When an ad specifies English such as here.. https://cgi.ebay.com/Shimano-bottom-b...QQcmdZViewItem

What do I need to know about my own bike to know if this will or won't work?

What frame do you have? Are you currently running a double or a triple ring crank? What groupset do you have?

you could measure the width of the bottom bracket shell on your frame. if it's 68mm, it's english. if it's 70mm, it's italian. or you could go by the rule of thumb that most italian frames use italian BBs, while most others use english.

to determine if it will work or not for your particular application:

1) for the BB to fit the frame, all you need to know is the threading - italian or english for most modern frames. for the BB, italian ones say 36x24T on them. english ones say 1.37x24T on them.

2) for the BB to fit the crank, you need to know what size spindle it takes. generally speaking, if you're buying a modern splined BB designed for a shimano double crank, and using it on a modern splined double shimano crank, then you shouldn't have a problem. if you're doing something funky, then you'll need to get the measurements of what width spindle a crankset requires.

I actually have an '88 handbuilt 653 from Chas Roberts (London) https://www.robertscycles.com/index.html. I am doing a complete overhaul and have just had the frame powder coated. It had Ultegra 600 throughout but all the componants are pretty well worn. I'm looking at Ultegra 6500 to replace with.

So, I probably am looking at the English style I guess but just want to make sure and also what would be the other differences in BB

those roberts frames look nice!

yeah, the BB should work fine. just be sure to get the 6500 ultegra double crank for it. if you want to use a triple, you'll have to look for a BB like the one above, but with a 118.5mm spindle.

you could also use a 105 5500 double crank on that BB, or a 7700 dura ace double crank on it. they all take the same size spindle.

Thanks Uber. I just measured the BB and was a little short of 2 3/4", also the cups and the axel have the 1.37 stamped so I'm positive it's English.