hi
I have a genesis CdF 2018. looking at a potential move to 105 disk brakes.
Can anyone recommend an adaptor as 105 comes with post mount but my frame is IS - I would be running 160mm rotors
thanks
Most IS to PM adaptors add a minimum of 20mm to the native rotor size.
I think Clee Cycles do a KCNC adapter which might allow this to work with some calipers. However, some calipers may clash.
What side rotor does your frame run with the IS caliper bolted on directly?
You'll need something like this:
https://www.chainreactioncycles.com/shimano-rear-post-to-is-disc-brake-mount-adaptor/rp-prod13749
Most IS to PM adaptors add a minimum of 20mm to the native rotor size.
Standard ones don't. A +20 adapter adds 20 mm. A +40 adds 40 mm. Hayes and Avid brakes were post mount back when frames and forks were ISO and the standard rotor size was 160 mm.
What side rotor does your frame run with the IS caliper bolted on directly?
That can depend on the caliper for ISO calipers. To change rotor size, you used to have to buy a half-caliper designed for a larger rotor.
I though 105 calipers were flat mount, not post mount. Do they come in both options then?
If they are post then it's a pretty standard adapter. I expect many people have an old one in the spares box if you ask around as it was very common but now less so
Most IS to PM adaptors add a minimum of 20mm to the native rotor size.
Standard ones don’t. A +20 adapter adds 20 mm. A +40 adds 40 mm.
Was just going to say the same.
Never had any issues just buying the size I needed (like the ones listed on the CRC site).
That's what has led me down this thought path.
The only bike I still have with IS mounts is a Decade Tripster running Hope original Enduro4 calipers. The rear is a number 3 caliper, the front is a number 5. Both use 165mm rotors. I also have 2x number 8 caliper halves for when they ran 205f/185r on a different frame.
There's 20mm difference between the front and rear with IS. Was it the front that proved difficult to fit 160mm post mount calipers to an IS fork?
Just considering Hope brakes as that's where I have most experience, this would need an F mount in the rear and an A mount on the forks. Both come with a note pointing out which calipers fit. I think that A mount in the front would only work with the X2.
Was it the front that proved difficult to fit 160mm post mount calipers to an IS fork?
No. That was fine and pretty standard. It was fitting 160mm IS calipers onto post mount forks that was difficult. That usually required adding 20mm to your rotor.
There is a +20mm difference between front and rear though, so you do want a front adapter to get a 160 disk.
Nickjb - I think you might well be right. I used to know that. I've clearly got to that age where I now don't know stuff that I used to. It's all downhill from here.
It was IS calipers on PM frames I was thinking of.
