Difficulty fitting bottom bracket

[sirmy]

I recently got a new frame but I'm having problems fitting the BB. I've got a Shimano BB but I've found that it will only screw about half way into the bracket before sticking. I've tried using plenty of grease but it seems to make no difference.

Any ideas?

[ferrit worrier]

Is the frame new or new to you? If it's brand new it might have something in the thread preventing full insertion of the BBshell is it the same on both sides? if so is it designed to take that particular BB ? ( not sure if there are diferences)

Malc

[sirmy]

The frames new. My first thought was paint in the threads but the resistance is very high. I'm ow trying to avoid thoughts of crossed threads and needin to return the frame or have the BB bracket reamed (if thats the right word).
The BB should fit as it's standard british size (68 mm) and a british frame

[tooley92]

Could be barking up the wrong tree, is the screw/rivet that holds the cable guide out of the way?

I had this problem when I put a cartridge bracket in my old Specialized Rockhopper which was previously fitted with a cup and cone bracket - a quick file down of the screw and all was well.

[York Commuter]

I've got this problem too with a frame I'm good to build up the goold lady wife.

The frame, a modern Raleigh steel frame, has been given to me by a friend, it has been used (I think) but he could not get a standard Shimano BB unit in to it.

before I even try it I've wondered about warming the shell by standing it in hot water (or even warming it with a hairdrier) so that it should expand and simulataneously cooling the BB in the freezer - i just wonder whether the differential expansion and contarction might be enough to get the BB in.

has anyone ever come across this?

regards

stephen

[NUKe]

check the screw first. I assume you know the lefthand side tightens anticlockwise
As it a new frame .likely causes
BB thread not cut far enough in
thread full of paint
Bottom bracket has distorted either by heat or dropped may be damaged in transit.

Best solution is to return it or get a good LBS to check it. It is one of the most difficult jobs on a cycle and it needs the right tools to cut the thread it.

[531colin]

New frames need the bottom bracket thread "chased" with a "chasing"tap- basically this cleans paint and debris out of the threads. any bike shop should be able to do this.On old frames the thread will have been cut to a depth suitable for old type bottom bracket cups used with loose ball bearings, and may not be deep enough for modern unit brackets which typically have a longer thread. The thread needs to be cut deeper with proper "in- line "taps, where left and right taps rotate on a shaft which keeps the taps and therefore the cut threads perfectly in line. This is much more expensive tooling used by shops providing a full workshop service or frame builders.

[sirmy]

Thanks all

The cable guide screw was my first thought so unscrewed that a bit, made no difference

Tried screwing in both sides - same result

The threads look clean, shiny metal can be seen on the threads

The threads appear to be cut mch further in on the B shell than on the BB o shouldn't be a problem

Might just have a trip to LBS with it over the week end, see what they think

[rogerzilla]

Go and get the LBS to tap it. It always works.

[ferrit worrier]

Just a long shot. are we sure that the thread pitch's are the same? in the absence of a thread guage. find a sliver of soft wood about 3mm thick and roll it inside the Bottom Bracket. this will pick up the thread pitch. Use the marks made to compare it with your BB shell. Might be handy if you have a magnifying glass. They should match spot on!

Malc

[MikewsMITH2]

York Commuter are you sure the Raleigh frame is "modern" and not just unused? If it old Raleigh (i.e. Notingham built) it will be 26TPI and modern BBs will not fit and will only go in a few turns. See Sheldon Brown on botton mbrackets and Old Raleigh.

[Mick F]

Another thought:

Is it just one side that won't screw in? If so, is it just the RH side that won't go in?
Perhaps you have an Italian BB?

Italian BBs have clockwise threads on both sides.

Edit: Just noticed it was both sides!!!

[MikewsMITH2]

Mick, Italian is a larger diameter then ISO and the Shimano BB would just slip through.

[rogerzilla]

If it's an On-One frame (they're actually Taiwanese, just a British brand, like most other stuff) then the frame prep is very basic and you should get an LBS to:

- chase and face the BB shell - just face the RH side if you're using a Shimano BB

- face the head tube

- face the disc caliper mounts, if any

The seat tube should be smooth enough as is - in fact, they over-ream them rather and you have to crank up the seatclamp to prevent twisting or slipping with the specified seatpost diameter.

[York Commuter]

mikeSMITH

thanks for your concern

I'm sure it's new - braze-ons for cantilevers/v-brakes, Shimano Alivio specific stickers, Freedom 200 model.

Anyway, because my friend had made a bit of a mess of the BB shell I've spalshed out on an unthreaded BB - you know the type for mangled BB shells - seems to go in nicley and as the bike is going to be my wife's spare it won't get much use.

regards

Stephen