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Hi,

Does anyone know why the newer ('03 & '04) Shimano LX and XT cranks have different spindle width recommendations? For XT Shimano recommends 113/118mm, but for LX they recommend 121/126mm. I've used LX Hollowtech cranks in the past, but always with either a 113 or 118mm spindle.

Why the switch to the wider bottom brackets? And just for LX? I thought the cranks were the same, with XT getting better chainrings. Reason I ask, Shimano now makes an LX crank with 48-36-26t gearing -- which, minus the granny, would be perfect for a 'cross bike. But, me thinks a 121mm bottom bracket would totally screw up the chainline on my 'cross frame.

I'd really appreciate any info or insight. Thanks!
 

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Cyclocross is Seasonal?
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Some considerations on mountain cranks with cross bikes.

The new XT is radically redesigned. It uses the same 2 piece, integrated bb with outboard bearings design that last year's XTR crank uses. That is the reason why the spindle has gotten longer.

The chain line is not affected solely by the bottom bracket spindle length. The design of the spider plays a large role in bb spindle length and chainstay clearance.

Take a look at your road cranks (assuming its shimano) and then your mtn bike crank (again, shimano) and you'll find the spider on the road crank is tapered so it is more inboard (toward the stays) than the mtn crank (tapered outboard away from the stays).

Even if you were to get a bottom bracket with a shorter spindle (say 109.5) the mountain crank would still space the rings farther out from the stays and thus throw your chain line off.

This of course assumes your cross frame was designed to work with a road crank. Some frames are designed around a mtn crank (Kelly for instance, though the chainline still isn't that good).

I purchased a 5 arm splined XTR crank for my cross bike looking for 36/46 up front. I knew that XTR used the same splines as the shimano road BBs so I figured all I would have to do was take the granny off and slap the crank on... No, it didn't work; the rings were too far out to maintain a decent chainline. My (temporary) solution was to reverse the spider on the crank. I don't recommend this; I did it for one race with a beast of a climb.

If you want to go down to a 36/46 gear combo, there are finally some cross-friendly options. FSA makes two road cranks with a 110 BCD (this is the "traditional" mtn BCD) one in carbon fiber and one in aluminum. These cranks are ISIS compatible I think. Ritchey is also coming out with a 110 BCD road crank. It's not available yet, but I suspect it will be out within a month (or less). It will be around $120-160 I imagine. Shimano octalink compatible.

Also, if you're on a real budget and don't mind taking a hit on the weight Dimension makes a "cyclocross" crank with a 110 BCD. It uses a square taper bottom bracket that will allow you greater freedom in dialing in your chainline.

The compact road crank is your best bet if your cross bike is designed around a road crank.

I'm going to try a 42t single ring next season...
 

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I run those cranks

I have that very crank on my Surly Cross Check. I’ve been using them about 3 months. I run an XT hub in the rear (135) and a 9 speed cassette. My shifting is flawless. The BB spindle is supper long but it works just right. I can’t tell that the “Q” factor is wider than any other cranks. The cranks are very stiff the BB is supper smooth. They are very good looking cranks. I think they are a great bargain.
 

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I'd look into a compact double

Colin_S said:
Hi,

Does anyone know why the newer ('03 & '04) Shimano LX and XT cranks have different spindle width recommendations? For XT Shimano recommends 113/118mm, but for LX they recommend 121/126mm. I've used LX Hollowtech cranks in the past, but always with either a 113 or 118mm spindle.

Why the switch to the wider bottom brackets? And just for LX? I thought the cranks were the same, with XT getting better chainrings. Reason I ask, Shimano now makes an LX crank with 48-36-26t gearing -- which, minus the granny, would be perfect for a 'cross bike. But, me thinks a 121mm bottom bracket would totally screw up the chainline on my 'cross frame.

I'd really appreciate any info or insight. Thanks!
I rode a LX triple for a .long time. Never used the granny at all, the chainline kinda sucked and the thing was HEAVY.

Now FSA offers a road double with 110 BCD spacing. They come with a 50/34T set up but you can change outthe outer ring to a 48 or 46 for that matter cuz the spacing is 110 BCD. Then run a nice narrow BB spindle to ensure a good chainline. The aluminum FSA compact double runs about $150 and will work with a square taper, ISIS or octilink BB.
 

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badass
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Colin_S said:
Hi,

Does anyone know why the newer ('03 & '04) Shimano LX and XT cranks have different spindle width recommendations? For XT Shimano recommends 113/118mm, but for LX they recommend 121/126mm. I've used LX Hollowtech cranks in the past, but always with either a 113 or 118mm spindle.

Yes. 03/04 LX crank is 572 model. And this crank fits only on 121/126 axle.
121 mm axle for 47.5 mm chainline, 126 mm axle for 50 mm chainline.
It's possible to install 572 crank on 118 axle but chainline would be 46 mm. It's not trouble free but if you intend to use only big and middle rings you can do it.
 
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