armybikerider

I'm getting ready to replace my 2009 SRAM Rival 53/39 crankset with a new Rival 52/36 crankset. The original has 61,000 + miles and is noticeably worn, although it still works fine. I'm really replacing due to the lower gearing.

My question is....should I replace the original GXP bottom bracket also, as a matter of course? There's no issues with the BB currently, other than it has 61,000 + miles on it. There's no discernible roughness or play or noise.

Thanks.

dsbrantjr

Never Fix A Running Piece

HillRider

+1 You can always spend the money on a new bottom bracket when the current one no longer runs.

armybikerider

Thanks. That's precisely what I was thinking......but second guessing myself for being cheap.

"Don't fix it if it ain't broke."

JohnDThompson 

Why replace a perfectly good crank and bottom bracket? If the rings are worn, just buy new rings in the sizes you want.

HillRider

I don't know if a 36T chainring would fit the old crank. If the bolt circle is the common 130mm it won't. I also wonder if the change from 39T to 36T is worth the expense. Why not get a "compact" (50/34) and get a usefully lower low gear?

JohnDThompson 

Good point. Depending on what compact crank is used, the OP may "get lucky" and be able to retain the old bottom bracket, but it's not given.

dsaul

61,00 miles on a GXP bottom bracket has to be some kind of record. I don't get more than about 4,000 before they develop some play or the drive side bearing seizes up.

HillRider

I have no experience with SRAM bottom brackets but I have two Shimano BB-6700 Hollowtech II bottom brackets, one with 24,000 and the other with 22,000 miles, and both are still in fine operating condition.

Phil_gretz

I agree. Who needs a 52T chainring, if they're not racing?

Marcus_Ti

Rings cost as much as a crank nowadays, generally.

zacster

In the old 5 arm days, the bolt ring diameter was different between full and compact sizes. 130 vs. 110 I think. I have no idea with the newer stuff. Also, the old rings were compatible across brands. I never knew what was wrong with that.

JohnDThompson 

Five-arm cranks came in a large number of bolt circle diameters, including 86, 94, 110, 118, 120, 122, 128, 130, 135, 144, and 151mm; maybe a few more I missed. But most recently 110 and 130 are the most common for road cranks.

Yeah, there's all kinds of mutually incompatible stuff these days as well. You know what they say: the nice thing about "standards" is you have so many to choose from!

TimothyH

Repair and maintenance are not the same thing.

In this situation there is nothing to fix because nothing is broken. Replacing a bottom bracket in this case is maintenance, not repair. It isn't semantics. Proper maintenance reduces the risk of needing repair and often prevents downtime.

Depending on cost and how much you value time, it might make sense to replace the bottom bracket now rather than having to pull it apart a second time. A worse case scenario is that the bottom bracket with 61k miles fails and leaves you stuck on the road or leaves you without a bike for a period of time.

If it is a $25 threaded bottom bracket then I would perform proactive maintenance without thinking twice, slap a new one in and be done with it. If it is a more expensive part and involved process, requires expensive tools such as bearing presses or expensive services from an LBS then make a judgement call.

Either way, 61,000 is a lot of miles for a bottom bracket. Personally, I value time and not getting stuck and would replace a BB with 61k.


-Tim-

zacster

Um, no. The bearings used today will last a lot longer than that. They are much more likely to be damaged by doing "repair" than by just riding them. Overtightening, undertightening, tapping them out, tapping them in, not seating properly are all much worse for bearings than spinning the pedals. If they are smooth there is no reason at all to replace them.

hokiefyd 

With as common as noises and ticks and such can be with cranks and bottom brackets (in general -- maybe the GXP is less prone to this than other types), I think I would value a known quiet BB/crank combination over replacing it with new parts. I'd even probably favor just replacing the crank rings on your original crank, even though it may cost the same as a new crank. If you can get the old rings off and the new rings on without pulling stuff apart, even better.

Over time, I've learned to not disturb anything that's running right, as simple as the parts or assembly seems to be. I think I'm more sensitive than average to creaks and ticks and noises, and I sometimes beat myself up for changing something that works trying to improve it or otherwise experiment, and end up creating a noise or something that wasn't there before. If your 61k mile bearings are still smooth, and there are no noises, I'd do my best to preserve that.

armybikerider

First - Thanks to all who have responded.


I'm replacing the crankset for 2 reasons - wear and also to lower the gearing to help with local short but steep climbs. The smallest ring I can fit on my current 130 BCD crank is a 39. I want to go to a 110 BCD crank so I can use smaller rings.

I ride rolling terrain in North Texas with some short but steep punchy climbs that I want to start including in daily rides. I can climb them now, but lower gearing would make the experience more pleasant! The difference in gear ratio between a 36X28 and a 34X28 is only .08. But I like to use the big ring also on flats and the back side of rollers and I'd lose some top end in my favorite 17, 19 and 21 cogs if I drop to a 50 versus a 52.

I'll make sure that any replacement crankset I get will fit the BB that I have now whether it's a compact or semi-compact.

I haven't pinned on a number in 25 years, but I still like to go fast and push the pace as much as I can.

I agree and have pretty much decided to retain the current bottom bracket when I replace the crankset. Plus, in almost 40 years of "serious" riding, including commuting, racing and touring both road bikes and mtn bikes I've never had a BB seize up so bad that I couldn't make it home. Any issues I've ever had with bottom brackets were developed over time with plenty of warning to rectify the issue before it became a "show stopper."

AndreyT

Replacement of a GXP bottom bracket is typically a very clean, fast and easy task. No need to do it in advance.