V brakes a no go on this frame?

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Sweep
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V brakes a no go on this frame?

Postby Sweep » 7 Feb 2016, 7:41pm

Maybe evident I am doing some tinkering today.

On the Ridgeback 520SX - late 90s hybrid.

A while ago I put V brakes on the front instead of the cantis it came with.

Went well and all works fine, better than before.

Front mech shifter combined with canti lever for the back packed in so I thought I'd put Vs on the back as well.

Already have rear V brake and lever and a new front mech shifter.

But here's the rub - it has just occured to me that I very probably can't put a V brake on the back - studs for mounting are there but the old 90s frame doesn't have the requisite mounts stops.

As set up at the moment with cantis, there is a cable stop at the front of the top tube, then the cable just runs in a non reinforced plastic tube along the top tube until it enters a squiggly bit of metal by the seat post:

like so:

https://www.flickr.com/photos/37034456@ ... ed-public/

then drops down via the straddle wire to the rear Altus brake.

So am I limited to my old Altus canti on the back?
Last edited by Sweep on 7 Feb 2016, 8:05pm, edited 3 times in total.
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Sweep
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Re: V brakes a no go on this frame?

Postby Sweep » 7 Feb 2016, 7:50pm

deleted - repetition of pic I eventually managed to insert in original post.
Last edited by Sweep on 7 Feb 2016, 8:03pm, edited 2 times in total.
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Vantage
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Re: V brakes a no go on this frame?

Postby Vantage » 7 Feb 2016, 7:56pm

You could run the outer brake cable all the way from the lever straight to the vbrake noodle. Just zip tie the cable to the frame at various points to stop it flapping around.
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fatboy
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Re: V brakes a no go on this frame?

Postby fatboy » 7 Feb 2016, 7:57pm

Vantage wrote:You could run the outer brake cable all the way from the lever straight to the vbrake noodle. Just zip tie the cable to the frame at various points to stop it flapping around.


That's what I'd do
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Sweep
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Re: V brakes a no go on this frame?

Postby Sweep » 7 Feb 2016, 7:59pm

Will that be a long lasting solution?

Will it be safe - ie will any braking force be lost?

Anyone else done this?

Please note that this is now my favourite/daily bike (I have 5) and I intend to take it on some tours, possibly long.
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jk49
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Re: V brakes a no go on this frame?

Postby jk49 » 7 Feb 2016, 8:04pm

yep, did this on my 90's hardtail about 3 months ago. It has improved the preformance of the rear brakes, but I think that is probably due to the cables and outers being brand new. Certainly no downsides so far. HTH.

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Re: V brakes a no go on this frame?

Postby Vantage » 7 Feb 2016, 8:07pm

It'll be perfectly fine :)
A few bikes had their cables run this way (maybe still do) years ago.
http://4.bp.blogspot.com/_SZx2oaxuJSA/R ... bles03.jpg
The only difference will be that yours are kept in place by cable ties rather than steel eyelets. Others had the entire cable routed within the frame itself, internally. They don't come under any pressure.
Last edited by Vantage on 7 Feb 2016, 8:09pm, edited 1 time in total.
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gregoryoftours
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Re: V brakes a no go on this frame?

Postby gregoryoftours » 7 Feb 2016, 8:09pm

Depending on the diameter of your top tube you could use a clamp with cable stop e.g
http://www.sjscycles.co.uk/origin8-clam ... prod26491/
http://www.sjscycles.co.uk/origin8-clam ... prod24825/
it would be a bit neater than a full cable outer run and potentially less draggy over time, although the former method would be reasonable, especially with some hydraulic hose guides.

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Sweep
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Re: V brakes a no go on this frame?

Postby Sweep » 7 Feb 2016, 8:47pm

Thanks all - what a wonderful lot you are. :)

I think I had the idea (physics was never my strong point) that I needed a rear stop in order to maintain cable pressure on the final run, thanks to interaction between cable inner and outer. But now I see that according to your posts I just need a simple clamping system.

Many thanks for the SJS suggestions gregory.

These also?

http://www.evanscycles.com/products/gen ... RRWidgetID

I see that at least one reviwer used them to do a similar switch from canti to V brakes on an older frame.
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gaz
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Re: V brakes a no go on this frame?

Postby gaz » 7 Feb 2016, 9:09pm

The SJS are clamp on cable stops, with a pair you would end up with a bare cable run along the top tube.

The Evans offerings are cable guides, to hold outer cable in place as an alternative to zip-ties. You'd need a full length outer cable from brake lever to V noodle.
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gregoryoftours
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Re: V brakes a no go on this frame?

Postby gregoryoftours » 7 Feb 2016, 9:16pm

If you go the continuous outer cable route you ignore the existing cable stop on the frame and run outer completely from the brake lever all the way to the noodle, in which case you could use the clamps you linked to in order to keep the cable outer tidily against the top tube of the frame - those are basically guides and don't act as cable stops.
The clamps I linked to actually have a cable stop integrated into them and would enable you to route the cable as you normally would for a v-brake, so the bit of outer from the brake lever would end in the stop near the front of the top tube, then a straight run of inner cable to the rear of the top tube where you would mount the clamp to replace the missing cable stop like this -
51-020_cable_stop_for_site.jpg
then a short bit of outer cable between this and the noodle, like a normal v-brake setup. Either method will work fine, whichever you prefer.

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Re: V brakes a no go on this frame?

Postby PH » 7 Feb 2016, 9:23pm

Sweep wrote:I think I had the idea (physics was never my strong point) that I needed a rear stop in order to maintain cable pressure on the final run, thanks to interaction between cable inner and outer. But now I see that according to your posts I just need a simple clamping system.

You've got it, a canti needs to pull against a stop, but with a V brake each arm is pulling against the other.
Just remember that the longer the cable run the more important the quality of the cable, the losses are due to compression and IME there are big differences between brands.

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Re: V brakes a no go on this frame?

Postby Brucey » 7 Feb 2016, 11:19pm

note that if you try to use a clamp-on cable stop for a brake, and the clamp is round a plain part of the tube (i.e. when it is loose it can slide easily) then it will probably move when you subject it to braking forces.

If the frame is built of heavy gauge tubing then a heavy clamp might tighten enough to be moderately reliable but a light-built clamp and/or a light-built frame will probably break somehow before an unstoppered clamp will withstand braking loads reliably.

Thus I'd use a clamp-on device for the gears, if I had to, or if it butted up against a stop (as per the photo above) for the brakes, but probably not otherwise.

BTW I have seen the seat lug canti guide tube you describe used as a cable stop for V brakes; you just need to engineer a suitable ferrule to go between the housing to the V brake and the projecting part of the guide tube (if there is one, you are a bit stuck otherwise) at the lug. I think the ferrule from the upper end of a V-pipe will often do, because the guide tube is often the same size as a V-pipe.

cheers
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Sweep
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Re: V brakes a no go on this frame?

Postby Sweep » 7 Feb 2016, 11:37pm

Sorry brucey, i don't quite understand you, particularly the second para. Are you saying that the preferred approach for the brakes would be to use the continuous outer run lever to noodle (with outer zip-tied or clamped) rather than subject a clamped STOP to forces it might have trouble with?

Re the final para i had the impression that using, even in an adapted way, that metal squiggly pipe near the seat tube wouldn't work as it would curve the inner one way and then it would have to curve straight back to attach to the v arm. Its original purpose of course was to get the cable in the centre for the canti.
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531colin
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Re: V brakes a no go on this frame?

Postby 531colin » 7 Feb 2016, 11:46pm

You could always use one of these Surly cable hangers that dangle off the seatpost clamp

Image

....or a seatpost clamp with a built in cable stop....

Image

OH NO!! BRAIN FART AGAIN! Those are for cantis!!
Last edited by 531colin on 8 Feb 2016, 10:48am, edited 1 time in total.