rallyrabbit

Hi guys, I've poured through as much data on bikeforums.net and roadbikeform trying to get anything that might help me.

First, some background. Having a small house, my wife told me we can have 2 bikes (hers and mine). Meaning, my mountain bike and road bike went to friends. Thus, I built a cyclocross bike trying to make a compromise to get me through the best of all worlds. I do some cross racing in winter, I do mountain bike racing on it and road races on it. It has pluses and minuses to every single one due to weight vs loss of tire size and no suspension to being heavier than most road bikes, so big deal, I manage.

My deal is brakes. On mountain bikes I used disc, v-brakes and cantis depending on the time period. Almost as soon as v-brakes came out, I switched. And I was never fully impressed with mechanical disc, so I switched back to V.

My road bike had calipers, of course, which stopped me well and on a dime when I needed it.

===================================

So, I read over and over how spongy cantilevers can be and that people don't recommend them for the road. So, for the past 2 years I used Tektro RX3 with Travel Agent. I was satisfied until both springs and moving parts gave out. So, I switched to the RX5, which they sucked and the springs were garbage (they just wouldn't retract) and now to the BX3v which also can't seem to stay in adjustment and squeal like crazy even with Kool Stop pads. I mean, seriously can't get it to stop.

The LBS is telling me to upgrade to Shimano XT or XTR V-Brakes because of their engineered movement that moves the pad parallel with the rim.

But at this point, I need cantilever opinions. Considering I ride on the road, are they an option? I can't find any listed on the Shimano website, but Sram has the Shorty Ultimate, 4 and 6. Are there any cantis that are going to give me good road stopping power?

Or, are there any opinions on a better V-Brake to get than the Tektro?

flargle

Why not mini-V?

DCB0

The key to good stopping with cantis is the setup. Generally speaking, with modern 'low profile' cantis, I try to set them up so the lower part (where the pad attaches) is vertical or paralell with the sidewall of the rim (or even close in if possible) when the pad is against the rim. THen the length/height of the straddle cable determines the amount of power for the same amound of pull at the lever. If the straddle cable is perfectly straight across when the pads are engaged (not really possible in practice) then the tension you put in the cable is multiplied by infinity as it becomes tension in the straddle cable pulling the arms in - i.e. the shorter the straddle cable, the more braking power you get - I think this is called 'mechanical advantage'. HOWEVER, there are tradeoffs - (1) as the yoke goes higher up when you actuate the brake, the mechanical advantage is actually decreased, and this effect is greater the shorter and more straight across the straddle cable you use, and the (2) more power you lose as the pads wear and the straddle cable goes higher to bring the pads to the rim. Also, (3) the mechanical advantage is so great that setting up brakes like this can feel mushy, and you may have to set the pads excessively close to the rim to get them to engage.
Conversely, if you put the straddle cable very high, the pads will move a lot for a given lever movement, and a nice 'crisp' feel, but not have a lot of power. The trick is to find the balance. I personally like having slightly soft feeling cantis that can flip you over the bars with one finger, so I set the straddle cable as low as possible, but this is a little harder to maintain. IF you only have one bike you need to maintain, this shouldn't be too big an issue for you.

Also remember that cable condition and quality and quality brake pads, and a clean smooth braking surface ont he reim are also very important (as with any rim brake).

One more thing - I have found thet the $12 cheap Shimano cantilever brakes are among the best working I have tried, and their extra low-profile (compared to Avid Shortys for instance) make is easy to run a very short straddle cable. Although they come with a non-adjustable straaddle cable that should be thrown into the garbage or made into jewlery when you first take it out of the bag. Buy a separate straddle cable and yoke set from the LBS to give you more flexibility in setup.

Edit: Or use mini v's like mentioned above, as long as you never intend to put wider tires on the bike as they have pretty limited clearance.
Edit2: I just saw that R5 and BX3v are mini vs. Never mind.

rallyrabbit

I was using Tektro Mini-V, that's what I am having all the problems with now. Are there others, outside of Tektro, that are worth trying?

rallyrabbit

The real question to those in the know.

Canti vs V-Brake.... under normal conditions, which is going to stop a bike more like Calipers on a road bike?

And if canti's, are the shorty or the long pull better at stopping like that?

Cynikal 

I just moved over to the TRP cx8.4 mini-V and can't say enough good things about them. I think they are on par with the high end V-brakes produced for MTB's like the XTR that you mentioned. If you have modern Shimano great (just the current generation) then you want the CX9 model.

Germanicus

Someone mentioned the TRP CX8.4. I haven't tried them but have heard good things from people who have. From what I understand the CX8.4 is designed for the pull ratio of SRAM levers while the TRP CX9 is optimized for Shimano. TRP is a subsidiary of Tektro. I believe it stands for "Tektro Racing Products" or something. They are Tektro's higher end components and are priced accordingly.

I'll keep an eye on this thread because I am also interested in getting new brakes for my Tricross. I have basic Tektro v-brakes (100mm) after coming from cantis and although they are much better, I still get some judder when hard braking on steeper hills.

fietsbob

Paul has introduced one.. the MiniMoto, made to work with road Brifters.

S curves the caliper arm for abundant clearance around tire.

Andy_K 

There are a lot of variations here, but the core concept is simple. I'm going to get all geeky here for a minute, but I promise I'll end up with a simple answer.

The key concept underlying it all is mechanical advantage. Mechanical advantage is basically a multiplier for the force you put into the lever. For instance, if your braking system has a total mechanical advantage of 2, the pads will squeeze the rim twice as hard as you squeeze the lever. In theory, two different braking systems with the exact same mechanical advantage will feel the same (with some variation due to flex in the brake calipers and squish in the pads). The key is to find the sweet spot for mechanical advantage. With too little MA, the brakes are weak. With too much MA, the lever feel is unacceptable. The other factor is that pad movement is inversely proportional to MA, so if you double the MA the pads have to be set up twice as close to the rims.

Different brake levers have different amounts of pull. You often see "short pull" and "long pull" but that's just an approximate grouping. The latest Shimano STI levers, for instance, pull a different amount of cable than the previous generation did. I would guess there are also small variations with other levers. The amount of cable a lever pulls is inversely related to its mechanical advantage. I should also mention that the mechanical advantage of the lever depends on how far from the pivot you pull on it. If you pull the bottoms of an STI, they'll give you more force than if you pull near the hoods.

V-brakes and mini-V's have a fixed mechanical advantage (which combines with the lever's MA). The MA for a V-brake is determined by its arm length. A shorter arm has less MA. A longer arm has more MA. But once you've chosen the brake, the MA can't be changed. Travel Agents change the cable pull being put into the brake, and so they effectively act like a divisor to reduce the MA of the brake (but increase the pad travel).

Cantilevers have variable mechanical advantage, depending mostly on how wide the brake arms are and how low the straddle cable is. On most cantilevers (Shorty Ultimate being the exception), you can't change the arm width. You can, however, always change the straddle cable height. The lower the straddle cable, the higher the mechanical advantage. Cantilevers have the additional quirk of having their MA vary slightly as the brake pad moves. This effect is greater for narrow profile cantilevers than for wide profile.

I believe that dual pivot caliper brakes have fixed mechanical advantage.

So, the (sort of) simple answer:

The brake that will stop more like a caliper is the brake that has the most similar mechanical advantage. If you can find a combination of V-brake (mini or otherwise) + lever + (optional)Travel Agent that matches the MA of a caliper, that will stop more like a caliper than a cantilever (because of the cantilever's variable MA through pad travel). However, a wide profile cantilever brake gives you the most options for fine-tuning the mechanical advantage to approximate the response you're looking for. It will just take a lot of trial and error to get there.

If you really want to geek out on this yourself, check out this link: https://www.circleacycles.com/cantilevers/

fietsbob

less MA allows more rim to pad clearance to have the braking occur
at the right portion of the lever arc..

Higher MA and there needs be a scant clearance . or lever bottoms out.

teeter totter vs crow bar,,

badger1

^^^ This. I use the CX9s (replaced the generic Tektro mini-vs on my bike). They are, quite simply, superb. Provided you use good cables, they go into -- and stay in -- adjustment like no other v-brake I've had (junk Promax, generic Tektro, various Avids). They've been on my bike (only bike; 3-season daily commuting, weekend distance rides) for a year and a bit -- not a single adjustment needed other than a bit of cable tension to take up pad wear. Stopping power/modulation as good as it gets, in my view. They are sold in boxed sets (f/r) with extra differently-angled noodles to allow for different cable runs. I was horrified by the price, but wanted 'em ... worth every dollar if you like powerful, easily-modulated, reliable brakes.
I think Germanicus is right about CX8.4>SRAM, CX9>Shimano road brifters, though you might want to check.

nikita_r

here is my 2 cents:

I use Tektro 926Al Minis with Campy Veloce levers. At first, I used them with Kool Stop Salmon MTB pads and I was kinda disappointed. At some point I switched to Kool Stop Cross Dura 2 pads and since then this is my favorite brake setup. Before you invest a lot of money into TRP CX8.4 or CX9 I would strongly recommend to try road type pads (either KS Cross Dura 2 or TRP Inplace Adjust M) with your Tektro RX5. And also I would recommend to pay attention to toeing your pads in properly.

nikita_r

btw TRP CX9 are sold with TRP Inplace Adjust M pads. That may be part of the reason why people think they are much better than cheap Tektro mini-Vs.