Disc brake adaptor mounts

[mbuttie]

Hello,
I will try to be as concise as possible with my problem.

I have changed the Shimano Alvine hyd disc calipers on my Cube Hooper to Avid BB7 cable operated calipers as part of a project to go from straight to drop handlebars. Rotors remain the same at 160mm front and rear.

Issue is with the Shimano adaptor mounts that were on the bike and those that came with the Avids (20mm IS) - in short which to use.

Not having done this job before I made an assumption (ho, ho, ho) and, starting with the rear caliper, removed the standard Shimano adaptor mount and fitted the BB7 using the 20mm IS adaptor Avid supplied it with - and it seemed(s) to have set up fine.

Problem was when I applied the same process to the front caliper - the BB7's straight pad tab clashed badly with the 20mm IS adaptor to an extent that it would not allow caliper to 'cover' the rotor in terms of pad / rotor depth. I solved the problem by reverting back to the Shimano adaptor mount which does have a different profile and allows the BB7 to sit over the rotor.

So question is - does it sound correct that I am having to use two different profile adaptors with the same calipers and rotors?

[nfmisso]

different adapters are not unusual.

Given your comfort level, you should have anything brake related checked out by a competent mechanic.

[RobAR]

Your question is not uncommon. You just got lucky on the rear adaptor. The front requires more thought but, you can do it. To be honest... even after having served as a bike mech for a quarter of a Century, I still have to stop and think.
I do think that Shimano has the superior calipers but I like SRAMs (Avid) mounting system better. When you start mixing the two, it gets confusing but can be done. My bet is that you already have the parts that you need. You just need to assemble everything in a Frankenbike manner. If you can spec which fork you have - I might have more info.

[mbuttie]

(09-10-2012, 10:19 PM)RobAR Wrote:  Your question is not uncommon. You just got lucky on the rear adaptor. The front requires more thought but, you can do it. To be honest... even after having served as a bike mech for a quarter of a Century, I still have to stop and think.
I do think that Shimano has the superior calipers but I like SRAMs (Avid) mounting system better. When you start mixing the two, it gets confusing but can be done. My bet is that you already have the parts that you need. You just need to assemble everything in a Frankenbike manner. If you can spec which fork you have - I might have more info.

Cheers for the input guys.
I returned to the workshop last night (I needed the bike for the daily commute) and applied the investigative techniques of Sherlock Holmes.

I compared the adaptor profile options against how the bike is set, Shimano adaptor on front forks, Avid 20mm IS on rear seatstay (this set-up seems to work, I have full pad / rotor cover and no pad tab / adaptor clashing) with the option of swapping adaptors.

What I know is that the Avid adaptor on the front (standard Cube Hooper / Editor IS fork) will not work, it seems too deep, pad / rotor cover is 60% at best.

Swapping out the rear Avid for the Shimano will not work as the shallow Shimano allows the caliper to clash with the rotor - I get too much cover!

So, up-shot is that unless I have missed something (quite possible!) using two different adaptors works. It looks right vis-a-vis pad / rotor alignment, I have adjusted the brakes - they work very well and I rode the bike to work today and did not embarass or damage myself, other life forms or bike.

Just seems odd that two identical adaptors came off, but two different ones were needed to go back.

One of lifes great mysteries I supose.