Quick Bottom Bracket Question

[bxcc]

I’ve seen that same setup on eBay. I assumed it wasn’t compatible with the 73mm BSA socket on the frame I purchased.

I think I need a 170 mm crank. I’m 5’9 with a 30.5 inseam. Most of the things I’ve read about crank length seem to be very subjective but I believe I fall into the shorter 170mm category over the longer 175mm.

At 5'9", you can go either way and be fine, it's personal preference. My wife has 170's on her Tallboy and I run 175, I can't tell the difference between the two.

These will up your budget some but it's good to have options. Any of the Sram GXP cranks will work, and the ones I've linked, have a removable spider. So if you go this route, you will need to remove the spider and get a direct mount chainring of your choice. You will also need a BB and those run around $25.

Aluminum crank arms with removable spider, comes with 32t ring. https://www.competitivecyclist.com/truvativ-descendant-6k-eagle-gxp-crankset-boost?skidn=TRU001K-BK-S170MM32T&ti=UExQIENhdDpNb3VudGFpbiBCaWtlIENyYW5rc2V0czoxOjE6Y2NDYXQxMDAxNDU=

This one has hollow aluminum crank arms and is a bit lighter. You will need to remove the rings and/or the spider and get the ring of your choice. This should have a 104bcd and you have the option of running a standard chainring on the existing spider.
https://www.competitivecyclist.com/truvativ-descendant-6k-eagle-gxp-crankset-boost?skidn=TRU001K-BK-S170MM32T&ti=UExQIENhdDpNb3VudGFpbiBCaWtlIENyYW5rc2V0czoxOjE6Y2NDYXQxMDAxNDU=

This one is carbon and since it's a 2x spider, you really can't use it on a 1x system and will need a direct mount ring. But it's the lightest of the bunch and relatively cheap.
https://smile.amazon.com/gp/product/B003UW490M/ref=ox_sc_act_title_2?smid=ATVPDKIKX0DER&psc=1

[0435235]

I know this is a little off topic, but has anyone tried carbon cranks from Aliexpress? Most cost as much as regular XT cranks and are specified to be ~300g lighter. Most people here seem to buy cranks from name brands ... is this because they're more trustworthy or were there major bad experiences with Aliexpress cranks?

[karstenhorn]

This one is carbon and since it's a 2x spider, you really can't use it on a 1x system and will need a direct mount ring. But it's the lightest of the bunch and relatively cheap.
https://smile.amazon.com/gp/product/B003UW490M/ref=ox_sc_act_title_2?smid=ATVPDKIKX0DER&psc=1

Just a heads up, the SRAM X0 comes with a detachable spider and you can buy a 1x spider for the same chankset all over Ebay:
https://www.ebay.com/itm/Bicycle-BCD104-Spider-Adapter-1-x-System-for-Sram-GXP-XX1-X0-X9-Crank-Convert/272687253945?hash=item3f7d6d49b9:g:qdMAAOSwYvFZJ2Fp

I do have this on one of my bikes and it is a fantastic crankset and a bit underrated.

 

[lRaphl]

I know this is a little off topic, but has anyone tried carbon cranks from Aliexpress? Most cost as much as regular XT cranks and are specified to be ~300g lighter. Most people here seem to buy cranks from name brands ... is this because they're more trustworthy or were there major bad experiences with Aliexpress cranks?

I think it was on MTBR forum, a weight weenie guy tried the chinese carbon crank with 104 BCD spider and broke it in no time where the bolts are holding the chainring. I would definitly go with a direct mount chainring option if I was trying those cranksets.

[surferjo]

Just took a look. For the price the weight is tempting.  I don't see any direct mount cranks. 

[bxcc]

The 3 Sram or Truvativ cranks that I posted links to all have a detachable spider. If it's a 3x crank, then it will use a 104bcd bolt pattern and you can put any 104bcd in the middle ring position. Or you can remove the spider and rings as a unit and put a direct mount chainring on. Absolute black, WolfTooth, RaceFace, Blackspire and many others make compatible direct mount rings. I have Absolute Black ovals and BlackSpire round rings and all have been great. The Blackspire is probably the cheapest option.

http://www.chainreactioncycles.com/us/en/blackspire-snaggletooth-narrow-wide-chainring-sram/rp-prod144516

There is about a 100 gram difference between the carbon X0 crank arms and the hollow aluminum X9 cranks arms. That's just the arms, no spider or rings attached. I'm not sure what the weight difference is between the hollow aluminum and the solid ones are.