# How do you choose the right gearing for your fixed?



## edindave (13 Aug 2013)

Do you base it on average cadence for your usual route?
Or just what your legs can take?

I was running 48x16, and my average cadence was in the low 70s.
I swapped the 16t for an 18t and, at roughly the same overall average speed on my normal route, my average cadence went up to about 85. 

So on the surface this seems like it should probably a better gear to be running. Or am I wrong? 
It certainly feels a bit different, lighter on the legs.

It just got me wondering how others decide on a gear.


----------



## Profpointy (13 Aug 2013)

Another thought is crank length. Despite being reasonably tall 6'. i've got 165mm cranks, running a lowish gear 44 x 17 if I recall correctly (hilly city bristol) and I'm not mega fit, and far from young. Spinning quite fast on shortish cranks seems to work for me


----------



## dave r (13 Aug 2013)

It tends to be trial and error, My Pearson came with 48x18 70 inch gear and 170 cranks, the 70 inch gear was fine on the commute but too high for long lumpier rides, I changed the chainring to 46, about a 68 inch gear which was better, and eventually changed the chainset to give me 165 cranks, which suited me better and settled on 44x18 65 inch gear and ran that for several years, last spring I changed the tires from 700cx28 to 700cx25 and the 65 felt a bit under geared and I went up to 68 again.


----------



## GrumpyGregry (13 Aug 2013)

It is determined by the maximum cadence I'm prepared to run on the biggest downhill on my commute home balanced by the longest gear I can honk uphill in on the chevrons I hit coming in to work (different road). A shorter gear makes the latter easier and the former less pleasant. A longer gear eases the former but makes the latter harder. But then your legs soon adapt.

70" or thereabouts works for me. On 175mm cranks. I'm shallow but I prefer the look of a smaller cog and a smaller chainring.


----------



## edindave (13 Aug 2013)

Must admit I hadn't thought about crank length. Mine are 165mm and I'm reasonably short at 168cm (5'6").

Interesting that the change of tyres led you to up the gearing @dave r - wouldn't have thought that would make much of a difference. In any case I'm running 23mm Contis.

I've noticed as well that I can at least use my legs a bit more for braking (or rather slowing) with the 18t cog. No skid-stops on the cards though!


----------



## edindave (14 Aug 2013)

GregCollins said:


> It is determined by the maximum cadence I'm prepared to run on the biggest downhill on my commute home balanced by the longest gear I can honk uphill in on the chevrons I hit coming in to work (different road). A shorter gear makes the latter easier and the former less pleasant. A longer gear eases the former but makes the latter harder. But then your legs soon adapt.
> 
> 70" or thereabouts works for me. On 175mm cranks. I'm shallow but I prefer the look of a smaller cog and a smaller chainring.


 
I was reaching about 120rpm yesterday and today quite comfortably. I'm sure that will increase - I do spin classes in winter so know I can spin faster, but am not used to doing anything higher than that in real life.


----------



## HLaB (14 Aug 2013)

My bike came with a 44x16t and I guess I've just adapted to it, if I couldn't I guess I try something different when it wore out.


----------



## GrumpyGregry (14 Aug 2013)

edindave said:


> I was reaching about 120rpm yesterday and today quite comfortably. I'm sure that will increase - I do spin classes in winter so know I can spin faster, but am not used to doing anything higher than that in real life.


What I can do on a spin bike, 'bolted' to the floor and stationary, and what I'm prepared do on a bumpy Sussex B road, in a crosswind, whilst being passed, despite the oncoming traffic, on the double-whites by a stressed mother in a 4x4 are utterly unrelated.

I can only work out my rpm post-hoc. And then only if I have the gps on the bike to catch the speed to then do the maths.


----------



## dave r (14 Aug 2013)

edindave said:


> Must admit I hadn't thought about crank length. Mine are 165mm and I'm reasonably short at 168cm (5'6").
> 
> Interesting that the change of tyres led you to up the gearing @dave r - wouldn't have thought that would make much of a difference. In any case I'm running 23mm Contis.
> 
> I've noticed as well that I can at least use my legs a bit more for braking (or rather slowing) with the 18t cog. No skid-stops on the cards though!


 
700cx28 is about the max for a Pearson with mudguards, I'd put new wheels on the Pearson just before Christmas and was having minor problems with clearance, narrower rims on the new wheels, that was what led to the change to 25's, feeling a difference in the gear was a surprise, I didn't think it would make a difference.


----------



## Norry1 (14 Aug 2013)

How exactly do you calculate gear inches? If I have normal 700 wheels, is it just 700/25.4 (to get inches) x 42/16 (gearing) ???


----------



## GrumpyGregry (14 Aug 2013)

2597125 said:


> To that I would add consideration of the number of stops and starts encountered. I used an 80ish gear for a while but spent more time cranking it up to speed or slowing to a stop than I did cruising it. A 74" gear proved quicker overall.


I'd concur. I've found that stop/starting in a longer gear that you then have little time to spin in is counter-productive.


----------



## GrumpyGregry (14 Aug 2013)

Norry1 said:


> How exactly do you calculate gear inches? If I have normal 700 wheels, is it just 700/25.4 (to get inches) x 42/16 (gearing) ???


I ask someone else to work it out for me.


----------



## MrGrumpy (14 Aug 2013)

Started on a 42 x 16 on my original langster, then when the frame broke, the new frame under warranty came with new cranks and a 48t front ring. Did not find it much different, just meant I was not spinning like a looney on my commute. I have now since went to 17t cog and it feels a wee bit better on the hills. Oh could still lock the rear wheel on the 48x16 just took a bit more effort.


----------



## Domeo (14 Aug 2013)

GregCollins said:


> I'm shallow but I prefer the look of a smaller cog and a smaller chainring.


 
I agree with the sentiment. I run 46X14.

edited: should have put 42X14


----------



## derrick (14 Aug 2013)

It's what suits you, i have a flattish 3.5 mile comutte and have a 48x14, a bit slow on getaways but once i get it spinning it's fine.


----------



## GrumpyGregry (14 Aug 2013)

2597993 said:


> Bigger = Smoother and quieter.


They do say that. But I've not noticed a lack of smooth and any particular noise thus far. I accept smaller probably means more chain/cog/chainring wear though. Small price to pay. In my ears eyes.


----------



## dave r (14 Aug 2013)

2597126 said:


> Nicer tyres?


 
Same make of tyre just different width

http://www.allterraincycles.co.uk/.Bontrager-Race-Lite-Hardcase-Road-Tyre_119612.htm


----------



## dave r (14 Aug 2013)

Norry1 said:


> How exactly do you calculate gear inches? If I have normal 700 wheels, is it just 700/25.4 (to get inches) x 42/16 (gearing) ???


 
I use this calculator, I launch it outside the browser

http://software.bareknucklebrigade.com/


----------



## Boris Bajic (14 Aug 2013)

It is a compromise.

Most seem to be between 65" and 69".

I've variously run 65" up to 72" on my fixed steel Claud Butler. All have been perfect on one stretch of tarmac and laughably wrong on another.

I've always found hills for which I'm geared too high and descents for which I'm geared too low. But it's always fun finding out.

I once saw a documentary programme about a burglar who not only tested to destruction the furniture in the house she entered, but ate all the porridge too.

Although from a moral standpoint her behaviour was dispicable, we can all learn from her when it comes to setting gear for a fixie.

Many of us will try all three before deciding that Baby Bear's porridge is just right.


----------



## jazzkat (15 Aug 2013)

Wot he said ^
I upped my gearing by one tooth at the back to make 70inches, so I could go a bit faster on the flat. I'm still spinning like a washing machine at 22/23mph but if I went any higher gearing wise I'd not get up some of the hills around here. Going downhill is a bit of a moot point to me as most downhills are pretty steep here and so I'm on the brakes most of the time so I don't end up going too fast
I might try going up another tooth as I get a bit stronger, but there will come a point where my knees will say enough's enough and 22/23 is pretty respectable I suppose!


----------



## Alien8 (15 Aug 2013)

What about big(ger) rings and flex?

My Bowery came with a 130BCD crank but due to this I may take the opportunity to move to 144BCD.

Any thoughts (I'm currently running 46T/15T)?


----------



## GrumpyGregry (15 Aug 2013)

2599126 said:


> 53x19


But you aren't shallow.


----------



## ayceejay (15 Aug 2013)

When riding fixed the usual length for crank arms is 165 to avoid toes overlapping front wheel and hitting the ground when cornering. Since changing a sprocket is way easier than changing a chain ring I would say stick with either 48 or 46 and play around with cogs. If you have ridden a geared bike on the same route and there is one combination in there where you feel most comfortable use the chart above to find out its gear inches and emulate this on your fixed.


----------



## GrumpyGregry (15 Aug 2013)

ayceejay said:


> When riding fixed the usual length for crank arms is 165 to avoid toes overlapping front wheel and hitting the ground when cornering. Since changing a sprocket is way easier than changing a chain ring I would say stick with either 48 or 46 and play around with cogs. If you have ridden a geared bike on the same route and there is one combination in there where you feel most comfortable use the chart above to find out its gear inches and emulate this on your fixed.


Surely toeverlap is more a factor of geometry than crank length? I've always thought short cranks were there to ease the problem of pedal strike.


----------



## Rohloff_Brompton_Rider (15 Aug 2013)

GregCollins said:


> Surely toeverlap is more a factor of geometry than crank length? I've always thought short cranks were there to ease the problem of pedal strike.


Me too, but also to allow faster spinning down hills.


----------



## GrumpyGregry (15 Aug 2013)

bromptonfb said:


> Me too, but also to allow faster spinning down hills.


Explain the maths of that to me please. The number of rpm is the same regardless of crank length for a given speed no? Sure my feet might have less distance to travel as the diameter of the circle is less on 165's but would it make a meaningful difference?

Maybe it is only me but footspeed has never been the limiting factor.


----------



## Rohloff_Brompton_Rider (15 Aug 2013)

GregCollins said:


> Explain the maths of that to me please. The number of rpm is the same regardless of crank length for a given speed no? Sure my feet might have less distance to travel as the diameter of the circle is less on 165's but would it make a meaningful difference?
> 
> Maybe it is only me but footspeed has never been the limiting factor.


Less distance travelled equals more spin.


----------



## Rohloff_Brompton_Rider (15 Aug 2013)

bromptonfb said:


> Less distance travelled equals more spin.


Take it to the extremes, could you spin as fast with 200mm cranks as you could on 150 cranks?


----------



## ayceejay (15 Aug 2013)

I think I am probably being old fashioned in thinking that fixed wheel = track geometry closer clearances and shorter wheelbase.
The only problem I ever had was striking a curb which wasn't fun.


----------



## yello (15 Aug 2013)

My choice is decided simply by the terrain I ride in.

My bike came equipped with a 48t chainring and an 18/20 flip-flop hub. 18 was too much like hard work around here so I ride the 20. Not too difficult a decision really.

I have brakes for the occasions that I need to control spinout. I'm comfortable (albeit bouncing) up to around 150.


----------



## smutchin (15 Aug 2013)

Boris Bajic said:


> Most seem to be between 65" and 69".


 
That sounds about right. When I first started riding fixed, I was riding about 69" and got on fine with it, now my fixed is geared at around 65" and that's fine too.

I think I chose my current gearing because it gives me an overall average cadence of around 90rpm (albeit peaking at a slightly teeth-jangling ~190rpm on certain descents).

Not that there's a huge difference in the way it feels, an inch or two either way, and I really don't think it's worth obsessing over.


----------



## fossyant (15 Aug 2013)

I started on 70" with a 74" on the other side. Very soon flipped the hub to 74". Ran that for a couple of years then upped to 77" that gives me a more comfortable cruising speed.


----------



## smutchin (15 Aug 2013)

Boris Bajic said:


> For me, that feels impossibly fast already - and it scares the crap out of me.
> 
> At that speed, I'm not pushing, I'm just letting my legs spin away as fastas I can. 170-ish is all I've managed.


 
When I first started riding fixed (only a few years ago), 150rpm was scary. I've got used to spinning a lot faster but 190rpm is still pretty terrifying - there's one particular local descent where I can hit that speed without much difficulty, but it's mercifully short. I don't think I'd like to be spinning that fast for more than very brief spells at a time. I'd like to break the 200rpm barrier one day though - I've been close a few times.




> 1. Do people actually push at those sort of cadences? I mean actually gain speed through leg power rather than gradient?


 
Maybe some people can but not me!



> 2. I reach higher cadences now than before I put the fixopholous together. Will I gradually be able to creep up towards 190-ish on descents if I keep plugging away at it? These are descents where even my modest levels of skill and courage bring 45mph+ with gears. It's my footspeed that keeps the speed down on fixed.


 
I've mostly learned to just go with it. Riding a short fixed gear has had other knock-on effects on my cycling. On the flat, my "cruising" cadence on fixed is now around 120rpm, and I find my pedalling style on gears has changed so I now naturally prefer a shorter gear and higher cadence.


----------



## dave r (15 Aug 2013)

GregCollins said:


> Explain the maths of that to me please. The number of rpm is the same regardless of crank length for a given speed no? Sure my feet might have less distance to travel as the diameter of the circle is less on 165's but would it make a meaningful difference?
> 
> Maybe it is only me but footspeed has never been the limiting factor.


 
For me 165 cranks are more comfortable at high cadence, but I am a short arse.


----------



## dave r (15 Aug 2013)

Boris Bajic said:


> 1. Do people actually push at those sort of cadences? I mean actually gain speed through leg power rather than gradient?


 
I'm still pushing the pedals round at 150rpm+


----------



## edindave (15 Aug 2013)

Crikey. I have been maxing out at about 120rpm on the flat so far. Some work to be done!


----------



## smutchin (15 Aug 2013)

GregCollins said:


> The number of rpm is the same regardless of crank length for a given speed no?



Yes, though strictly speaking, the same combination of chainring and sprocket but different crank length = a different gear. (A crank being a type of lever, a longer crank gives a lower gear.)

Traditional "gear inches" ignore this but Sheldon Brown's "gain ratio" method factors crank length into calculating gear size, and takes into account the actual distance travelled by the pedals.


----------



## Sharky (29 Aug 2013)

Norry1 said:


> How exactly do you calculate gear inches? If I have normal 700 wheels, is it just 700/25.4 (to get inches) x 42/16 (gearing) ???


 
( Wheel size*Chainring teeth)/Sprocket teeth e.g. 27*54/18 = 81"

This equates to riding a penny farthing with a diameter of 81"

Used to be simple when wheels were either 27" or 26", but with metric and different tyre sizes, you need to use a table - look at the Sheldon Brown website - http://sheldonbrown.com/gain.html - also discusses Gain ratios which bring in the difference cranks make.

Cheers Keith


----------



## rb58 (7 Sep 2013)

Boris Bajic said:


> I
> 
> 1. Do people actually push at those sort of cadences? I mean actually gain speed through leg power rather than gradient?
> 
> .


I try to. Allows me to feel more in control than when I'm just letting momentum carry my legs round. I max out at about 165/170 rpm these days, although that number has crept up over time.


----------

