SHIMANO Caliper Brake BR-R451 Front Black

These calipers are amazingly strong, they went on my 1970’s commuter, displacing the crappy center-pull brakes which were common at the time. The reach is plenty long for 27″ rims, and when closed they easily clear my 32mm wide tires.

Unfortunately these calipers are mounted a little differently than the old styles, which had a bolt running through the steel frame and an acorn nut on the back. Bikes with caliper brakes nowadays have a flat bottomed recess in the backside of the front fork. The caliper bolt reaches from the front hole, and you catch it with a “connector nut” inserted from the back. Since the bolt isn’t supposed to go all the way through, you may want to replace it with a longer one since you need a long bolt that can pierce your whole front fork.

Despite what other reviewers have said, I find the brake pads more than adequate. Then again, I have been using Dia Comp brake blocks for the last few years.

TLDR: If you have an old bike, buy two front calipers since the only difference is that the front calipers have a longer bolt.

Have a Trek Aluminum bike with V Cantilever brakes. The reason. I wanted these is that my cantilever brakes just weren’t braking well even after replacing the pads. After a good amount of research, I read that Caliper brakes are stronger and react better. I didn’t want to upgrade to disc brakes as that seemed overkill. I saw that my frame had a center hole for the upgrade and figured Trek holes would be universal. So I went ahead and ordered. Well, here’s the good:
The brake caliper themselves were quality construction and well padded for shipping to prevent scratching on the black painted finish. The install itself went well, but I was unprepared for all the custom work in terms of parts, tools and instructions. Here’s a list of the things I went through.
The manual just has a link to a downloadable PDF. But the PDF is just a part diagram of assembly. But no install instructions. Granted, the install instructions seemed obvious. But I was able to look on youtube to reference how to install a dual pivot caliper brake.

Custom things I had to do
1) The Cantilever brakes I previously had were easy to remove, but there were two cantilever posts that had to be removed from the forks. That proved really challenging. The only way I was able to remove them (turned counter-clockwise) was to use a vise grip wrench. (do a search on removing Cantilever posts on youtube and you’ll see what I mean) Any other wrench just stripped the cantilever posts. (1 1/2 inches long).
2) The pivot hole for the Caliper brakes was too small so I used a 6mm metric or 15/64 US metal drill bit for the front side hole. But the nut on the back side is recessed nut that requires the hole on the backside to be bigger than the front side. That hole turns out to be 8mm metric or 5/16 US in size. DON’t drill both the front and back of the fork with 8mm. just one side with 6mm and the nut side for 8mm.
3) To remove the cantilever brake I had to cut the brake wire to remove the cable cap. I was able to use a needle nose plier to cut the cable without buying a metal cutter.
4) Once the new brakes are installed, you have to cap the cable that you cut. I didn’t have any caps so I had to buy a pack of 100 here on Amazon for $5. After cutting the cable with the pliers, the metal cable was frayed so it was a hazard for anyone grabbing the bike near the brakes. So you I really did feel that I needed to cap the cable.
5) Lastly, the rear brakes are tilted for the mounting hole in such a way that the seat post prevents you from drilling the rear hole. So the only solution was to buy a right angle drlll adaptor for my power rdrll that could fit up to 8mm / 17/64 drill bit size. Costs $23 on Amazon. Be careful that the drill adaptor you buy does at least fit up to 8mm drill bits and that the angle is short enough to fit. A few turned out to be too long as I checked their measurements.

6) optional – some people noted that the brake pads on this set could be better. Although many didn’t comment. I went ahead and bought Origin 8 brake pads for $7 here on Amazon as the reviews on facebook were great and they weren’t too expensive.

So after all that.. I hope this gives you an idea that upgrading from Cantilever to these Dual Pivot Calipers isn’t a quick project without some preparation. In truth, it’s doubtful that any upgrade from another manufacturer would be any easier. So It’s not a Shimano thing. But just the nature of the upgrade. If you have an existing center pivot caliper brake, you could just use the nut from the old set without having to drill a 8mm hole. I’ve seen some instructions from people that got that to work well. These Shimano’s are a great price and really do look good. Secondly, there is a snap pivot switch tab that you flip when you remove the tires. Not something that’s mentioned anywhere that I could see.

Love the style color and sleekness!

Took a 26′ wheel MTB, converted it to a drop bar 700cc road bike. The bike has micro-shifters for Nexus8 drive system, and needed a good brake for rear wheel that had good cable routing and a longer reach. This brake fit the need 100% and the feel was better than expected.