Anyone know anything about disc brakes?

Thank you (again) hippy, tester and Ed for comments on this. I bought new 105 callipers as they were on sale on PBK, and by the time I’d bought new pads for my previous calipers it was an extra ~£30.

I had no idea that they aren’t backwards compatible. To be fair I hadn’t even investigated what generation of 105 I had…

I have now learned that shimano changed the internal bore diameter of the hoses. This will likely not be news to any of you lot on here, but it might be helpful to someone in future (correct me if any of it is wrong) I know understand:

105 5800 -

RS505 calipers (no 105 branding) use BH59 hoses (which may be lower pressure and more flexible) and have a 2.3mm bore.

Shifters have bigger bulbous heads and fatter levers.

105 r7000 -

BR-R7070 calipers (105 branding on the side) use BH90 hoses and have a 2.1mm bore.

R7020 shifters are generally a bit neater/slimmer.

————
I believe the hoses have the same olives/fittings etc so will all fit but the brakes will just not work that well.

My overall goal was to get the best possible braking to stop 135kg of me + bike or sometimes ~150kg of me + bike + luggage so I’m not sure what to do next. 1) Make the old ones work (but I think a piston seal might be screwed, not sure), 2) buy new hoses and levers (painfully expensive for presumably minimal upgrade), 3) just try it as is with the new calipers, 4) buy a new set of rs505 calipers 5) buy something else!!?

Edit: got the bores the wrong way round

FFS. Thanks Hope. Different brakes, different bike, spot the difference:

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Looks like that top one isn't quite finished.
CNC machine ran out of batteries?

There's more to it than that, but still the kind of running design change which wouldn't necessarily mean a new part number

I wish it had!

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I think someone faced it, it was a cheap eBay “oh awesome that’s exactly what I need” after I’d already not read the hope site properly and bought an A adaptor (which does tbf clearly say it won’t work with these calipers)

I believe the hoses have the same olives/fittings

Same olives, different barbs, silver for bh90 brass coloured for bh59, you won't have any real issues mixing the two systems, but you should use the correct barb for the hose.

Thank you! What (if any) minor issues might there be? Will they work worse?

None if you just use the right barbs.

BH 90 is the new hose with the smaller bore, BH 59 is the old one.

IRL seemingly none, but technically they might have a slightly different feel.

Cool, thank you. So I’ll need barbs for bh59 (but my new calipers will have come with barbs for bh90)

I should buy two of these?

Excellent. I don’t know the terminology for brake feel but I want more “touch the brake slightly and you feel like you’re going to fly over the handlebars” than the other end of the scale 🤗

We’ll see. Thanks all for being v helpful as usual!

Are you cutting the hose? You can probably just unplug the old and plug in the new, bleed and go.

THANK YOU! I was just coming back to ask why I wouldn’t be able to do that.

Fuck me my LBS had me running around planning to spend more money!

£5 please.

Good plan

:D

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Ha, nice one.

Any 160 centrelock rotor recommendations?

ice tech shimano

Seconded. M800 are the basically same as m900 minus some black paint on the rotor (which allegedly absorbs more heat because it’s black). (Didn’t meant to reply directly)

I'd get one from Hope or Swiss Stop. ;-)

Morning!

Shimano GRX rear.

Good lever travel (stops 10mm from bar), as pads hit the rotor. Reasonably solid feel - feels like the front which isn’t causing me any problems.

There’s very little bite* between the pads (resin) and the rotor. I have cleaned both using dry wet n dry paper and then Muc Off disc brake cleaner (allowing to evaporate and wiping off the excess).

*the brakes drag, but I can’t lock the wheel up. And there’s squealing if I really try to grab a proper handful**.

Are the pads and disc (either or) contaminated? Can I fix it? Will they bed in following my cleaning them?

Do I need to bleed the brake again?

**ooh matron

Sounds like contaminated pads, but check the rotor, wheel and caliper is all tightened up properly too. Proper bedding in after the cleaning/new pads helps too.

Once you've cleaned them, you need to bed them in again.

Did you do the 5-6 stops from 30kph or whatever bollocks they say?

It's why I don't bother cleaning them these days. Only if they're actually contaminated will I bother cleaning them. The best tactic is to keep them clean as possible to begin with.

Thanks! I haven’t bedded them in consciously - just ridden into the office.

Everything is nice and tight so it sounds like bedding in is the answer. Or they’re contaminated beyond help!