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BMX BB cup length

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Turbo Monkey
Nov 17, 2006
2,059
5
austin
not sure about the mm. . . . but the 4 kinds of bmx bottom brackets are American, Mid, Spanish, and Euro.
 

-dustin

boring
Jun 10, 2002
7,165
1
austin
first, I would opt for FSAs euro bb. I like their use of an adjustable cup.

Second, like american bbs, it'll come with necessary spacers and such to fit your shell.
 

BikeSATORI

Monkey
Apr 13, 2007
723
0
one world...
you're not looking for a "BB cup length"... that's irrelevant in bmx since the cups are free floating.

Spindle length is what you seek... but seems you realize that now.

Profiles should fit a 68 shell no worries (most common in bmx), as they usually come in 5 3/4" lengths (sometimes 6" in mtb apps.)... where some FSA's spindles (all FSA ti) come in only 5.5" and make for a squeeze on some bikes depending on the spacers you run between the bearing and the arm.
I've also gritted out more FSA euro bearings than any other. The lockring is a nice and easy way to dial it in if your internal tube spacer isn't exactly correct, but that usually isn't too much of a problem if you set-up correctly with the fixed cups. I had the best luck with Wethepeople bearings when they used a double wide single bearing on each side, instead of just two regular bearings next to eachother in each cup... don't think those are still made though.
hope that helps a bit.
 

BikeSATORI

Monkey
Apr 13, 2007
723
0
one world...
You're bound to need the 6'' spindle, as opposed to the 5 and 3/4'' spindle that comes on their bmx cranks.
hey snaky, what's up.
I gotta disagree though. I was running the short FSA ti 5.5" spindle on my Molly before I went with the fly cranks (which are also short and only fit 68mm and under). The only time I needed the full 6" spindle was on mtbs with 73mm shells and larger, AND with a chainguide set up and 9spd chainline, like on my SplinterMX for example.
Profile 5 3/4" will be plenty on the Dob.
 

ThePriceSeliger

Mushhead
Mar 31, 2004
4,861
0
Denver, Colorado
hey snaky, what's up.
I gotta disagree though. I was running the short FSA ti 5.5" spindle on my Molly before I went with the fly cranks (which are also short and only fit 68mm and under). The only time I needed the full 6" spindle was on mtbs with 73mm shells and larger, AND with a chainguide set up and 9spd chainline, like on my SplinterMX for example.
Profile 5 3/4" will be plenty on the Dob.
Exactly what I wanted to hear. Thank you.
 

snaky69

Monkey
Feb 10, 2007
188
0
Quebec, Canada
hey snaky, what's up.
I gotta disagree though. I was running the short FSA ti 5.5" spindle on my Molly before I went with the fly cranks (which are also short and only fit 68mm and under). The only time I needed the full 6" spindle was on mtbs with 73mm shells and larger, AND with a chainguide set up and 9spd chainline, like on my SplinterMX for example.
Profile 5 3/4" will be plenty on the Dob.
Yes, but you're running bmx spacing and a 24''wheel. I'm running 135mm spacing, it makes the chainstays flare out more and I need a 6'' spindle on my nempro(currently have a 5 and 3/4'' and I bent it due to the cranks not having enough insertion), this is also what profile recommends on their website for people with 68/73mm bottom brackets.

Mind you, without a spider or anything of the like(bash guard, what have you) I figure 5 3/4 might be enough. I guess it's time for the OP to pull out a ruler and check it out.
 

BikeSATORI

Monkey
Apr 13, 2007
723
0
one world...
Yes, but you're running bmx spacing and a 24''wheel. I'm running 135mm spacing, it makes the chainstays flare out more and I need a 6'' spindle on my nempro(currently have a 5 and 3/4'' and I bent it due to the cranks not having enough insertion), this is also what profile recommends on their website for people with 68/73mm bottom brackets.

Mind you, without a spider or anything of the like(bash guard, what have you) I figure 5 3/4 might be enough. I guess it's time for the OP to pull out a ruler and check it out.
Ran wethepeople royal cranks with the same 5.5" FSA ti spindle on my Eastern26 Proto, with 135mm disc rear spacing/hub... and plenty of clearance for a 2.4" tire too. No chainline probs.
Honestly, the 6" is almost Too wide for my SplinterMX, if I weren't running the external Fly euro-spanish bearing converters, my crank arm bolts might bottom out on the spindle unless I replaced that 20mm of extra width with spacers. You must be running a good amount of spacers between your crank arms and bearings on your 68 shell.
 

snaky69

Monkey
Feb 10, 2007
188
0
Quebec, Canada
I'll send a picture your way when my Profile crankset arrives at the LBS, it's the holidays so I don't expect it to come before january, most suppliers are on a holiday too methinks.
 

rpet

Turbo Monkey
Jun 9, 2003
2,943
280
El Lay
how much insertion is necessary? I'm running demolition Medials LTs on 68mm/euro on my eastern. works fine so far (only 3 rides), but it would suck to bust the ti spindle.

thx
-r