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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.
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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
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t.o.
snottyotter
In our workshop we usually recommend both to be changed, even if the rotor have minimal wear, it can greatly affect the braking performance.
Different rotor like Magura tend to offer more power due to the difference in steel.
Sound like your brakes is one of those Shimano one that’s pretty hard to get it to feel nice and sharp, a new hydraulic hosing help improve it but there’s only so much we can do