Post 1 of 9 views. How often do y'all replace them. Any suggestions for a non ceramic upgrade? Chris King? Let food be thy medicine Re: How often do you replace your bottom bracket?
Post 2 of 9 views. Mine has the pf30 bracket. I replaced the bearings at 38k miles, as they started to make all kinds of funny noises and scratching sounds. I have 22k on the new bearings and all is fine. I did have it cleaned and serviced a week ago. Bearings are fine though. I would say to expect k miles from the bearings. Mike Alexander. Post 3 of 9 views. JackStraw13 wrote:. Along came a spider and behold the sealed BB was born. First models simply replaced the loose balls with sealed bearings but still square taper.
They are still in use and come stock on many bicycles, especially lower end ones. These bottom bracket units can actually be pretty sturdy and can last for years or decades and the user pretty tosses in a new one when it seizes up in a rainstorm.
Fast forward to current bikes and a ton of different types of bottom brackets but they all share similar features of sealed bearings and cups to hold them in the frame. Once you replace these low end units with a high quality Wheels Mfg Bottom Bracket , you can easily maintain them. The two biggest wear factors are miles and contamination. In my experience contamination is the most important. Ride a lot of miles and that will do it in as well.
In our lab at Wheels Mfg, I tested bottom brackets for mileage wear. Keep in mind we are in a lab without any environmental concerns like dust or moisture.
To remove the crank, first you must loosen the pinch bolts using a 5mm allen key. They can be at a funny angle, and are done up fairly tight, so avoid using a ball-end allen key if possible. Remove the compression cap. Keep hold of it and try not to lose it, spares are strangely difficult to get hold of.
With a small flathead screwdriver, disengage the safety catch — which is located between the two pinch bolts — by gently pushing it upwards. Pull the crank arm off its spindle — it should slide off easily without much force. If you found the safety catch difficult to remove and full of grit now is a good time to give it a quick clean. Lift the chain off the smallest chainring and let it rest on the bottom bracket shell.
It was joined by Power Torque in which used a single piece axle fixed to the right crank and used outboard bearings. Campagnolo provides bearings to fit both cranks to most bottom brackets including threaded and press-fit.
With the advent of carbon fibre and the development of lightweight and stiff race frames, came the advent of the press-fit bottom bracket. The solution was to press bearings directly into the frame. The benefits included more design freedom and stiffness and weight advantages over threaded designs. There now exist numerous flavours of press-fit bottom bracket, but most are not compatible with other designs, though in some cases conversion kits are available.
Cannondale, with the invention of BB30 in , came up with a solution. BB30 saw the bearings being pressed directly into a huge 42m diameter carbon shell and a larger, 30mm diameter bottom bracket spindle made from aluminium.
It offered more stiffness and less weight. Cannondale evolved it with BB30A. It uses an asymmetrical shell that is 5mm wider on the non-drive side to create a wider, stiffer base. The non-drive side crankarm angle is changed to maintain the same Q factor and even out ankle clearance on both sides.
In Cannondale developed it further, introducing PF30A which moved away from bearings held in place by clips to press-fit bearings in plastic cups that pushed straight into the carbon bottom bracket shell.
This change also required a bigger bottom bracket shell, so it grew from 42 to 46mm. BB30 required extremely precise machined aluminium bottom bracket shells with strict tolerances to contain the bearings and clips. SRAM press-fit 30 and launched it to the world in The shell size few from 42 to 46mm to accommodate the plastic cups containing the bearings. It uses the same 30mm axle as BB30 and 68mm width for road bikes and 73mm for mountain bikes.
It made it possible for frame designers to create carbon fibre frames with oversize bottom brackets for stiffness and weight benefits. It didn't require as strict tolerances compared to Cannondale's BB30 design. This has led to many of the issues associated with press-fit bottom brackets because you're hoping the fit between the plastic cup and carbon shell is good enough to prevent any unwanted movement which can lead to creaking.
Shimano developed its press-fit standard using 41mm diameter bearing cups with an Trek developed its bottom bracket for its road and mountains bikes. The bearings pressed directly into the frame with a No wonder Trek has adopted T47 on its new Domane road bike. This is a standard introduced by FSA in that aimed to solve some of the issues with compatibility, designed as it was work with most current bottom bracket standards.
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