Weak Braking

cassettequestion

Hi there,

I've installed a pair of Shimano BR451 brake calipers on my Tiagra (4700) equipped road bike. Braking performance is now worse and I don't know why.

Appreciate it may be hard to know without seeing what I've done but any suggestions as to what I might have done wrong?
I have the pads about 1mm from the rim and have pulled the cable as tight as I can before clamping.

One thing I didn't understand was after I set up the front brake by squeezing the caliper against the rim, pulling the cable through tight and clamping it, an initial pull of the lever seemed to cause slack to appear as the calipers would move away from the rim?

Anyway, if anyone can make sense of this, would be appreciated

keef66

cassettequestion wrote:

Hi there,

I've installed a pair of Shimano BR451 brake calipers on my Tiagra (4700) equipped road bike. Braking performance is now worse and I don't know why.

Appreciate it may be hard to know without seeing what I've done but any suggestions as to what I might have done wrong?
I have the pads about 1mm from the rim and have pulled the cable as tight as I can before clamping.

One thing I didn't understand was after I set up the front brake by squeezing the caliper against the rim, pulling the cable through tight and clamping it, an initial pull of the lever seemed to cause slack to appear as the calipers would move away from the rim?

Anyway, if anyone can make sense of this, would be appreciated

Well I have BR450s on my winter bike and they are operated by Tiagra 4500 levers and they work OK.

What did you have on there initially? ie what are they worse than?? Did you clean the brake tracks before using the new brakes?

Are they brand new? The Tiagra calipers I had on the summer bike seemed to be getting worse; I think the brake blocks were getting a bit long in the tooth. Replaced them with some nearly new 5800 calipers and the difference is startling.

I often find I get better braking if the brake blocks aren't too close to the rim.

cassettequestion

keef66 wrote:

cassettequestion wrote:

Hi there,

I've installed a pair of Shimano BR451 brake calipers on my Tiagra (4700) equipped road bike. Braking performance is now worse and I don't know why.

Appreciate it may be hard to know without seeing what I've done but any suggestions as to what I might have done wrong?
I have the pads about 1mm from the rim and have pulled the cable as tight as I can before clamping.

One thing I didn't understand was after I set up the front brake by squeezing the caliper against the rim, pulling the cable through tight and clamping it, an initial pull of the lever seemed to cause slack to appear as the calipers would move away from the rim?

Anyway, if anyone can make sense of this, would be appreciated

Well I have BR450s on my winter bike and they are operated by Tiagra 4500 levers and they work OK.

What did you have on there initially? ie what are they worse than?? Did you clean the brake tracks before using the new brakes?

Are they brand new? The Tiagra calipers I had on the summer bike seemed to be getting worse; I think the brake blocks were getting a bit long in the tooth. Replaced them with some nearly new 5800 calipers and the difference is startling.

I often find I get better braking if the brake blocks aren't too close to the rim.

A pair of Tektro brakes. New bike so didn't need to clean anything really. And yep, new brakes as well.

sungod

check the rims are clean and pads centred, adjust for 1-2mm gap between pad and rim

bike may be new, but the rims may have been contaminated by oil/whatever during assembly

shimano's basic pads aren't especially good, especially in the wet, if all else is ok you might consider fitting better ones (swissstop or koolstop for instance)

the reason slack appeared after first squeezing the brakes is probably that under braking force the outer and ferrules get snugged down (the force is far higher than you manually tensioning the cable during fitting) so the cable tension is reduced, same thing occurs with gear cabling

this is why it's best to fit cables with adjusters at/near minimum tension position, then that you have plenty of room for adjusting, if it's really low you can always reclamp the cable

andy_wrx

Swap the pads for the old ones - if braking is suddenly decent again, it's because the new pads are rubbish.

Costs you nothing to try it, before you go forking-out for new pads

Kitz

Brand new blocks? May just need a few miles to bed in the new blocks to the braking surface. As said before, try the old blocks. If that doesn't work, new cable time maybe?

jermas

The shifter-caliper combination you have is not ideal due to a different cable pull ratio. Those calipers are designed to be used with the 4600 series (earlier model) shifters. Softer brake pads, as mentioned above will improve things.

dj58

As above, the Shimano compatibility chart shows that they are not compatible. You really needed to use the matching 4700 brake calipers or better still, as has already been mentioned the 5800 105 calipers, unless you particularly want a long reach caliper because you want to fit mudguards?, then you need to look at an alternative caliper.

Re-fit the tektro calipers and set them up properly then bed the pads into the rims, if you are still not happy with the braking power, try a pad change first, SwissStop BXP flashPro blue. What model are the TeKtro calipers, are they long reach?

cassettequestion

Hi thanks for the responses. Seems it's the compatibility issue then..

I don't need to fit mudguards but the bike is designed for them so think I need the long-drops to reach the rim. I could go back to the Tektro calipers but I haven't tried them with the 4700 levers either as I installed them at the same time as the Shimano calipers...

cassettequestion

PS Tektro R315

dennisn

andy_wrx wrote:

Swap the pads for the old ones - if braking is suddenly decent again, it's because the new pads are rubbish.

Costs you nothing to try it, before you go forking-out for new pads

I having trouble buying into the idea that new pads are rubbish. This seems to be a recurring theme with lots of different items. Blame the item and don't even consider that this might be installer(you) error.

andy_wrx

dennisn wrote:

andy_wrx wrote:

Swap the pads for the old ones - if braking is suddenly decent again, it's because the new pads are rubbish.

Costs you nothing to try it, before you go forking-out for new pads

I having trouble buying into the idea that new pads are rubbish. This seems to be a recurring theme with lots of different items. Blame the item and don't even consider that this might be installer(you) error.

No Dennis, it's trying it and seeing.
Try all the possibilities, discount those that don't work, eventually you come to the solution.
Keep an open mind and you learn something in the process.

bill57

Much as I hate to disagree with Dennis (I do, I do!) ...........

My "winter" bike (a joke, as I hate riding in winter at my age) is an Ambrosio, so I bought Ambrosio 57mm calipers for it, since the were cheap on Ebay, and thinking it would be nice to have same name components on the bike. But they were truly awful, not just the braking, but the manufacturing quality, so in the end I threw them away and bought a pair of Shimano R650 calipers, which at the time were almost the benchmark for good quality replacement long drops.

Now I know little and understand less about pull ratios (ok I know it's basic mechanics and mechanical advantage etc) and especially why Shimano keep subtly altering it with new products. But my R650's, operated by 8 speed Sora levers on basic alloy rims, were not very great, in fact very disappointing, and I was asking myself the same questions as the poster here.

Cut a long story short (I can hear the yawns), I bought some Shimano R55C3 pads from Chain Reaction and taaraaah! Decent braking at last. I bought two sets and I've just checked the numbers on the spare set, which I've never used yet.

So in my experience anyway, the original pads from Shimano were just rubbish. Which does beg the question, why do they do this? Why not just fit the decent pads on all their brakes?