SouthFLSteve

Hello All and thanks to those in advance who reply. I have a Schwinn hybrid bike that had a problem with the bottom bracket not turning freely. I suspected it got sand in it so I had the brilliant idea of replacing the stock BB with a Shimano cartridge bottom bracket. The bottom bracket shell is 68mm and I got the Shimano that had the closest spindle length as the one I had, it was about a millimeter longer. I ran into a problem installing it. The non-drive side screwed in perfectly but the drive side went in as far as I could turn it but sticks out from the shell by about a millimeter as you can see in the attached picture. I can only guess that the shell's internal threads are not enough to accommodate the Shimano. I have not adjusted the derailleur yet so don't know if that will also be a problem. Assuming I am able to adjust the derailleur so it can shift, should I live with this or is this going to be a problem? Is this a common issue? Thanks for all suggestions.

Bill Kapaun

For smallish gaps like that I'll-
Back off the DS, Seat the NDS and then "drive home" the DS.
You can make a simple tool holder with the right length 8x1.0mm bolt (not the more common 8x1.25mm) and a few washers.
It'll allow you to crank harder by helping keep teeth engaged.
I assume the NDS is a plastic cup?
If not leave the gap on the NDS.
They also make spacers for "some" BB's to fill such gaps where 1 BB Cartridge is designed for 2 different BB widths. (68-73?)


Also, with the gap on the DS, your extra length of the new spindle is exaggerated by the amount of the gap.

Russ Roth

The two important things are that you have the crank arms equally spaced to the frame and a proper chainline. If you've got both of these then you can get a small spacer to fill the gap and that will be fine. If not you may have to take it to a shop to clean the threads. Only other thought is did you buy an e-type bb which can have longer drive side threads since a front der would fill that gap.

dsbrantjr

I take a similar tack, I use a square drive BB tool and a torque wrench, there's no place for a bolt so I just put a bar clamp across the wrench and BB spindle to hold the tool in place. I start the DS first, then the NDS, then I torque the DS then the NDS.so any gap is on the NDS.

JohnDThompson 

Probably the threads in the shell should be chased to seat the cartridge fully. A bike shop with proper taps is the ideal way to deal with this, but you can make a low-budget thread chaser out of an old bottom bracket cup by using a Dremel to grind some slots through the threads:

trailangel

Drive Side First.

02Giant 

This last weekend I had the same experience. 1980 Schwinn, replacing the cup & cone bottom bracket with a Shimano UN-55. Either side on it's own will thread in fully seated. Installing both, something bottoms and won't allow both sides to seat fully. I can get one, the other, or split the difference.

Bill Kapaun

OP has never stated the amount of torque used.
It might be a simple case of simply not tightening enough.

leob1

I just had the same problem with my Trek FX 7.5. The old cups where a bear to get off, they are pretty chewed up from getting them off. When I put the new ones on, neither would screw all the way in, even without the cartridge. I looked at the old cups and noticed the the innermost threads were squashed. Not stripped or crossed. It look like when it was put together it was just forced until it was in all the way. Looking at the shell, it was as if the threads weren't cut deep enough into the sheel for the new cups to fit without squashing them too. I have access to a BB tap set, so I was able to cut the threads deeper. Then the new cups went in all the way without a problem.
Maybe take you bike to a shop and have them cut the threads a bit deeper? Shouldn't be too expensive if you bring in the bare frame.

dedhed

With sq taper cartridges, I always install DS first bring it almost in install the NDS most of the way, finish installing the DS and then snug up the NDS. The important one is the DS. The NDS really just centers and supports the NDS

Wilfred Laurier

I have tried to install modern cartridges on older frames (Raleighs and CCMs) and there is often not enough threading in either side of the BB shell to allow the cups to be fully threaded in. Also, the seat and down tubes and chainstays are often left sticking partially into the BB shell, which does not interfere with old loose ball BB cups, but blocks the wider cartridge threads from going all the way in. I used a Dremel to cut back the tubes before getting a shop to chase or lengthen the threads with their taps.

If the Schwinn in question was made after ~1985 then I suspect these things will not be a problem.

trailangel

Read the instructions. DS first.

SouthFLSteve

Thanks to all for the replies, some good info here! To answer some of the questions, the new BB is a Shimano UN-55 (metal one, not plastic) and bike was made around 2017. I did initially try putting in drive side first but the spindle was not centered so I figured I'd need to put the NDS in first to allow centering the spindle and that did work. Based on replies I'll try backing out the NDS and see if I can screw in the DS further but if I recall I think it wouldn't go in further even without the NDS installed. But I don't remember too well so I'll try re-doing everything based on suggestions here. I don't know about the torque value as I don't have a torque wrench but I screwed it in as far as it would go using all my strength. Believe me it's in as far as it will go, at least with NDS installed. Maybe those threads will have to be cut deeper, we'll see. Anyway thanks again guys, really appreciate it!

Bill Kapaun: really great idea for keeping that tool from slipping!

Bill Kapaun

Does the BB shell have a cable guide screw sticking in from the bottom causing interference?