Cycling UK Forum

I am planning to swap a bottom bracket from an old Coventry Eagle steel frame to an 80s Falcon steel frame, 531 frameset. I am 'assuming' it's a straight swap but we all know what assuming does. What should I measure to check first? It is a cartridge type bb.

Measure the bottom bracket shell of the frame from face to face with a calliper, most frames are 68mm or 73mm. Also check the threads are the same pitch. If both match then it will be a straight swap.

I assumed that the pitch of the threads were standardised for BBs.

However, there are "English" and "Italian?" threaded BBs. The English BB has a conventional thread on the left hand side and a "left hand thread" on the right hand (drive) side. The Italian BB has conventional threads on both sides.

All above correct. An English threaded BB will be 68mm, Italian 70mm, 73 is usually MTB. When you get the old cartridge out there may well be a label with the sizes on it. The Italian are a different diameter as well.

I've recently refurbished a 1985 Falcon 531 frame and had a problem finding a BB axle to fit. I needed a longer axle than the original since I was swapping from a double to a triple. It was only once I'd bought a new axle that I realised that although the BB was an "English" thread, the BB shell was 70mm, and not 68.

I'm not sure with a cartridge whether it will cope with the extra 2mm or not, but an old style loose axle with cups and bearings won't. luckily I found a size '5SS' axle in a LBS.

What type of Falcon is it? Mine was branded as a Falcon Special. From the components I've dated it to 1985. It had 531 butted tubes and 531 forks, and was equipped with Sachs Huret, Stronglight and Weinmann parts.

To be honest, I'm not sure what type of Falcon it is, it was a skip rescue job after it was abandoned at work. It's not an Ernie Clements. Bit of a mongrel: I suspect early 80s, Weinmann centre pulls, Stronglight oval shaped cranks spookily enough, some mountain bike front and rear mechs but ticks along quite nicely. I've measure the BB widths as recommended and they are the same so when I'm ready I'll swap them over. I'm just waiting to get some JP Weigle Framesaver from ceeway, (?) so I'm going to do this first before the BB.
Thanks for all the advice.

Hi

I've just acquired an old Coventry Eagle from my Dad. I believe it was new in the 70s.

It's a nice bike but it needs a new bottom bracket. Does anyone have any idea what size I need or where I can get one? I want to restore the bike but I'm pretty new to this so any advice/explanation is much appreciated.

Thanks