Severe bottom bracket bearing corrosion in 2019 Cannondale Synapse

Friend of mine who rides a Synapse was complaining of mysterious thudding sounds when pedaling. After checking the bike I decided to pull out the crankset, and discovered some seriously corroded BB30 bearings.

There’s a rectangular rubber cover that fits into a cut out in the frame on under side of the bottom bracket. The cover has a hole for water drainage, but on this bike the hole was plugged with a rubber bung. Corrosion from water trapped in the frame got pretty bad.

Scratching my head on this happened … is this how Cannondale ships the frame out to dealers? Did someone plug it up with a random thing they found on the floor?

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At the risk of being unhelpful, the words ‘Cannondale’ and ‘bottom bracket issues’ are as common a combination as fish and chips, or salt and pepper. Suffice to say that even without having seen this particular flavour of clusterfeckery before, I’m wholly unsurprised.


I’ve got a 2014 Synapse but the cover looks similar. No hole in my cover but the cover is not waterproof anyway so I think it would allow water to drain slowly. I have never had corrosion issues. I have had pitting where the axle rides on the bearings. Solution has been to replace the axle every couple of years.

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I have a 2017 Synapse carbon that came with a BB30A setup too. Neither version of the plastic covers (part numbers are KP299 or KP298) have drain holes. Someone has drilled that hole and put in the plug.

By looking at the picture of the BB shell, it looks like there are tiny flakes of metal against the circlip, and it is those that have rusted, not the shell or the circlip, which are both stainless steel. So, that leaves the bearings themselves as the source of the corrosion. Without knowing how often the BB area was cleaned and lubed to keep the corrosion at bay, they could just be the original bearings and they’ve had a hard life and need to be replaced, or they spun in the shell a little and have scrapped some metal off the outer race. The rest of the crud on those bearings and the spindle just looks like caked on grease.

If you use good quality bearings, mount them in the BB shell with Loctite, then keep up a regular lubrication and maintenance schedule, then BB30 / BB30A is as reliable and creak-free as any other press-fit BB. The notorious BB30 creaks are often the spider / crank assembly.

… HOWEVER, about 2 years ago, when the time came to replace the original, worn out bearings as well as both chainrings, it worked out easier and cheaper to convert the whole BB30A setup to Shimano style 24mm spindle instead with a Wheels Mfg BBRight screw-together BB, and to install a Shimano 105 crankset. The whole setup has been quiet and trouble free.

frankly, it’s bloody mind blowing somebody would plug a drainage/ventilation hole in anything that that’s favored with one.

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This is true. Fortunately (or not?) I’m used to servicing my SuperSix which also has a BB30 so had the tools and spare bearings to hand…

And you can do that with a PF30 (or PF30A ? I think that exists too) screw-together bottom bracket to keep the original crankset.