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Discussion Starter · #1 ·
Hi,

I like to run a 2x9 setup with 26 or 27T Inner and 38T Outer chain rings on my 29er.
I am looking for a clean and quality setup with good chain line. Here are a couple of options I am looking at. Does anyone have experience with either? Please help.

A) Middleburn RS7 Duo cranks with Phil Wood square stainless steel BB.

B) XTR M970 cranks with Blackspire Super Pro chain rings.

FYI, currently I am running a 2x9 with 32x42 chainrings, shifting is good but I want to go with lower size chainrings for XC racing purpose.

Thanks.
 

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I think you will get a better chainline with a dedicated 2 ring crankset like a middleburn with the duo spider. If you are going to run a triple spider with a bashring then it is a tossup between the two.
 

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juliofbaez said:
Hi,

I like to run a 2x9 setup with 26 or 27T Inner and 38T Outer chain rings on my 29er.
I am looking for a clean and quality setup with good chain line. Here are a couple of options I am looking at. Does anyone have experience with either? Please help.

A) Middleburn RS7 Duo cranks with Phil Wood square stainless steel BB.

B) XTR M970 cranks with Blackspire Super Pro chain rings.

FYI, currently I am running a 2x9 with 32x42 chainrings, shifting is good but I want to go with lower size chainrings for XC racing purpose.

Thanks.
You can get the Duo rings in 27T inner and 38T outer for Middleburn (Mtn.Bike Tandems here in the U.S. is the distributor).



Phil Wood or White Industries make some nice square taper BB's if you go square, and SKF or Crank Brothers make some nice ISIS BB's if you go that way (I have both a square and an ISIS set). Great chainline with the 113mm spindle length and smooth shifting. I can use the full range of my 9 speed cassettes with both rings. I have 29/42 and 27/40 Duo rings (run with an 11-34 in the rear). I've used both for XC racing the last few years. You've got the option of going to a UNO ring for 1 x 9 or 1 x 10 as well with the Middleburns, but you'd need a chainkeeper for that.

You've got plenty of 2 x 10 options as well.

BB
 

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Your Best Friend
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I ran 26/38's (Blackspire Super Pros) on my 970 cranks. It doesn't really work. Not without spacers anyway. It takes shims to get the spacing right for the 38.
 

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Discussion Starter · #5 ·
Phil Wood square taper BB, how do I know which BB leght to get?

If I go with Phil Wood square taper BB, how do I know which BB leght to get for best chain line and most important, to ensure it will clearn the chainstay area?
 

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You can buy the new XTR crank with those rings.
As silentfoe said....you will have to add spacers to the 970 crank because of the slight offset of the stock chain rings.
I'm running a Rotor Agilis.....plenty of rings for those
 

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The XTR 970 or other 104BCD cranks are a viable option (the XTR's do need ~2.5mm spacers on the granny) - I did it a little while back- here is the thread for refernce it might be helpful as there is some good input and info- Personally I decided to go with a 24/32/42 tripple set up on my full squish 29er for now-

http://forums.mtbr.com/showthread.php?t=672753

I also have a set of Middleburn RS7's with an ISIS BB which I like as well- you can buy the DUO which BruceBrown mentioned which is a 3 bolt set up and you have to use middleburn rings (not a problem just a note). They also now make a double ring set up which is a std 104BCD with no Granny holes and it adjusts the chain line accordingly- but you can't go as you would like to gearing wise- The beauty of the Middleburns is the versitility Uno direct mount single ring, 4 bolt, 5 bolt, 3 bolt duo.... etc.... I must admit the only negative is the BBs Phils etc... are great but not too cheap, SKF stopped making their ISIS and the others are not quite as durable (I am running an American Classic which is working surprisingly well for the weight and I picked up some Enduro bearings for it when it does die)- Plus One of my current bikes has a press fit so only external style cranks fit... I am personally not fond of the Middleburn X-type cranks- not nearly as purdy as the RS7's tha tBonesetter posted-
 

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I have to say I have found the ISIS set up for middleburn to be sub par. I would never get one again. Both cranks have stretched on the interface and have play, even after meticulous attention to setup and maintenance. I am trying shimano now because they have pinch bolts. The FSA BB was actually really good after the first repacking. The original packing was poor and got rough at the first sign of water but has been great ever since.
 

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Shimano SLX . Use Middleburn chain rings for a economic setup that is surprisingly light .
 

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AZ.MTNS said:
Shimano SLX . Use Middleburn chain rings for a economic setup that is surprisingly light .
Bingo!
You can find those cranks for under $130 now...and the cranks themselves are as light as XT.
Put some good rings on them and ride.
 

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finch2 said:
I have to say I have found the ISIS set up for middleburn to be sub par. I would never get one again. Both cranks have stretched on the interface and have play, even after meticulous attention to setup and maintenance. I am trying shimano now because they have pinch bolts. The FSA BB was actually really good after the first repacking. The original packing was poor and got rough at the first sign of water but has been great ever since.
I had the exact opposite experience. I have a isis middleburn setup and it has been perfect for about 2 years now. I had a shimano external setup before that and had to replace the bearings about every 12 months.
 

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the mayor said:
Bingo!
You can find those cranks for under $130 now...and the cranks themselves are as light as XT.
Put some good rings on them and ride.
What about the chainline? Sorry to highjack the thread, but how does the weight and chainline compare between the Middleburn Duo and the SLX with good rings on it.
 

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jeremy524 said:
What about the chainline? Sorry to highjack the thread, but how does the weight and chainline compare between the Middleburn Duo and the SLX with good rings on it.
Chainline is great when using SLX duo , weight of the crankarms is about 10 grams heavier than XTR . The SLX chain rings are heavier , thus the recommendation of Middleburn chain rings to make it a nice light package on the cheap . Hope this helps you , good luck .
 

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mvi said:
SLX Q factor?
I have googled and googled and can't find any numbers.
I asked the same question and here is the reply...

Thanks for contacting Shimano. The Q-factor of SLX crank sets - measured outside to outside - is 173.5mm, XT measure 171.5mm. I hope this is helpful, feel free to contact us again.

I'm just waiting to put them on my new frame!
 

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BeerCan said:
I had the exact opposite experience. I have a isis middleburn setup and it has been perfect for about 2 years now. I had a shimano external setup before that and had to replace the bearings about every 12 months.
I wish I was so lucky. One crank would be bad enough, but both? Yes, I haven't used the shimano BB's yet but I've heard conflicting reports. I would have had to replace my FSA BB if I didn't bother with repacking.
 

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juliofbaez said:
If I go with Phil Wood square taper BB, how do I know which BB leght to get for best chain line and most important, to ensure it will clearn the chainstay area?
Middleburn website recommends a 113mm spindle for ISIS and Square Taper to get the best chainline for the Duo. That may or may not be a perfect arrangement on every frame. For instance, new bikes - such as a couple I have from Niner - have increased the chainline due to using fatter tubes which moves the FD more to the right and or making room for wider tires in the rear which has the chainstay/yoke area sticking out a bit more. I use a different crank with a 2 x 9 on my JET, and to get a perfect chainline and clearance for my rings with the chainstay yoke, I need a BB with a 121mm spindle on that set up. Yet, that length dials in a perfect 2 x _ chainline for that frame.

You can read all about chainline and dialing it in here:

http://www.sheldonbrown.com/chainline.html
http://www.sheldonbrown.com/bbsize.html

I have used and do use the Race Face Taperlock square taper spindle with 110mm on an Air 9 and a Dos Niner. The Taperlock has an adjustable chainline which I assume the Phil Wood BB's have as well - so you should have a little bit of leeway. I just don't understand all the offset R+4, R+3 vs. symmetrical system the Phil Woods use without reading more about them. A phone call to customer service I'm sure would help you get the right BB. Comb the Middleburn technical section where they talk about chainline and BB spindle length. 110, 113, 115-6mm would probably all work - or wider if your frame requires a chainline that is more to the right than some of the older frames with narrower tubes for the FD to attach.

Do you know the chainline (at least of a triple set up) of the bike frame you are thinking of installing a 2 x _ drivetrain?

BB
 
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