MTB Groupset - Bottom Bracket Query

MTB Groupset - Bottom Bracket Query

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Discussion

tjdixon911

Original Poster:

1,911 posts

237 months

Wednesday 6th May 2015
quotequote all
My 29er Groupset is on its last legs, its done a lot of hard work and I am thinking of replacing the lot, its currently a SRAM X7 / X9 mix, I prefer the Shimano stuff on my other bike so was considering a SLX set up like this;

http://www.ribblecycles.co.uk/gsd/road-track-bike/...

My frame (Giant XTC 1 Aluminium) has a Press Fit bottom bracket, I've only ever had experience of swapping these out in threaded BB's, will this still fit my frame? I will more than likely replace the BB while I'm at it...


BadgerBenji

3,524 posts

218 months

Wednesday 6th May 2015
quotequote all
The chainset will fit into your existing bottom bracket as will be a 24mm axle commonly known as HTII, but the bottom bracket will be for a threaded shell.

richardxjr

7,561 posts

210 months

Wednesday 6th May 2015
quotequote all
I think you're going to need a Shimano BB71 press fit BB

Removal of the old GXP easy enough with a screwdriver & hammer, fitting the new one, not so easy.

POXY press fit BBs frown



tjdixon911

Original Poster:

1,911 posts

237 months

Wednesday 6th May 2015
quotequote all
Thanks for the responses.

I imagine the installation of a push fit BB is similar to a headset - maybe a job for the LBS.

Whats the advantages of a push fit BB, This bike and my 2 more recent purchases (Road & MTB) are all Push Fit - guess it removes the risk of cross threading...


gazza285

9,810 posts

208 months

Wednesday 6th May 2015
quotequote all
tjdixon911 said:
Whats the advantages of a push fit BB, This bike and my 2 more recent purchases (Road & MTB) are all Push Fit - guess it removes the risk of cross threading...
Cheaper to make.

Kermit power

28,642 posts

213 months

Wednesday 6th May 2015
quotequote all
I'm a bit confused by these press fit bottom brackets....

I've just been looking at this Bike Radar guide on how to replace them. It looks straightforward enough, but they're suggesting using a flat piece of wood as a drift to bang the bearings in if you've not got the proper tool.

The last press fit bearings I fitted to a bike were for the headset on my HT, although I assume the principle is largely the same for a BB?

I didn't have specialist tools for the job - and fortunately hadn't read any of the various internet comments I've seen subsequently along the lines of "I'll do anything on a bike, but I always get my LBS to fit my headset!" - so I just positioned the bearings either side of the head tube, then used my workbench vice to gently wind them in, with a couple of rags between the headset and the vice grips, until they were snugly seated where they were meant to be.

I've not had any problem with the headset, and I don't see why I wouldn't replace the BB in the same fashion, but I assume I must be missing something here, or the likes of Bike Radar would surely be recommending this method over banging it in with a lump of 2 by 4, as it's altogether more gradual and controlled????

Am I missing something obvious here, or do people just not have workbench vices any more?

tjdixon911

Original Poster:

1,911 posts

237 months

Wednesday 6th May 2015
quotequote all
Kermit power said:
I'm a bit confused by these press fit bottom brackets....

I've just been looking at this Bike Radar guide on how to replace them. It looks straightforward enough, but they're suggesting using a flat piece of wood as a drift to bang the bearings in if you've not got the proper tool.

The last press fit bearings I fitted to a bike were for the headset on my HT, although I assume the principle is largely the same for a BB?

I didn't have specialist tools for the job - and fortunately hadn't read any of the various internet comments I've seen subsequently along the lines of "I'll do anything on a bike, but I always get my LBS to fit my headset!" - so I just positioned the bearings either side of the head tube, then used my workbench vice to gently wind them in, with a couple of rags between the headset and the vice grips, until they were snugly seated where they were meant to be.

I've not had any problem with the headset, and I don't see why I wouldn't replace the BB in the same fashion, but I assume I must be missing something here, or the likes of Bike Radar would surely be recommending this method over banging it in with a lump of 2 by 4, as it's altogether more gradual and controlled????

Am I missing something obvious here, or do people just not have workbench vices any more?
I used the old 2x4 and mallet method to install a headset once - I got it in and in the process had manged to dent the top tube of the frame (slipped off the blocks) - it wasn't bad, just added a bit of character to a new frame!

The vice sounds like a good controlled method - I don't have a vice though....

gazza285

9,810 posts

208 months

Wednesday 6th May 2015
quotequote all
tjdixon911 said:
The vice sounds like a good controlled method - I don't have a vice though....
Everybody should have at least one vice.

Kermit power

28,642 posts

213 months

Wednesday 6th May 2015
quotequote all
gazza285 said:
tjdixon911 said:
The vice sounds like a good controlled method - I don't have a vice though....
Everybody should have at least one vice.
I have several!!! There's only one that I'd like to try and knock in a bottom bracket with though! smile

richardxjr

7,561 posts

210 months

Wednesday 6th May 2015
quotequote all
No vices here so threaded bar, lumps of wood, metal plates and couple of nuts also works well smile


Yes, the only advantage in these things are with the frame manufacturers.

tjdixon911

Original Poster:

1,911 posts

237 months

Friday 22nd May 2015
quotequote all
Last night my BB got a lot worse, time for a change!

This evening, I have used the hammer and screwdriver technique to extract the BB (surprisingly easy) so much filth in there mind!

My LBS has a SRAM replacement in stock, but I am assuming this will limit me to the SRAM cranks. I currently have the offer of some XT cranks so wondering whether I should opt for the alternative BB and fit these now or just stick with the SRAM.

How long would the install take my LBS? I've got myself some threaded rod but not much more to make a press, I was hoping they may be able to install quickly for me in the morning.

Nighthawk

1,757 posts

244 months

Friday 22nd May 2015
quotequote all
It should only take a few minutes to press in the new BB if you've already cleaned the frame. My LBS do stuff like that as a while you wait if you've made an appointment to have the work done.

tjdixon911

Original Poster:

1,911 posts

237 months

Friday 22nd May 2015
quotequote all
Nighthawk said:
It should only take a few minutes to press in the new BB if you've already cleaned the frame. My LBS do stuff like that as a while you wait if you've made an appointment to have the work done.
I've not made an appointment, but called them earlier and they generally don't do maintenance on Saturdays due to footfall - they did say they maybe able to do it if there not busy at the time so having stripped and cleaned it will hopefully help with getting it done.

If not, I'll get some bits from screwfix to hopefully finish my press.

Nighthawk

1,757 posts

244 months

Friday 22nd May 2015
quotequote all
If you do it your self remember to fit the BB the right way round (depending on your chosen part) smile