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V-brake / Canti boss into a 4 bolt mount


narrowbars

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Looking for some advise really off people who have done this mod.

Recently started using a rear v-brake as I have suffered with arm pump for years using a rear Magura and so far I've had zero arm pump with the v-brake :) Only trouble I'm currently having is the hold the brake offers isn't as much as my old Magura was and also the look of the adaptors then v-brake then booster brings it so far off the seat stays it looks like a piece scaffolding hanging off the seat stays lol.

My current set up:

Shimano Xt lever

Odyssey linner cable oiled

Avid Ultimate

Tried Heatsink adaptors and Neon adaptors

TNN lgv pads

Generic alloy booster

Onza Limey 4 frame

I've googled the subject a fair bit and done some reading and found how to do it, Adam from Tarty said on another site "Bottom 4-Bolt hole + 6.5mm drill bit + M8x1.25 tap + M8 V post = job done."

Is it really as easy as that and also are there any potential issues I should look out for? I'm a competent mechanic working in the trade for over 10 years so pretty sure I could carry this mod out easy enough, just a little worried if it doesn't work out and I wreck my frame.

People who have done this how long did it last and were the performance gains by moving the pivot location of the brake worthwhile doing the mod?

Looked to have a set up like this ideally

post-7131-0-52703300-1359150837_thumb.jp

Edited by narrowbars
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Size of the brake mount could be the problem, on my frame there wasn´t enough space to fit M8 posts, so I had to machine them down to M6...Then you have to get some metal plate or piece of carbon and drill 2holes in it,1for the pivot and one to secure the vee´s spring. That´s pretty much it, not very hard to do and difference in stiffness is very noticable.

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Size of the brake mount could be the problem, on my frame there wasn´t enough space to fit M8 posts, so I had to machine them down to M6...Then you have to get some metal plate or piece of carbon and drill 2holes in it,1for the pivot and one to secure the vee´s spring. That´s pretty much it, not very hard to do and difference in stiffness is very noticable.

Thanks for the reply, I've seen m6 canti studs available and was tempted with them. How long have you been running your set-up?

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Not long really but can´t see why it shouldn´t last, the worst thing which could happen is stripping thread on the frame and even that seems unlikely to me as the thread size is bigger and also longer than bolts I have used on adaptors, so overall surface should be almost the same. Ali C used to use it for quite some time I believe, so I´m sure he will chime in once he is around :)

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I could get some canti studs made at work with an m6 thread on the bottom no problem. steel or ally ?

Thanks for the offer mate but I can buy m6 canti studs fairly easily, there rare but not impossible to get.

My concern with m6 studs would be the strength of the studs over time and weather they would flex/bend or even snap after a period of time with the amount of stress we as trials riders put through the rear brake.

This must be one of the reasons hardly any manufactures use m6 studs and why m8/m10 are the more common sizes.

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It's hard to say how long it would last. If it came lose at all and you didn't notice that would have the potential to damage the treads. Personal I would get some made up with a finer pitch tread. 8x 1mm pitch or maybe even 0.75 would make it alot stronger

Your beat off using some decent stud fitt to.

Also don't tap it by hand. Use a pillar drill if you can. By tapping it by hand you will have a much slacker thread

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I did this to a Speedrace Fans frame. I used an M8 brakes boss (can't remember the pitch), drilled and tapped by hand, bit of carbon for the spring to sit against and it was lovely. Really low profile, stiffer and just generally better.

I can't really comment on it's durability as I only ever rode the bike on some walls outside work as I decided it wasn't as fun as my inspired. I would definitely go with M8 though, I wouldn't trust M6 at all.

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Why wouldn´t you trust it Ali? M8 ones like stan for example are only 6mm dia in the thinnest part where the thread ends, which is where the most stress of braking goes to or isn´t it? So I think they could only strip easier, but not break easier. If they do strip, I will just helicoil it like I would with all 4bolt mounts...

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I'ved tried m6 before and they were really flexy, they just made me nervous

Original m6 or machined down from m8? Maybe normal m6 are thinner in that part in the same way as m8 are, in that case I would be affraid too :) I haven´t found any pics of m6 so can´t tell if that´s the case. Only thing I can tell is they feel miles stiffer than heatsink adaptors.

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Thanks for the advise guys :)

Tempted to try m6 bosses first then as i can always fit a heli coil into the m6 thread I cut to bring it back down to m5 if i ever wanted to change back to a Magura or sell the frame.

Just measured the width of the 4 bolt mounts on the frame and there 10mm. Do people think theres enough width there to get to m8 if I needed to?

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Well after I found 1pic of m6 I can imagine m5 being quite scary canti-studs-brake-bosses-in-size-m6.jpg

pretty sure my Speedrace ones were around 10mm square

Mine were too and 1,5mm of material per side seemed too little hmmm. If you can get m6 ones easily, your idea of trying them first could be the best ;)

Edited by ghostrider88
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Thanks for the advise guys :)

Tempted to try m6 bosses first then as i can always fit a heli coil into the m6 thread I cut to bring it back down to m5 if i ever wanted to change back to a Magura or sell the frame.

Just measured the width of the 4 bolt mounts on the frame and there 10mm. Do people think theres enough width there to get to m8 if I needed to?

If you do a google search 'timecert' I think the Od thread is 7x1

Regarding the boses it depends on what material they are made from. Some cheap mild steel is going to be alot softer and flexible than some higher grade tool steel

Ideally you want some with a larger shoulder, as big as you can get away with

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