Hello. I have a 2006 Raleigh Grand Prix, and its bottom bracket and crank set are pretty worn out. On the catalog it says that the BB is Truvativ Power Spline Cartridge, but I cannot find any other information concerning the size of BB. Is there a standard that most road bikes follow? I measured that the shell width of the bike is 68mm. So, can I just bike a crank set that comes with a BB for 68/73? Also, if the original crank set on the bike is a triple(52/42/30), do I need to do anything if I want to upgrade to a 52/39 double?
The website of crank set that I was thinking of buying is : https://www.jensonusa.com/Cranksets/S...00-Crankset-Oe.
Thanks for the help.

I doubt that the current BB will work with a double crankset. You will need to figure out what length BB spindle you need with the new crankset. It should be approx. 5mm shorter on the drive side.

So if a new external bottom bracket is included in the sell, do I need to worry about the spindle length? Thanks.

Assuming that it's meant for 68mm wide bottom bracket, yes, you're right. Often times the "package" includes one or more spacers that allow you to "tune" the chainline. Otherwise, if you find that the chainline is NOT 43.5mm, you can always purchase spacers of varying sizes on the 'Bay to account for variances between frame and BB models. I wouldn't worry about it.

Everything you need is included with that crankset, except for the tools to install it. The spindle is an integral part of the crankset, so no worries about spindle length.

As for switching from a triple to a double setup, you may be able to make it work by locking out the extra shift with the stop screws on the derailleur. It won't be ideal, but I have made it work on mountain bikes.

Oh, yeah, what was I thinking!? dsaul is right, the bottom bracket should fit as long as it's from the same manufacturer. Sorry...