Hi, I have touring bicycle (cube cross) with shimano br315 brakes and rt-56 disks in 160 size. Because i am quite big guy (2m, 100 kg) i came across idea of upgrading the front disc to 180mm version.
i have bought the adapter and the new disc - shimano rt-64 180mm. Today i have opened the box and the first view revealed that the disc is a big too narrow (i had no idea what i bought - i saw only 180mm and metal compatible
So before selling the rotor i wonder, has anyone use the rt64 rotors on teh br315 (or any other wide pads caliper)? Does it work OK'? do the pads wear as normal?
If you use 'wide track' calipers with 'narrow track' discs the spokes in the discs wear abnormally fast. Not recommended. You can grind the pads so that they have a narrow track of friction material but unless you also reposition the calipers, the pistons won't be centred over the track, and this will make the brakes a bit crap.
Essentially you had Deore/Xt M555/M755 with an older pad type, and these were replaced in 2002 with Deore M525 (b type/wide) and xt m765 (a type/narrow).
The updated Deore m535 (2005) had a pads, and then there wasn't another b pad till 2007 m485, which is a sub-Deore non-series type.
So in terms of compatible discs there wouldn't have been that many, as for example in 2004 there were sm-rt52 (non-series) and sm-rt62 (Deore LX) introduced, and the first Deore lx brake was m585 , also 2004, using the narrow pad type.
So Shimano never really introduced their higher quality discs in 'wide' pad because almost from day 1 their brakes were narrow.
The proliferation of cheap brakes is more recent, from around 2013, when Shimano kept rebadging wide calipers with new part numbers.
And of course you needed a wide disc to go with it, which don't exist in many choices because the earlier model years were in the 'premium' Deore/SLX/xt , not the non-series m315 or similar, so there aren't (m)any to choose from if you want say a metal-pad-compatible disc.
At any rate 6- (SLX) and 7- (xt) part numbers are non-starters
Another thing to consider: are your forks ok to use with 180mm rotors? It does make a difference in terms of stress the fork blades go through
It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are...
Gattonero wrote:Another thing to consider: are your forks ok to use with 180mm rotors? It does make a difference in terms of stress the fork blades go through
you generally don't need to change levers or hose when you change caliper.
Technically the br8000 is sold with bh90 rather than bh59, but there are other brakes where both are used, so it doesn't seem to matter.
also the slx and xt calipers are the same.
and if you just want a narrow pad, then you can get deore m6000/m615, which might be cheaper. These have resin rather than the ceramic pistons of the slx/xt.
it would surely be cheaper to get the right rotor though
thelawnet wrote:you generally don't need to change levers or hose when you change caliper.
Technically the br8000 is sold with bh90 rather than bh59, but there are other brakes where both are used, so it doesn't seem to matter.
also the slx and xt calipers are the same.
and if you just want a narrow pad, then you can get deore m6000/m615, which might be cheaper. These have resin rather than the ceramic pistons of the slx/xt.
it would surely be cheaper to get the right rotor though
The hoses are the same external, it is only the internal bore that differs. Also some times the fittings vary between models (straight or banjo). But the hoses seem perfectly cross compatible.
I replaced my m315 brakes with m6000s and am happy. But this is a mtb lever , so you may prefer the longer t6000s for touring, but then you already have long levers so not much gain there
And in all honesty I don't think you will get much benefit for your use case since what you are after is more.stopping power on a loaded bike, not what I was looking for which is control off road.
I don't see their being much benefit in the new caliper for you, as opposed to just getting a new and cheap 180mm rt10 or similar.
I think your existing levers are fine (and you are not proposing to change them) and you likely won't notice any change from the new caliper, so you should really stick with getting the right disc and forget the caliper change,.bleed kit, and all the rest
@thelawnet Thank you so much for your explanations;
To give you a bit more background why do i want 180mm better quality disc.
On longer descents i usually break on rear brake only because i want to keep the front brake cool for the case of emergency braking. The example of this descent (where the rear brake was overheated was Muswell Hill in london towards the crouch end) the properties of my breaking technique on this kind of descent are: -rear brake constantly engaged, because i cannot go faster of the vehicles before me and not slower because of the vehicles behind me -speeds high enough to actually worm up the brakes but not high enough so the bicycle would need less breaking than due to the air resistance -because i go with the traffic the air is cut by the vehicles before me -I occasionally press the front brake just to apply a bit more braking force on the moments.
last Thursday from Muswell Hill towards crouch there was literally smoke coming from the rear brake when i stopped (also when heated it did not brake as much as it should; but that was not a worry because the front brake was still cool). I guess the colour of the disc can tell the amount of energy absorbed during that descent. Also you can see the paint on the caliper being burned. That is why I am a bit sceptical about the calipers with the resin pistons (and not any kind of metal or ceramic); Good knows what would be if i had this kind of descent for few KM with few hundred meters of fall.
The bleed kit i already have; i am from Europe used to the rear brake right and front left and i needed to change it after i have bought bicycle here.
If i read specs correctly the 315 has steel piston. so overheating of the piston itself should not be an issue. The problem is that the rt54 is a bit cheap version of the rotor (also unsuitable of metal pads). Because of that i was thinking to upgrade to rt64 and apply a bit more brake also to the front when going downhill, as it will definitely be able to absorb enough energy to keep cool enough for emergency braking. But since m6000 are the ones that would fit without any kind of complication and have resin caliper it does not seem to make sense to upgrade to this one. Also it seem to be a bit too complicated to change to 8000s due to different hose fitting. So i guess that i will stay with the current calipers, sell the 1800 mm rt64 and get the rt54 in 180mm.
FYI. I weight about 100kg, together with bicycle, backpack and equipment i am around 120 KG.
if the disc had got really hot it would most likely have turned blue. If you saw smoke it could easily have been contamination burning off. Fitting a larger disc will help with the disc temperature but it won't help with the caliper temperature in the same way.
FWIW metal pistons are a mixed blessing; they conduct heat into the fluid rather well and this risks a boil-up. The idea that resin pistons might melt is a concern until you realise that the maximum temperature of the piston is limited by the seals on the piston anyway, and they are liable to fail before the piston does.
Dragging one brake is a recipe for trouble; much better to alternate between the two so that the other gets a chance to cool off.
petercek wrote:If i read specs correctly the 315 has steel piston. so overheating of the piston itself should not be an issue. The problem is that the rt54 is a bit cheap version of the rotor (also unsuitable of metal pads). Because of that i was thinking to upgrade to rt64 and apply a bit more brake also to the front when going downhill, as it will definitely be able to absorb enough energy to keep cool enough for emergency braking. But since m6000 are the ones that would fit without any kind of complication and have resin caliper it does not seem to make sense to upgrade to this one. Also it seem to be a bit too complicated to change to 8000s due to different hose fitting. So i guess that i will stay with the current calipers, sell the 1800 mm rt64 and get the rt54 in 180mm.
FYI. I weight about 100kg, together with bicycle, backpack and equipment i am around 120 KG.
You could buy the banjo separately.
btw, I'm not sure if metal pads are necessarily better, but anyway if you wanted fancy rotors, then you might be looking at RT81 or similar, which dissipates heat to the aluminium core.
