simple question...

[reohn2]

...what's the difference in cable pull between canti's/dual pivots and V's,I know that V's pull less cable but by how much.
It's to do with a possible drop bar conversion on the Longitude which runs MTN BB7's.
I'm thinking of midge bars,Kelly's,Tektro RL520's,but want some crosstop levers and I'm wondering if I can get away with caliper/canti RL721's

[irc]

Do V levers not pull more cable hence they work with full size v brakes? Normal road levers pull less cable so work with mini Vs.

[mjr]

Use the mechanical advantage and how much you need the pads to move to work out the pull distances, but I think this from the legendary Brucey means V brake levers basically pull over three times as much cable as sidepull calipers:

I guess a typical mini-V caliper MA is about 3:1 then, although it could vary greatly with pad height.

This compares with;

~3.5 or 4:1 for a full 'V' brake caliper
~1:1 for an old-style side pull with about 50mm drop,
~1.3:1 for a typical DP with a 57mm drop

Both side pull (exactly) and DP (approximately) increase MA pro-rata with reduced drop. So I measure about 1.5:1 with short reach ultegras.

[531colin]

http://forum.ctc.org.uk/viewtopic.php?f=5&t=63112&start=45
....About seventh post, Brucey gives the lever MAs

[reohn2]

irc
Trust me to get it frack to bunt

mrj and Colin
Thanks for the link,looks like it's a non starter for the crosstops

[RickH]

irc
Trust me to get it frack to bunt

mrj and Colin
Thanks for the link,looks like it's a non starter for the crosstops

Tektro RL740s (or 741s if you have a 31.8mm centre to your bars) work with V Brake pull brakes

I've "dropised" my Circe tandem using the 740s (beer can shimmed to fit 22mm bars), coupled with RL520 levers, Thorn bars (bought because of the narrow centre bulge & trimmed to 490mm) & Origin8 Drop Bar Bar Ends (giving a similar drop/reach to FSA Veros which I have on my road bike). Shifters are the original flat bar ones (front double derailleur/ Alfine 8 rear). I'm happy with the results.

Rick.

[stewartpratt]

For what it's worth, for years I've used old-style canti levers (which, AFAIK, have the same pull as road caliper levers) with V brakes. And I've also used mountain (ie V-pull) BB7s with Avid Speed Dials would in for extra mechanical advantage, though I'm not sure how close to canti pull that brings them.

Those figures quoted above aren't cable pull, they're mechanical advantage at the brake. Brucey gives the lever MA figures in this post:
viewtopic.php?p=542120#p542120

But even then that's not the full story, because different levers may have different travel. The fundamental question is: Can you set the brake up so it can be fully activated but without any rubbing of the pads when the levers are at rest? And that's the product of many factors.

I suspect you could just about get it working, but knowing how close BB7s need to be run to the rotor, I suspect the bite point at the lever would be too close to the bars for my taste. I've not personally tried road levers with MTN BB7s, though

[Brucey]

.... but knowing how close BB7s need to be run to the rotor, I suspect the bite point at the lever would be too close to the bars for my taste. I've not personally tried road levers with MTN BB7s, though

spongy, powerful, dangerous; in a single descent, some pad types might wear enough for the lever to come back to the bar.

BTW unless the reach of the lever is unusually short or long, the MA is pretty good guide to the available cable pull; higher MA giving shorter cable pull and vice versa.

IME using short pull road levers with mini-Vs can be marginal (CJ feels strongly on this point IIRC); with full V's it is ~25% worse. You would have brakes that need adjusting every five minutes, and that would rub if the wheel is the slightest bit out of true or anything flexes.

R2 should be able to use V-specific brake levers and V-specific cross-tops for his proposed conversion; this would certainly be the best solution.

cheers

[stewartpratt]

BTW unless the reach of the lever is unusually short or long, the MA is pretty good guide to the available cable pull; higher MA giving shorter cable pull and vice versa.

Indeed: lever MA, not caliper MA as given above, though.

R2 should be able to use V-specific brake levers and V-specific cross-tops for his proposed conversion; this would certainly be the best solution.

Mm, certainly what I'd be doing. I've not mixed pulls with drop levers but (and because) from the feel of them it seems they'd be a lot more sensitive to changes than flat bar levers are.

[reohn2]

Thanks RickH for the heads up on the V compatable cross tops.I knew I'd seen them somewhere but couldn't remember where,googling didn't throw anything up,so I thought I'd dreamt it.
It's my age you know .

...R2 should be able to use V-specific brake levers and V-specific cross-tops for his proposed conversion; this would certainly be the best solution.

cheers

FWIW,I've ordered the Midge bars in 31.8mm and plan to try the GL with Kelly's with an 8sp 14-34 cassette,I loose the top two 11&13 cogs,which I don't use anyway, and the lowest gear is 1" higher with the 34 instead of the 36 currently on the 10sp cassette.
The main thing is getting a comfortable climbing position as I'm too upright on the Space Bugels currently fitted.
The midge bars should give me a similar position to my drops position on the Vayas but 10mm less reach to the hoods and the drops 10mm higher with an 80mm + or - 10 degree stem I already have.
I have the brake levers,Kelly's, 8sp DT levers and a Deore M591 9sp mech.
So initially,for the cost of the Midge bars and some bar tape it's worth a dabble,if it goes well I'll buy the V brake compatible crosstops in RickH's link.