficiency being achieved when the brake lever is pulled hard in and the angle between the the operating cam spindle, the cable nipple, and the cable is exactly 90 degrees.  That is perfectly true - but there's a catch.  For some reason I've never been quite able to work out, if the included angle - shown by the white arrow in Picture 2 - is a bit less, even quite a bit less, although you don't have maximum achievable efficiency, it's not that far down - yet once the included angle is even slightly more than 90 degrees, the efficiency drops off very sharply, and out of all proportion to the increase in angle.  So I think the best bet for all of us apart from Bantam racers is to give ourselves a bit of room to allow for wear, and set the brake up so that the angle is definitely less (though not seriously less) than a right angle.

Brake-Wear-2.jpg

                      Picture 1                                                                   Picture 2

You may have noticed from the above that I'm a bit fanatical about brakes and brake efficiency.  To se why, these are the sort of slopes we have where I live - and the roads are liberally sprinkled with blind bends, blind summits, headbangers on racing pushbikes with their noses just above the wheel and their backsides in the air, and sheep with a deathwish . . . I give you the Cat & Fiddle Road!

Cat-+-Fiddle-Road.jpg

Pretty, innit?

With best regards,

Jack

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Number6
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April 26, 2020 - 7:49 pm
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I learned something recently that may be useful – been looking at my brakes recently and fitting new shoes, springs etc. (I'm rebuilding a D1)

With the shoes assembled and testing the lever, I observed that one shoe travels further than the other, by virtue of which end of the cam is operating on it. Archimedes principle; the cam end nearest the centre of the drum also has the shortest distance to the fulcrum (pivot point for both shoes) whereas the other cam end is the furthest away. Ergo, the cam end closest to the fulcrum has greater leverage and thus pushes its shoe the furthest distance. The difference is about 1mm if not slightly over. This means, for new shoes, both being equal, this shoe will touch the drum first because it moves the greatest distance. The other (the least travelled shoe) may never touch the drum until the first has worn down enough. It turns out, for the rear brake the shoe that moves the furthest, and thus touches the drum first if the shoes are new, is the leading shoe, whereas for the front, being as the brake plate is reversed i.e. is on the righthand side, the shoe that moves the furthest is the trailing shoe. Hence recommendations to remove material from the front trailing shoe, which will allow the leading shoe to at least touch the drum at all. The shoes I took out of mine albeit old fashioned type (having rivets) the leading shoe has no marks on it at all, only the trailing shoe is showing any signs of use. In other words the leading shoe never reached the drum.

Mike H --

Murphy's 4th law of motion states that any small object that is accidentally dropped will immediately hide itself under a larger object.

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nickjaxe
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April 26, 2020 - 11:01 pm
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Mmmm thats interesting...look into that next time I look at mine.

My Bantam video              https://www.you.....jpOFmzRZRI

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JackE
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April 26, 2020 - 11:16 pm
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Many thanks for passing that on, No.6 - it constantly surprises me the way I'm still learning about the most basic aspects of bikes, after all this time.  Such as most pre-mid60s BSA fasteners being CEI, when I always assumed that (apart from small electrickery) they were Whitworth, BSF, and Cycle threads on ball and cone bearings.

With best regards,
Jack

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mcafee
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April 30, 2020 - 8:51 am
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Morning just to follow on from Mikes post I also found that the trailing shoe touches the drum first.With the wheel off the bike I chalked the new shoes and spun the wheel and gently applied the brake,hardly any chalk was removed from the leading shoe.As an experiment and I m not recommending this,I reprofiled the cam to try and equalise the lift of the shoes and repeated the chalking several times.I managed even the lift somewhat such that the chalk was removed fairly evenly from both shoes.On refitting the wheel I found that the braking wes improved but this maybe a subjective assessment but it was certainly no worse.

David

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nickjaxe
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April 30, 2020 - 10:45 am
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I have had to use shims/spacers on my 50 year Landrover for similar reasons with shoes available now....when good quality British Made Parts were still available say 25 years ago....I could put a set of shoes on it and would have full contact with the shoes/drum in no time.

My last set were Mintex...but they are prob made in China now.

My Bantam video              https://www.you.....jpOFmzRZRI

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BantamBaz
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April 30, 2020 - 11:32 am
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Going on from Nicks Land Rover story, many years ago we had a Landie in the workshop with a very long pedal travel.

The customer had changed all the cylinders & shoes to try & sort it but to no avail. After lots of time spent checking every thing, we found that the guy had had 2 drums skimmed during his overhaul, I refitted the old drums & problem solved. So be careful if you think to have your drums skimmed, you can make things worse.

Barrie.

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nickjaxe
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April 30, 2020 - 11:38 am
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Indeed Landrover go to the trouble to mark the drums with max oversize.

My Bantam video              https://www.you.....jpOFmzRZRI

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chickensoup
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April 30, 2020 - 9:39 pm
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Hi Nick, what a great job.

May try copying your lever for the D7. Need to check out the front brake on the D1 as last time I went out on it, I was finding that the front brake was nearly locking the wheel in the dry.

Nick

1950 BSA D1 Plunger   242 UYW

1966 BSA D7  LBF 62 D

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Blue Heeler
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April 30, 2020 - 9:52 pm
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chickensoup said
Need to check out the front brake on the D1 as last time I went out on it, I was finding that the front brake was nearly locking the wheel in the dry.

Sounds dangerous Nick.

Could be cam trying to jam at getting on for 90deg turn in shoes. Or maybe a shoe lining is unbonding or rivets popped, if it`s that type?

I have seen both linings off the shoes situation.

Blue

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Bee175
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April 30, 2020 - 9:55 pm
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chickensoup said
Hi Nick, what a great job.

May try copying your lever for the D7. Need to check out the front brake on the D1 as last time I went out on it, I was finding that the front brake was nearly locking the wheel in the dry.

Nick  

Agree with Blue on this. Unless someone has greased your front tyre, this doesn't sound right for a Bantam front brake on any of the series.

BSA Bantam B175 1971 and BSA C15 1966

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Sponge
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May 1, 2020 - 9:02 am
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I had the same problem with my D1 about 20 years ago. I had just aquired the bike ( as a good runner !!! - here we go again), and on first ride I found that it would lock the front wheel with the slightest pressure and threaten to have me off.  There was no grey area - either off or locked up solid !! 

On inspection all was fine - I could see nothing wrong - the drum was fine, the set up was fine, the shoes were slightly worn but well within normal tolerance, the wheel bearings were fine......etc.  On re-assembly the problem was still happening. 

On a whim I rang C&D autos and ordered a set of new front brake shoes and fitted them to the bike - nothing else was changed, no engineering etc. Lo-and-behold the problem was solved - just normal braking - restored. 

On closer inspection it was evident that the original front brake shoes were not exactly the same size as the new ones - they looked correct but I suspect that had come from a 'dubious' - offshore source - possibly manufactured to metric tolerances (converted to imperial at an infinate number of decimal places etc. The small difference had made a large difference at the wheel. 

Lesson learned:  Take nothing at face value - if somebody tells you a bike is a good runner / stopper - don't believe them - especially when it comes to brakes - 

Lesson Learned:  If you have a set of original BSA Brake shoes - then clean them up and keep them as a pattern in order to compare any new parts with them - it is a sad fact that there are cheap pattern parts out there - they may look shiney but do they work properly ? 

Lesson Learned: Only buy your brake parts from a reputable supplier - 

Nuff said - sorry to go on and on - but this info may save somebody's life .....

Sponge

 

 

   

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chickensoup
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May 2, 2020 - 8:29 pm
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Thanks Guys,

Will check out soon and let you all know the out-come. I suspect the shoes are worn out and the cam is almost rotating through 90 degrees as stated. shoes have only done 1000 miles, so they could be the bad reproduction ones also. 

Well done again Nick on your sound modification.

Nick

1950 BSA D1 Plunger   242 UYW

1966 BSA D7  LBF 62 D

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nickjaxe
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May 2, 2020 - 11:03 pm
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Thanks Nick...good luck with yours...still work in progress...want to get say 100mls on it and look at the shoes again.

My Bantam video              https://www.you.....jpOFmzRZRI

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Number6
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May 17, 2020 - 12:05 pm
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I've had this locking on thing too. Was my old D3, old shoes still in it, worked fine (as far as they can!) while the drums are cold, but during a 20 mile commute into northeast London in the summer drums expanded and front locked on, as said because cam goes 90 degrees. Used to have reach forward with my right toe to knock it off at each traffic light etc. 

Still, was better than ramming cars up the back because it couldn't stop quick enough! I got into this bad habit used to follow vehicles much too close, a consequence of zero riding tuition in those days (just get a provisional licence [which could be renewed every year], pair of 'L' plates from Halfords, 5 quid for road tax, 30 quid for insurance [TPFT] and off you go)

Mike H --

Murphy's 4th law of motion states that any small object that is accidentally dropped will immediately hide itself under a larger object.

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Lone Wolf
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May 18, 2020 - 11:09 pm
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JackE said

You may have noticed from the above that I'm a bit fanatical about brakes and brake efficiency.  To se why, these are the sort of slopes we have where I live - and the roads are liberally sprinkled with blind bends, blind summits, headbangers on racing pushbikes with their noses just above the wheel and their backsides in the air, and sheep with a deathwish . . . I give you the Cat & Fiddle Road!

Cat-+-Fiddle-Road.jpg

Pretty, innit?

With best regards,

Jack  

Wotcha.

Hmm - since when has the Cat and Fiddle been in Romania ?  laugh

^..^

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Blue Heeler
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May 18, 2020 - 11:39 pm
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Lone Wolf said

Wotcha.

Hmm - since when has the Cat and Fiddle been in Romania ?  laugh  

Hehe, you did a google image search too eh? ** Please log in to view **

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Lone Wolf
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May 18, 2020 - 11:42 pm
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Blue Heeler said

Hehe, you did a google image search too eh? ** Please log in to view **

Wotcha.

Indeed not - perish the very thought. whistle

 

I used ** Please log in to view ** wink

^..^

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