Some members are well aware of my many mountain bike and electric mountain bike builds over the years.

A week or two ago I was talking to a local bike shop owner about technology. There was a German cycling event and he was discussing the odd aerodynamic things teams and manufacturers have been doing to gain an edge on the competition. Some of the tech is far more advanced than I ever expected to see.

I probably shouldn’t have been so surprised. Motorcycle Grand Prix racing teams started using modified mountain bike levers to activate or lock the bikes suspension depending on where it is on the track.

I recently learned the hard way that Shimano engineers their brake adapters to the extreme and pushing an adapter past its maximum manufacturer specified limits will cause the part to fail.

Case in point. I swapped two of my three disc brake adapters over when I upgraded to 220mm rotors. I forgot the front adapter because it looks so similar and I had other issues I was trouble shooting on the bike occupying most of my focus.

A normal 203mm adapter vs my bent adapter.


Here is the 203mm brake adapter (top) with the slightly beefier 220mm adapter.
There is only 1.5-2.5mm more aluminum alloy in high stress areas on the top post mount. It’s wild that small amount makes such a difference.



I can buy a new caliper for $53 and bleed it myself but it’s still a frustrating lesson to learn from because it was avoidable.

“If it doesn’t break, it’s too heavy”

They were quite serious about the “203 rotor only” warning.

I do have to give accolades to Shimano. When the adapter bent and the caliper mounts broke they didn’t fail spectacularly. The rotor moved a bit simulating a bent rotor which was weird because it would come and go. It made me examine the brakes and discover the cracked mounts.

I’m glad it didn’t fall off and dive into the spokes. That would have sucked big time.

It's actually a pretty good lesson in:
Just because it fits doesn't mean it'll work.

It isn’t a total loss. There is a silver lining in every grey cloud.

I now have a spare set of brake pads with only 500 or so miles.

Electric bikes tend to be a bit hard on the brake pads. It isn’t just because of the speed associated with electric bikes. The battery, controller, dash, throttle and motor add about 65-70 lbs to the bike.