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XD600 as double? crank question

Old 03-24-09, 10:39 PM
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xcapekey
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XD600 as double? crank question

Ok...quick question...when I'm touring, I find I'm hardly in the big chainring. I was thinking about simplifying the drivetrain and maybe getting a narrower tread, by turning my XD600 triple into a double.

Will I run into any problems? I don't think so, but when I did a quick search on the internets, I read about people dremeling parts off?

My goal is to run a 48/24 on the 110/74. It's just a matter of 1)removing big ring 2)replacing the double chainring bolts with a singles for the 110 3)leaving the 24 that's on the 74BCD alone....right?
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Old 03-25-09, 06:23 AM
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Using the XD600 as a double is easy as that's what I do, but 48-24 won't work as the largest middle chain ring I've seen for 110mm BCD is a 46. Even 46-24 is a heck of a jump. The way I did it was to do 42-26 using
a 105 double derailleur, with a 11-34 cassette I get a range of 103" to 21"
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Old 03-25-09, 06:33 AM
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Vuelta makes 110BCD chainrings with up to 60 teeth. Go nuts.

Just make sure your front derailleur can handle the difference in teeth from largest to smallest chainrings. Current gen Shimano stuff (Deore XT, for example) can handle a 22 tooth difference so your proposed setup would be out of that range. (48 - 24 = 24)
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Old 03-25-09, 08:08 AM
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I can sympathize with wanting to simplify the gearing and have a double up front rather than a triple. Most recreational riders don't need the tallest gears on their bikes. A bike I've set up as a "sport tourer" has a compact up front with 34/46. I like the 46 much better than a 50 because the shifting is smoother, and I find the chainline straighter at typical cruising speeds.

But the 24 tooth jump you're proposing is huge. Even if the derailleur could handle it, shifting the chainrings would require many shifts of the rear cassette each time. If you're running a typical 9 speed 11-32/11-34 cassette, then 48 teeth up front is really more than you need. I figure it's only necessary to be pedaling up to around 25 mph when touring. Faster than that, and I'm happy to coast and stretch my legs, back, etc.

With an 11 tooth sprocket in back and typical 700c touring tires, you can go 25 mph while pedaling 90 revs/min with a 38 tooth chainring. If you had a 26/42 set up, your shifting up front would be smooth, and you'd have all the gearing you'd need.

I'm waiting for someone at a major component manufacturer to figure this out and start making "extra compact" double cranks with a 80-90mm BCD and come equipped with 26/42 or 28/44 rings. I think they would be ideal for most recreational riders and tourers.

The 52-53 tooth ring on a road bike is really a vestige of the time when the smallest sprocket on a freewheel was 13 or 14 teeth. 52-13 is the same as 44-11 !

Last edited by northboundtrain; 03-25-09 at 08:14 AM.
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Old 03-25-09, 08:24 AM
  #5  
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Originally Posted by jaypee View Post
Vuelta makes 110BCD chainrings with up to 60 teeth. Go nuts.

Just make sure your front derailleur can handle the difference in teeth from largest to smallest chainrings. Current gen Shimano stuff (Deore XT, for example) can handle a 22 tooth difference so your proposed setup would be out of that range. (48 - 24 = 24)
Vuelta makes a middle 110 BCD ring up to 48, but 60 in the middle won't work. Peter White says it better than I can

"Modern chainrings are designed to be used either in the outer position, the inner position of a double, the middle position of a triple, or the inner position of a triple. Attemps to use a chainring in a position for which it was not designed are doomed to fail. Some people are desparate to make outer position rings work in the middle position of triple cranks, because chainring manufacturers don't make large enough middle position rings for the screwball half-step gearing some people are determined to use. Outer chainrings don't work in the middle position of a triple crankset."

To make a 110/74 double out of a triple you have to use the middle and inner ring positions and adjust the chain line out a couple on mm. You also can't exceed (by too much) your FD capacity. I recommend friction shifting on the front as you'll have to trim the FD for some gear combinations if you are using a 9 speed cassette. Here's Sheldon Browns implementation using the Cyclotourist

http://www.sheldonbrown.com/harris/french-cranks.html

As far as FD goes I use a double to limit the possibility of over shifting. I'm not sure how a triple FD would work as you'd have to limit it's range to throwing the chain off.
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Old 03-25-09, 08:38 AM
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Originally Posted by northboundtrain View Post
I can sympathize with wanting to simplify the gearing and have a double up front rather than a triple. Most recreational riders don't need the tallest gears on their bikes. A bike I've set up as a "sport tourer" has a compact up front with 34/46. I like the 46 much better than a 50 because the shifting is smoother, and I find the chainline straighter at typical cruising speeds.

But the 24 tooth jump you're proposing is huge. Even if the derailleur could handle it, shifting the chainrings would require many shifts of the rear cassette each time. If you're running a typical 9 speed 11-32/11-34 cassette, then 48 teeth up front is really more than you need. I figure it's only necessary to be pedaling up to around 25 mph when touring. Faster than that, and I'm happy to coast and stretch my legs, back, etc.

With an 11 tooth sprocket in back and typical 700c touring tires, you can go 25 mph while pedaling 90 revs/min with a 38 tooth chainring. If you had a 26/42 set up, your shifting up front would be smooth, and you'd have all the gearing you'd need.

I'm waiting for someone at a major component manufacturer to figure this out and start making "extra compact" double cranks with a 80-90mm BCD and come equipped with 26/42 or 28/44 rings. I think they would be ideal for most recreational riders and tourers.

The 52-53 tooth ring on a road bike is really a vestige of the time when the smallest sprocket on a freewheel was 13 or 14 teeth. 52-13 is the same as 44-11 !
+1 my sentiments exactly. I use a 26/42 with an 11-34 on my tourer. The biggest issue with such a small "big ring" is the large gap that's required between the FD and the chainring so that it clears the chainstay
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Old 03-25-09, 09:24 AM
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Originally Posted by xcapekey View Post
Ok...quick question...when I'm touring, I find I'm hardly in the big chainring. I was thinking about simplifying the drivetrain and maybe getting a narrower tread, by turning my XD600 triple into a double.

Will I run into any problems? I don't think so, but when I did a quick search on the internets, I read about people dremeling parts off?

My goal is to run a 48/24 on the 110/74. It's just a matter of 1)removing big ring 2)replacing the double chainring bolts with a singles for the 110 3)leaving the 24 that's on the 74BCD alone....right?
If you hardly ever run the 'big ring', do you mean you want to run 36/24?
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Old 03-25-09, 09:35 AM
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Thanks for the responses....I guess there's no dremeling involved...

Yes...looking at the rings this morning I suppose I would try to run my triple as a 39/24.

Another question..

So if I did this, would I have to run the 39 on the inner or outer position on the 110? Or does it matter and is it largely a question of aesthetics at that point?
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Old 03-25-09, 10:01 AM
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Originally Posted by xcapekey View Post
Thanks for the responses....I guess there's no dremeling involved...

Yes...looking at the rings this morning I suppose I would try to run my triple as a 39/24.

Another question..

So if I did this, would I have to run the 39 on the inner or outer position on the 110? Or does it matter and is it largely a question of aesthetics at that point?
You have to run the 39 on the middle position
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Old 03-25-09, 10:43 AM
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Originally Posted by northboundtrain View Post
I'm waiting for someone at a major component manufacturer to figure this out and start making "extra compact" double cranks with a 80-90mm BCD and come equipped with 26/42 or 28/44 rings. I think they would be ideal for most recreational riders and tourers.
Lots of 'em used to make cranksets in the 94/58 BCD standard. A couple still do. TA Specialities, Middleburn, White Industries, etc.

I run Middleburn cranks with a 30/44 chainring setup. Couldn't be happier. The spider is also interchangeable so I could run different BCD settings or even just a single ring if I felt like it.
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Old 03-25-09, 12:43 PM
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I looked at White's solution, but the variable BCD is a bit strange for me and I like running TA rings.

http://www.whiteind.com/cranks/roadcranks.html

The 94/58 BCD cranks out there are triples. TA gives you lots of options with their new spiders, you can do a 94/58 triple or they also have a 94 double with a smallest inner of 30 and a biggest outer of 50t, but the old Pro Vis 5 is designed so you can set up a wide double with an inner down to 26t and an outer up to 50t. I like TA cranks, but they are expensive

Last edited by nun; 03-25-09 at 12:46 PM.
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Old 03-25-09, 01:14 PM
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I took Nun's advice on gearing 5,000 miles ago and haven't looked back.
http://www.flickr.com/photos/2797683...7604620197554/

BTW thanks nun.
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Old 03-25-09, 02:25 PM
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greaterbrown! that's exactly what I was envisioning...

which 44t ring are you using? Is it pinned and ramped or just flat?
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Old 03-25-09, 04:28 PM
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I like that Kogswell.

Would there be any advantage to a subcompact double over just running two rings on a triple? Does the drive side of a doublized triple look funky due to the extra flats on the arms? I can kind of see it in some of Greaterbrown`s pics, but not close up.
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Old 03-25-09, 06:50 PM
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Greaterbrown,
I'm glad that you like the wide double. I decided to go that way after I got frustrated with a 46-36-24 triple
and all the FD changing. I looked at the gear ratios I use most and figured a 42t front ring was all I really needed and a 26 for "stump pulling" as you say.

When you do a a triple crank as a double you don't use the outer position. You can either use single chain
bolts and leave the flats where the outer ring would sit visible or you can install a chain guard. This
is how the original Quickbeam from Rivendell was set up, Chainguard-40-32 rings. The difficulty of setting up
a wide double on a conventional crank is just fitting the teeth into the single BCD they have. The widest range is had with the 94mm BCD 50t to 30t. The 74mm BCD goes down to 24t but only up to 36t. I suppose you could make larger 74mm BCD rings, but there might be flex issues with the ring being mounted so far from the circumference.
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Old 03-25-09, 08:21 PM
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Originally Posted by xcapekey View Post
greaterbrown! that's exactly what I was envisioning...
which 44t ring are you using? Is it pinned and ramped or just flat?
It's a Salsa single. No pins, no ramps.

Originally Posted by rodar y rodar View Post
I like that Kogswell.
Does the drive side of a doublized triple look funky due to the extra flats on the arms? I can kind of see it in some of Greaterbrown`s pics, but not close up.
I like that Kogswell too. She's a smooth long distance machine. Yes, the "doublized" triple is a bit odd looking. I placed the bolts inboard and the nuts to the outside because they nest better in the crank arms that way. But it does look a little funky.

Originally Posted by nun View Post
Greaterbrown,
I'm glad that you like the wide double. I decided to go that way after I got frustrated with a 46-36-24 triple and all the FD changing. I looked at the gear ratios I use most and figured a 42t front ring was all I really needed and a 26 for "stump pulling" as you say.
Yup. You gave me the confidence to "go low". Similar to your experience, I spend 98% of my time in the 44T (which equates to your 42T since the Kogs is a 650B bike). When I'm cooked from a hilly 200K or hauling stuff in panniers, I'll drop to the 28T and smile. If only there had been a tiny "nun's Guide to Proper Gear Selection" book in the check out line of my grocery, I would've picked one up years ago and been much happier.
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Old 03-26-09, 07:47 AM
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sugino is soon coming out with a wide range 110/74 double. Maybe a bit more elegant than running a double-triple setup, unless you already have the xd600.

the new crankset will also have outboard bearings, see here:

http://4.bp.blogspot.com/_C1XrRVl3W8...gino+crank.jpg

(via velo orange)
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Old 03-26-09, 08:53 AM
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Originally Posted by positron View Post
sugino is soon coming out with a wide range 110/74 double. Maybe a bit more elegant than running a double-triple setup, unless you already have the xd600.

the new crankset will also have outboard bearings, see here:

http://4.bp.blogspot.com/_C1XrRVl3W8...gino+crank.jpg

(via velo orange)
If only it came in square taper
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Old 03-26-09, 11:40 AM
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Originally Posted by nun View Post
If only it came in square taper
Yeah, and they painted it! A black Sugino? Outboard bearings? Sheesh!
But it seems to me Shimano now offers 22-36 doubles, I don`t know what BCD.
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