Cantilever brakes help needed.

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Hobbs1951
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Cantilever brakes help needed.

Postby Hobbs1951 » 14 Aug 2017, 8:59pm

My tourer currently has some rather old and needing replacement Shimano* cantilever brakes, can the helpful folk on the forum suggest a modern, more efficient alternative with which to replace them ?

Thanks in advance.

John.

*1980s Deore I think, arms out at right angle to frame.

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531colin
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Re: Cantilever brakes help needed.

Postby 531colin » 14 Aug 2017, 9:07pm

Nothing at all wrong with these....

Image

set them up as here......https://forum.cyclinguk.org/viewtopic.php?f=5&t=57410....arms as high as possible, straddle bridge as low as possible.
Among current stuff, Shimano CX70 are OK, but no better. than those pictured
Or Tektro RX 6 mini-vees, but you need a noodle with adjuster and true wheels
Last edited by 531colin on 14 Aug 2017, 9:09pm, edited 1 time in total.

Brucey
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Re: Cantilever brakes help needed.

Postby Brucey » 14 Aug 2017, 9:08pm

choice of brakes depends on boss spacing, but one model canti that works very well is Shimano BR-CX70. It is so adjustable it will work with any feasible boss spacing and indeed lever (provided you are happy to fit standard straddles and fiddle with the straddle length).

You probably have BR-AT50 or similar at present. These are decent brakes and can be made to work well, with

a) different brake blocks
b) good (new, well lubricated, not old rubbish) cables
c) attention to setup.

BR-AT50 won't work very well with current model STIs.

cheers
Last edited by Brucey on 14 Aug 2017, 9:57pm, edited 2 times in total.
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old_windbag
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Re: Cantilever brakes help needed.

Postby old_windbag » 14 Aug 2017, 9:45pm

I put Tektro CR720 on my dawes super galaxy replacing the standard canti brakes. They are very good and of same frog leg style as colins image above. My CX bike has similar brakes but made by kona( came with bike ).

Both brake well but I have used 4 makes of pads over around 10 years on the CX bike and the one brand from the 4 that stands out as excellent( for me anyway ) is:-

http://www.wiggle.com/kool-stop-v-brake-v2-dual-compound-inserts-for-h2-h12-1/

You can buy the v-brake holders with pads in situ or just replacements. In wet weather/drizzle they really do perform well and are quiet, it seems they don't require toeing in. The V2 has extra brake material, pricey but they are good.

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531colin
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Re: Cantilever brakes help needed.

Postby 531colin » 14 Aug 2017, 9:50pm

CR 720 have the cable attachment more or less level with the pivot
The old Shimano ones have the cable attachment more or less level with the pads.
.....a small but real difference when you are setting up for maximum mechanical advantage.

Brucey
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Re: Cantilever brakes help needed.

Postby Brucey » 14 Aug 2017, 10:01pm

BR-AT50 on wide-spaced bosses can be set as mid-arm cantis

Image

but if the bosses are set very narrow the arms have to be more horizontal (= less power)

CR720 will not fit narrow bosses at all and arms sit horizontally on wide-spaced bosses.

cheers
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gaz
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Re: Cantilever brakes help needed.

Postby gaz » 14 Aug 2017, 10:02pm

531colin wrote:Nothing at all wrong with these....

Image

+1
2020 : To redundancy ... and beyond!

old_windbag
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Re: Cantilever brakes help needed.

Postby old_windbag » 14 Aug 2017, 11:48pm

Brucey wrote:
CR720 will not fit narrow bosses at all and arms sit horizontally on wide-spaced bosses.



When you say narrow bosses is this a change from old frames having parts with imperial measurements to modern bikes being for the most part metric?

Edit: I misread what you were meaning by that, I thought you meant narrow boss as in diameter for mounting and wide-spaced as in distance between them. You meant width between them for both references, sorry I misinterpreted it. :(


At the time I fitted them I'd researched opinions as to the best way to improve the lx cantis fitted and I kept getting references to the tektro's. They fit my super galaxy bosses fine( 98), positioning wise they look the same as your image( just checked the non tektro CX's and they look the same ). They felt a big improvement over the original lx brakes on the dawes.

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531colin
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Re: Cantilever brakes help needed.

Postby 531colin » 15 Aug 2017, 4:57am

As I said above, the detailed geometry of the brake governs the mechanical advantage, not the brand name on the caliper.
Brucey's image....
Image
.....would have a higher MA with the straddle bridge lower. See the thread i linked earlier.

Brucey
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Re: Cantilever brakes help needed.

Postby Brucey » 15 Aug 2017, 10:17am

CR720 has the cable attachment barely above the height of the pivots (on wide-spaced bosses)
Image

which means (strength or weakness...?) there is very little scope for adjusting the brake MA; altering the height of the straddle makes little difference.

cheers
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old_windbag
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Re: Cantilever brakes help needed.

Postby old_windbag » 15 Aug 2017, 10:55am

531colin wrote:the detailed geometry of the brake governs the mechanical advantage, not the brand name on the caliper.


I think it's intuitive when you play with the straddle wire that lower is better in terms of MA. The maths is fine, I had the pdf document from several years back and have seen your thread also. When I refer to a brand name and part number it is only as a reference point, other brand names were mentioned by others too in that respect. The pads playing a big part in stopping performance. I'm lucky in that I only have to stop around 80kg total normally and 100kg at a max.

One limit on how low with this can be wrt these brakes is the tyre size/mudguard/light fittings/brackets etc. Mine are set as low as within those "hardware" constraints, I can only optomise the yoke angle to that limit. That may mean MA has a small range.

( my boss spacing is 75mm f, 80mm r ).

Hobbs1951
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Re: Cantilever brakes help needed.

Postby Hobbs1951 » 16 Aug 2017, 8:42am

Thanks everyone for the discussion on cantilevers. My Shimano bosses are 2.5 inches centre to centre on the rear and 2 .25" front, I must admit the main reason for thinking about a change is the cosmetic condition. However the arms have now polished up nicely, but I do need new (x4) chrome pivot bolts and a set of brake pads - an ideas where they might be sourced ?

I'll get some new straddle wires as they've seen better days and look old...I'm intended to have the frame restored hence the preoccupation with appearance, but not at the expense of the best mechanical condition I can get.

John.

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gaz
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Re: Cantilever brakes help needed.

Postby gaz » 16 Aug 2017, 9:06am

For brake pads, I'd recommend these. Be sure to order the unthreaded version.

Avoid V-brake versions for your front brake if you use wide rims. The pads extend back between the fork blade and rim, if you have wide rims and narrow forks there may not be sufficient space.
2020 : To redundancy ... and beyond!

Brucey
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Re: Cantilever brakes help needed.

Postby Brucey » 16 Aug 2017, 10:05am

Hobbs1951 wrote:Thanks everyone for the discussion on cantilevers. My Shimano bosses are 2.5 inches centre to centre on the rear and 2 .25" front, I must admit the main reason for thinking about a change is the cosmetic condition. However the arms have now polished up nicely, but I do need new (x4) chrome pivot bolts and a set of brake pads - an ideas where they might be sourced ?

I'll get some new straddle wires as they've seen better days and look old...I'm intended to have the frame restored hence the preoccupation with appearance, but not at the expense of the best mechanical condition I can get.

John.


The bosses are spaced narrow, which means that your choice of new brakes is likely to be limited.

For pivot bolts, M6x1mm threaded stainless steel bolts with various head shapes are available and will work. Screwfix and toolstation sell them at reasonable prices. If you want to go fancy, the heads can be further polished.

Whether longer (V-pattern) brake blocks are any good for you is dependent on how wide the brake blocks are and how wide the fork blades are spaced; there are three conditions;

1) won't fit at all (not enough clearance for them between the fork blade and the rim)
2) clearance to run but not enough to allow the tyre to come out without being deflated
3) no problem (as per most V-brake installations).

The latter is usually the case if the forks are rather wide and/or the tyre is rather narrow. The slimmest V- brake blocks are this type;

Image

eg clarks CP522 and offer cartridge brake blocks.

I think if the spacing between the fork blades is ~10mm wider than the centre spacing of the bosses, (or the fork blades are ~20mm further apart than the width of the tyre) the wheel should come out OK; if the clearance is any more than this, the parts of the brakes over the boss will be the minimum restriction width for the wheel/tyre. IIRC correctly Gaz has very narrow spaced fork blades and he has condition 1). On an oldish touring bike condition 2) is quite likely.

cheers
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Hobbs1951
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Re: Cantilever brakes help needed.

Postby Hobbs1951 » 16 Aug 2017, 10:18am

Thanks for that Brucey.

So more thought needed, it may encourage me, later in the year when I have the frameset restored (it's an oldie but from a highly respected builder), to remove the canti' bosses and fit caliper brakes...

John.