What's bottom bracket fair wear and tear?

Roadtoad

My Giant Defy has just got a new bottom bracket bearing. The bike is 2.5 yeas old (Thanks, minister) with about 8000 km up, mostly flat Leinster roads, some mountain sportifs and touring. I weigh about 100 kg.

This seems very premature to me. Its a sealed-for-life job, with no user lube point. Should I feel cheated? What do the high-usage guys get?

(the bike is on its second set of tires, second chain/casette and its second back wheel, but they are all very user use/abuse related, and I've no complaint in these areas)

Home:Ballyhoura

Sounds about right to me, nothing to be worries about there, that would be about normal given the mileage, weight & use

seamus

Sounds about right to me too. My commuting mileage is 5000km a year, and then cycling mileage on top of that and I'm on my third BB in two years (though literally just changed it a month or two ago).

Weather obviously plays a part. If you never ride the bike on wet roads, you'll get longer out of the BB. If you ride through the wet conditions, it will fail sooner.

C3PO

Lucky you - I get about 6 months out of the bottom bracket on my mountain bike! Very dependant on conditions I would say - distance, wet/salty roads, weight/pedalling style of rider etc.

manwithaplan

Mine is beginning to creak a bit after a year and a half. I have done a lot of miles on it though, many of them through manky conditions. I was hoping to get the winter out of it before replacement but it doesn't look likely now.

-K2-

I got 8000km out of an FSA MegaExo BB-4000 . The "sealed" design means it's easy for water to get in but almost impossible to grease-up properly as the end-caps shatter if you try to take them off.

The easiest service approach was to swap out the entire part, cups and bearings included, all it required was a Shimano BB tool. Otherwise special tools are required to replace the bearings in the cups.

Diarmuid

Jeez, I need to check my BB then. I've put up 10k+ km on mine and haven't noticed any problems.

Chips Lovell

It's one of the things that annoys me about sealed cartridge bearing BBs, once they're done, that's it.

If you think replacing a BB regularly is a bit much you could investigate whether there's a compatible servicable BB on the market. Presume it's Shimano?

Lusk Doyle

My god - I've my bike for nearly four years now and have never changed the bracket or even thought about it! Now I know what that noise is :eek:

Chips Lovell

It would depend more on the mileage it has and the conditions its been used in. If someone is a fair weather cyclist, their BB would last longer even if they were putting big mileage in, than someone who's going out in all conditions.

manwithaplan

He's calling you a fair weather cyclist, Lusk Doyle. Want me to hold your coat?

Lusk Doyle

manwithaplan wrote: »

He's calling you a fair weather cyclist, Lusk Doyle. Want me to hold your coat?

Oh it's on like donkey kong mother flipper :mad:

NeedMoreGears

I has a Giant SCR and put up around 12,000km before it was stolen. Chain rings, chain and cassette worn out but BB seemed ok. Cycled all weathers but probably not so much in the winter (say 50km/week instead of 100km in the summer). On the assumption that it mightn't have actually been ok, what would I look out for to give an indication that the BB is past it's best?

petethedrummer

Servicing a shimano one.

http://forums.mtbr.com/drivetrain-shifters-derailleurs-cranks/outboard-bearing-bottom-bracket-service-guide-pics-497220.html

Roadtoad

NeedMoreGears wrote: »

.... On the assumption that it mightn't have actually been ok, what would I look out for to give an indication that the BB is past it's best?

Crank was developing a click, not apparent always, but quite noticable when it wanted to be heard.
The easy test was the rock in the chainwheel when wobbled by hand.
Replacement cost about €50 in the LBS inc fitting, so I didn't feel hard done by financially.

seamus

Yeah, clicking is the most common one. You can somewhat mitigate this on Hollowtechs by jamming a whole pile of extra grease in there, but it does mean the BB is on the way out.
I've found that you don't get much play in a worn hollowtech BB as they're quite tightly packed. If it's really bad you can feel it when spinning the cranks with the chain removed, but in most cases I've had to remove the crankset and spin the bearings with my finger to feel the roughness.

A standard square taper BB is much easier to feel for roughness and play.

seve65

just replaced my second fsa bb 6000 after 5 months (about 5000km). For those that dont know, symptoms can be clicking, gritty sounds and outright pin-ball machine sounds when its really bad. First BB could have had about 15000Km (including a dodgy service by yours truly) so I guess thats ok. Same thing wrong this time around, grit and worn bearings. Didnt do a bodge of a service on the sealed bearings this time. So replaced instad with shimano bb5700. As others have reported the gossamer cranks were a tight fit (i.e. gentlish back with a hammer required). Lot cheaper than FSA. So lets see how the commute goes tomorrow ! Should have bought Chris King in the first place...

Cerdito

Going to jump in here with a question rather than starting a new bottom bracket thread:

I removed the one on my Giant Hybrid at the weekend to see if it needed servicing/replacing, seems fine but I'd like to have the option of replacing it at some point.

My bottom bracket is a RPM 68 x 124.5 square taper, this seems to be quite difficult to source the same size, on the net anyway.

I notice that you can get most Shimano square tapers in 68 x 122.5 - could this size be installed instead of the 124.5? I know there are some considerations around chainline, but I can't really get my head around the concept!

Mycroft H

Why did the cup and cone design die out? they were fully serviceable and easy to take apart and grease.

Was it just panned obselence? The newer catrerige bb would fail earlier and keep shimano in business

ednwireland

BX 19 wrote: »

Why did the cup and cone design die out? they were fully serviceable and easy to take apart and grease.

Was it just panned obselence? The newer catrerige bb would fail earlier and keep shimano in business

External bottom brackets allow you to have both large bearings and a large, hollow bottom bracket spindle. A large hollow spindle can be designed to be as stiff as a small solid spindle for less weight. Smaller bearings reduce the longevity of a bottom bracket, so the typical bottom bracket design allows a narrow range of suitable spindle sizes and bearing sizes - to get the weight savings from a larger spindle you need to sacrifice durability. Moving the bearings to the outside effectively removes this tradeoff.

hope stuff tends to serviceable
http://www.chainreactioncycles.com/Models.aspx?ModelID=24172


oh and dont get me started on cup and cone ive removed more bearing paste from minced up loose bearings thsan i care to remember, square taper seaklesd shimano units were a godsend even if you cant strip them