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  1. #1
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    Mountain bike crankset on a road bike

    I've been planning to purchase a Sram Rival equipped road bike which is going to have a compact crankset and a 11-28 cassette. I'm going to use it mostly for casual road riding and some races. However I have some thoughts of a cross-Europe tour which made me think about the gearing. 32 gear inches might be too little for some huge ascents with load so I've been thinking of putting a triple crank to the bike for this possible tour.

    The thing is, I want to keep the costs as minimal as possible. Best option would be touring specific bike but I don't have the money to buy yet another bike. I do have a mountain bike that has a Shimano Deore triple crankset and derailleur. I believe that they are compatible with the 10-speed drivetrain but Rival shifters can't of course handle triple.

    Are there any cost-effective ways to utilise the Deore crankset? Would there be any sense using the crankset and installing separate bar-end shifters for the front? If it's possible, which bar-end shifters would work? Or could I possibly use also the shifter from my mountain bike. I realize that it is made for different bar diameter but maybe it could be fixed some way?

    So what do you think? All ideas are welcome.

  2. #2
    Bianchi Goddess Bianchigirll's Avatar
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    what kind of 'racing' are you going to do? why not buy a bike with a triple crankset already on it? the weight penality would be minimal and would be cheaper and less frustrating than upgrading the bike later. there are lots of triple bikes that have a geomentry very close to racing but have brazeons for a rack for day touring.
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  3. #3
    Senior Member BCRider's Avatar
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    I hear you on the lack of need for a big ring for casual riding or for touring. I'm running compact sets with a 44 big ring on all my "road" bikes. I just can't go fast enough for long enough at my age and due to previous medical issues to worry about taller ratios.

    The only issue you MAY run into is that the granny ring might end up rubbing the chain stay with your BB axle length. I've seen this happen both with older "deep offset" road cranks mounted to regular length BB axles as well as when trying to fit MTB triple sets to a road frame with the old BB still in place. All this is just part of the fun when building up bikes from junk box parts selections. If this happens you'll need to figure out some sort of compromise and buy whatever is required. Personally I'd do what's required to keep the granny ring since you never know what you'll run into with loaded touring. Perhaps there's a compromise BB length that will work with both cranksets. In any event there's only one way to find out. Spend an hour popping off the cranksets on both bikes and try the swap for yourself. No need to torque it down for the test. It'll be pretty obvious if there is going to be an issue. Typically torqueing them down sucks the rings in closer to the stays by 2 to 4 mm depending on the fit. If you think it'll be a close issue torque the crank on most of the way up to about 1/2 the required torque. By that time it won't move much farther if any.

    And of course all this assumes that you're using a compatible BB system on both bikes.
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  4. #4
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    If he's buying an SRAM Rival bike, it's either going to be external BB or BB30. I was going to recommend using the Deore crank with only two rings and a 46/30 or 44/28 set up (using the inner and middle positions only) but the biggest 64mm BCD inner ring I can find is a 26 (Truvativ). 104mm BCD outer rings are pretty rare in 46 tooth form and non-existant in 44T. Of course, this is assuming a 104/64mm crank (which I believe all Deore's are).

    So, I'm changing my position and will now suggest that your best bet is to stick with the compact crank and use a wider ratio cassette. Shimano RD's are often used with 32 tooth rear cogs even though the spec is only up to 27T. A longer b-tension screw should get you clearance if you have the jockey wheel hitting the large rear cog. 10 speed wide ratio cassettes are available from IRD, or if you have the $$$, you can now use an SRAM XX cassette. A 12-32 cassette paired with the 50/34 crank will offer a considerably lower low gear than stock. However, for extended touring, something even lower would likely be nice.

    Back to that Deore crankset, you'd have some limitations on top speed, but you should be able to get a 42/26 crank to shift ok, and easily find chainrings (you probably have the 42 already). It may take some playing around to shift it with a road derailler and it may never shift perfectly but you aren't racing with this setup, right? Paired with an 11-32 cassette, you could still spin up to 30+ mph which is nothing to be ashamed of.

    If the crankset is square taper, you have more room for adjustment of the chainline by adjusting BB length. If it's Octalink, you are likely stuck with whatever chainline the recommended BB yields. Assuming your SRAM shifters have a trim position, you should be able to reach all of the cogs without derailler rub though your chainline won't be as perfect as you might prefer.

    One last ditch option is to give an SRAM MTB RD a try with your road shifters. SRAM claims the two are not compatible but maybe they really are. If you could make that work, you can use an 11/34 or 12/34 cassette. Not as low a gear as the double Deore setup mentioned above though but you'll retain your top gear.

    Let us know what you do and how it works out. I'm interested.

  5. #5
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    I guess this will fall under the "all ideas welcome" catagory.

    Have you considered the EuroTour on your mountain bike? It will already have all the gears you need for fully-loaded touring, it'll take a beating in the tough spots, and you can run some street tires on it. Touring isn't usually about speed, and, depending upon the geometry of your two bikes, the MTB might be more comfortable than a 'race' bike.
    Minimal outlay and you won't have to mess around with your 'race' bike.

    Just some thoughts from an old guy who sometimes rides centuries on his 20+ year old MTB.
    Last edited by bretgross; 01-19-10 at 07:36 PM. Reason: Left out the word 'geometry'.

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    Thank you all for your suggestions.

    Have you considered the EuroTour on your mountain bike?
    To be honest, not really. I have done one lightly loaded cross-country (Finland) trip on a road bike and I really liked the feel on that bike. Geometry suits me and it is occasionally fun to go fast.

    what kind of 'racing' are you going to do
    Some local and some national amateur races.

    why not buy a bike with a triple crankset already on it?
    Not a bad suggestion but I have a good deal for a full Rival groupset and the compact Rival seems perfect for 99% of my riding. I like the simplicity of the two front chainrings. I'm not worried about the triples weight penalty but I don't like the idea of using a triple in my normal riding when I would practically never use the small ring.

    And of course all this assumes that you're using a compatible BB system on both bikes.
    The Rival group has GXP BB and I don't think they are compatible. However, if I ever decide to swap the mtb crankset I might as well swap the bottom brackets.

    will now suggest that your best bet is to stick with the compact crank and use a wider ratio cassette
    This was my original option but it's just that I can't be sure if it works. I didn't find any wider road cassettes near my location so it would suck just to order the wider cassette from e.g. USA and then see that my derailler can't handle it. SRAM XX would definetely solve this problem but it's way out of my budget.

    but you should be able to get a 42/26 crank to shift ok
    This is an interesting option. So did I get it right: This one for the middle ring and this one for the small ring?

  7. #7
    Gear Combo Guru Chris_W's Avatar
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    Read the discussion in this recent thread: Mountain Cassette/RD on SRAM Rival Drivetrain. I recommended getting a Truvativ Rouleur crankset, which you can use with your current BB and can put just two rings on - I would go with 26 and 42 teeth for touring. You could then keep the rest of your drivetrain as is.

    However, I used these chainrings and a 11-28 cassette when touring once and found that I spent a lot of time in between the 19 and 22 cogs on the rear, and the cadence jump between the two was bigger than I'd like. The BBB 12-28 cassette is therefore a much better choice because it tightens up the spacing at the lower end (19, 21, 23, 25, 28 instead of 19, 22, 25, 28).

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    Great State of Varmint Panthers007's Avatar
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    You're advised to check the chain-line between the road crank and the mtn. triple. If they are within the same specs - it should work. BUT - your front-derailleur may need replacement(FD). And you may have issues with the rear-derailleur as well.

    Read: You may have to replace your entire drive. I'll leave it to you to figure out - I'm not there. It will require a bit of work regardless. So, if you're not a bike-mechanic, take the plans to someone who is and get a estimate what this will require and cost.

    Good luck!
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    Senior Member BCRider's Avatar
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    Quote Originally Posted by Myrkur View Post
    The Rival group has GXP BB and I don't think they are compatible. However, if I ever decide to swap the mtb crankset I might as well swap the bottom brackets.
    That's fine if you don't mind the extra effort of moving the BB over. But before you do check to be sure the BB shell on both bikes is the same width. Fairly often MTB's are 72mm while most road bikes are 68mm. There is a lot of 68mm MTB's though so you make get lucky.

    Even with the smaller cranks on the front I suspect you'll still want to go with an MTB cassette on the rear for the wider set of ratios it offers. The issue there is the amount of chain wrap that your roadie derrailleur will support. You may have to switch to a long cage version if you're running a short cage right now.
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    i just swapped out the double on my ancient puch for a 90's square shimano 105 crankset triple. i already had a long rd since i changed that from a 5 to 8 spd with 32t on the high side. i got the 105 triple fd and a new bb in the deal. so i did a road to road replacement. if you start looking at mtb fd's you will see they are designed for a different seat tube angle. i had no experience with how that would work out on a road frame, so i avoided the situation. i have not put many miles on the triple set up since i have been riding my snow bike. the gearing is 30/42/52- 11/32.

  11. #11
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    Quote Originally Posted by BCRider View Post
    That's fine if you don't mind the extra effort of moving the BB over. But before you do check to be sure the BB shell on both bikes is the same width. Fairly often MTB's are 72mm while most road bikes are 68mm. There is a lot of 68mm MTB's though so you make get lucky.
    Yes, they are both 68mm so I got lucky.

    So let's say that I change the crank. I use the 68-110mm UN26 bottom bracket and Shimano FCM-442 crank from my mountain bike. I replace the smallest chainring to 26T and the middle chainring to 42T as joejack951 suggested and then adjust the Sram Rival front derailleur to switch between those two. If this works, I think it would make a great combination! Especially since those two chainrings would cost about 40$. Of course there are still those possible issues with bad chainline or I can't get the front derailleur to change correctly but this just might be worth risk.

    I haven't changed chainrings before so I have one question about it. If I change the two inner rings for this tour and I only use those two, is it possible to remove the outer ring (44T) completely? There's no use for it I guess since I can't change to it.

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    Quote Originally Posted by Myrkur View Post
    I haven't changed chainrings before so I have one question about it. If I change the two inner rings for this tour and I only use those two, is it possible to remove the outer ring (44T) completely? There's no use for it I guess since I can't change to it.
    You will need shorter chainring bolts if you leave off the outer ring. This is done quite frequently by single speed guys using road doubles with a single ring. Since you have the 44T ring already, it might be worth giving it a go with the 26T inner ring. That's a big jump between rings but stranger things have been made to work. You could always order the 42T and have it as a backup. Those rings you linked to above seem like they should do the trick.

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    Quote Originally Posted by joejack951 View Post
    You will need shorter chainring bolts if you leave off the outer ring. This is done quite frequently by single speed guys using road doubles with a single ring. Since you have the 44T ring already, it might be worth giving it a go with the 26T inner ring. That's a big jump between rings but stranger things have been made to work. You could always order the 42T and have it as a backup. Those rings you linked to above seem like they should do the trick.
    Ok, I'll definitely try this out. Thank you for the info and suggestions.

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    If this is a racing bike how do you plan to attach racks for a loaded tour?

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    Prices are LOW on used bikes right now. I got my Cannondale t700 for less than $200 and its set up for loaded touring.

    I admire your wanting to save a buck, but the colder months are a great time to consider N+1.
    1993 Cannondale T700 - 1994 Specialized Rockhopper - Actionbent T1 (Electrification in progress!)

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    Quote Originally Posted by davidad View Post
    If this is a racing bike how do you plan to attach racks for a loaded tour?
    Here is a picture of my last touring setup:


    Setup was pretty good but for my next tour I'm planning to install rear rack instead of seatpost rack if I can find a way to install it. I've heard that some people have installed rear racks using p-clamps and I might have to try the same.

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    Quote Originally Posted by corkscrew View Post
    Prices are LOW on used bikes right now. I got my Cannondale t700 for less than $200 and its set up for loaded touring.

    I admire your wanting to save a buck, but the colder months are a great time to consider N+1.
    Good find. However in my home country there aren't that many touring bikes available for some reason. At least not used. It's not really about the money but more that I like riding road bikes and it is fun to tinker with them.

  18. #18
    Gear Combo Guru Chris_W's Avatar
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    Quote Originally Posted by Myrkur View Post
    Here is a picture of my last touring setup:

    Setup was pretty good but for my next tour I'm planning to install rear rack instead of seatpost rack if I can find a way to install it. I've heard that some people have installed rear racks using p-clamps and I might have to try the same.
    You can do it without putting p-clamps on tubes that might not have thick enough tubing to handle the weight well. For the lower mounting point, get a set of Tubus mounts that attach using the quick release. For the upper mount, get a seatpost clamp that has an integrated set of rack mounting holes, local bike stores in the US can get them from Quality Bike Parts in all standard sizes. In Europe, the 31.8mm size is available re-branded by some dealers, but other sizes aren't, elsewhere in the world I'm not sure.

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    Quote Originally Posted by Myrkur View Post
    Good find. However in my home country there aren't that many touring bikes available for some reason. At least not used. It's not really about the money but more that I like riding road bikes and it is fun to tinker with them.
    I agree that they aren't that common. I hunted CL for a few months before I found the Cannondale. They say patience is a virtue after all, whatever the hell that means.
    1993 Cannondale T700 - 1994 Specialized Rockhopper - Actionbent T1 (Electrification in progress!)

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    Small update to my plans. I tested taking out the middle ring of my broken Acera crank (bent crank arm). In the picture it now has 42t large chainring and 22t small ring. If this is going to work, I'm putting the 42t cog to my working Deore crank and I get a new 26t ring to it.

    However, in the picture below you can see that these chainring bolts come out a couple of millimeters. Do you think that those will cause shifting problems? I thought about filing them a bit but that might be asking for trouble.. If you have suggestions please tell me.


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    Would these do the trick? They seem to have lower profile.

  22. #22
    Gear Combo Guru Chris_W's Avatar
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    The chainring bolts that Myrkur linked to probably won't help much because it is the nut-like thing that the bolts screw into that is the problem, not the length of the bolt itself (which can easily be fixed by using spacers on the outside of the crank that we can't see. The main problem here is trying to use an outer ring in the middle position. The outer ring doesn't have the recesses for the bolts to sit in, so they jut out. This isn't going to affect shifting that much, but it will limit the gears that you can use when the chain is on the inner ring, because when you try to use the upper half of the cassette then the chain will constantly rub on the bolts. Filing down the bolts sounds like a bad idea, it would only partly solve the problem, and would mean that you might not be able to ever remove the bolts again becuase you would have to file off the grooves in the nut-like part that allow you to hold the nut in place.

    To get 26/42 gearing, I use a road crankset (130mm outer BCD). You can then easily find a 42 tooth ring that is designed to go in the middle position - I don't think you'll be able to find one of those for a MTB crank.

  23. #23
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    Quote Originally Posted by Chris_W View Post
    The chainring bolts that Myrkur linked to probably won't help much because it is the nut-like thing that the bolts screw into that is the problem, not the length of the bolt itself (which can easily be fixed by using spacers on the outside of the crank that we can't see. The main problem here is trying to use an outer ring in the middle position. The outer ring doesn't have the recesses for the bolts to sit in, so they jut out. This isn't going to affect shifting that much, but it will limit the gears that you can use when the chain is on the inner ring, because when you try to use the upper half of the cassette then the chain will constantly rub on the bolts. Filing down the bolts sounds like a bad idea, it would only partly solve the problem, and would mean that you might not be able to ever remove the bolts again becuase you would have to file off the grooves in the nut-like part that allow you to hold the nut in place.

    To get 26/42 gearing, I use a road crankset (130mm outer BCD). You can then easily find a 42 tooth ring that is designed to go in the middle position - I don't think you'll be able to find one of those for a MTB crank.

    Thanks for your thoughts. Brand-X bolts look slightly lower than the ones I have. The ones that I have have these "nut-like things" come out 2 millimeters and Brand-X narrow version seems something like 1-1.5mm.

    But I missed one point. In my picture the crank has the old 22t inner ring. If I use a 28t inner ring, the chainring diameter will become so much wider (about 116mm) that I don't think those chainring bolts are going to be in my way anymore. But if they do still limit the use of inner ring and upper half of the cassette I don't think that's a problem. The inner ring is just a bailout gear anyway.

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