New rotors or not

[2manyoranges]

also....this might be a different source of leak....and an easy fix....

Leaking Shimano Calipers - possible solution

April 28, 2017 - Folks, I think a few of you have posted over the last few years of leaking calipers from various Shimano brakes. For me it has been their RS785 road

singletrackworld.com

 

[rwm1962]

That's an issue I'd fix with Hope.

 

[2manyoranges]

Hmmm….rwm….I feel very much the same way. Made in Barnoldswick. I got the last heavily discounted Hope E4 and x2s (160.00 and 114.00) from CR since they were 'handed' the wrong way - ten minute fix and a bleed - and yep, one was amber and the other purple. Mad colour mix doesn't seem to prevent the extreme stopping power from kicking in though....

 

[kalex]

also....this might be a different source of leak....and an easy fix....

Leaking Shimano Calipers - possible solution

April 28, 2017 - Folks, I think a few of you have posted over the last few years of leaking calipers from various Shimano brakes. For me it has been their RS785 road

singletrackworld.com

I've got my toilet paper around the caliper now with the brake block in and lever clamped. Not sure how long I need to leave it till I check though. ( I did clean around the caliper first to make checking it easier )

 

[2manyoranges]

I think cycle the lever quite a few times - each time, if it is leaking, a spray might occur.....

 

[kalex]

Both calipers are fully dry after testing

 

[2manyoranges]

Well that's good. Next questions....which brake hose have you got? The BH90 thin bore (good and powerful - stainless barbs) or the big bore BH59 (terrible, mushy and nasty - brass barbs). This can make a huge difference. Also, full bleed and refill using Finishline green brake oil (thick and vicous and less compressible) rather than the Shimano pink (OK but nowhere near as good as the green FL). File pads, clean with MucOff cleaner, wash rotors, give them a good clean with Spontex and MucOff pink wash, then MucOff Brake Cleaner.

 

[mattr]

or the big bore BH59 (terrible, mushy and nasty - brass barbs). This can make a huge difference.

Seriously?
The difference is barely measurable at MTB brake pressures. Certainly well below what's perceptible without accurate measuring equipment.

 

[kalex]

I haven't a clue unless the hose is stamped. I've still got the standard hose that came on it, Whyte T130RS 2018 if that helps.

The rotors have been lightly sanded, cleaned with car brake cleaner, petrol, meths and now electrical contact cleaner in that order.

 

[2manyoranges]

Oh dear - have I said something silly? I was basing it on the following....which led me to read a bit about the two: I put some BH59 on a jump bike and did a proper bleed - and I mean proper - and the difference was really tangible. Mushy. I thought perhaps there was an air bubble in the caliper somewhere so did another bleed - all the usual tapping and moving the bleed port to the highest spot etc - still mushy. So I hooked some BH90 out and put that on, and the performance was immediately back to normal - much sharper at the bite point. This had happened in the past and I had just put it down to a small bubble trapped somewhere. But then I read this https://singletrackworld.com/forum/topic/bh-59-vs-bh-90-performance-differences/
Some seemed to think it did, and some it didn’t. I thought the difference was definitely down to the hose - do you think it was more likely a bleed problem? Shimano calipers can be a irritating sometimes with voids....