Removing and replacing BB on Downtube FS 2006
 

hi,

I am contemplating replacing the BB on the Downtube. I removed the cranks but I am having difficulties removing the BB to find the size of the BB.

Any help on how best to remove the BB is much appreciated.

Anyone know the size of BB on the Downtube so I can start looking for what I like to replace with. Or, any suggestion on the BB and crank sizes and chain rings.

Thanks

PM Yan, his handle on the forum is downtube

I found an article at Sheldon's website on BB removal. Please check out http://www.sheldonbrown.com/tooltips/bbcups.html

Thanks,
Yan

I just removed mine to tighten and re-lube since it got loose and cruddy (see my previous post on my "downtube problems/failures".) It's a little better now, but the bearings are shot. So I measured and ordered a sealed cartridge bb. my DT VIII has a 115mm spindle length and standard english threaded 68mm size.
I ordered from harris cyclery
Shimano UN53 68x115mm axle
Qty: 1
Price: $24.95
Total: $24.95

you remove by first unthreading the lockring on the non-drive side. (counterclockwise and you don't have to take it all the way off; just a few turns.)
then you take an adjustable wrench to the same non-drive side cup and remove it entirely, again, counterclockwise. Mine was a little "sticky" coming off, but threaded back on nicely. this is all that's needed for cleaning, repacking and adjusting. replacement involves removing the fixed cup on the drive side. I am not looking forward to removal of the fixed cup (see the sheldon brown article Yan linked to)

At the same time, I also re-packed and re-lubed my headset because it was loaded with really poor grease.

good luck.

Thanks for the reply.

I am having a hard time removing that lockring. Tried to without the special tool and it would not budge and I stripped it a bit. I am going to buy the special tool right now.

How did you remove it? Did you used the special tool?

Also, Yan PMed and wrote that the BB size is 125mm. I am wondering if BB length will effect the shifting. I guess that it also depend on your crank set size.

Anyhow, I am really new at this ( 1st time ) and just having questions in my head.

Thanks for shedding light on the matter.

I am going to do service on mine too to get it ready for saltwater exposure. If these are sealed cartridge type, can you still add grease? If you are tearing into it is it just about as easy to replace with a better BB? I have a 2005 FS and 2005 Standard DT.
Thanks.

The BB is on all our bikes is 115mm. For some reason I was thinking about my one of my other bikes...my old Suntour XC Pro MTB, I swapped out that BB recently. Sorry for the confusion in the PM.

If you pay shipping both ways I can have a used Park Tool HCW2 sent to you.
Thanks,
Yan

Thanks,
Yan

These are completely sealed....no adding grease. My last UN BB lasted over 10,000 miles. An added bonus....they never need adjustment. My two favorite BB's are Shimano UN's and the old XC Pro's with grease guard.

Thanks,
Yan

Yan, so are you saying there is not need to do anything to my stock 2005 BB, in terms of adding or replacing
grease? What does "UN" refer to?
Thanks again,
Hbob

The OEM BB bearings on a DT are not sealed. You can replace the OEM BB bearings with a sealed BB unit. Shimano BBs include a sealed type, a UN series. Within the UN series there is a part with 68mm diameter and 115mm length that fits the DT BB.

I'm sorry for the confusion. The most popular sealed cartridge BB is Shimano's UN series, hence the reference. I was not referring to the Downtube BB.

Thanks,
Yan

Cool, thanks for that. Saves some research. My experience with other Chinese products I have,
bearings are usually the poorest quality, particularly in their seals. Don't ever buy one of those
cheap Chinese red trailers you see at Costco or Home Depot unless you swap the bearings as soon as you
get home.

What is the difference between hollow and solid spindle. Are they threaded the same for the cranks?
Is it just a weight issue?

Cranks go on the same...assuming they are both square taper (do not buy ISIS drive BB's with your current cranks). The hollow spindle will be lighter.

Thanks,
Yan

hollow cranks are lighter. heavy riders should use solid cranks. thread pitch is either standard English or standard Italian. for more, see Sheldon's site.

Thanks for everyone's input and help. I bought a UN-73 68x115 at performance bike for about $28. Replaced the original BB and now the drivedrain is much smoother. However, the front chainline changed from 50mm to 48mm but still enough clearance with original crank set.

I bought the same UN-73 (eBay) and am waiting for it to arrive. Did you do the work yourself?
I don't have the tool, so I may take Yan up on his offer of a loan. I purchased a cable tool
as I figure that would come in handy more often since I have several DT's to swap my cables on
and I can probably use elsewhere around the shop.
Hbob