bottom bracket help

[Stoogecurly]

im in the process of building a bike and i just bought a new trek bike with a 73mm bb52 thats neither a isis or squared taper its hollow.... i wanted to go with a mid drive but i have no idea and cant find anything about if and how i can convert it to a squared taper or a isis or if i even need to change it. if anyone can give me abit of help here it would be appreciated.

this is the bike i went with.

 

[PitbullOnAcid]

YouTube or Google is your friend. The kit has 2 options I believe. One is for fat bike the other is for standard. Regardless the kit will replace your bottom bracket and crank so compatibility isn't an issue. Just check you bb spacing and double check that it doesn't use a special threading. All would work in most frames. It's the same as swapping a bb but instead there is a motor.

 

[amberwolf]

trek bike with a 73mm bb52 thats neither a isis or squared taper its hollow....

It is probably this:
https://bike.shimano.com/en-EU/technologies/component/details/hollowtech-2.html

If so, then you just need to compare the bb's threading and width with the middrive unit you wish to use (this info would be available from the drive manufacturer (or seller, if they can be bothered), assuming the drive will replace the existing cranks and bb (this is what many of them do). If they are the same, then the system should fit there. Then the problems you may encoutner are fitting the outer diameter of the bb shell, and/or fitting up to the downtube, etc. You may wish to look at other threads using the same middrive you wish to use, with similar bike bb's.

If the middrive you wish to use does nto replace the existing cranks and bb, then it doesnt' matter what the bb type/etc is, except those that must add a chainring or freewheeling chainring to the crank spider, which means the spider must be the same bcd and type as the one to be added, and there must be space for it. To find that out you'd need to get the details from the middrive manufacturer (or seller, if they can be bothered), and match that to measurements you make with teh same method they used.


there are also several threads here about various bb's and compatiblity lists of different units to different bb's, but they are scattered around so you may have to use the google site search to find them.

 

[Stoogecurly]

Thanks for the reply guys! I went with the 73mm squared taper bb and as a precaution i emailed the company with my bike specs asking if it would fit or would i need other parts.

 

[MadRhino]

Your bottom bracket is a Shimano Deore Hollowtech SM-BB52,73