Avid BB7 to BR-M446 conversion problem

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Stradageek
Posts: 1657
Joined: 17 Jan 2011, 1:07pm

Avid BB7 to BR-M446 conversion problem

Post by Stradageek »

Hi, can anyone help

My HP Velotechnik Speedmachine is fitted with Avid BB7 brakes on 160mm discs using adaptors to match the IS frame mounts.

I have been gifted some Shimano BR-M446 hydraulic brakes (calipers, cables and adaptors) that I want to retrofit.

The problem is that the apparently correct Shimano adaptors do not align the calipers with the full braking surface. The caliper needs to be about 5-10mm closer to the disc centre.

Looking at the BB7 calipers (which use the same adaptor as supplied with the M446's) they sit 'lower' in the adaptor cradle, if you can visualise that, and contact the full braking surface.

I can't seem to find any adaptors that will move the caliper further down. The front adaptor I have is already labelled IS 0mm!

Any suggestions as to what to buy/where to look or have I hit a total incompatibility - the Speedmachine is 15+ yrs old

Many thanks

Stradageek
Stradageek
Posts: 1657
Joined: 17 Jan 2011, 1:07pm

Re: Avid BB7 to BR-M446 conversion problem

Post by Stradageek »

Possibly solved it and the problem is with the gifted parts.

Although the adaptors given to me with the calipers look like the correct Shimano parts I now believe they are actually AVID adaptors.

Shimano parts now on order, here's hoping :wink:
Jupestar
Posts: 920
Joined: 29 Feb 2020, 3:03pm

Re: Avid BB7 to BR-M446 conversion problem

Post by Jupestar »

Adaptors are pretty standard as long as the body of the caliper can fit in, which they normally can. So I'm not sure a new adapter will bring the caliper closer

IS O means it should fit a 160mm front disc or 140 mm rear disc.

I believe the BB7 are designed to sit on a couple of spacers. So it could be that if they were not their your BB7 was sitting closer than the design.

I'd also check double check the disc size... Not all 160mm disc are equal...
Stradageek
Posts: 1657
Joined: 17 Jan 2011, 1:07pm

Re: Avid BB7 to BR-M446 conversion problem

Post by Stradageek »

Thanks Jupestar, you've helped confirm the issue.

It's now clear that the freebie M446 calipers were provided with inappropriate AVID adaptors and spacers. What I also didn't realise (because I've only recently started tinkering with hydraulic brakes) is that Shimano hydraulic calipers don't use any spacers. However, without the spacers the AVID adaptor fractionally fouls on the caliper body and the caliper sits fractionally too low fouling the disc edge.

I'm pretty sure a washer or two would raise the caliper enough to make it workable but this sounds more than a little risky.

The rotors are definitely 160mm and you have helped confirm that even a 15+ yr old IS mount will still be 'standard' and the new spacers should work - fingers crossed :)
Jupestar
Posts: 920
Joined: 29 Feb 2020, 3:03pm

Re: Avid BB7 to BR-M446 conversion problem

Post by Jupestar »

IMO. Adding spacers/washers between the caliper and the adaptor is perfectly normal. some come with big 10 or 20mm spacers. just add enough so that the calipers clears the disc. .too many and you may need longer caliper bolts.
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