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  1. #1
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    Changing Shimano Deore 24/38 to 24/32

    Hi guys, long time reader first time poster.

    I'm currently running Shimano Deore 24/38 cranks with 11x36 rear. A lot of my technical riding on the flat and climbs has me riding in 38 front and 36 rear and despite being a 2x10 drive train the chain line doesn't look or sound too crash hot. The higher end of my cassette never gets used. It also means when I have to drop down to the granny more often than I'd like. Basically i'm fussing with my gears more than necessary in order to maintain an efficient cadence.

    Now I could go to a 1x10 drive train but honestly I don't have the legs to make it up some of the 35% gradients around here without the granny gear.

    So could I have the best of both worlds by changing my 38 chain ring for a 32 and keeping the granny? This would open up the rest of my cassette and improve chain line while also keeping granny gear for the steeps. Would I have any shifting problems if I fitted a chain ring like this?

    Shimano SLX FC-M660 Chainring 32T Black

    It says for triple chain ring setups...

  2. #2
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    First, running the 38/36 combo is going to wear your components out quite a bit faster. At that ratio, you're better off in the 24 up front and somewhere around the middle of the cassette out back. Google "cross chaining" for more info.

    As far as switching the front, it's possible, but I wouldn't recommend it for most folks. If it's like my XT, it'll require the VERY careful use of a dremel. Easier solution would be using a 3x crankset that's designed for the ratios you're talking about. Jenson's having a REALLY good sale on them right now for the Deore. Shimano Deore M610 Crankset > Components > Drivetrain > Cranksets | Jenson USA

  3. #3
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    Thanks for the reply, I probably should have put the correct term "cross chaining" in my original post. I'm aware running big/big is not ideal hence I'm looking for a solution. You're absolutely correct switching to granny and middle of the cassette yields a similar ratio with a better chain line, however I then have a lot of gear changes to do for the downhills. A better solution in my mind, is to stay out of granny and use slightly smaller chain ring.

    So out of curiosity, what is it about the 2x crankset that requires cutting with a dremel? I was hoping if the BCD was correct a new chain ring would just bolt right up.

    If I were to buy the 3x cranks, can I take off the outer chain ring?

  4. #4
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    Not sure what trails you ride, but if I'm going up in the small front/mid rear combo and then crest the top of the hill, I just push the front onto the big ring and am ready to head back down. It's easy to shift onto smaller cogs out back going down. Easy as pie once you get used to it (at least where I ride).

    Re: the dremel thing - I only have experience with XT, but the crank spider has an odd shape that extends out and interferes with the chain on a 32t cog. It's not much, but it's there and I don't like dropping chains. 34t should be fine though with far less trouble and it'll still give you an easier big gear.

    Changing Shimano Deore 24/38 to 24/32-shimano-chain-contact.jpg

    3x - yep, you sure can take off the outer ring. I'd suggest using a bash guard or shorter chainring bolts. You could probably reuse the 2x bolts from your old Deore if you didn't want the bash. Bonus - with the 3x used this way, your chain line is actually better even if you're completely cross-chained because your big ring is what used to be the middle (both are slightly inboard from a 2x setup). It does make the small/small combo a little worse, but you didn't mention that as an issue. You'll just have to fiddle with the front (if it's Shimano, flip the switch on the shifter from 2x to 3x and move the limit screws on the derailleur so it doesn't accidentally shift off the outside). Can't remember what I did with SRAM to make it work, but I think it took more fiddling...been a while.

  5. #5
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    Quote Originally Posted by maldotcom2 View Post
    Thanks for the reply, I probably should have put the correct term "cross chaining" in my original post. I'm aware running big/big is not ideal hence I'm looking for a solution. You're absolutely correct switching to granny and middle of the cassette yields a similar ratio with a better chain line, however I then have a lot of gear changes to do for the downhills. A better solution in my mind, is to stay out of granny and use slightly smaller chain ring.

    So out of curiosity, what is it about the 2x crankset that requires cutting with a dremel? I was hoping if the BCD was correct a new chain ring would just bolt right up.

    If I were to buy the 3x cranks, can I take off the outer chain ring?
    2x cranks and fr der can only jump down so far in ring size. You're better off switching out to a 3x crankset and derailleur, installing ring guard(BBG's are least expensive I think) and adjust your front derailleur limit stops accordingly.
    Last edited by JMac47; 10-27-2015 at 05:43 AM.
    Wait whuuut, who did he tell you that!?!?....

  6. #6
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    I guess it comes down to a combination of riding technique and strength. I'm envisioning being able to stay in the big chain ring for 95% of the ride and only using granny for the stupid steep stuff. Using front derailleur is best avoided imo.

    Thanks heaps for the pic too, that really makes sense now. Probably just a touch on the linisher would solve the interference problem.

    Looking at a gear chart using Meters Development, by dropping from a 38t to 32t chainring I'm effectively moving the chain one sprocket outwards on the cassette for the same ratio, thus improving chain line and giving me a little more head room before having to engage granny gear.

    Changing Shimano Deore 24/38 to 24/32-chart.jpg

    The 3x crank is worthy of consideration though due to reasons you mentioned, and I never use small/small.

    I've got some thinking to do

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    Quote Originally Posted by JMac47 View Post
    2x cranks and fr der can only jump down in ring size.

    Can you elaborate on this? Are you saying the front derailleur on a 2x is designed for 24/38 and problems would occur with 24/32?

  8. #8
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    Quote Originally Posted by maldotcom2 View Post
    I guess it comes down to a combination of riding technique and strength. I'm envisioning being able to stay in the big chain ring for 95% of the ride and only using granny for the stupid steep stuff. Using front derailleur is best avoided imo.

    Thanks heaps for the pic too, that really makes sense now. Probably just a touch on the linisher would solve the interference problem.

    Looking at a gear chart using Meters Development, by dropping from a 38t to 32t chainring I'm effectively moving the chain one sprocket outwards on the cassette for the same ratio, thus improving chain line and giving me a little more head room before having to engage granny gear.

    Click image for larger version. 

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    The 3x crank is worthy of consideration though due to reasons you mentioned, and I never use small/small.

    I've got some thinking to do
    While I don't agree with avoiding the front derailleur, if it works for you then cool. 3x/bash would definitely be easier on the pocketbook long term if you stick with the way you ride now. BBG is definitely a good option for a bash guard. Great product and guarantee. I think shipping outside the US is more...something like $10, so $20-25 total. Don't know what prices are there so take that into consideration. You can run bare with no bash. Just looks a little different.

    You're welcome! Pics are always good. Yeah, careful sanding as the aluminum is a pretty soft metal - easy to take too much and game over. Wouldn't be a first choice.

    Quote Originally Posted by maldotcom2 View Post
    Can you elaborate on this? Are you saying the front derailleur on a 2x is designed for 24/38 and problems would occur with 24/32?
    Not sure what he's saying, but can hazard an educated guess. 2x isn't designed for the same range as the 3x (22/32/44 is 22t difference whereas 24/38 is only 14t total) and some of the cages are shaped differently. Not sure what the max range is for one, but if using a 2x as a 3x the cage plates may rub or it may not shift as smoothly. Mine set up ok, but I remember having to fiddle with it more than usual to make it happy. Definitely makes setup easier to have the 3x derailleur. JMac47, if I'm wrong tell me. I like learning new things.

  9. #9
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    Ok a couple of things. One the chain ring you posted is for a triple cranks middle position. Two, Have you thought about just going to a 34t chainring? I ran a blackspire one on my Anthem X 29er. It was a SRAM S1000 104 bcd double crank that originally came with a 38t. I think the Shimano double is also 104 BCD. The only issue I had is when I tried to move it over to ROS 9 the direct mount front DR wouldnt go low enough, didnt have the issue with the Giant since the front DR was a band type. So I did what you should do go SS!!! Blackspire - SuperPro 104/64 BCD Chainrings | Blackspire

  10. #10
    NedwannaB
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    No, pretty much same what I inferred.

    Not knowing what vintage drivetrain or budget the OP has either I would think cost of switching over to components for a 3x drivetrain (to essentially get a 2x again...) might be $$ better spent on ditching the fr derailleur all together and getting an extended cog/wide range cassette and a ring to run in the 64bcd spot sized accordingly to hit the desired hi/lo gearing range. Might not find that sweet spot gearing though since the riding conditions varies widely.
    Wait whuuut, who did he tell you that!?!?....

  11. #11
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    What no apathy is referring to about shaving the cranks just a hair is true with running a 32T big ring. Wolf Tooth also refers to the issue if buying their 32T ring (or they suggest running a spacer to move it out enough for the chain to not rub). Guess it's just the the design. I would maybe suggest running a 34T big ring to avoid those hassles? Like what jdgang and others suggest, maybe try just running a 34T 1x front instead? If you really need the 24T then maybe pop it back on and run 34/24T.
    2011 Yeti 575 Enduro - full XT group, Thomson cockpit, and Chris King upgrade

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    I've made a decision, thanks to the input from everyone.

    I decided to buy the 3x Deore M610 cranks and run the 24/32 chain rings it comes with, maybe with a neat bash plate down the line. Even with postage to Aus that's super cheap and it will be a direct swap with my current BB. I can get a 3x derailleur cheap enough.

    Shimano Deore M610 Crankset > Components > Drivetrain > Cranksets | Jenson USA

    This will offer the best chain line over my current 2x cranks and will also allow me the flexibility to go 1x10 in the future if I find I can go without the 24t. If I find the 32t too short I could opt for a 34t at that point in time too.

    Using a Oneup or WT 40t or 42t in the rear is always an option, however my current cassette is not compatible, and they're still at fad prices. That may be an option to investigate if I ever go 1x10 and need more low end.

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    I just went through some of this by installing an old school XT 3x crankset to get a 2x 32/24 crankset. Ideally I would have gone with the new XT 34/24 crankset, but it wasn't released when I bought my frame and it would have been an extra $100.

    Problem I ran into, old XT 2x FD didn't like the 32/24 set up. I got some rubbing, the 32T ring seemed too small for the older FD. A 3x FD would work, but for a 2X setup, it seemed huge, it almost rubbed my rear tire.

    I ended up getting the new side swing XT 2x 8020 derailleur and it works fine with the 32/24 set up.

    On the 32, having a granny too, I would probably prefer a 34T big ring just for a bit of top end, but really I rarely spin out.

  14. #14
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    Yeah that XT 34/24 is too pricey to justify on this kind of setup. Better off going 1x11.

    I think i'll be right with 32, looking at the chart I posted earlier I'm only effectively losing one top end ratio, and I don't even use the 11t cog as it is. I suppose gear ratios is a very personal thing and depends on the riding you do.

    I'm expecting some FD issues, even more so because I run direct mount low pull which limits my options. I'll update this thread with results anyway.

  15. #15
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    Quote Originally Posted by maldotcom2 View Post
    Yeah that XT 34/24 is too pricey to justify on this kind of setup. Better off going 1x11.

    I think i'll be right with 32, looking at the chart I posted earlier I'm only effectively losing one top end ratio, and I don't even use the 11t cog as it is. I suppose gear ratios is a very personal thing and depends on the riding you do.

    I'm expecting some FD issues, even more so because I run direct mount low pull which limits my options. I'll update this thread with results anyway.
    Not really familiar with the direct mount stuff - I think what Shimano calls an e type should fit the bill if you just remove the bottom part (check picture and compare to what you have). This thread seems to support it, but definitely double check (it's 3x9, but same mount as far as I can tell). Check post #11.

    Shimano XT FD-M780 3X10 Front Derailleur > Components > Drivetrain > Mountain Front Derailleurs | Jenson USA

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    That must be a different kind of direct mount. My direct mount is at the top of the FD.

    I think I need something like this:

    Shimano SLX M676-D 2X10 Front Derailleur > Components > Drivetrain > Mountain Front Derailleurs | Jenson USA

    The issue is it says 48.8mm chain line and the cranks are 50mm.

    Edit: Scratch that, just read that if I take the big ring off my 3x (50mm) cranks the new chain line will be 47.5.

    So that would explain why the FD above says chain line 48.8. It suits 2x and 3x cranks and has to compromise on chain line.
    50 - 47.5 = 2.5
    2.5 / 2 = 1.25

    47.5 + 1.25 = ~48.8
    50 - 1.25 = ~48.8



  17. #17
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    Quote Originally Posted by maldotcom2 View Post
    That must be a different kind of direct mount. My direct mount is at the top of the FD.

    I think I need something like this:

    Shimano SLX M676-D 2X10 Front Derailleur > Components > Drivetrain > Mountain Front Derailleurs | Jenson USA

    The issue is it says 48.8mm chain line and the cranks are 50mm.

    Edit: Scratch that, just read that if I take the big ring off my 3x (50mm) cranks the new chain line will be 47.5.

    So that would explain why the FD above says chain line 48.8. It suits 2x and 3x cranks and has to compromise on chain line.
    50 - 47.5 = 2.5
    2.5 / 2 = 1.25

    47.5 + 1.25 = ~48.8
    50 - 1.25 = ~48.8


    I don't think I've ever cared what the chainline in relation to a front derailleur (cranksets, yes). If it'll shift far enough to get to all the chainrings I'm using then all is good in the front shifting world. Maybe that's not the case with direct mount? One day I'll probably have to figure this out. As it's nearly midnight here, it won't be happening tonight. lol

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    I would double check the specks on that 2x derailleur to be sure that it will work with the 32T chain ring. My XT 786 2x derailleur was designed around a 38T and bigger big chain ring, I couldn't get it to work right without rubbing.

    The 3x10 derailleur will work fine, but look funny with the converted 3x crankset.

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    Decided to just go with a M781 3x10 and hope it doesn't cause any issues with rear wheel clearance. Seems like the only valid option.

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    I ended up using a new 8020 FD and it works great. Specs say it works down to 34T, but its working fine with my 32/24 set up. I get just a bit of rub when in the 24 chain ring and the 11T rear, but I never actually use that combo so no biggie.

    I have an 3x FD - direct mount, its brand new. Only mounted it, decided it wasn't for me and ordered the 8020. PM me if you want it.

    It's like this one:
    Shimano XT M781 Direct Mount 3 x 10 Front Derailleur - Modern Bike

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    Cheers for the offer, but I'm in Aus so I ordered one locally. I can probably exchange it if it just won't fit.

    I'm surprised you don't have any major chain rubbing issues with the 11sp FD. I read there's barely enough clearance for 11sp chains let alone a 10sp. Apparently people are using 10sp FD on their 11sp bikes due to this.

    In any case, what made you choose the 8020 front pull FD as opposed to the 8025 dual pull? I was seriously considering the 8025 until I read about the chain clearance issues.

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    I have an HD3. It's internal cable routing is ideally set up for a side swing derailleur, and the new 8020D side swing derailleur came available as I was sorting out my FD issues.

    I managed to use the 2x 786 FD for a few weeks with a bit of rubbing and a weird bend in the cable routing, and finally just decided to spring for the 8020. All in all, I could have bought an XTR 9020D from the get go considering the money I spent on XT front derailleurs until I got the ideal one for my bike. Lesson learned.

  23. #23
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    Markiel,

    With your 8020 FD setup did you have to use an 11sp chain with it or did the 10sp chain have enough clearance?

    Looking at my M781, being direct mount, I'm concerned I may not be able to slide it down close enough to a 32t chain ring. May have to exchange it for a 8025 dual pull, I just need to know about chain clearances.

  24. #24
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    The 8020 FD works fine with a 10 speed chain and setup.

    If you go M781, you need to set it up like it's still a 3x. The FD has ridges for the 24, 32, and 42? chainrings. So you'll have it set as if the 42ish chainring is still there, 1-2 cm above the 32T chainring. That way the ridges for the middle ring will engage and give you good shifting.

    Other than looking funny with all that space between the 32T chainring and the FD, it should work fine.

    Good luck - Mark

  25. #25
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    Ok well my package from Jenson arrived today with my M610 Crankset and BB. I dunno, I think something is missing...

    Help me out guys.


    Changing Shimano Deore 24/38 to 24/32-img_0083.jpg

    So THAT'S why it was so cheap.

  26. #26
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    They must have made a mistake...

    I got my XT 3x crank from them - it had all the parts, but one of the crank arms had a minor scratch. I figured I would scratch myself soon enough anyway.

  27. #27
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    My set looks like a credit return. All the bags were torn open which allowed the pieces to just float freely around in the box lol. Amatuers. Anyway I sent them an email expaining how hard it will be to pedal with one crank arm and to please send me the left arm. See how we go...

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    LOL, so that's why they were selling left crank arms under clearance section, haha. JK
    Yeah, I haven't had much problems with them until recently. Not sure if management changed up or what, I placed an order and everything was in stock at the time I submitted payment. Few days later only part of my order shipped, I thought ok, maybe they ship from different locations. Following day, i still haven't gotten an update. I contact them and the girl says "hmmm, it's showing we have it in stock, I'll see what's going on and update you via email, if that's ok?" A few hours later I get an email that my item shipped out. Like how difficult is it to check the order to make sure you've pulled every item? SMH

    Hope they get you up and running soon!
    2011 Yeti 575 Enduro - full XT group, Thomson cockpit, and Chris King upgrade

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