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Bipolar roller
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Anyone tried this A2Z disc brake adaptor? Any other products out there?

I would like to use this A2Z on a steel frame, but it says they “recommend you use only for aluminum rear triangle frames.”

Anyone know of why this wouldn’t work or might cause damage if used on a steel frame and not an aluminum frame?

Would steel flex too much?
(I found at least 1 pic of it being used on a steel Karakoram)

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The first photo above conveniently shows a large flat plate alloy dropout. There is a lot of real estate to clamp that thing on. Interestingly, that frame already has a disc mount on its chainstay.

I don't think most steel bikes have a dropout area with as much flat clamping area as the pictured bike. Steel bikes are a little more sculpted there.
I have one older bike that is disc front, V rear. I don't mind it, though I'm not allowed the matching wheelset like the GT above.
If your paint job is simple you can have the disc mount brazed on without too much touch up. Steve Potts has offered that service for older Ibis ti frames. Someday I may take him up on it, but mostly I like old bikes and rim brakes.
 

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Air Pirate
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I had one of those on a GT LTS-1. That bike was perfect for that adapter, as it had nice large flat dropout plates for the two steel adapter side plates to sandwich over, and most importantly, those dropout plates were thick, which gave a specific part in the A2Z adapter plenty of metal to rest against. The part I am talking about can be seen in the photo of the DM-UNI installation instructions, in step #1. It is the little silver part with a large hole in it...in the Step #1 photo it is in between the silver side plate on the left and black middle piece (that attaches to the brake caliper). This part needs to sit flat and flush against the edge of the dropout plate...it is about 1/4"-38" thick. The GT LTS dropouts were almost exactly the same thickness. This part attaches to the outer adapter plates with a chainring bolt. I believe it is intended to serve as a torque/force stop...when the brake is actuated its position against the dropout lets the forces in play push against the frame evenly...and it keeps the whole adapter and brake assembly from moving forward along the path of force/braking energy. I understand that with many steel frames, the rounder tubing/dropout profile doesn't keep this thing in place well enough as it has a reduced contact and allows for too much lateral play.
 

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There are a few different styles available on Ebay, when I was looking late last year there was an A2Z on there as well but that is obviously hit or miss. I ended up sending my frame to Gene Spicer (spicerscycles.com) and he welded/brazed on a tab, looks awesome and zero hassle. My frame is polished AL though, so I didn't have to worry about paint. AL750_11.jpg AL750_13.jpg al750_done 3.JPG
 
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