fitting new v brakes

[blazingsaddles]

I'm not sure the new V brake I'm fitting to my Marin Hamilton frame is compatible and I would really appreciate some advice please.

The pin fits into the middle slot for the v brake, however, there remains a gap between the brake and the frame as the shoulder of the boss is a little too long. Is this acceptable?

Perhaps the attached Photo explains more.

Many thanks,
bs

[531colin]

Does the brake need to be snug up against the collar part of the boss?
As long as you can tighten the bolt and the brake arm is still free, and the spring/pin can't slip out of the hole in the frame boss, and everything works, I can't see a problem?

[blazingsaddles]

Does the brake need to be snug up against the collar part of the boss?
As long as you can tighten the bolt and the brake arm is still free, and the spring/pin can't slip out of the hole in the frame boss, and everything works, I can't see a problem?

Thanks. I think it will be ok also. Although its the first v brake i've fitted. The boss also finishes about 5-6mm prior to being flush with the brake arm, but I think that's not an issue as the bolt will tigten that up.

[Valbrona]

Hmm ... I am assuming your new brake is new and isn't some kind of relic that you have extracted from the attic. I say that because I have only ever known these brake pivots to come in one length. To my knowledge they have only ever been one length, even in the cantilever days and before V brakes were developed.

[blazingsaddles]

Hmm ... I am assuming your new brake is new and isn't some kind of relic that you have extracted from the attic. I say that because I have only ever known these brake pivots to come in one length. To my knowledge they have only ever been one length, even in the cantilever days and before V brakes were developed.

Yes. Its a Dia Compe V767. Brand new. Bought from the following link.

http://www.ebay.co.uk/itm/BARGAIN-PAIR- ... 35cdb00998

I'll photo the back later and upload here.

Thanks

[531colin]

I have been in the situation where the bronze bush in the brake was too long for the frame boss, so when you tightened the bolt the brake was stiff. This was cheap brakes on cheap bikes, and the manufacturers solution was to leave the bolts loose. Taking an end mill to the "frame" end of the bronze bush (where the spring goes) was the correct answer.

.....I'm a bit concerned over 5-6mm difference between the frame boss and the brake.....?

[blazingsaddles]

I have been in the situation where the bronze bush in the brake was too long for the frame boss, so when you tightened the bolt the brake was stiff. This was cheap brakes on cheap bikes, and the manufacturers solution was to leave the bolts loose. Taking an end mill to the "frame" end of the bronze bush (where the spring goes) was the correct answer.

.....I'm a bit concerned over 5-6mm difference between the frame boss and the brake.....?

Yes, I think what you are describing here is the situation I have. I'll try and upload more photos shortly!

[blazingsaddles]

ok. Got some more photos. In a way I was wrong about the boss falling 5-6mm short of being flush with the front of the brake arm. The new brake is parallel push and has a linkage system which adds about 3-4mm.The brakes are the same depth except for the linkage mechanism. So in effect the boss falls about 2mm short of being flush with the brake arm. That 2mm is of course caused by the gap between the rear of the brake arm brake arm and collar.

The reason I can't put the brake arm fully against the collar is hopefully visible in the photos which show the different design between the old brake and new brake.

Hope this makes sense!

Many thanks

[531colin]

If the frame boss is 2mm inset from the end of the brake, and the brake pivots freely with the bolt done up, then the brake has its own pivot, the brake isn't pivoting on the frame boss.
So if that's the case and the spring/peg can't come out of its hole, I would just ride the thing.
I didn't get much from your photos, what brake is it?

[blazingsaddles]

If the frame boss is 2mm inset from the end of the brake, and the brake pivots freely with the bolt done up, then the brake has its own pivot, the brake isn't pivoting on the frame boss.
So if that's the case and the spring/peg can't come out of its hole, I would just ride the thing.
I didn't get much from your photos, what brake is it?

Now I fully understand, thanks. It does not have its own pivot and when tightened up does not move. I've just got in touch with the ebay seller so we'll see what happens. I think, although I can not be fully sure that the bolt that goes through the v brake boss should have come with a shoulder the same width as the boss.

I should have just bought those standard Deore v brakes!

Thanks again

ps they are Nos dia compe parallel push v brakes. here's a link to the brakes

http://www.ebay.co.uk/itm/BARGAIN-PAIR- ... keparts_SR

[blazingsaddles]

I've decided to make my own shoulder for the fixing bolt out of some cheap v brake bosses I've just bought online. I'll cut them down to required size I reckon then it'll be ok

[531colin]

I've never seen these brakes, are they these ones?....http://www.mtbr.com/cat/brakes/brake-system/dia-compe/747-v-brakes/prd_350727_108crx.aspx
Making up the length of the frame boss with a sleeve on the bolt should be OK. The only thing I would say is make sure the bolt comes well into the frame boss, like reaches the larger diameter bit next to the frame, if its tapped. I'm sure I read that somewhere as a recommendation for every brake, although in the past the bolts were much shorter, and I never broke anything.
I'm still not clear about the structure of the brake.....if the arm itself pivots on the frame boss, what exactly does that bit of parallel push mechanism on the end pivot on?
For longer bolts, google "Westfield Fasteners"

edit...it doesn't help, but I think good old XT pivot the brake arm and the parallel linkage on a sleeve, and their bolts have a bit of a shoulder

[blazingsaddles]

I've never seen these brakes, are they these ones?....http://www.mtbr.com/cat/brakes/brake-system/dia-compe/747-v-brakes/prd_350727_108crx.aspx
Making up the length of the frame boss with a sleeve on the bolt should be OK. The only thing I would say is make sure the bolt comes well into the frame boss, like reaches the larger diameter bit next to the frame, if its tapped. I'm sure I read that somewhere as a recommendation for every brake, although in the past the bolts were much shorter, and I never broke anything.
I'm still not clear about the structure of the brake.....if the arm itself pivots on the frame boss, what exactly does that bit of parallel push mechanism on the end pivot on?
For longer bolts, google "Westfield Fasteners"

edit...it doesn't help, but I think good old XT pivot the brake arm and the parallel linkage on a sleeve, and their bolts have a bit of a shoulder

Not sure if they're the brakes in the link. I don't think so. I did see on the net last night the shoulder on the bolt for the xt and I realised they really should have been sold with such. The link attaches to pins top and botton. The bottom pin is fixed as it is attached firmly to the bronze bush that goes right though. The top link to the section that holds the brake pad. I'll try and photo in sequence and upload, probably tomorrow. Thanks for the link for longer bolts!

[blazingsaddles]

Thanks for all replies and info Colin. I've given up on these though. Taking an age!

Best regards,
bs