Cranks and rings and different speeds - what makes an 11 speed crankset 11 speed?

[thatmattwooding]

Hello RetroBike,

I had a box of bits left over from years of MTB and road riding and thought it'd be fun to build a budget/retro bike.
I got a Giant NRS frame and tried to fit my old Ultegra cranks to it. Obviously that didn't work so I'm looking for something that'll actually fit
The frame has a Shimano BB52 bottom bracket. I'd like to keep using that as that's what my other bikes have.
I found a set of cranks that are described as 11 speed but come without a chainring (here). What makes these 11 speed? Could I get them and stick a 9 speed chainring on them? I have a pile of 9 speed parts that I'd like to re-use (I was thinking of going 1x9). Is there a better alternative?

Thanks.

--Matt

 

[KermitGKona88]

Hello RetroBike,

I had a box of bits left over from years of MTB and road riding and thought it'd be fun to build a budget/retro bike.
I got a Giant NRS frame and tried to fit my old Ultegra cranks to it. Obviously that didn't work so I'm looking for something that'll actually fit
The frame has a Shimano BB52 bottom bracket. I'd like to keep using that as that's what my other bikes have.
I found a set of cranks that are described as 11 speed but come without a chainring (here). What makes these 11 speed? Could I get them and stick a 9 speed chainring on them? I have a pile of 9 speed parts that I'd like to re-use (I was thinking of going 1x9). Is there a better alternative?

Thanks.

--Matt

From my limited understanding, it is the chainring width to accomodate a narrower chain, but the chainline may also be slightly affected too, although running 1x9 should be fine.

 

[legrandefromage]

front mechs are narrower, space between chainrings is narrowerererwereower

 

[thatmattwooding]

Thanks both.
I had assumed that the rings were what mattered.
Time to spend some money and find out...

 

[ishaw]

What didn't fit about the ultegra cranks?

If you are using bits from your stash, I'm sure you could get a cheaper set of slx cranks, good used for sure.

I have wondered myself how a 9sp chain would work on a 10 or 11sp narrow wide chain ring, as the 9sp chains are a little wider. Considering this myself so would be good to know more from those with the knowledge.

 

[thatmattwooding]

The cranks hit the chain stays. Looking, quickly, at the XT cranks on my hardtail, I think that MTB cranks flare out away from the frame more. The road cranks were straighter. This might be called Q factor.

I tried adding the spacers that came with the BB but once I'd got the cranks to (just) stop hitting the frame the axle was too short. The nylon tensioning bolt didn't reach the thread on the inside of the axle.

I've been looking on eBay and other places for older cranks. Prices are high and there's less out there than I'd expected.
Though perhaps I'm not looking right.

 

[minor_LEGEND]

It'll work fine, it's the narrow 11sp chain that won't like the wider 9sp teeth supposedly.

I haven't viewed the cranks linked above, but many shimano 11sp cranks have the chainrings profiled to match the shape of the crank arm spider in order to sit flush. 105 rings don't match Dura-Ace etc. So fitting generic 11sp chainrings isn't possible + the bolt pattern is not equidistant around the bolts.

 

[novocaine]

Chain internal dimensions don't change by gear no. Rings are the same width. Gap between rings can change but not between 7 to 10 speed for shimano.

There is a difference between gaps on road and mtb cranks.

Q factor between road and mtb is different too.

 

[hamster]

Road cranks are designed to clear a frame with a narrower rear end and also chainstays that are closer together as they only have to wrap round a narrower tyre. As a result the Q-factor is lower, while the chainrings are closer to the frame's centreline.
Between 7&10 speeds the inside of the chain barely changed, although the plates got thinner and the rivets went flush. At 11s the teeth got narrower too.
It's a bit variable whether the ring spacing at the front also got closer - on some chainsets it definitely has, others not.
As time goes by groupsets get less flexible to mix and match like the old days. With square taper you could easily tweak such things with different bottom brackets.

 

[ishaw]

I'd naively assumed narrow wide chain rings came later than 9sp so would have been designed around 10sp chains and above. Useful to know that it's only the outer dimension on a chain that changes rather than the inner one.

As for cranks, depends on how much cosmetics worries you. Had a quick search for things that are more 'normal' than the silly bcds and proprietary splines for 'spiderless' cranks. Here are a few examples that might suit. I've got a set of deore in silver if you are interested, probably other options too. Anyway these aren't mine but available online:

2018 Shimano Deore Crankset 175mm For Sale

2018 Shimano Deore Crankset 175mm For sale on Pinkbike buysell

m.pinkbike.com

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