Specialized brose E06855-200 motor Bold have a breast fracture

[BobJung]

After 6500 km 3 years old of peddling the motor just suddenly went wobbling. My initial thought was the right bearing of the crank, but looking down the motion was way to big. Seems the motor mount was just breast in two. I have some foto's of the motor bold made on the microscope. I am a mechanical engineer and like to know how to handle this on the Brose motor. Until now Specialized did offer me a replacement motor with 35% reduction, since it is out of warranty, if this is a fair offer I am in doubt. But it would be far easier just to unscrew the bold and replace them. My biggest fear they are cast in place in the mold.

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[Greg Watts]

After 6500 km 3 years old of peddling the motor just suddenly went wobbling. My initial thought was the right bearing of the crank, but looking down the motion was way to big. Seems the motor mount was just breast in two. I have some foto's of the motor bold made on the microscope. I am a mechanical...

Welcome to the forum, and sorry it's a motor mount snapping in half that's brought you here rather than something less exciting.

On the mount itself: from what you're describing - sudden play at the crank, way more than a bearing would ever give you - that's consistent with the alloy motor mount bracket on the Brose S Mag failing rather than anything inside the drive unit.

Before you go anywhere near unbolting anything, it's worth checking a few things with that microscope of yours:

• Look at the small bracket bolts for hourglass-shaped wear - that tells you they'd been slipping under load for a while before the bracket let go.

• Check the mounting holes themselves for ovalling - if they've gone oval rather than staying round, that's fatigue from repeated micro-movement, not a one-off overload.

• Note the fastener types - larger bolts are usually Torx Plus, smaller bracket bolts security Torx, which matters for what tooling you'll actually need.

As for whether the bracket bolts are captive/cast-in or genuinely serviceable threaded inserts - I honestly can't confirm that construction detail for the S Mag from what's in front of me, and I'd rather say that than guess and have you strip something that was never meant to come apart.

That's exactly the kind of thing an independent Brose specialist can tell you from the part number stamped on the bracket rather than from a forum reply.

On the 35% off offer - I can't tell you if that's fair without knowing your local RRP for the unit, but it's worth benchmarking against the reconditioned-motor route some dealers offer independently.