Gear inches

Gear inches

Postby Sprocket » Mon Aug 19, 2013 11:33 am

I've seen a bit of discussion on here about how low to take your gearing on a touring bike. My touring bike has a lowest gearing of ~22 gear inches and a highest of 119 GI. I have used it on a semi-loaded trip over rolling hills and my distinct feeling was that 22 wasn't nearly low enough - fine for that particular trip but anything with a bit more relief was going to be a struggle.

To stay within the capacity of the derailleurs sometimes you need to drop some of the top end gears in order to lower the low gears - so my question is: what is the lowest top gearing you would be happy with riding a loaded to semi-loaded touring bike with?
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by BNA » Mon Aug 19, 2013 11:56 am

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Re: Gear inches

Postby rkelsen » Mon Aug 19, 2013 11:56 am

I've not been touring, so you can probably take this with a grain of salt, but my favourite bike has a top gear of 100". I'm a big fan of low gears.

This is sufficient for me to hit mid 50s, albeit at a fairly high cadence (for me... ;) ). At a "comfy" cadence, it'll sit between 35 and 40kph all day (depending upon hills/wind).

Do you need to go faster than that? I'd have thought that 40kph would be a bit fast for touring, but I'm probably talking out my hat... :lol:

How difficult is it to push 119" with 20kg worth of panniers on the bike?

There are some experienced tourers on here. It'll be interesting to see their opinions.
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Re: Gear inches

Postby RonK » Mon Aug 19, 2013 12:09 pm

I'm using an 11-34 cassette with a 44/32/22 chainset. With 700C wheels this gives a low gear of 17.5 gear inches and a high gear of 108 gear inches.

108 gear inches at 90 rpm will propel me to 46.5kph. I could only ever reach that speed downhill, but rarely let the bike run that fast. It's difficult to pull up a loaded touring bike so unless I have a very clear view of the road well ahead I keep the speed at around 30kph max.

In reality, the best daily average speed I have ever acheived on a fully-loaded tour was around 22kph, with more typical averages around 17kph. So to drop even smaller than the 44T trekking outer chainring I'm using would make no difference, but this is probably the most common arrangement for trekking/MTB chainsets and it works very well.
Last edited by RonK on Mon Aug 19, 2013 12:21 pm, edited 2 times in total.
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Re: Gear inches

Postby WestcoastPete » Mon Aug 19, 2013 12:19 pm

I personally don't mind it being well under 100", somewhere about 90" is fine. I rarely use it, and if I run out, I must be cruising along, so I just grin and carry on.
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Re: Gear inches

Postby }SkOrPn--7 » Mon Aug 19, 2013 12:40 pm

Sprocket wrote:My touring bike has a lowest gearing of ~22 gear inches and a highest of 119 GI. ?


What size wheels are you running?
Chainrings? Cranks TRIPLE/DOUBLE ?
Cassette? 7-8-9-10 SPEED?

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Re: Gear inches

Postby Sprocket » Mon Aug 19, 2013 1:20 pm

}SkOrPn--7 wrote:What size wheels are you running?
Chainrings? Cranks TRIPLE/DOUBLE ?
Cassette? 7-8-9-10 SPEED?

Ricky


Hi Ricky - although preceded with my current bike configuration the question was more a hypothetical one. I spend a lot of time (too much time!) reading about bikes and different configurations. However reading is not the same as on the seat experience so I thought I'd poll the tourers often found lurking on these pages :)

For what it's worth - my bike is running the off-shelf gearing on the 2012 VWR. So:
Wheels = 700C
Chainrings = 48/36/26
Cassette = 9sp : 11->32
Front derailleur = Tiagra for triple
Rear derailleur = Deore LX

With only about 3,500km on it, there's still a heap of wear left in everything and as it's absolutely fine for commuting on and weekends away on rolling hills I'm waiting for things to wear out or the lure of a decent trip to justify tinkering with the current setup.

Has anyone used the SRAM Centro Via? It's 10-speed so I'm wondering whether that's robust enough for touring on? Or whether it's something to bear in mind for setting up a light-weight tourer with?

Selena
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Re: Gear inches

Postby il padrone » Mon Aug 19, 2013 6:39 pm

I've been riding a touring MTB with a top gear of 100" for about the past 25 years. I never feel that the bike is running out of gears on descents, simply because on such descents where the speed builds to that level the road is either so winding that I'm braking and coasting, or on steep straights at 55-60kmh with a load, getting into an aero 'tuck' will make much more impact on speed than any pedalling.

These days I ride a Rohloff IGH with a top gear of 96" and this gives me a very useful 17" bottom gear. I occasionally find the top gear spins out for me but at 55kmh it is a fairly minor thing - as I said a tuck will get me more speed, if I really want it.

Your 700C tourer has road derailleurs. They limit the gear choices and you would be much better swapping for a MTB crankset, but road derailleurs are then your problem, especially the front. 22" is really a bit too high if you intend to load up the bike for a camping tour and ride in hill country. I know plenty who do it, but they struggle on long climbs and are forced to walk unless they are real gear-grinders.
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Gear inches

Postby RonK » Mon Aug 19, 2013 6:46 pm

You didn't mention the VWR in the original post. .

For this bike with a road triple the simple solution is to fit a 24t inner chainring, as other owners have done.

It's a simple and inexpensive mod and won't alter your high gear.
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Re: Gear inches

Postby }SkOrPn--7 » Mon Aug 19, 2013 7:19 pm

Selena if you were to upgrade when things wear out and change to MTB cranks with a long cage derailleur you could have a 20-33-48 chainrings. Get a 11-36 cassette so your top end would still remain up around the 119GI but your low end could be as low as 15GI.

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Re: Gear inches

Postby il padrone » Mon Aug 19, 2013 8:41 pm

A bit of work with a gear calculator could be worthwhile. Something like this one

It's a bit rough copying it but this is one result for a 48/36/24 crankset and 11-32 cassette. 20" is a better low, but something like 17" or 18" would be even better.

gear inches

frontrear 11 12 13 15 17 20 23 28 32
48 118.9 109.0 100.6 87.2 77.0 65.4 56.9 46.7 40.9
36 89.2 81.8 75.5 65.4 57.7 49.1 42.7 35.0 30.7
24 59.5 54.5 50.3 43.6 38.5 32.7 28.4 23.4 20.4
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Re: Gear inches

Postby Sprocket » Mon Aug 19, 2013 9:25 pm

Thanks for all the interesting responses. I wasn't looking at specifically changing my gearing anytime soon. Was just curious as to what top end gearing people were happy running with. Looks like somewhere around the 100".
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Re: Gear inches

Postby WestcoastPete » Tue Aug 20, 2013 12:17 am

My current tourer is similarly geared to yours, but I changed the cassette to an 11-34 to achieve about a 20" low gear, and I used it. The other alternative, as has been suggested, is to swap out the granny cog to a 24t, which might be a better idea, but I had the 11-34 cassette and didn't have a 24t cog. Of course if you did both, you'd have lower gear still, without changing the higher gear, or swapping to a MTB crankset. You'd have to swap to one if you wanted to go any lower though.
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Re: Gear inches

Postby }SkOrPn--7 » Tue Aug 20, 2013 12:24 am

Selena I also run a 48T chainring like you do and my top end is 104GI but I spin out at anything above 46kph so that for me is plenty because most of the time on the downhill side of things I just coast but my bottom end is 11GI. Hauling a load on the flat and sitting on 25 is more than enough for me to cover ground each day.

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Re: Gear inches

Postby STC67 » Tue Aug 20, 2013 8:32 pm

I have done a bit of research on this and came up with a table of lowest gear inches for various bikes.


Model Chainring Cassette Gear Inches
Allegro Complete 30/40/52 11-34 23.8
Kona Sutra 30/39/50 11-32 25.3
Fuji Touring 30/39/50 11-34 23.8
Scott Hybrid 26/36/48 11-32 21.9
Surly LHT Complete 26/36/48 11-34 20.6
Vivente 24/36/46 11-32 20.3
Allegro Mod 26/36/46 12-36 19.5
Salsa Fargo 2 26/39 11-36 19.5
Ronk's Sabbath 22/32/44 11-34 17.5
Salsa Fargo 3 24/32/42 11-36 18.0
Trek 4300 MTB 26in 22/32/44 11-34 16.8

I am looking at the Allegro modification.

My current bike is the Trek MTB and there is no need to go lower as you won't ride fast enough to keep it upright.
The Scott Hybrid is the bike I toured on in France including riding Mont Ventoux (unloaded).

Feel free to add you bike to the bottom :D :D :D
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Re: Gear inches

Postby STC67 » Tue Aug 20, 2013 8:32 pm

Sorry
I'm having some trouble formatting the table. Looks good in the preview pane but won't keep the formatting.

Any ideas?
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Re: Gear inches

Postby Uncle Just » Tue Aug 20, 2013 10:48 pm

what is the lowest top gearing you would be happy with riding a loaded to semi-loaded touring bike with?


Anything around 90-104". Top end gearing is neither here nor there. Touring s/not be about high speeds anyway. I find I'm often in the middle ring and rarely get into big gears. Although if you had a roaring tailwind on flat terrain and wanted to do a big day you may wish for higher gears. On long descents it could come in handy but semi loaded touring bikes don't handle like a svelte road bike in the fast twisty stuff.
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Re: Gear inches

Postby rifraf » Fri Aug 23, 2013 1:31 am

I'm a fan of low gears and couldnt tell you what my high gear was like to pedal on the flat and I've only been in it once or twice on a very steep decline.
My Ogre has 700c wheels currently shod with 2.00 inch tires.
According to Sheldon http://www.sheldonbrown.com/gears/
I run 17.2 to 90.2 gear inches.
I prefer my Moultons 16.7 (from memory) GI but want to keep my Ogres Rohloff with recommended limits.
Not knocking anyone elses ride at all but no way would I be wanting to spin a minimum of 20 GI loaded with panniers as I'd be doing too much pushing and killing my knees.
My advice would be to think about your knees and keep your gearing as low as you find comfortable (I know some prefer higher gearing - more power to them).

Model Chainring Cassette Gear Inches
Allegro Complete 30/40/52 11-34 23.8
Kona Sutra 30/39/50 11-32 25.3
Fuji Touring 30/39/50 11-34 23.8
Scott Hybrid 26/36/48 11-32 21.9
Surly LHT Complete 26/36/48 11-34 20.6
Vivente 24/36/46 11-32 20.3
Allegro Mod 26/36/46 12-36 19.5
Salsa Fargo 2 26/39 11-36 19.5
Ronk's Sabbath 22/32/44 11-34 17.5
Salsa Fargo 3 24/32/42 11-36 18.0
Trek 4300 MTB 26in 22/32/44 11-34 16.8
Ogre (Rohloff) 29in 34/16 17.2
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Re: Gear inches

Postby Sprocket » Thu Aug 29, 2013 5:10 pm

I found this list:

■ No load: High-125″, Low-30″
■ Light load with or without sag wagon: High-115″, Low-28″
■ Medium load with or without sag wagon: High-110″,Low-25″
■ Heavy load without sag wagon: High-108″,Low-22″
■ Heavy load with camping: High-100″,Low-18″
■ Extra heavy load, expedition: High-100″,Low-16″
■ Heavy load, mountain bike: High-98″,Low-16″

Seems pretty reasonable to me.
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Re: Gear inches

Postby GregLR » Fri Aug 30, 2013 6:24 pm

Sprocket wrote:I found this list...Seems pretty reasonable to me.

Consistent with what others have been saying on this thread, I think that the high gears above 110" on that list for no load, light load, etc, would only be useful if you are a strong road racer type. While I have two road bikes with a high of 110" (53/13), my 5 other road bikes (including two touring bikes with 46 teeth big rings & a couple of others used for audax with a 50 big ring) have a high in the range 96-104" which I find ample - on those bikes I have to be riding at 60-65km/hour down a hill to require a higher gear and if I was going any faster I'd be freewheeling so bigger gears would be a waste.

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Re: Gear inches

Postby il padrone » Fri Aug 30, 2013 6:55 pm

Yes, I'd tend to agree pretty much with this. I know I am a spinner, but even on my road bike I only have a 100" top gear and I never find problems with spinning out of gears. I've certainly never used a 125" top gear in my life.... ever.

[edit] Checked again - the roadie's top gear is actually 104"
Last edited by il padrone on Fri Aug 30, 2013 10:02 pm, edited 1 time in total.
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Re: Gear inches

Postby Uncle Just » Fri Aug 30, 2013 7:47 pm

Well you've never drafted a truck then. Or gone hard down a mountain such as Hotham, Falls or Buffalo where in the right spots you can hit 85km/hr+. You will easily spin out on anything less than a 50/11 (122") even coming off Mt Dandenong to Montrose. You don't have to be a strong road racer to push a gear >120" down a mountain, but you must be a good, safe descender and use the brakes judiciously to do it well. Sprinting on the other hand....
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Re: Gear inches

Postby rifraf » Fri Aug 30, 2013 8:08 pm

Uncle Just wrote:Well you've never drafted a truck then. Or gone hard down a mountain such as Hotham, Falls or Buffalo where in the right spots you can hit 85km/hr+. You will easily spin out on anything less than a 50/11 (122") even coming off Mt Dandenong to Montrose. You don't have to be a strong road racer to push a gear >120" down a mountain, but you must be a good, safe descender and use the brakes judiciously to do it well. Sprinting on the other hand....

85kmph?
Safe descender?
Judicious braking?
:shock: :shock: :shock:
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Re: Gear inches

Postby rkelsen » Fri Aug 30, 2013 9:48 pm

Uncle Just wrote:... 85km/hr+...

On a touring bike?
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Re: Gear inches

Postby il padrone » Fri Aug 30, 2013 9:58 pm

Uncle Just wrote:Well you've never drafted a truck then.

Yes, done that often enough. But usually not on huge descents, rather on flattish roads with a tailwind, where the speed I 'd get to will be about 50-60. Descending a mountain behind a truck.... the truck will normally pull away at 90-100 on open roads. You won't hang on to him.

Uncle Just wrote:Or gone hard down a mountain such as Hotham, Falls or Buffalo where in the right spots you can hit 85km/hr+.

Yes, done that often enough as well. I've done 80-85 on occasions but usually on straight descents, with a good tail-wind or a tandem to draft. Winding descents you simply don't hit these sorts of speeds with safety IME

Uncle Just wrote:You will easily spin out on anything less than a 50/11 (122") even coming off Mt Dandenong to Montrose. You don't have to be a strong road racer to push a gear >120" down a mountain, but you must be a good, safe descender and use the brakes judiciously to do it well. Sprinting on the other hand....

A descent off the Dandies will not see me spin out, even with a 104" gear. To spin out I'd have to be doing over 60-65kmh and with all the curves and corners it is just not sustainable. To add another factor, on long straight descents I have always found that there is more speed increase to be gained by doing a tight aero tuck, rather than trying to pedal to boost the speed. Pedalling hard may add 2-3kmh, a tuck will give you an extra 5-10kmh. Just my experience.

These days I am a bit more conservative - generally happy to sit on 50-65kmh on a descent.
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Re: Gear inches

Postby Uncle Just » Sun Sep 01, 2013 9:16 am

The thread moved onto road bikes not touring bikes. I've not gone much over 70 down hill on a loaded tourer but a road bike can obviously attain higher speeds. This is not meant to be a pissing match but you can safely descend at high speed if you have developed the skills and have good tyres etc. In my youth like many, I rode motor bikes and the principles of cornering and reading the road apply to push bikes in many ways. I met an old work colleague at Mordi a few years back and he had just been to the TdF. He was over 60 and slow as on the climbs but because he had ridden and raced motorbikes in his early years he could descend faster than anyone on his tour group. I agree with Ip that as we age we tend to back off as we consider self preservation a higher priority. I still love a flowing fast descent but I don't bounce as well anymore. :wink:
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