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Gearing choices for 6 and 7 speeds?

Old 08-22-19, 07:30 AM
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Gearing choices for 6 and 7 speeds?

I'm looking to do some longer rides on a couple of 6 and 7 speed classics. Locally I have variety of flatland century's to start off with. After that the DC Randonneurs brevets are the closest events, and I assume more likely to include some hill climbing. Right now I have a 700c 12 speed to work with, road double up front, 6 speed freewheel in the back. Next year hopefully I'll have a 650b with a road triple up front and 7 speed cassette in the back. So I'm sort of looking for some gear inch theory to get me started. Thanks, Woody

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Old 08-22-19, 08:50 AM
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What's the crank; what chainrings does it have now, and what's the smallest you can fit?

The number of gears doesn't really matter; the important things are what's your lowest gear, and what's your highest gear.

The bike I rode on the Vermont 400k earlier this month has eleven distinct gears, ranging from 28 to 106 gear inches (1 x 11). The other bikes that I usually ride on brevets have similar gearing (2 x 9 on one, 2 x 10 on the other). With that gearing I can get up pretty much any hill, and I don't generally spin out on the descents.


Now and then I'll ride one on a three speed (49, 55, 86 inches, if I recall correctly) or a single speed bike (69 inches or so).

Obviously, when I ride the single speed my cadence varies a lot, from very fast on the descents to very slow when climbing, and occasionally walking the steep parts. The same goes for the three speed, but it's less extreme. As you add more gears, you can keep your cadence in an increasingly narrow range. That has some advantages, but I wouldn't overstate them.
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Old 08-22-19, 09:59 AM
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+1 on Rudi's thoughts.

When I started randonneuring, I stumbled across an article by Clifford Graves that passed along this advice: "Velocio himself advocated wide-ratio gears for touring: from 35 to 85. His normal riding gear was 72." So when I built up my rando bike ahead of PBP 2015, I followed suit: a 35-100" range, provided by a 50/38 crank, 13-28 cassette (7-speed ) on wheels roughly 26" in diameter. I've since changed it to a 48/34 crank and 13-26 cassette, but the overall range is about the same.

Jan Heine has some good thoughts here: https://janheine.wordpress.com/2012/...ur-chainrings/ I especially like this part: "Put the base gear [the gear I mostly use on flat roads when spinning along] in the middle of the rear freewheel/cassette, so that I can adjust to changes in speed and terrain with a simple shift or two in the rear." I've found that I prefer a 65-70" gear when riding at rando pace on flat ground, so the 48/19 in the middle of my cassette is perfect for that.

P.S. I like this website for dinking around with virtual gearing: Bicycle Gear Calculator

P.P.S. My first brevet season was on a different bike with a 52/42/32 triple crank and 14-28 6-speed freewheel. That worked pretty well, but I noticed after a few brevets that I never (well, hardly ever) left the middle ring, and that there was a lot of duplication, so I decided to pare it back.
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Old 08-22-19, 10:17 AM
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I pretty much agree with everything in posts 2 and 3. I run 6-7 speeds on my long distance bikes. There is no denying though that it is harder getting closely spaced gearing on a 6-7 speed than when running 9 or more in the rear which is why I think that a triple makes a lot of sense for older bikes.

Here is a good piece on the topic:

https://www.bikehugger.com/posts/the...compact-crank/

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Old 08-23-19, 04:37 AM
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My miyata 1000 had a 48/38/24 and a 14-34 freewheel and it worked well for loaded touring with the low gears,. For rando I can by with 27 gear-inch on the low end now but used to run a bit lower. I have no use for anything beyond the 112gi I have currently. For a 7 spped setup a 110/74 crankset gives a lot of choices for chainrings a d they are fairly easy to find.
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Old 08-24-19, 06:05 AM
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I got as far as getting my bike off the ceiling and onto the stand. It will be another week before I get to overhauling it for the the "Fall Campaign".Hopefully I will get out in the shop this week to get a tooth count on the present gearing. I did ride the bike on the small chain ring last year, predominately small to small and then usually only shifting down one or or two cogs for wind and terrain. That was mostly to keep my self from hurting my knees as I was upping my mileage pretty quickly. Mashing felt good in the moment, but I overdid it quickly. I'll be a month out of summer touring/fighting weight when I get back on the road so I plan on spinning for a while.

I found this training and ride log of a couple guys who took their classics across Pennsylvania the wrong way. I'm assuming their animals, and that I would gear down a bit. Scroll down to Bike specs.
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Old 08-24-19, 06:06 PM
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Originally Posted by rhm View Post
What's the crank; what chainrings does it have now, and what's the smallest you can fit?

The number of gears doesn't really matter; the important things are what's your lowest gear, and what's your highest gear.

The bike I rode on the Vermont 400k earlier this month has eleven distinct gears, ranging from 28 to 106 gear inches (1 x 11). The other bikes that I usually ride on brevets have similar gearing (2 x 9 on one, 2 x 10 on the other). With that gearing I can get up pretty much any hill, and I don't generally spin out on the descents.


Now and then I'll ride one on a three speed (49, 55, 86 inches, if I recall correctly) or a single speed bike (69 inches or so).

Obviously, when I ride the single speed my cadence varies a lot, from very fast on the descents to very slow when climbing, and occasionally walking the steep parts. The same goes for the three speed, but it's less extreme. As you add more gears, you can keep your cadence in an increasingly narrow range. That has some advantages, but I wouldn't overstate them.
The bike is set up with 52 and 40 130BCD Biopace chainrings and a 14-28 6 speed free wheel. I've a low mileage Suntour Superb 14-30 on top of the pile and couple more of unknown history buried in various spots but I kind of like indexing with the down tube shifters. Different 130BDC chainring's might be stolen from from other bikes. I could set up a 48 and 38 110bdc road triple as a double pretty easily. A triple as compact double would need a new bottom bracket. A triple would need a new bottom bracket and front derailleur? Race day is Oct 5......

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Old 08-26-19, 05:53 AM
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With a 110 mm bcd crank you can get down to 34t. With the 130 mm bcd the smallest one sees is 39t though I have heard 38t is an option.

There are some square taper double cranks that allow considerably smaller rings.
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Old 08-26-19, 06:07 AM
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Originally Posted by rhm View Post
There are some square taper double cranks that allow considerably smaller rings.
I picked up an FSA 48/32 crank and they are also available in 46/30 for under a 100$. They are black 4 arm modern looking things but could be made nicer if you wanted to deanodize and polish.
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Old 08-26-19, 07:03 AM
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The two options I'm considering based on time, money and parts bin are to buy a 38t 130bdc chainring and scrounge a round 52t from another bike. that would give a range of 36.6 to 100 gear inches.
I have a 50t chairing but with the freewheel (14-28) The 50t and 38t set up seems to have a lot of redundancy's. If I can scrounge a 48t ,that would be an option.

I have a 110BDC RSX road triple crank and a set of 46t and 36t chain rings. This would give a gear range of 34.6 to 88.5. I am assuming that if I do not use a triple cog I can use the same bottom bracket.
The gear calculator makes a 48t and 34t looks pretty good with a range of 32.7 to 92.4. If I can keep my bottom bracket with the RSX crank this seems like a good set up, but I will be throwing money at a theory...

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Old 08-26-19, 10:09 AM
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Redundancy is annoying when looking at the numbers on the screen, but when I'm actually riding the bike I pay no attention to it at all.

My suggestion would be to put the bike together with the best setup that can be achieved with parts on hand, and give it a try. It may not be perfect, but you'll get a much better idea of your needs than you can get in the abstract. If you don't have a gear low enough for the hills, you will be forced to go up them faster than you like, but it probably won't kill you; if you think the end is near, get off and walk. I mean, if it came to it, you could ride 200 km on a fixed gear (trust me!).
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Old 08-26-19, 10:45 AM
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I can admit to staring at the gear calculator a bit to much. A couple of the combinations had an exact match at around 70 gear inches. That seemed like a good spot to be able to shift between chain rings with out changing cadence. My touring bike is geared 46, 36+26. Day 3, after 150 mile of melted tar heatwave, I was riding the granny gear. So I think the a 46+36 would be a safe choice. Present bike go's back on the road next week, one way or another. This week training starts with pulling a 50 pound kid in a trailer with a single speed...

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