CX Farmer

Hi,
I've searched all over and haven't turned up any info on this.
I'm building a 2017 Raleigh RXM as a 1x10 and don't know what
size bottom bracket I should go for. The rear spacing is 142mm
Any thought or pointers appreciated.

Thanks,
Scott

motorthings

Not sure what you mean by "size" of BB.
If you keep the stock shimano BB, just use a 1x crank that works with it.

wsteve464

It is not clear from the OP what you have, just a frame? if so it appears Shimano does not have a 1x road crankset. SRAM makes 1x road cranksets. From the look of the bike it has an english threaded BB. You will have to purchase a BB specific to either SRAM or Shimano when you select your crankset. The SRAM english BB is called GXP, don't know what Shimano is called.

https://bike.shimano.com/en-EU/compo.../crankset.html

https://www.sram.com/sram/road/family/sram-force-1

Facanh

Yup, we need more info!

What kind of crankset are you going to use?

Usually the chainring or the crankset itself if it's 1x specific will be offset for the correct chainline, the BB has nothing to do with it. Unless you're running square taper...

CX Farmer

It's a Sugino XD Single using a Square tapered BB. I'm trying to choose the spindle length of the BB. I had a 120mm lying around and installed that but it seems too long
to get a good chainline. So, I don't know if I should go for a 103, 107, 110, 113 etc. Thought maybe there was some guide that would help, as in rear spacing of 142 minus X = 107 or something.

Scott

wsteve464

This may help

Sheldon Brown's Bottom Bracket Size Database

Facanh

Well, it's not easy with square taper cranks. Even if you use the same length BB, the rings on one crankset might sit closer or farther compared to another crankset. There can be big differences in the "profile". Unless you find someone that's running the exact same combo, it's gonna be trial and error.

For a non boost rear end the ideal chainline for a 1x10/11 is 48-50mm. Don't let the 142 fool you, really it's the same as 135 when it comes to cassette spacing:

https://www.pinkbike.com/news/12x142-explained.html

• Cassette and disc rotor are in the exact same relation to the hub's centerline as a standard 135 mm QR hub
• Wheel dish remains the same as a 135 mm quick release wheel
• Frame dropout's have 3.5 mm of inset per side that hub endcaps fit into - just as with a 10 x 135 mm QR wheel

So you can do some measurements, but the most square taper BBs are not symmetric, the drive side is usually longer than the non drive side. The problem is you don't know how much longer the driveside is, at least I haven't seen a manufacturer that would give out this information.

If it's possible also try the chainring on both the inside and outside.

Ronsonic 

Uh, sorry to drift of topic, but ..... So what's the point of it?

Back to the OP I'd use the data point from the 120mm spindle and measure just how much further in you want it to go.

Sugino should be able to tell you just which BB you want as well.

Facanh

Read the article I posted and/or watch the video in it.

fietsbob

Raleigh USA is sourced via Pac Rim, Taipei, so British-Asian standard all the way ..

New trend is external BB pipe axle fixed to drive side crankarm .

you don't choose , you just buy the whole thing as a set.