Mountain to Cross Frankenbike?

[dianne_1234]

MTBs can make excellent FrankenCross bikes!

One word of caution though: Don't use drop bar levers with V-brakes! I've done it and didn't like it at all; it felt unsafe.

I don't think your STI levers pull enough cable to operate V-brakes properly. Sheldon Brown hints at this here: http://www.sheldonbrown.com/gloss_u-v.html

"V-Brake ®
A Shimano trademark for a direct-pull cantilever brake. This is a cantilever which does not use a separate transverse cable. It has two tall arms, one of which has a housing stop and the other an anchor bolt. The exposed part of the cable runs horizontally from one arm to the other.
V-Brakes and other direct-pull cantilevers have more mechanical advantage than other brakes, so they require special hand levers with less-than-average mechanical advantage to keep the overall mechanical advantage in a useful range."

On that page the words "special hand levers" hyperlink to the text quoted below. Basically, you're talking about the first type of mismatch: "Old short-pull lever, new direct pull ("V type") cantilever".

Bottom like: Maybe consider keeping the flat MTB bars (and brake levers) at first?


Begin quote:
Brake Lever Types
Brake levers (handles) for use with cable operated brakes come in 4 basic types.
The differences depend on the handlebar type they are to be used with, and on the amount of cable travel required:


Upright Handlebar, Standard Pull
Drop Handlebar, Standard Pull
Upright Handlebar, Long Pull
Drop Handlebar, Long Pull
Handlebar Type
Levers for drop ("road" "racing") handlebars curve toward the handlebar, to follow the curvature of the handlebar. These levers also mounting clamps to fit the 23.8 mm (15/16") diameter of almost all drop handlebars.
Levers for upright ("mountain" "cruiser" "BMX") handlebars mount on a straight section of the handlebar, and the lever curves away from the bar for better clearance. These levers have mounting clamps to fit the 22.2 mm (7/8") diameter of almost all upright handlebars.

Cable Pull
Standard pull levers are designed to work with caliper brakes or traditional center-pull cantilever brakes.
Long pull levers are designed to work with "direct-pull" cantilever brakes, such as Shimano "V-Brakes" ®

Direct pull cantilevers have twice as much mechanical advantage as traditional brakes, so they require a lever with half as much mechanical advantage. Long pull levers pull the cable twice as far, but only half as hard.


Mismatched Lever Issues:
Old short-pull lever, new direct pull ("V type") cantilever
The excessive mechanical advantage of this combination will make it difficult to modulate the brake, and it may be all too easy to lock up the wheel.
The lever feel will be very soft and mushy.

The lever will travel too far before engaging the brake, and it may bottom out against the handlebar. Thus, the brake may be super powerful at first, but as the brake shoes wear, the lever bumping up against the handlebar will prevent full application. This is likely to be a particular problem in wet conditions.

New long-pull lever, old caliper or traditional cantilever
The reduced mechanical advantage will require unusually high hand strength to get barely adequate braking force.
Paradoxically, the lever will feel very solid, the brake will engage with a very short amount of lever travel...but won't actually be squeezing very hard on the rim.

Most disc brakes are designed for long-pull levers, but discs designated as "road" models are usually compatible with traditional short-pull levers.
There are stepped pulley devices to permit mixing otherwise incompatible levers/brakes. The best known is the QBP Travel Agent ®.

[KnottedYet]

When I was thinking about switching around a bike, my LBS found some drop bar brake levers that work with V-brakes.

Can't remember for the life of me who made them, but there was only one brand available and they were something like $80.

(I bought a new bike instead, surely a financially wise decision? )

[SadieKate]

50 bucks will get you a pair of Dia Compe 287 levers that will work with your V-brakes.

http://www.speedgoat.com/product.asp...=30&part=39164

OR

for 15 bucks (a piece I think) will get you Problem Solvers Travel Agents.

http://www.jensonusa.com/store/produ...vel+Agent.aspx

All kinds of Problem Solver Products here.
http://www.speedgoat.com/results.asp

[wavedancer]

Dianne, thanks for the info from Sheldon Brown.

We have hooked up the road levers and V-brakes, but I haven't tried them out yet. I will be adding "Travel agents" which should take care of the short pull lever/direct pull V-brake mismatch. Those won't be in until later this week, but I plan to give it a little test ride (not downhill ) tomorrow.

We have also gone with the 34T road crank, removing the outer ring. I found someone who makes chain guards for $14 shipped BBG Bash guard, and will be putting one of them on the outside, with a Third Eye inner chain guard. We left the mountain derailleur and cassette and they seem to work OK with the 105 shifters.

I decided to go with an aluminum rigid fork from Spicer Cycles.

When it's all together I will post some photos. This is really a fun project! Hope I like how he (Frank) rides!