Author Topic: I need lower gears!  (Read 1809 times)

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Offline denver_whitest185

I need lower gears!
« on: May 03, 2010, 12:29:14 pm »
so, ive been training for a tour and im handling the distances well (50-60 mile training rides) but i can't seem to tackle this one hilly area near my place that has 8-10% grades (maybe even steeper). i have a 80's centurion Lemans with a triple front (48,38,32) and a 6-speed rear (14-28). i think if i could get a larger rear gearing or a small front chainring so i could get a 1:1 ratio maybe even a 28 on the front and a 30 on the back, i think i would be fine.

Does anyone know where i could get these from, or am i asking for something that doesn't exist?

Offline rvklassen

Re: I need lower gears!
« Reply #1 on: May 03, 2010, 12:47:34 pm »
Given the vintage of your ride, you'll find it challenging to do much with the freewheel.  Harris does have a 13 - 15 - 18 - 21 - 24 - 32  and a 14 - 15 - 18 - 21 - 24 - 34.  Google Sheldon Brown.

On the front, you can replace just the 32 with a 28, 26, or possibly a 24.  Depends on what you're using to shift the front. 

The other thing to be aware of is you may have to replace the RD in order to have one with a longer cage.  If you put on a larger cog on the back you will need more chain.  If you have more chain, you'll need an RD capable of taking up that much slack.  If you put a smaller chainring on the front, you don't need more chain, but you still need an RD capable of taking up more slack.

Offline paddleboy17

Re: I need lower gears!
« Reply #2 on: May 03, 2010, 12:59:12 pm »
If you are able to find a replacement inner chain ring that small, you may find that the bike does not shift well.  You won't know until you try it.

A good back up plan would be to replace the front crank.  A Shimano LX, SLX, or Deore mountain bike crank would be a pretty good crank for touring.  Your front deraileur would have to be moved down to accommodate the smaller bolt circle of the crank.  Also, you may have to replace the front deraileur if it won't play nice with the new crank.  The chord of the deraileur has to match the bolt circle of the crank, but some deraileurs are more forgiving than others.  I have an Ultegra front deraileur working just fine with an XT crank on one of my bikes.
Danno

Offline whittierider

Re: I need lower gears!
« Reply #3 on: May 03, 2010, 01:46:16 pm »
5-speed and 6-speed freewheels are being made even today.  See these at loosescrews.com , especially the 14-34 Megarange which is kind of like a 7-speed 14-34 that's missing 2nd gear, so to speak, so you can have the 34 "bail-out" gear without losing the tighter spacing between the higher gears.



Our tandem has an 18-tooth difference between the tiny and middle rings, and it shifts fine and does not drop the chain.  However what is commonly missed in the setup is that to make it work well, the front derailleur cage needs to be rotated very slightly farther out at the rear, instead of perfectly parallel to the chainrings.  The common 74mm BCD allows you to go down to 24 teeth.

Offline Tourista829

Re: I need lower gears!
« Reply #4 on: May 03, 2010, 11:24:12 pm »
I have an older Santana Tandem and was looking to change my gearing. I had the correct length dérailleur but had two problems. The rear was a freewheel, not a cassette. (Since you have a circa 1980's bike, you most likely have a freewheel) I had a tough time finding the range I wanted, which was an 11-34. Someone told me about Phil Wood and I spoke to him. He had one in a freewheel. (I was looking for an 11t high gear, my original freewheel was 14-28)

For my front crank, I was able to go down to a 24t front gear. (my original was 28-39-54) The new set up was so low, that I had to keep the cadence above 90rpm, while climbing, to keep the bike upright. For your front crank, if you can find a hole pattern that matches, if possible, I would switch your middle ring from a 38 to 36 and your smallest "granny gear" from a 32 to a 24 if possible. If the holes do not match, you may have to replace the entire crank. With a 24-36-48 in front and 11-34 in the rear, you will be able to climb anything. With almost a 100" spread you should be good on the low and high ends.

Offline whittierider

Re: I need lower gears!
« Reply #5 on: May 03, 2010, 11:59:17 pm »
Quote
I would switch your middle ring from a 38 to 36 and
If it's a standard road triple, the BCD for the middle and outer rings is 130mm, and the smallest you can go in that size is 38 teeth.  Below that, the bolts would interfere with the chain.

When you're going downhill or have such a tailwind that you'd use an 11T cog however, you'll get there plenty fast even if you just coast; so especially if you only have six cogs, it would be desirable to forgo the smallest ones in order to get closer gear spacing in the range you ride more.  54/11, with 700c wheels, is a gear I would not use below 42mph.  48/11 with the same wheels is a gear I would not use below 37mph (same as my 52/12).  Our tandem came with a 52/11 high gear, and although we had it over 50mph a few times, we were not spun out.  There really is no need to have a gear that high.  I replaced it with a 13-34.

Offline briwasson

Re: I need lower gears!
« Reply #6 on: May 04, 2010, 10:22:44 am »
>"If it's a standard road triple, the BCD for the middle and outer rings is 130mm, and the smallest you can go in that size is 38 teeth.  Below that, the bolts would interfere with the chain."

A standard road triple back in the '80s had 110/74 BCD, as another poster noted. With a 74BCD you can go down to a 24-tooth chainring.

If looking to upgrade the rear, I'd highly suggest moving up to at least a 7-speed cassette hub from your 6-speed freewheel. Cassette freehubs tend to be stronger due to the way the axle is supported, a factor when under touring loads. Plus, it's easier to remove a cassette even when it's been subjected to a lot of torque, like it would be under when climbing with a load. You could either pick up a used wheel that takes 7-speed cassettes, which is likely to be cheap since they aren't in much demand, or get a wheel with a hub that will take a 7-8-9-10 speed cassette to allow yourself upgrade options down the road. You can run a 7-speed cassette on an 8-9-10 speed hub by using a spacer.

If upgrading the wheel, you'll likely also need to change the spacing in your rear dropouts. You probably have 126mm spacing back there, and modern hubs either use 130mm (standard road spacing) or 135mm (MTB spacing, also often used in touring/hybrid wheels). If you have a steel frame, it's no a big deal to move from 126mm to 130mm. You can either have this done professionally by a bike shop or you can just spread the dropouts by hand each time you put the wheel on/off.

Offline velo

Re: I need lower gears!
« Reply #7 on: May 08, 2010, 10:28:48 pm »
The suggestion of a mountain crank is a good one. A 24:34:44 gearing combo will probably work nicely for most touring needs. You can also just try to swap a smaller inner ring onto your current crank. Chain rings are cheap (under $15) so it'd a worth a try.