Gear inches? Good and Bad
DonDaddyD
Posts: 12,689
OK another silly question but with bike repairs and the purchasing of intricate parts comes a desire to understand.
So, I recently got a new cassette a 8speed 12 - 23. My big chain ring is a 53.
What is the average (so not Lit's) gear inch a person would normally commute in.
Right now:
I push off in my second cog a 53-21t (66.3inch),
Move up to the 3rd to cruise a 53-19t (73.3)
Then start my sprinting/riding fast in my 53-17t (81.9inch) - I certainly ain't spinning is this gear.
Is around 80inches the norm or the 'expected inch' for the average commuter on a roadbike?
Personally I think I need to go by MPH, but the holding thingy for my computer broke during transit of bike to the bike shop prior to repair :x
So, I recently got a new cassette a 8speed 12 - 23. My big chain ring is a 53.
What is the average (so not Lit's) gear inch a person would normally commute in.
Right now:
I push off in my second cog a 53-21t (66.3inch),
Move up to the 3rd to cruise a 53-19t (73.3)
Then start my sprinting/riding fast in my 53-17t (81.9inch) - I certainly ain't spinning is this gear.
Is around 80inches the norm or the 'expected inch' for the average commuter on a roadbike?
Personally I think I need to go by MPH, but the holding thingy for my computer broke during transit of bike to the bike shop prior to repair :x
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A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game
A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game
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A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game
It Depends.
The gear you're in links your cadence to your road speed. Cadence is an individual thing, though it's sometimes claimed or observed that experienced riders tend to pedal faster.
eg: POBSO riding Shopper 50-60rpm, leisure cyclist 60-70rpm, tourist/commuter 80-90rpm, fast roadie 100+ rpm.
This is the sort of rough rule of thumb that doesn't bear close scrutiny!!
Obviously road speed varies, too- that's why we have gears (well, some of us).
So, if you like to spin, say, 90rpm and commute on flattish roads at, say, 18mph, you'd typically want a gear of about 67" . A less spinny rider, cruising downhill at 20mph might prefer 75rpm, and would then want a gear a little over 90".
Is 80" the norm? I dunno. How normal are you, anyway :-). It seems a bit high to me, but bikes are often geared high- inexperienced riders like a low cadence and experienced riders like to go fast... Maybe I'm a bit wierd, cos I prefer to cruise at a fairly high cadence but I'm not fit enough to sustain 20+ mph.
Cheers,
W.
Hang on a mo - are you saying you start on your big chainwheel on your second biggest cassette sprocket? Surely that's going to be a pretty bad chainline which might explain some of your wear problems. What do you use the smaller chainwheel for?
I'm not familiar with bikes with 2 chainwheels as my tourer and mtb both have three - normally I start in the middle cog and middle sprocket so expect to move between middle and big chainwheels as a matter of course. I'd assume the same would apply on a bike with 2 chainwheels.
When you say chainwheel I take it you mean chain-ring. In that case yes, yes and yes. I recently got a new 8speed cassette a 12-23 (I didn't have it before) my big ring is a 53. I didn't realise that my gear inches would be so high before I've even gotten into my fourth cog. With hindsight I probably would have gone with a 12 - 25.
I'm running a triple and though loathe as I am to do so, I may use the middle ring.
A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game
My philosophy towards the fixie and the GI I run is I want a hard gear on hills etc, to build leg strength, and something I can spin out downhill to work on leg speed, and a bit of resistance on the flat to encourage me to try and spin. 80 GI works for me at the moment, but I suspect that will change given time.
Ultimately whatever works for you is fine, there's no hard and fast rule
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Why are you reluctant to use the middle ring?
There's no point having a 21 speed powertrain and restricting yourself to six gears, especially if the lower ones are inefficient and causing increased wear.
There are various ways to set up your gear ratios, but with modern multi-speed setups, I think it's normal to have less overlap than in the past. You should be able to set up a close-ratio cassette and triple so that you can do most of your riding on the middle ring, instead of having to double-shift frequently. Move to the big ring for descending/tailwinds/SCR-sprints and use the small one for climbing & headwinds.
You should find you can build up to a "better" cadence, get a quieter, more efficient chainline and reduce wear by doing so.
If you prefer not to be seen without the chain on the biggest ring you have, then get a double, use a shorter BB axle and get your chainline sorted. If you bring the outer ring into line with the middle of your cluster you can use the whole range of sprockets with the big ring in normal riding, and just use the inner 'ring as a bail out gear with the largest few sprockets for hills....
Cheers,
W.
Worse with a triple then - I remember when I got my Dawes (about 1990 - if you can remember that far back
I think if you have gears, you should use them. I can't imagine your small chain ring is much use in London but the others should be. I tend to regard the middle ring as flat cruise default and the big ring as downhill and fast cruise default. I have no objection to using the middle on the flat or slight uphills - especially if there are headwinds. If you only use the big one, you might as well ditch the front mech entirely!
In traffic I tend to stick to the 50T there is little point flicking between chainrings in traffic and london at least central, flicking between the chainrings I find is bit pointless.
once out of town yes use those rings. in traffic I tend not to or you spend your life clicking though gears.
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Sorry DDD but you're asking impossible questions today. As your last one boiled down to numerous factors including quality/cost/maintenance, so this boils down to preference adn to some extent, terrain. I run a 50x16 on my SS. My boss runs a 48x18. Run what ever gear feels right to you. If my commute involved hills i wouldn't run 50x16...
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The answer to the question 'what's the average?' would be 'the middle one'. Cadence though is usually between 80 & 95.
It took some time to convince my boys that they should change gear when they want to - there are no rules about what ratio suits any specific road condition - too many variables, including the boys themselves.
<facetious mode>What gear do I commute in? Warm top now and a Ron Hill leggings from tomorrow...</facetious mode>
Correct me if I'm wrong, but surely gear inches are a whole lot more then saying 48x16 etc... You and your boss could be running the same gear inches despite one being 50x16 and the other 48x18. But I do know what you mean
My SS MTB runs about 56", I calculated 56" on my 27 geared MTB, but they both felt very different. Possibly lower weight, straight chainline and crank lengths might have had a big factor in that
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Hmm, only a little bit more: crank length makes a little difference and wheel size (including tyre) a bit more...
50x16 is around 84" whereas 48x18 is nearer 72... That's a pretty big difference.
Well, yes... that's part of the point of an SS/FG, isn't it? But the gear ratio is the same, even if it feels different because of the differences between the bikes.
It's easier to push a 70" gear on my fixie than on my tourer, but it's still a 70" gear... and my cadence will be the same, if I'm doing the same speed.
Cheers,
W.
You made a large assumption there though. You assumed the same wheel size and tyre width, which isn't necessarily true.
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Yes, sometimes there is a need to change to middle and then drop down on the rear to compensate but that is only inconvenient on downtubes.
However if you need big-big on the flat you aren't strong enough to be in the big ring.
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I think Buns just assumed I'd taken that into account, which I had.
Can I suggest that this this Website for some of you.
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I run my commuter with a gear ratio of 44:16 (2.75) which is not far off your 53:19 (2.78)
Have you taken into account wheel and tyre size difference between road and MTBs?
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Hah! pedant!
[ patronising tone ]
Yes, I did. Well spotted. Did you notice which wheel size I'd assumed?
Now, is it a reasonable (or large?) assumption?
Let's assume that the boss has a 29er with 1.9" tyres (I think this is unlikely). His 48x18 will then give him a 74.3" gear. Let's further assume that BuckledRims is running Inch & a quarter slicks on 26" rims (more plausible), he'd then have a 76.5" gear.
The difference would then be quite a bit smaller, and if they had radically different crank lengths, then the effective ratio might get pretty close.... but they still wouldn't be running the same "gear inches"....
[/patronising tone]
I think the point is sound, though I'll happily concede that if each of them happened to have the most extreme wheel+tyre sizes available, it's conceivable that they might end up with the same gear.... :-)
Cheers,
W.
Umm, no: sorry: Assuming a nominal 26" wheel, the 22:32 would be 22/32 * 26 = 18" (eek!) whereas the 32:22 would be 32/22 * 26 = 38".
Yes, not far off, assuming the same wheel size.
Cheers,
W.
err, no.
22:32 = 36.2 inches
32:22 = 17.1 inches
assuming a 26" wheel with 1.5" tyre, and 170mm cranks for both calculations
EDIT: beaten to it by poster above.