I've been experimenting with mini-V's on my bike and I thought I'd share what I've found. In my experience, they're generally easier to deal with than cantilever brakes, but not necessarily better in every respect. These are my experiences -- YMMV.
I have some very short brakes (80mm) and some slightly short ones (95mm). For comparison, Shimano V-brakes are 107mm and "standard" Tektro V-brakes are 102mm.
Pro:
- Very cheap.
- No squeal or shudder.
- Simpler to set up, especially in the front.
- No need for cable hangers and related cable routing issues.
- Did I mention no squeal or shudder?
Con:
- Quick release can be difficult. (see below)
- No cable adjustment. (see below)
- On some bikes, might not leave enough clearance for fenders.
The quick release issue isn't really a problem if you use Campagnolo levers, which have a QR on the brake lever. Also, if you get noodles with barrel adjusters, or have inline cross levers with adjusters, they can help give you the necessary clearance. Finally, you can file down the end of the noodle so that you don't need to pull it as far to release the brake.
One important factor to pay attention to is the vertical distance between the brake posts and the rim. ("Vertical" isn't exactly vertical, but rather measured along the length of a v-brake arm.)
In the first three pictures, the distance is approximately 29 or 30mm, measured center of post to middle of braking surface. The brake in these pictures have 80mm arms, resulting in a mechanical advantage of about 2.66. I find that this gives me good braking power (better than the cantis I had) and even with a 32mm tire, there's plenty of mud clearance (see pictures 7 and 8). They also have plenty of clearance to the rim (see pictures 5 and 6). Using brakes with longer arms will result in more braking power but less rim clearance.
On the rear of one of my bikes, the vertical distance is about 38mm. You can see this in the fourth picture below, where the brake pads are set to the highest possible position. When I had cantilevers on here, the back brake was almost useless because, in addition to the somewhat low mechanical advantage of that brake design (Avid Shorty), the higher pad position resulted in even lower MA -- that is, more travel and less force (also, a firm brake feel at the lever). When the post-to-rim distance is greater, you need a longer arm to clear large tires. In this case, I'm using 95mm arms, which gives a MA of 2.5, similar to the others. If I used 80mm arms, there would be less vertical tire clearance, but the MA would be greater, at 2.1, resulting in more rim clearance and less power.
I've heard others say that tire clearance is an issue, but it hasn't been for me. Even the very short 80mm arms leave plenty of space for the tire -- slightly more than the fork crown shown in the pictures with fat tires.
I think that one of the reasons that there's more braking power is not just mechanical advantage -- it's also that there's less flex in the entire system when you brake, compared to cantilevers. And I think the reason there's no shudder or squeal is because there isn't the feedback loop where the arms and/or hanger flex and pull the cable a little tighter, increasing the pressure and friction on the rim, and then once the arms get pulled far enough, the pads let the rim slip and this cycle gets repeated.
If you find that you want more or less mechanical advantage, the thing to do is get a brake with different length arms. Fortunately, they're very cheap. I paid between $9 and $13 a set, so for the price of a single Paul brake, I can equip about four whole bikes!
I made a list of different brake lengths, using information from the Tektro web site (which seems to be down right now). There may be others, but this is just what I found:
- 75mm: 917A
- 80mm: 926AL
- 85mm: BX3V, BX1V, RX1, RX3, RX5
- 90mm: RX6 (this seems to have a special quick release; it might solve the QR issues)
- 95mm: BX25, 930AL, BX310, 918AL
- 102mm: Tektro "standard" V-brakes
- 107mm: Shimano V-brakes
- 110mm: Tektro "long" V-brakes
If you're thinking about getting mini-V's, try measuring the post-to-rim distance (although this isn't easy), then multiply by the desired mechanical advantage to get the arm length. As I mentioned earlier, MA=2.5 to 2.6 gave me good power and adequate rim clearance. In my case, 2.6 x 30mm = 78mm, so 80mm arms worked. Or you can just buy a whole bunch and see what works!
A side note: I gather that Shimano's new Dura-Ace 7900 levers pull more cable than their previous models, so maybe these and other future Shimano STI levers will allow for longer V-brakes with more clearance...
I have some very short brakes (80mm) and some slightly short ones (95mm). For comparison, Shimano V-brakes are 107mm and "standard" Tektro V-brakes are 102mm.
Pro:
- Very cheap.
- No squeal or shudder.
- Simpler to set up, especially in the front.
- No need for cable hangers and related cable routing issues.
- Did I mention no squeal or shudder?
Con:
- Quick release can be difficult. (see below)
- No cable adjustment. (see below)
- On some bikes, might not leave enough clearance for fenders.
The quick release issue isn't really a problem if you use Campagnolo levers, which have a QR on the brake lever. Also, if you get noodles with barrel adjusters, or have inline cross levers with adjusters, they can help give you the necessary clearance. Finally, you can file down the end of the noodle so that you don't need to pull it as far to release the brake.
One important factor to pay attention to is the vertical distance between the brake posts and the rim. ("Vertical" isn't exactly vertical, but rather measured along the length of a v-brake arm.)
In the first three pictures, the distance is approximately 29 or 30mm, measured center of post to middle of braking surface. The brake in these pictures have 80mm arms, resulting in a mechanical advantage of about 2.66. I find that this gives me good braking power (better than the cantis I had) and even with a 32mm tire, there's plenty of mud clearance (see pictures 7 and 8). They also have plenty of clearance to the rim (see pictures 5 and 6). Using brakes with longer arms will result in more braking power but less rim clearance.
On the rear of one of my bikes, the vertical distance is about 38mm. You can see this in the fourth picture below, where the brake pads are set to the highest possible position. When I had cantilevers on here, the back brake was almost useless because, in addition to the somewhat low mechanical advantage of that brake design (Avid Shorty), the higher pad position resulted in even lower MA -- that is, more travel and less force (also, a firm brake feel at the lever). When the post-to-rim distance is greater, you need a longer arm to clear large tires. In this case, I'm using 95mm arms, which gives a MA of 2.5, similar to the others. If I used 80mm arms, there would be less vertical tire clearance, but the MA would be greater, at 2.1, resulting in more rim clearance and less power.
I've heard others say that tire clearance is an issue, but it hasn't been for me. Even the very short 80mm arms leave plenty of space for the tire -- slightly more than the fork crown shown in the pictures with fat tires.
I think that one of the reasons that there's more braking power is not just mechanical advantage -- it's also that there's less flex in the entire system when you brake, compared to cantilevers. And I think the reason there's no shudder or squeal is because there isn't the feedback loop where the arms and/or hanger flex and pull the cable a little tighter, increasing the pressure and friction on the rim, and then once the arms get pulled far enough, the pads let the rim slip and this cycle gets repeated.
If you find that you want more or less mechanical advantage, the thing to do is get a brake with different length arms. Fortunately, they're very cheap. I paid between $9 and $13 a set, so for the price of a single Paul brake, I can equip about four whole bikes!
I made a list of different brake lengths, using information from the Tektro web site (which seems to be down right now). There may be others, but this is just what I found:
- 75mm: 917A
- 80mm: 926AL
- 85mm: BX3V, BX1V, RX1, RX3, RX5
- 90mm: RX6 (this seems to have a special quick release; it might solve the QR issues)
- 95mm: BX25, 930AL, BX310, 918AL
- 102mm: Tektro "standard" V-brakes
- 107mm: Shimano V-brakes
- 110mm: Tektro "long" V-brakes
If you're thinking about getting mini-V's, try measuring the post-to-rim distance (although this isn't easy), then multiply by the desired mechanical advantage to get the arm length. As I mentioned earlier, MA=2.5 to 2.6 gave me good power and adequate rim clearance. In my case, 2.6 x 30mm = 78mm, so 80mm arms worked. Or you can just buy a whole bunch and see what works!
A side note: I gather that Shimano's new Dura-Ace 7900 levers pull more cable than their previous models, so maybe these and other future Shimano STI levers will allow for longer V-brakes with more clearance...