Advertise on Bikeforums.net



User Tag List

Results 1 to 13 of 13
  1. #1
    Junior Member
    Join Date
    May 2011
    Posts
    5
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Changing mtb gearing, shifters, need a WAY bigger top ring!

    Hi, I'm trying to convert my Novara mtb into an everything bike. I spend time both in the back country biking mountain roads and in the city/ places in between biking on asphalt. My issue is, I'm blowing out cassettes right and left because I've maxed out the top gear range of the bike!

    Thus far the highest gear ratio I've got is 44/11. There's no way I can fit on a smaller cassette. I've examined the front derrailer and noted that I've got at least 5mm distance between the derrailer arm and the tip of the chain ring gear teeth.

    Now, I'm told that I can't hope to put a new front chain ring on (ideally I'd fit a 52) because this creates too much of a gap between the top and middle chain rings, and derrailer adjustment will be very, very tricky.

    I'm told I need to get a whole new road crankset, just so the gears are spaced appropriately. At 300-400 bucks this is WAY more than I'm willing to pay when I have yet to be convinced I don't just need a new top ring!!

    So... I'm proposing to put some vintage suntour friction shifters on the bike, then throw the biggest possible top chain ring on, given clearance of both the frame and the derraileur. I'm hoping the friction shifters can make up for any incremental travel adjustments I'd otherwise have to sweat over with the trigger shifters, and, I figure, if there is 1mm clearance for both the top and the bottom chain rings I'll be fine.

    Any opinions? I've talked to numerous pro mechanics about it and their opinions are varied...

  2. #2
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    571
    Mentioned
    31 Post(s)
    Tagged
    0 Thread(s)
    Way bigger: Schlumpf High speed drive, there is a planetary overdrive gear
    in the crank-set.
    when engaged, a heel button where crank axis is,
    gears are all 2.5x higher, or a slightly smaller gain, Speed drive: 1.6X

    fine Swiss engineering, I own one of Florian Schlumpf's reduction geared cranks
    the engaged gear is '/. 2.5 smaller so as if a 50 , 20 crankset.
    my 3 speed hub is used a 2nd time in low range, for 6 ratios.

    http://www.schlumpf.ch/hp/schlumpf/antriebe_engl.htm
    Last edited by fietsbob; 05-27-11 at 09:52 AM.

  3. #3
    Senior Member Retro Grouch's Avatar
    Join Date
    Feb 2004
    Location
    St Peters, Missouri
    My Bikes
    Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
    Posts
    23,825
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I don't know if it will give you as large a boost as you'd like but probably the cheapest solution would be a 48t big ring. That's what I did with my recumbent. My existing front derailleur works fine (after raising it to clear). I also installed a new, longer chain.

  4. #4
    Senior Member
    Join Date
    May 2011
    Posts
    140
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    How fast do you ride? What's your cadence? How fast do you accrue mileage to be "blowing out" cassettes right and left?

    Most MTB front DERs can easily accommodate a 22 tooth differential between the smallest and largest chainrings. You likely have a triple crankset with 22-32-44 tooth rings. Do you use the 22? If not, your front DER could potentially accommodate a 52 tooth ring. That said, I doubt you'll be able to find a 52t ring that will fit the BCD of your compact MTB triple. Alternatively, you should be able to pick up an Alivio crankset (28-38-48) for about 50 bones.

    Just for reference, assuming a 26x1.5" "all purpose" tire mounted, 44-11 combo should yield 99.5 gear inches. 48-11 will yield 108.5 gear inches, and 52-11 combo will give you 117.6, a sizable 18.2% increase from the 44t ring. That's a big gear to push.

  5. #5
    Senior Member
    Join Date
    May 2011
    Posts
    140
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Also, someone correct me if I'm wrong, but changing the diameter of the chainring shouldn't interact with shifter indexing, provided the derailleur is set up properly.

  6. #6
    Banned.
    Join Date
    Apr 2011
    My Bikes
    CCM Torino 76
    Posts
    937
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    If you can't easily adapt a 52 tooth chainring to your mtb crankset, consider simply training yourself to spin faster... According to Sheldon Brown's gear calculator, with a 44-11, if you can spin your legs at 90 ROM you will be going 44 km/h. If you go up to a 48 you can reach 48.4km/h, and if you can make a 52 tooth fit, at 90 rpm you will be going 52 km/h.

    On downhills, 44km/h is easy to reach, but if you can maintain 44 km/h on flat ground on your mtb then you shouldn't be reading posts about bikes on the internet, you should be on the national time trial team!

  7. #7
    Elitist Troglodyte DMF's Avatar
    Join Date
    Jun 2006
    Location
    Dallas
    My Bikes
    03 Raleigh Professional (steel)
    Posts
    6,896
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by eddiearniwhatev View Post
    My issue is, I'm blowing out cassettes right and left because I've maxed out the top gear range of the bike!
    This makes no sense. Wear is what ruins cassettes. (Well, that and hammers.)

    As mentioned above, unless you want to change the whole crankset (et al.) you are restricted to replacing the big ring with one that will fit on the crank - probably a 48T.

    Or this: http://cgi.ebay.com/100-MPH-High-spe...ht_1173wt_1029


    You do know that you can stop pedaling on downhills, right?
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  8. #8
    2 Fat 2 Furious contango's Avatar
    Join Date
    Nov 2010
    Location
    England
    My Bikes
    2009 Specialized Rockhopper Comp Disc, 2009 Specialized Tricross Sport
    Posts
    3,989
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by eddiearniwhatev View Post
    Hi, I'm trying to convert my Novara mtb into an everything bike. I spend time both in the back country biking mountain roads and in the city/ places in between biking on asphalt. My issue is, I'm blowing out cassettes right and left because I've maxed out the top gear range of the bike!

    Thus far the highest gear ratio I've got is 44/11. There's no way I can fit on a smaller cassette. I've examined the front derrailer and noted that I've got at least 5mm distance between the derrailer arm and the tip of the chain ring gear teeth.

    Now, I'm told that I can't hope to put a new front chain ring on (ideally I'd fit a 52) because this creates too much of a gap between the top and middle chain rings, and derrailer adjustment will be very, very tricky.

    I'm told I need to get a whole new road crankset, just so the gears are spaced appropriately. At 300-400 bucks this is WAY more than I'm willing to pay when I have yet to be convinced I don't just need a new top ring!!

    So... I'm proposing to put some vintage suntour friction shifters on the bike, then throw the biggest possible top chain ring on, given clearance of both the frame and the derraileur. I'm hoping the friction shifters can make up for any incremental travel adjustments I'd otherwise have to sweat over with the trigger shifters, and, I figure, if there is 1mm clearance for both the top and the bottom chain rings I'll be fine.

    Any opinions? I've talked to numerous pro mechanics about it and their opinions are varied...

    I'm far from a pro mechanic, so take this as being worth what you paid for it.

    My bike (Specialized Rockhopper) has a 44-32-22 chainset and 11-34 9-speed cassette. A while back I was looking at putting a bigger outer chainring on it, with a view to doing something like 48-32-22. I wanted higher gearing from the outer chainring while also keeping the low gearing for a few big hills.

    My front derailleur lists a minimum tooth difference between the outer and middle chainrings of 12 and a maximum difference between outer and inner of 22. So if I went for a 48t outer ring the 32t middle ring would still work but I'd need to go to a 26t inner. Since 48-32-26 makes little sense I might as well have gone for 48-36-26. And Shimano make just such a set, IIRC it's about 150 (so about $250) which gets you the three chainrings, cranks and bottom bracket. If you buy the chainrings separately I'd guess you'd be looking at 90, which in your money is about $150.

    The owner of my LBS said you may be able to get away with 48-32-22 but it's the kind of thing you'd have to try in order to find out if it worked well, kind of worked, or didn't really work at all.


    ETA: I agree with what others have said about wondering why you need higher gearing. I looked into it because I thought I was routinely cruising in the second-highest gear I had, when it turned out I had two more gears to go and plenty of potential to pedal faster. As my LBS said to me, if I really want to be going faster than is practical with a 44-11 combination then perhaps I'd be better off looking to change the bike rather than trying to convert a mountain bike into a fast road machine.
    Last edited by contango; 05-27-11 at 11:35 AM.

  9. #9
    Senior Member
    Join Date
    May 2011
    Posts
    140
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DMF View Post
    This makes no sense. Wear is what ruins cassettes. (Well, that and hammers.)
    I assumed he meant wear from over-using this gear combination.

  10. #10
    Senior Member
    Join Date
    Apr 2010
    Location
    Sunnyvale, CA USA
    Posts
    3,012
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by eddiearniwhatev View Post
    Hi, I'm trying to convert my Novara mtb into an everything bike. I spend time both in the back country biking mountain roads and in the city/ places in between biking on asphalt. My issue is, I'm blowing out cassettes right and left because I've maxed out the top gear range of the bike!

    Thus far the highest gear ratio I've got is 44/11. There's no way I can fit on a smaller cassette. I've examined the front derrailer and noted that I've got at least 5mm distance between the derrailer arm and the tip of the chain ring gear teeth.
    Your gearing is sufficiently high. With 1" slicks that's a 29-31 MPH cruising gear around 100-110 RPM and 35-40 MPH sprinting gear at 120-140. Taller tires will net even higher speeds. You just need to learn to pedal faster.

    22x34 is way more than you need for paved roads. Running something like 11-19 on road might provide much more pleasant spacing between gears.

  11. #11
    Junior Member
    Join Date
    May 2011
    Posts
    5
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    cadence, chain clearance, derraileur action

    Thanks for all the great replies!

    Yeah, to "blow out" means generally to destroy or render unusable. California slang...

    I have been working on my cadence, It's just that I grind through the 11 tooth smallest cassette gear faster than I've been replacing chains... annoying...

    I did some searching and consulting and found a nice 48T & 36T to replace the 44 & 32 I've got. It should fit fine, with a little derraileur tweaking.

    Basically, it was explained to me that the chainrings are machined with grooves and pegs which direct the chain from ring to ring with the help of the derraileur. If there is too huge a gap, the chain might have issues travelling efficiently, especially if you're rolling with index shifters.

    I threw on some nice suntour friction shifters to get over that problem, as I might end up feeling like I need road cranks to tour on this bike.

    Don't ask why I'm putting so much time and money into a used mtb frame I picked up at REI for 200 bucks... I guess I'll replace the frameset once it blows out or proves useless. So far so good...

    Lastly, from what I can tell the only thing keeping me from bumping it up to a 52 is simply the type of chainrings available for my crank, a 4 hole firex. From what I can tell if I want more leverage through a higher high gear I'm going to need to switch to a road crankset, which has five holes.

    But I'm not trying to drop too much bank on this project if I can avoid it.

    We'll see how the 48 serves, and I'll keep the cadence issues in mind.
    Last edited by eddiearniwhatev; 05-27-11 at 05:47 PM. Reason: spelling

  12. #12
    Junior Member
    Join Date
    May 2011
    Posts
    5
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Here's another, related question, something which has been nagging me in the back of my head for a while: What's up with the ergonomics of an mtb vs. road/ touring bike? I feel that I have to stand up to go "all out" with mtb frame geometry, as when I'm seated I'm in somewhat of an upright position relative to a road or touring frame. I feel ever so much "scrunched" over when I lean over the handle bars, and I feel I'm not engaging my legs muscles in the same manner. However, when I have to sprint up a steep hill or weave through traffic (useful skills in San Francisco!) I find the frame accomodates what I do way better than road bikes, though on the straight away the latter rock out. Any observations? -curious.

  13. #13
    Senior Member
    Join Date
    May 2011
    Posts
    140
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    First, it's nearly impossible to achieve the same riding position for a road bike and a mountain bike. You can get close, but you'd probably be making serious compromises either way. The way I see it, road bike geometry prioritizes comfort and power delivery while seated over long distances, whereas with MTB geometry, the priority is handling and stability on rough terrain. It is likely this handling and stability that makes you feel more comfortable going all out on the MTB frame. Downhill and freeride bikes have head angles that are so slack, that when coupled with plush, long suspension travel, some designs can barely be pedaled efficiently at all, but they are astonishingly awesome for their intended purpose (drops and steep rollers that would have lesser bikes sending you over the bars every time). A cross-country hardtail is a somewhat of a compromise between these designs.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •