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As i've just ordered a carbon road frame with a press-fit BB i'd like to know how they work.
Is it a case that the cups are a one-time press-fit & the bearings are replaceable or does the whole thing have to be removed & re-fitted each time?
Depends what press fit bb, some will require the whole unit to be replaced some you can just replace the bearings in the cups.
It's a BB30 apparently. I have five bikes & so far i've managed to avoid press-fit stuff.
I've got one, the BB lasted 3 years and was renewed in the LBS for a few quid plus the BB price. They're no hassle at all.
BB30 is bearings directly into the frame without any cups.
So a BB30 in a carbon frame is a non home tooling job?
Hmmm..
The original bearings in my road BB30 lasted 6 months and that was without doing high milage though the warranty bearings are still running smooth 12 months later.
So a BB30 in a carbon frame is a non home tooling job?
I'm sure it can be done without too much trouble, but I couldn't be bothered!
I'd have a go in an Alloy MTB frame, but a lightweight carbon Dolan? Not a chance!
This is a useful guide...
http://www.bikeradar.com/gear/article/workshop-how-to-service-bb30-press-fit-bottom-brackets-29544/
Press fit are not really different to headsets. Bang the old one out and press or tap in the new ones. Very easy. Great for manufacturers as far quicker to ream and install.
In a carbon frame, is the BB30 sitting against carbon or is there an alloy sleeve in the BB area?
It's an alloy sleeve inside the carbon frame with two grooves into which a circlip fits. The bearings are pressed directly into the sleeve against the circlip. A washer like cover gives over the bearing much like a headset, and the drive side crank and spindle is inserted. On the non drive side a wavey washer gives on top of the cover before the final crank arm is slotted on and tightened to a torque value with a 10 or 12mm Allen key.
Oh and today I had my second set of bearings in 18 months. As you might tell from my description above, there's not a lot stopping wet and shite getting to the bearings. What's worse is that most frames and sleeves aren't drilled so water sits inside the sleeve (which is aluminium) and helps to corrode the bearings.
Cheers for the explaination!
Not convinced to be honest, but i've ordered it now so will have to suck it up! Gives me an excuse to make sure it only comes out on sunny days.
BB30 bearings on my mtb tend to last around 6 months. As others have said, the main issue is water collecting in the bb area rather than the normal muck you might face during a ride. Packing the bearings with grease and removing the cranks every now and again to release trapped water seems to help, much like any other bb really.
Its on a carbon road bike so I'm not going to be riding it through mud, crud & deep puddles - in fact it won't come out at all if its wet!
Never having had a press-fit BB before i was a bit worried about them but with more info I'm a little happier 🙂
Never understood protecting a roadie in the shed unless it's all about saving expensive carbon rims- pretty much every component would be fine for months off road if you really wanted to 😀 Certainly the BB30 shouldn't be a huge concern for you, even if ridden hard all winter. Having said that, it is one of the few things I prefer to get fitted at the LBS though to make sure it is in straight and won't develop any creaks. The right tools seem to go a long way to avoiding annoying noises!