44 tooth chain ring for Shimano XT Dynasys?

[bcroslin]

I made the decision to modify my mountain bike to do a few cyclocross races this season instead of doing my annual buy-a-cross-bike-sell-it-after-the-season nonsense. I set up my Santa Cruz highball with a Whiskey carbon fork and it's under 20lbs with 700x35's installed. It seems that I'm just as fast on the mtb as on the CX bikes I've raced in the past but I'm a little worried I'm under geared. My mtb is set up with Shimano XT dynasys double 40-28 cranks and I'm wondering if there's a way to put a 44 chain ring on it. I don't need to swap the 28 because I'll essentially be running the bike as a 1x.

My googling hasn't produced much results on running other chain rings larger than the 40 but I've found a few scary threads other places detailing chain suck and broken derailleurs. Is it possible to run something larger with the cranks I'm running or am I opening up a can of worms with broken derailleurs at the bottom?

Thanks,

Bob

[christian]

Can't you just get an 11-25 Dura-Ace cassette or something? I ran 39x12-25 on my cx bike last year and rarely wished for anything taller.

[vav]

Christian; do you have pics of such setup? Just curious, what crankset/chainring do you have? I am assuming this is a 1 x 10, right?
Thanks



Can't you just get an 11-25 Dura-Ace cassette or something? I ran 39x12-25 on my cx bike last year and rarely wished for anything taller.

[bcroslin]

Can't you just get an 11-25 Dura-Ace cassette or something? I ran 39x12-25 on my cx bike last year and rarely wished for anything taller.

I hadn't even thought of that. I'll give that a shot.

I have a few SRAM 1070 cassettes laying around. Any idea if they'll play nice with the Dynasys?

[christian]

Christian; do you have pics of such setup? Just curious, what crankset/chainring do you have? I am assuming this is a 1 x 10, right?
ThanksDura-Ace 7700 crank. Single ring DA 39t ring. Front dérailleur as chain guide. I don't have a picture, but I'm pretty sure you can imagine that. This is on a dedicated cx bike, NOT a mtb, so the ring sits in the inner position. No clearance issues.

I hadn't even thought of that. I'll give that a shot.

I have a few SRAM 1070 cassettes laying around. Any idea if they'll play nice with the Dynasys?Should work fine I think. AFAIK, SRAM and Shimano cassettes are identical (well, from a spacing and freehub perspective). But I'm 100% a Campagnolo guy, that D-A crank notwithstanding. So check with someone better versed than I.

[carpediemracing]

A quick Google says that your cranks have a 104mm BCD. There are a bunch of 44T chainring choices with 104mm BCD, including ones from Shimano.

[christian]

Yes, but:

1). Does any Shimano rd have capacity for a 44-28/12-34 combo? Doubt it.

2). MTB cassette gaps on a cx course would be annoying, at least at the grass crits in the NE. The required gearing is much more like road gearing, only lower, in my humble cat 5 experience.

[bcroslin]

A quick Google says that your cranks have a 104mm BCD. There are a bunch of 44T chainring choices with 104mm BCD, including ones from Shimano.

You found a 44T Shimano Dynasys chainring? I know there's other 104mm BCD chainrings out there but I'm looking for a 44T that is Dynasys compatible.

[carpediemracing]

Not Dynasys but if you're using it as a 1x10 that shouldn't be an issue? I admit I don't know what makes the Dynasys a Dynasys, if there's a weird chainring configuration or something (like it sits on the inside or outside or whatever). For a 1x10 you just need a chain guide and a chainring. 104mm BCD means the chainring bolts should line up. Mismatched appearances aside it should work.

I've mounted chainrings "backwards" meaning the indent for the bolts were against the spider. I understand that rotation direction is important - I'd sacrifice the indents to maintain direction.

[Mikej]

Yes, but:

1). Does any Shimano rd have capacity for a 44-28/12-34 combo? Doubt it.

2). MTB cassette gaps on a cx course would be annoying, at least at the grass crits in the NE. The required gearing is much more like road gearing, only lower, in my humble cat 5 experience.

Should be ok - I m running 970 w/ 44 t and a 12 36. You need the long cage and be sure your chain is properly sized. Be aware that the m985 44t is an 88 and only compatible with 985 double race cranks.

[bcroslin]

Thanks Christian and everyone else for helping out. I installed a SRAM 1070 11-26 cassette and it's working perfectly. My poor Santa Cruz looks a bit silly but it's better than dropping $4k on a carbon CX bike.