Advertise on Bikeforums.net



User Tag List

Results 1 to 14 of 14

Thread: granny

  1. #1
    Junior Member
    Join Date
    Jul 2006
    Posts
    6
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    granny gear

    I'm currently running a 48-38-28 up front and am considering trying to get more of a granny gear, possibly 24. Since I'm a noob, I'm wondering if I can simply swap them out, or will I have trouble with the front derailleur, etc.? It's a Marin and I think the crankset is a Suntour


    thanks

  2. #2
    hello roadfix's Avatar
    Join Date
    May 2003
    Location
    Los Angeles
    My Bikes
    thank you for asking
    Posts
    18,502
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Your crank arms are mostly likely 110/74 BCD. You can mount a 26 ring but I'm not so sure about 24...
    .cinelli.olympic.surly.long.haul.trucker.kona.ku.surly.steamroller.
    .litespeed.classic.litespeed.firenze.bianchi.pista.dean.colonel.plus.more.

  3. #3
    Senior Member mechBgon's Avatar
    Join Date
    Jul 2002
    Posts
    6,957
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    74mm bolt circles will take a 24. 7075 aluminum is a good material to look for, here's some for example: http://www.cambriabike.com/shopexd.asp?id=11671

    Oh, and make sure the chainrings really are removable. Also, you're going to need a crank extractor to do the swap.

  4. #4
    Year-round cyclist
    Join Date
    Apr 2002
    Location
    Montréal (Québec)
    Posts
    3,023
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    My daughter has a Marin and it's a 4-arm crankset. I can't remember the bolt circle diameter (BCD), but I know it definitely accepts a 24 because that's what I installed. And her Shimano derailleur with indexed Rapidfire shifters works fine with 48-38-24. I don't think a 22 would have worked properly with her derailleur, however.

    BTW, if you don't know the BCD, carefully measure the distance between two bolts (centre-centre). Then visit this page from Sheldon Brown to know the BCD. If you look at the second table, you'll see that, for example, if you measure 45.3 mm between two bolts (3rd column), you need a chainring with 64 mm BCD and the smallest you may install is 22.
    Last edited by Michel Gagnon; 09-07-06 at 09:11 PM.
    Michel Gagnon
    Montréal (Québec, Canada)

  5. #5
    Junior Member
    Join Date
    Jul 2006
    Posts
    6
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    thanks folks, I'll do some more investigating.

  6. #6
    Senior Member
    Join Date
    Oct 2005
    Posts
    5,437
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    How much more of a granny gear do you need? With a 28 front, you should be able to use a 24 rear, which gives you almost 1:1 gearing, which is very low. Do you want to go below 1:1?
    Il faut de l'audace, encore de l'audace, toujours de l'audace

    1980 3Rensho-- 1975 Raleigh Sprite 3spd
    1990s Raleigh M20 MTB--2007 Windsor Hour (track)
    1988 Ducati 750 F1

  7. #7
    Mad bike riding scientist cyccommute's Avatar
    Join Date
    Nov 2004
    Location
    Denver, CO
    My Bikes
    Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
    Posts
    15,883
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by The Fixer
    Your crank arms are mostly likely 110/74 BCD. You can mount a 26 ring but I'm not so sure about 24...
    Could also be a 130/74BCD. In either case, a 24 will fit. If it's a 110/74 BCD everything is hunky dory. If it's a 130/74, shifts to the lowest gear with a 24 may get trapped in between the middle ring and the inner ring. In either case, your derailer is just fine
    Stuart Black
    Solo Without Pie. The search for pie in the Midwest.
    Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
    Days of Wineless Roads. Bed and Breakfasting along the KATY
    Twisting Down the Alley. Misadventures in tornado alley.
    An Good Ol' Fashion Appalachian Butt Whoopin'.

  8. #8
    Mad bike riding scientist cyccommute's Avatar
    Join Date
    Nov 2004
    Location
    Denver, CO
    My Bikes
    Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
    Posts
    15,883
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by San Rensho
    How much more of a granny gear do you need? With a 28 front, you should be able to use a 24 rear, which gives you almost 1:1 gearing, which is very low. Do you want to go below 1:1?
    Go as low as your masculinity will allow Me, I'm a whimp. All my bikes have 22 or 20 with a 34 in the back but then I have these big rocks in my backyard that kinda force me to do that
    Stuart Black
    Solo Without Pie. The search for pie in the Midwest.
    Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
    Days of Wineless Roads. Bed and Breakfasting along the KATY
    Twisting Down the Alley. Misadventures in tornado alley.
    An Good Ol' Fashion Appalachian Butt Whoopin'.

  9. #9
    hello roadfix's Avatar
    Join Date
    May 2003
    Location
    Los Angeles
    My Bikes
    thank you for asking
    Posts
    18,502
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by San Rensho
    How much more of a granny gear do you need? With a 28 front, you should be able to use a 24 rear, which gives you almost 1:1 gearing, which is very low. Do you want to go below 1:1?
    I'm a whimp too.... I'm running 22/32/44 and a 11-32 cassette on my mountain bike.....
    .cinelli.olympic.surly.long.haul.trucker.kona.ku.surly.steamroller.
    .litespeed.classic.litespeed.firenze.bianchi.pista.dean.colonel.plus.more.

  10. #10
    GATC
    Join Date
    Jul 2006
    Location
    south Puget Sound
    Posts
    6,618
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Below 1:1 rules!

  11. #11
    biked well well biked's Avatar
    Join Date
    Jul 2005
    Posts
    6,876
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Definitely sounds like a 110/74 BCD crankset. 24t will work with the 74 BCD, it's the smallest ring you can put on it. I think it will shift fine; it's usually a big jump between the middle and outer ring that can cause difficult front derailleur shifting on a triple, at least that's been my experience...........I run a 46/36/24 setup with my 110/74 BCD cranks on my old commuter/tourer/whatever-else bike, with an 11 x 32 cassette in the rear. A very nice range of gears IMHO-

  12. #12
    Junior Member
    Join Date
    Jul 2006
    Posts
    6
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The casette is an 11-32 I believe. I have no idea what less than a 1:1 ratio signifies, light in the loafers?

    I have to cross the Potomac on my commute (which I've done twice with panniers, 20 miles each way) and going uphill with a load can tax my noodly legs. I'm not one to pack lightly (for me at least) and I tend to go for distance and carrying capacity over speed.

    A wider range of gears seems appealing as my manliness prohibits me from dismounting and pushing the bike up a hill. I have noticed that I 'm getting better on hills, but I've been in situations where I've thought...."man, if this hill were any steeper, I wouldn't make it". I want to be able to do ALL THE HILLS.

    pondering it more, thanks for the input again, I really appreciate it

  13. #13
    Year-round cyclist
    Join Date
    Apr 2002
    Location
    Montréal (Québec)
    Posts
    3,023
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Bob N
    The casette is an 11-32 I believe. I have no idea what less than a 1:1 ratio signifies, light in the loafers?

    Right now, you have 48-38-28 in front and 11-32 in the back. Your lowest ratio is 28/32, so it's less than 1:1. If your smallest chainring was a 32, you would have 32 front / 32 rear, or 1:1. The smaller the (front/rear) ratio, the easier it is to pedal.
    Michel Gagnon
    Montréal (Québec, Canada)

  14. #14
    Senior Member
    Join Date
    Oct 2005
    Posts
    5,437
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cyccommute
    Go as low as your masculinity will allow Me, I'm a whimp. All my bikes have 22 or 20 with a 34 in the back but then I have these big rocks in my backyard that kinda force me to do that
    Wow, that is low gearing I guess I ride the road most of the time and when I do occassionally ride off road, its flat as a board (Miami, Fl.) so I've never had the need, really. More power to yah
    Il faut de l'audace, encore de l'audace, toujours de l'audace

    1980 3Rensho-- 1975 Raleigh Sprite 3spd
    1990s Raleigh M20 MTB--2007 Windsor Hour (track)
    1988 Ducati 750 F1

Posting Permissions

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