Disc Brake Rotor Problem

[MrJamie]

So, im not sure if i messed up here.

I ordered some Avid BB7s, decided id go with the 200mm, didnt realise theyd need clearance rather than just going inside the fork . Anyway it's such a close call, the wheel goes on alright, but the "lumps" in the rim of the rotor very slightly clips the fork. I spun it and it took a little groove out of the fork in just a few rotations and marked the rotor.

Im not really sure what to do with it now... If i were to buy a 180mm rotor would it fit the current setup or would it need a different kit? Could I reasonably file the a mm or two off the rotor?

 

[Red Light]

I would recommend going for a smaller rotor which will mean buying new rotors and the appropriate adapters for the calipers. The problem you will face otherwise is the rotor will bite into the forks as they flex and twist a bit under the loads of riding and you will always be needing to check very carefully when you take the wheel out and put it back that you are not touching.

 

[MrJamie]

I'm getting quite irritated with what should have been relatively simple...

I decided rather than mess about just to go for the 180mm, so that finally arrived from Germany but unlike the 200mm which came with 3 mounts (IS40mm(front) IS60mm (rear) and a post mount) it just came with the IS40mm which i believe for a 180mm rotor is rear only and I need a IS 20mm for the front. Can anyone confirm if that's correct?

 

[Cubist]

Can you post a link to the site you bought them from? Most modern calipers are the same size, and are adjusted by using different mounts.

For example, to mount a PM Deore caliper to a 160mm rotor you bolt it direct onto a PM fork. .
For a 180 rotor front you need a +20mm adapter, for a 203 you need a +40mm.

If Avids sell different sized calipers, you may need different mounts. Don't forget, if you buy a RH lever and caliper in the Fatherland you'll be buying a rear brake, so they will have sent you what they think is the right mount.

To be as accurate as possible, what sort of fork are you using?

If you are struggling I have some +20mm spacers and long bolts which will solve your problems for you, but only if you are mounting onto Post Mount forks, otherwise I have a 180mm IS fork to PM caliper mount that will fit.

 

[MrJamie]

Can you post a link to the site you bought them from? Most modern calipers are the same size, and are adjusted by using different mounts.

For example, to mount a PM Deore caliper to a 160mm rotor you bolt it direct onto a PM fork. .
For a 180 rotor front you need a +20mm adapter, for a 203 you need a +40mm.

If Avids sell different sized calipers, you may need different mounts. Don't forget, if you buy a RH lever and caliper in the Fatherland you'll be buying a rear brake, so they will have sent you what they think is the right mount.

To be as accurate as possible, what sort of fork are you using?

If you are struggling I have some +20mm spacers and long bolts which will solve your problems for you, but only if you are mounting onto Post Mount forks, otherwise I have a 180mm IS fork to PM caliper mount that will fit.

I'm just replacing the front vbrake with a disc brake, perhaps doing the rear at some point in the future. Its a Suntour suspension fork (probably not great but does the job for now), with IS mounts.

The 200mm kit - caliper, mount, rotor all fitted the bike fine (with 40mm IS mount) except that the rotor touched the fork because it was huge. The 180mm kit kinda looked like theyd thrown the box contents into a bag and mailed them out with just a single 40mm (rear) mount, so I suspect they just forgot to put the 20mm (front) one in.

180mm: http://www.bike-discount.de/shop/a71583/bb7-mountain-mechanical-disc-brake-180mm.html?lg=en&cr=GBP
200mm: http://www.bike-discount.de/shop/k496/a71730/bb7-mountain-mechanical-disc-brake-200mm.html
The calipers for both kits are identical, like you say it seems they just change the mount size.

CRC sell the same mounts http://www.chainreactioncycles.com/Models.aspx?ModelID=75477 and kindly seem to list the sizings. I ordered one of the 20mm IS ones as its consistent with what I expected and I got hugely impatient.

 

[Cubist]

Sounds like you've sorted it then!

 

[Drago]

You need to check that your forks are rated to safely handle the forces that such a large rotor can produce. Most manufacturers quote 180 or 203mm, so I guess its 50/50.

 

[MrJamie]

Sounds like you've sorted it then!

Thanks for your help though, I'm not too bad at figuring stuff out with the help of Google and enjoy the learning part, but its easy to overlook things and end up in a mess. It's been two weeks since I ordered the kit, so getting a little impatient with mistakes

You need to check that your forks are rated to safely handle the forces that such a large rotor can produce. Most manufacturers quote 180 or 203mm, so I guess its 50/50.

I swapped to a 180mm now and just downloaded the fork's owner's manual, it says max rotor size 180mm so should be alright. Its another thing i wouldn't have thought of though

I'm thinking it (Giant Roam 2) will still make a decent hardtail for trails etc in the future even if i do buy n+1 for roads, so i figured id go for the upgrade as the current vbrakes are dangerous in the wet with my momentum.