lineinthewater

I'm looking at the Shimano R451 brakes. According to most retailers' product description, the R451s are Super SLR brakes, and:

"Must be used in conjunction with ST-4600, ST-4603, ST-5700, ST-5703, ST-6700 or ST-7900 STIsfor correct leverage ratio"

Ok, but then if you look at Shimano's own compatibility chart, it has the dotted line between those shifters and the R451s, indicating that:

"Braking power is slightly less than standard combination"



So, am I to interpret this as the R451s have a different pull than the standard line of BR-5700s, BR-6700s? And that it is designed (exclusively) for those generation of shifters, but it's not optimal?

The real question I was trying to answer, originally, was whether the R451s (I already have a set) would work adequately with older Sora 3300/3304 shifters? I need medium/long reach brakes for this build. If not, any suggestions?

CACycling

If you already have the brakes, why not build the bike and see if the function is acceptable? If you don't like the feel, you can easily change them out and aren't out anything but a little time.

fietsbob

wiggle.com | Shimano BR-R451 Dual Pivot 57mm Drop Brake Caliper | Rim Brakes

since Leverage is composed of the relative length of the 2 distances on either side of the pivot (fulcrum)

a 57 reach will be somewhat different from a short reach Brake that barely clears a 25 wide tire.

But If you have a frame that needs a longer reach brake caliper like that , You Cope.

Its not Incompatible just not as ideal as a small clearance , short reach race bike would have.

You just set the pads closer to the rim so the hand lever stroke feels Ok.

You may like the clearance such a frame provides to run Mudguards , to catch the wheel spew.

noglider 

Somewhere, Sheldon Brown wrote a good article explaining the ramifications of leverage on brakes. Basically, if you have too little, the brake gives a nice positive feel but either it won't stop well or it will after you apply a lot of force to the lever. If you have too much, the brake will feel spongy. With too much leverage, your lever might hit the handlebar before you are applying full force, and this is unacceptable.

Some of this depends on your tolerance and strength. I have long fingers and strong hands, so if I have to squeeze hard to brake fully, I don't mind. It's entirely unacceptable for people with weaker hands. I seem to adjust quickly when switching from bike to bike. All of my bikes have adequate brakes, but when people try them, sometimes they tell me my brakes don't work.

lineinthewater

Well, I have the brakes, just not in front of me. They are on my friend's other bike, and I'm building this bike for him too. So, it will take a little effort, and inconvenience, to get them. But, I will probably end up doing exactly as you say, and simply test it out.

I just constantly see those warnings from Shimano: do not use newer calipers with older levers.

I think fietsbob is hitting on the issue I'm trying to understand. Is Shimano saying that because these are longer reach calipers, they will tend to fall somewhere between a super SLR pull and the old pull of say a 5600 caliper - and so, the older levers won't be as incompatible with the R451s as they would be with say a 5700 caliper? Am I making sense?

fietsbob

Why not get older cable out the top non aero Brake levers* ? they have a cable pull ratio

between that of short pull aero levers and the Much longer pull /lower MA of a V brake lever..


Like this : https://2.bp.blogspot.com/-oB0m3y_z0O...0/P2280157.JPG