Bottom bracket query
#1
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Bottom bracket query
Hi - first time post!
Literally got forced in to bike maintenance last week after my commuter bike's BB bolt sheared off (UK Carrera Kraken 2010). I wanted to do it myself so ordered a replacement BB - truvativ 118 x 68 power spline sealed unit. It was a straight swap but on tightening up the left adapter cup (non-drive side) I noted that the adapter was not flush with the frame - it sits about 3mm proud with thread showing (couldn't upload pic :/). I should've taken a pic before disassembling to see if this was normal, but didn't. It's all been well tightened both sides and no issues with thread. But when I replaced the crank arms and went through the gears everything was well out. I'm part way through trying to calibrate them all but just wondered if a) it's normal for the non-drive side adapter cup not to sit flush and b) is it normal to have to rejig all the gears after BB change out?
Many thanks in advance!!
boz.
Literally got forced in to bike maintenance last week after my commuter bike's BB bolt sheared off (UK Carrera Kraken 2010). I wanted to do it myself so ordered a replacement BB - truvativ 118 x 68 power spline sealed unit. It was a straight swap but on tightening up the left adapter cup (non-drive side) I noted that the adapter was not flush with the frame - it sits about 3mm proud with thread showing (couldn't upload pic :/). I should've taken a pic before disassembling to see if this was normal, but didn't. It's all been well tightened both sides and no issues with thread. But when I replaced the crank arms and went through the gears everything was well out. I'm part way through trying to calibrate them all but just wondered if a) it's normal for the non-drive side adapter cup not to sit flush and b) is it normal to have to rejig all the gears after BB change out?
Many thanks in advance!!
boz.
#2
Senior Member
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 33,656
Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!
Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2026 Post(s)
Likes: 0
Liked 1,096 Times
in
742 Posts
The nds cup on cartridge bottom brackets isn't a bearing race, it's just a stabilizer for the nds end of the cartridge so having it stick out a bit isn't a problem. However, changing the bottom bracket shouldn't upset all of the gearing. Having to do minor trim to the front derailleur's limit screws and cable tension should be all that is needed, if that. It should have no effect on rear shifting.
Are you sure your ordered the correct spindle length for your replacement bottom bracket? Installing a triple length spindle instead of a double, or vice-versa would throw the front shifting off quite a bit.
Are you sure your ordered the correct spindle length for your replacement bottom bracket? Installing a triple length spindle instead of a double, or vice-versa would throw the front shifting off quite a bit.
#3
Senior Member
Join Date: Nov 2014
Location: Eugene, Oregon, USA
Posts: 27,547
Mentioned: 217 Post(s)
Tagged: 0 Thread(s)
Quoted: 18374 Post(s)
Liked 4,509 Times
in
3,351 Posts
I would adjust the front derailleur after changing the bottom bracket as a small difference could show up in the shifting.
As far as the BB sticking out on the left side, it used to be that it would stick out and one would install a locknut. But, that was with adjusting cones. It isn't as big of a deal when using cartridges, so I think they normally end up flush. But, I wouldn't worry about it as long as all is tight, and the cranks fit ok.
When the crank arms pass the chainstays, do they appear to be the same distance on both sides?
As far as the BB sticking out on the left side, it used to be that it would stick out and one would install a locknut. But, that was with adjusting cones. It isn't as big of a deal when using cartridges, so I think they normally end up flush. But, I wouldn't worry about it as long as all is tight, and the cranks fit ok.
When the crank arms pass the chainstays, do they appear to be the same distance on both sides?
#4
Senior Member
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,319
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1438 Post(s)
Liked 1,092 Times
in
723 Posts
Cannot comment on Power Spline issues, but slight limit and indexing adjustments may be needed with any component swap, if due to nothing other than manufacturing variations/tolerances.
#5
Old fart
Join Date: Nov 2004
Location: Appleton WI
Posts: 24,784
Bikes: Several, mostly not name brands.
Mentioned: 153 Post(s)
Tagged: 0 Thread(s)
Quoted: 3587 Post(s)
Liked 3,400 Times
in
1,934 Posts
That you couldn't get the NDS cup fully seated probably means your chainline has been shifted outboard, which means you need to re-adjust your derailleurs.
Probably best to try and figure out why you couldn't get the cup fully seated, though. I'd remove the bottom bracket and clean out the threads in the shell with a stiff wire brush, or better yet, chase them with a tap.
Probably best to try and figure out why you couldn't get the cup fully seated, though. I'd remove the bottom bracket and clean out the threads in the shell with a stiff wire brush, or better yet, chase them with a tap.
#6
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
The nds cup on cartridge bottom brackets isn't a bearing race, it's just a stabilizer for the nds end of the cartridge so having it stick out a bit isn't a problem. However, changing the bottom bracket shouldn't upset all of the gearing. Having to do minor trim to the front derailleur's limit screws and cable tension should be all that is needed, if that. It should have no effect on rear shifting.
Are you sure your ordered the correct spindle length for your replacement bottom bracket? Installing a triple length spindle instead of a double, or vice-versa would throw the front shifting off quite a bit.
Are you sure your ordered the correct spindle length for your replacement bottom bracket? Installing a triple length spindle instead of a double, or vice-versa would throw the front shifting off quite a bit.
#7
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I would adjust the front derailleur after changing the bottom bracket as a small difference could show up in the shifting.
As far as the BB sticking out on the left side, it used to be that it would stick out and one would install a locknut. But, that was with adjusting cones. It isn't as big of a deal when using cartridges, so I think they normally end up flush. But, I wouldn't worry about it as long as all is tight, and the cranks fit ok.
When the crank arms pass the chainstays, do they appear to be the same distance on both sides?
As far as the BB sticking out on the left side, it used to be that it would stick out and one would install a locknut. But, that was with adjusting cones. It isn't as big of a deal when using cartridges, so I think they normally end up flush. But, I wouldn't worry about it as long as all is tight, and the cranks fit ok.
When the crank arms pass the chainstays, do they appear to be the same distance on both sides?
#8
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
#9
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
That you couldn't get the NDS cup fully seated probably means your chainline has been shifted outboard, which means you need to re-adjust your derailleurs.
Probably best to try and figure out why you couldn't get the cup fully seated, though. I'd remove the bottom bracket and clean out the threads in the shell with a stiff wire brush, or better yet, chase them with a tap.
Probably best to try and figure out why you couldn't get the cup fully seated, though. I'd remove the bottom bracket and clean out the threads in the shell with a stiff wire brush, or better yet, chase them with a tap.
#10
Senior Member
Join Date: Jan 2013
Location: South Jersey
Posts: 2,266
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 714 Post(s)
Liked 800 Times
in
475 Posts
It looks like you got a 73mm BB to replace the original 68mm BB. The "68E/73" means that it fits a 68mm bottom bracket with an E-type derailleur or a 73mm bottom bracket. In that case you should have installed a 2.5mm spacer on the drive side. Without that spacer, the bottom bracket and cransket will be shifted 2.5mm toward the non-drive side and cause the problems you describe.
#11
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
It looks like you got a 73mm BB to replace the original 68mm BB. The "68E/73" means that it fits a 68mm bottom bracket with an E-type derailleur or a 73mm bottom bracket. In that case you should have installed a 2.5mm spacer on the drive side. Without that spacer, the bottom bracket and cransket will be shifted 2.5mm toward the non-drive side and cause the problems you describe.
Yep. Think you're right. I'll order the spacer. I'm hoping there are instructions on how to insert it - is it straightforward enough?
I put the old one back on today to see how it looked and it was def. more flush on the nds but much the same as the new unit on the ds, so I'm wondering why it would affect the front derailleur so much.
Pain in the proverbial. But will know better next time and will not be swayed by Amazon prime's promise to 'get it tomorrow' again!
Thanks all for very helpful comments.
boz
#12
Senior Member
Join Date: Jan 2013
Location: South Jersey
Posts: 2,266
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 714 Post(s)
Liked 800 Times
in
475 Posts
The spacer goes onto the bottom bracket cartridge before it is inserted into the frame, so it sits between the drive side of the bottom bracket shell and the flange on the bottom bracket cartridge. Most 73mm bottom brackets come with a spacer to install them in a 68mm shell, but yours was intended for an E-type front derailleur, so perhaps one was not included because the E-type bracket takes the place of the spacer. I have a stack of unused spacers that were acquired with bottom brackets over the years. I suspect that your local bike shop has plenty of them laying around.
#13
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
The spacer goes onto the bottom bracket cartridge before it is inserted into the frame, so it sits between the drive side of the bottom bracket shell and the flange on the bottom bracket cartridge. Most 73mm bottom brackets come with a spacer to install them in a 68mm shell, but yours was intended for an E-type front derailleur, so perhaps one was not included because the E-type bracket takes the place of the spacer. I have a stack of unused spacers that were acquired with bottom brackets over the years. I suspect that your local bike shop has plenty of them laying around.
#14
Junior Member
Thread Starter
Join Date: May 2018
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Hi
I bought 2.5mm spacers but they didn't seem to fit. I've just installed the BB without them and had a crack at calibrating the front and rear derallieurs and all seems to be working fine now, after a bit of fiddling of course. Thanks again all for contributions.
I bought 2.5mm spacers but they didn't seem to fit. I've just installed the BB without them and had a crack at calibrating the front and rear derallieurs and all seems to be working fine now, after a bit of fiddling of course. Thanks again all for contributions.
Thread
Thread Starter
Forum
Replies
Last Post
Bahnzo
Classic & Vintage
21
11-05-20 09:57 PM
HooKooDooKu
Bicycle Mechanics
11
08-14-13 08:54 PM
Tristanh666
Bicycle Mechanics
10
12-29-11 03:18 PM