Gearing

Stronglight 42t, 135mm bcd campag
Depends on your cranks though..

stock cranks off a bianchi pista, looks about right. bolts are 135mm, 5 bolts. Unbeliveable how many different things you gotta look out for on bikes, god forbid i ever have to worry about weird threads!

don't forget the other set of numbers too... 3/32 or 1/8

I'd change the cog, more teeth = less wear. I used to ride 48/18, pretty sweet.

Mr Conan,

There is a difference between changing a chainring and a sproket. I dont know the sums but the chainring controls the leverage (torque) which is not greatly affected by the sprocket until you get down to track sproket type sizes (14t). Using a small chainring (39t or less) is good for low cadence pedalling. Attempting to spin such a gear is difficult because you need a lot of muscle tension to keep it smooth and comfortable. Using a large chainring (above about 41t) promotes a spinning cadence, because the leverage is low and resitance is more even around the pedal circle. A 46x18 gear and a 36x14 are both about 69", but when used througout a range of pedal speeds they would feel quite different from one another. In summary: 44x16 is quite a usable gear for london(and will be better for skids and tricks than your current). If youre looking to develop your spinning (or youve got poorly knees) you might like 42t instead, but dont go smaller for road use.

Surely the "leverage" is related to crank length and has nothing to do with chainring size?

"A 46x18 gear and a 36x14 are both about 69", but when used througout a range of pedal speeds they would feel quite different from one another."
I gotta try this!

"you might like 42t instead, but don`t go smaller for road use."
So what about the 39T that appears on almost every standard road chainset? Why is this ok?

I changed my 16T to a 17T today. Spinny fun!

I was a little surprised how much difference that one tooth made. Took me from approx 80 inches to approx 75 inches.

I've not found my speed was affected, just that now I spin and spin. Much more fun.

See? Spinning is fun! :D
I'm on the Soma today - it's 42/16 SS? Spin spin sugar!

Here's a nice big discussion about the big/big small/small chainring thing:
http://www.bikeforums.net/archive/index.php/t-297528.html

Went up to a 18t on the back eventually so 48/18. Yeah 2 teeth make a massive difference, not going as fast but having way more fun grinding my tyres into the tarmac doing ridiculous skids. So much fun!

I ride 48/18 too - I was riding 48/16 - the difference is very noticeable - I kind of like going a little slower, it feels much more relaxed.

simontwosheds Mr Conan,

There is a difference between changing a chainring and a sproket. I dont know the sums but the chainring controls the leverage (torque) which is not greatly affected by the sprocket until you get down to track sproket type sizes (14t). Using a small chainring (39t or less) is good for low cadence pedalling. Attempting to spin such a gear is difficult because you need a lot of muscle tension to keep it smooth and comfortable. Using a large chainring (above about 41t) promotes a spinning cadence, because the leverage is low and resitance is more even around the pedal circle. A 46x18 gear and a 36x14 are both about 69", but when used througout a range of pedal speeds they would feel quite different from one another. In summary: 44x16 is quite a usable gear for london(and will be better for skids and tricks than your current). If youre looking to develop your spinning (or youve got poorly knees) you might like 42t instead, but dont go smaller for road use.

I'm totally puzzled as to how the size of the chain ring effects the leverage. The moment of the cranks is equal to the crank length multiplied by the force applied to the cranks. This is going to remain constant regardless of the chain ring size. :-S

Read that link I posted. There's a bunch of trackies going on about it. As usual it's a load of old wive's nonsense and certainly nothing to care about for street fixin'.

Oh I didn't see that link :) Either I missed it or my browser is caching too much..

velocity boy I changed my 16T to a 17T today. Spinny fun!

I was a little surprised how much difference that one tooth made. Took me from approx 80 inches to approx 75 inches.

I've not found my speed was affected, just that now I spin and spin. Much more fun.

I went to 17 as well. I think I'm actually going faster, and my knees are thanking me for it.

simontwosheds Mr Conan,

There is a difference between changing a chainring and a sproket. I don`t know the sums but the chainring controls the leverage (torque) which is not greatly affected by the sprocket until you get down to track sproket type sizes (14t).
Using a small chainring (39t or less) is good for low cadence pedalling. Attempting to spin such a gear is difficult because you need a lot of muscle tension to keep it smooth and comfortable.
Using a large chainring (above about 41t) promotes a spinning cadence, because the leverage is low and resitance is more even around the pedal circle.
A 46x18 gear and a 36x14 are both about 69", but when used througout a range of pedal speeds they would feel quite different from one another.

Balls.

Sorry.

Still balls.

Yep.

I studied a lot of mechanics in maths A level at college and I can't think of a single reason how any of that can be true...

ha, looks like a lot of people switched from 48/16 to 48/18! i'm part of the gang. but i have a 17t waiting on my desk for me to try.
first thing i realised is that my speed isn't really affected at all. i'm absolutely enjoying the spin on the 165 cranks, so much so i want to find 165 cranks for my 2 road bikes. i rode them the other day and i just feel that i can't go back to 170 anymore. they just dont feel right.

another thing is since the gears are less heavy it's much easier to skid, much easier to track stand, and it all made me feel much better at handling the bike.

yeah i don't think the chainring's got anything to do with leverage. the only thing about the chainring size is just wear and fine-tuning gear-inches. say i'm on 48/18, but i don't like the 2 even numbers so i think i'll go for a 46/17 later when i get the cash to replace my pair of cranks (currently a super weird 80's sugino 153BCD).

i started on 48/19, then went down to 48/17. 48/18 is probably exactly right for london I reckon - 19 was too spinny at the kind of speed I like to go to keep up with traffic, but while I have no problems handling 17 generally, I do wonder if all the standing starts are going to take a toll on my knees eventually.

edmundane ha, looks like a lot of people switched from 48/16 to 48/18! i'm part of the gang. but i have a 17t waiting on my desk for me to try.
first thing i realised is that my speed isn't really affected at all. i'm absolutely enjoying the spin on the 165 cranks, so much so i want to find 165 cranks for my 2 road bikes. i rode them the other day and i just feel that i can't go back to 170 anymore. they just dont feel right.

I've just switched back to 170s. Probably lost 5-10rpm top end spin, but like the extra 5mm for climbing and 'jumping'. The world's just a great big melting pot, init.

I lost to a roadie today. The shame. I totally blame it on my lack of inches.. my gear inches, gutter-minds!
42/16 or 42/18 or whatever the hell the freewheel is means I kinda loose going downhill. Then I got every light into the city.

You stopped for the lights?

That's why you lost.

velocity boy You stopped for the lights?
That's why you lost.

No. I lead him out down a hill on a tiny gear. That's why I lost.
I stopped at the intersections to avoid death. I never ran reds in Oz.. now I run some, but not many.

I started fixed riding on 48/16, which seemd good as I was on flats and like to mash. Couldn't do any tricks so moved to 48/18 which was perfect, on my IRO I'm on 46/17 which is good. But I notice on a long stretch I can't really hit that top speed and have to pedal like a muthafuka to stop the roadies overtaking me.

i like 48/18 seems just right for my rides,
i have noticed with a half link chain at the mo i have more skid spots????????
tyre seems to be wearing evenly...

I just got a 49t chainring for my 18t cog.

Makes little difference to the gearing but gives 18 skid patches, rather than the three with 48/18.