Rohloff chainline - is this an acceptable way of hitting 54mm?
First things first: I'm something of a bike noob, and in my months of research, I've found MTBR to be an invaluable resource - thanks guys!
OK, so I was given a Rohloff in trade for some tech support (I fixed some of the Geek Squad's "work", among other things. The horror stories are true!), and building a bike around it is turning out to be challenging.
If a Shimano Deore Crankset (Octalink V2 kind, like the M530/M540) has a 50mm chainline with a 113mm spindle, wouldn't it have a 54mm chainline if used with a 121mm spindle?
The way I understand it, if you add 8mm to the spindle, it will move the chainline outboard by 4mm, and in this case put the middle chainring right in line with the Rohloff sprocket. Am I missing anything? Is moving the 44t big ring to the center position likely to work? Is it going to look horrible?
I suppose I'm not married to the Shimano stuff, but it seems like really good hardware for the price and I'm not a hardcore rider (but I am a bit over 200lbs). I'd just like a nice bike with super low maintenance, but without going broke in the process. If somebody has a surefire solution to the Rohloff chainline, I'd love to hear it.
I'm learning that building up a bike, while fun, can be stressful. Some nights I go to bed with my mind still juggling parts combinations around, trying to settle on the perfect arrangement .
4mm is a little over 1/8", one cog width. I'd order the cranks and mount them. If the line is off too much, you can order a different width spindle bb. If my chainline was off 1/8", I'd consider it close enough.
Thanks for the reply. Are you suggesting I order the 113mm BB for the recommended 50mm chainline, and see if that works well enough? I'd firgure even with the 50mm chainline, the big ring would be closer to 54mm than the middle (50mm vs ~56mm).
Would it even be possible to mount the big ring in the middle ring position?
I've never had good luck getting everything just right without dorking around. I guess a 121mm would be closer, can you order cheap cranks with the wider bb spindle? It can't hurt to make it closer.
You can mount the ring to either side of the crank spyder, if you put it on the inside it may hit the frame if it's too large diameter-wise.
So exactly which crankset is it?
My understanding is the M530 and M540 are different. The 530 is supposed to have the 113/50, but the 540 supposedly has the 121/47.5.
So if you do in fact have the 530, you could opt for the lighter, better quality ES71 (if you can still find one) and...
- you'll get 50mm middle / 56.5mm outer with a 113 spindle
- you'll get 52.5mm middle with a 118 spindle
or stick with a 121mm spindle and you'll hit 54mm from the middle.
If you've got the 540, the 121mm spindle ES30 will put the outer ring right around 54mm.
I've got a tech doc confirming the fc-m530 BB / chainline, but only sketchy retail references for the FC-M540 (and retailers have gotten this wrong before).
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Ahh, I haven't ordered yet, so I can go either way. I didn't know that difference in chainline between the two. In fact, I thought they looked identical except for the 540 having a steel middle ring, but I found this which suggests 121mm or 126mm spindles which would coincide with a 47.5 or 50mm chainline.:
Looks like I should go with the FC-M540 + 121mm spindle, and then I stand a good chance of having the outer ring be 54mm. If it turns out to be the same dimensions as the 530, then I'm no worse off for it - just have to use the middle ring.
Here's another thing. The bikeparts.com page lists th FC-M540 as be a "K crank", which I gather means offset. I think, if that is correct, I would need to get the ES51-K offset bottom bracket.
A description of the ES51-K says "K model to be used with K model and non K model cranks from Shimano". So does this mean I'll be OK with the ES51K either way?
This is making me dizzy.
Don't worry, I'm dizzy, too.
The 'K' designation is new to me, but here's the whole deal:
Shimano started with Octalink v1 XTR & 112.5mm spindles for a 47.5mm chainline.
Then they introduced Octalink v2 XT (M751) and LX (M571), which used 113 for 47.5.
But cheap bastards like me were buying the awesome LX cranks and pairing them with the ES70 bottom brackets, instead of the heavier ES50s.
So next go-around, Shimano jacked up the LX (M572) interface and forced those cranks to use 121mm spindles for 47.5mm chainlines. Those longer spindles weren't available in the ES70/71 range of bottom brackets, only the heavier ES50s and 30s. These must be what they're referring to as 'K' cranks.
But that same time period, the lower-level Deores and some OEM stuff Specialized was using still used the original 113mm bottom brackets! Confusing!
This whole deal with the M530 + 113 spindle = 50mm (instead of 47.5) is yet another version. What a mess of an otherwise solid bottom bracket / crank interface standard. Too bad.
If you can find an XT 751, 752 or LX 571, any of those mounted on a 113mm spindle will give you a Speedhub-compatible chainline from the outer ring position.
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