Chainrings spacing
- Thread starter Jimmy2021
- Start date
trailstar82
GT Fan
- Feedback
- View
Generally a 22/32/42 for compact drive (94/56bcp)
Or 24/36/46 for ATB (110/74 bcp)
What crank did you get?
Or 24/36/46 for ATB (110/74 bcp)
What crank did you get?
Sorry, that's Aramaic to me
I don't know the jargon, so please forgive me for the following.
I've dry fitted the chainrings to the spider and they seem to just sit in the correct place, evenly spaced.
I paid attention to the bolts' head grooves so the bolts would sit in them (other side of the chainrings is flat, no grooves).
Also I lined up those "prongs" with the crank arm.
Is this correct?
TreaderSteve
Senior Retro Guru
Interesting one this - I have no real idea what 'compact' means in any MTB-related terms - I thought it was a smaller BCD.
I took Jimmy's post as being what spacers between chainrings? I've seen all sorts of spacers fall out of cranks when whipping them apart - fatter washers, very thin washers - who knows?! I've generally only ever took apart to turn into single front ring though hence the not caring.
I took Jimmy's post as being what spacers between chainrings? I've seen all sorts of spacers fall out of cranks when whipping them apart - fatter washers, very thin washers - who knows?! I've generally only ever took apart to turn into single front ring though hence the not caring.
trailstar82
GT Fan
- Feedback
- View
I did think that at first but then thought that was too obvious and took spacing to mean the jump in chainring sizes. Most cranks are designed with the correct offset (between rings) so hence the confusion. But a picture is worth a thousand words so now we know…there’s no need to worry about spacing and everything looks fine as it is.
Uncle Grumpy
Devout Dirtbag
Sorry, that's Aramaic to me
I don't know the jargon, so please forgive me for the following.
I've dry fitted the chainrings to the spider and they seem to just sit in the correct place, evenly spaced.
I paid attention to the bolts' head grooves so the bolts would sit in them (other side of the chainrings is flat, no grooves).
Also I lined up those "prongs" with the crank arm.
Is this correct?
BCP or BCD is bolt centre pitch, or bolt centre diameter. It dictates the diameter of the circle drawn through the chainring bolts. There are 2 primary chainring BCDs.
Here, enjoy the minefield of standards... https://www.sheldonbrown.com/cribsheet-bcd.html
Evenly spaced is good. Tick!
Prongs in line with the crank arms?! What the hell?! Just kidding, you nailed it, all good!
No name carbon cranks imitating Ritchey logos - bzzzzt. Good luck there, you might be fine.
Grumps
They're light and seem pretty well made.
If they crack at first ride I let you know
Thanks!
Right (not so right), new problem.
I dry fitted the cranks and new BB and if I put a bb spacer each side, the right crank arm touches the frame!
If I put both spacers on the right side, the right crank arm clears the frame but touches the front derailleur cage when in higher gear.
If I adjust the limit screw to clear it (just about) then the bike doesn't shift in higher gear at front.
Measurements are all the same as before, but new crank arms are straight instead of having a bend out.
What do I do???
I dry fitted the cranks and new BB and if I put a bb spacer each side, the right crank arm touches the frame!
If I put both spacers on the right side, the right crank arm clears the frame but touches the front derailleur cage when in higher gear.
If I adjust the limit screw to clear it (just about) then the bike doesn't shift in higher gear at front.
Measurements are all the same as before, but new crank arms are straight instead of having a bend out.
What do I do???
