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Old 09-07-06, 05:58 PM   #1
Bob N
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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
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Old 09-07-06, 06:06 PM   #2
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Your crank arms are mostly likely 110/74 BCD. You can mount a 26 ring but I'm not so sure about 24...
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Old 09-07-06, 06:33 PM   #3
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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.
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Old 09-07-06, 08:05 PM   #4
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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 08:11 PM.
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Old 09-07-06, 09:27 PM   #5
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thanks folks, I'll do some more investigating.
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Old 09-08-06, 10:04 AM   #6
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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?
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Old 09-08-06, 12:04 PM   #7
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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
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Old 09-08-06, 12:07 PM   #8
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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
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Old 09-08-06, 12:10 PM   #9
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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.....
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Old 09-08-06, 12:35 PM   #10
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Below 1:1 rules!
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Old 09-08-06, 03:27 PM   #11
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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-
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Old 09-08-06, 05:55 PM   #12
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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
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Old 09-08-06, 09:26 PM   #13
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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.
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Old 09-09-06, 12:40 PM   #14
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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
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