Originally Posted by
jackyharuhiko
Thanks so much for the detailed analysis. Just had a chat with the bike shop mechanic and he said both Birdy and the new Dahon K3 Plus have the same situation with the front brake disc on the right side. He said that the Shimano Ice Tech disc can only be installed in one direction and cannot be flipped over. But he emphasised that for Shimano’s disc (the one that I am using is exactly RT86), it’s fine for it to be rotated ‘backwards’, however, for Hope’s brake disc, he would recommend to flip it over (and it can be flipped over) to retain the direction of rotation.
Right, thanks for the info. Given that this mechanic is experienced with this kind of bikes and the issues with reversing disks, it could be safe to do as he says. The disk will see less extreme forces on the Birdy than on the big wheel bikes it is designed for, anyway. So there could be a good enough safety margin here.
Originally Posted by
CEBEP
I discussed this with my mechanic. He said that there should be no issues with alignment simply because it’s a standard Shimano brake caliper using standard rotor. So using another Shimano rotor should make no difference in alignment. Makes sense to me.
The disk is designed to have the right side contacting the hub. If you flip it, the left side contacts the hub. If the bolt hole part of the disk is thicker than the brake surface, the disk is now misaligned outwards by (bolt hole thickness) - (brake surface thickness). A 2 mm difference means 2 mm misalignment, for example. According to jackyharuhiko's mechanic, this is the case for the ice tech disk. But if the thickness is the same, it's fine, as with the Hope disk example, and with the original disk delivered with the Birdy. Those can be flipped.
Originally Posted by
CEBEP
RT86 rotor also looks much stiffer to me compared to ultra light design. However there will be much less rotational forces for same braking effort considering 18 inch wheels and it should probably be fine. At least my mechanic said it will be and warranty on the rotor will hold.
This is true, and if they are willing to keep the warranty on it, it could be fine.
Personally I see no good reason for this kind of experimentation, but: Your bike, your decision
