Gearing

you can get bigger cogs than 19, though.

RPM hippy rides 69 GI..
he ain't exactly slow. spins like a mutha..
so it can't be all that difficult, seeing as he's really fat.

LMAO! (and then back on with tonight's curry and beer..)

Aye! Tis true!
http://www.thehippy.net/nucleus/index.php?itemid=894

I'm thinking about going lower still.. like 65" but I need to sort out the Armstrong.

danger joel thanks glow, ill see if i can find a 19 toof clog to try that out.

Like one of these?

(Obviously, I'm no pro with photoshop)

Hello all.
After riding an old road bike and not ever changing gear I've finally bought a cheap and cheerful single speed off eBay for £225.

At the moment I think the gearing is 44 x 18, but I find that a bit too easy. What gearing would people recommend? And how much roughly will a new chainring cost?

Thanks for any help

Luke

You need to provide a bit more information on where you ride / what the chainset is etc. is there not a bike shop near you?

If you look through the recent posts and even the search function... you will find all the answers to your questions.

Shin

I run 49/16 on my single speed, but i do have a 19 that i'm gonna try on the back, as in winter the knees take a hammering! But i find that a pretty good ratio, gonna run something lower on the Bridgstone when it's built though.

If you never changed gear on your road bike, I'd recommend that as your starting point for fixed.
See how it feels and adjust as necessary.
Cost will depend on manufacturer, usually cheaper to change the rear sprocket.

Check out Sheldon Brown's Gear Inch calculator (google it).

And then bear this in mind:
mid-50's and below = granny gears for hills and polo
mid-60's = spin to win (low effort, easier to skid, lower top speed but greater acceleration)
mid-70's = mash (lots of leg effort, hard to skid, high speed when you manage to spin)
mid-80's and above = track racing

I think you will find that the majority of people on this forum, for day to day London riding would recommend something between 68 and 72 gear inches.

Thanks for the replies. I'll check what I was running before and try and match that.

I'm currently riding a crappy street/hybrid thing running single speed on 44/16. According to the gear calc that's 74,3 gear inches. If I move to a nice fixed gear running 48/17 (that's 76.2 gear inches), is the difference going to be noticeable? I'm guessing I'll benefit from a lighter bike, less traction etc.
Currently the ratio feels about right, in that my speed is good and I don't need to get out of the saddle too much, which is how I like ti ride.

^^^ less traction?

^read as friction you Pedant!
@fake35 - I think you will notice a slight difference in the gearing, but not much, then after a while you will get used to it.. then you can compare gearing to other people whilst wobbling at traffic lights. :-)
(ByTheWay - stay away from that Pedantry thread... it's gone crisp-shaped. I think tynan needs some pom-bears?)

I'd go slightly lower for SS than for fixed.
You can spin away merrily up the hills and don't damage your knees, then you can freewheel down the other side. I'm spinning 69" fixed, and prefer 67" for SS commuting.

48x16 or 50x16 is great for SS. I'm now fixed using 48x19

I'm currently riding a crappy street/hybrid thing running single speed on 44/16. According to the gear calc that's 74,3 gear inches. If I move to a nice fixed gear running 48/17 (that's 76.2 gear inches), is the difference going to be noticeable? I'm guessing I'll benefit from a lighter bike, less traction etc.
Currently the ratio feels about right, in that my speed is good and I don't need to get out of the saddle too much, which is how I like ti ride.

Those wheel sizes (gi) are for 27" tyres. I suppose that may be true if you've got chunky hybrid tyres on.

If you get a 25mm tyre and run 48x17, you'll still be pushing about 74.5 gi but it'll feel quicker and easier because of the lighter tyres. The winning factor is less to do with friction, but less rotating mass DOES make a difference - I have some light 25mm tyres and some heavier 23mm cheapies. The 25mm ones are noticibly faster.

48x16 or 50x16 is great for SS. I'm now fixed using 48x19

Sorry guys, but I'm starting to see red here. Blindly quoting ratios doesn't help anyone out. You've gotta say what size tyres + rims you're running. It does make a difference:

700c 19mm tyres at 48x17 = approx 73.4 gi.
700c 23mm tyres at 48x17 = approx 74.3 gi.
700c 32mm tyres at 48x17 = approx 46.3 gi

For me at least 1 gi makes a difference, you will definitely notice 2 gi.

Work it out:
700c has a bead seat dia of 622mm. dia is increased by approx 2x tyre size, 622 + (2 x 23) = 668mm. Or 26.3 inches.

26.3 x 48 / 17 = 74.3 gi

P.S. Tyre pressure makes a difference to effective diameter, friction, and comfort and punc****s. Find what best suits you.

Mate, I hated maths & physics at school and I just put my tryes on, pump and go.

I have two 23"x700 on a 48x19

Do want my inside leg measurement too? ;-)

Currently on fairly fat 27" tyres. I reckon I'll handle another couple of gear inches on 700x25 tyres.
Ta

700c 19mm tyres at 48x17 = approx 73.4 gi.
700c 23mm tyres at 48x17 = approx 74.3 gi.
700c 32mm tyres at 48x17 = approx 46.3 gi

The maths does not compute

The maths does not compute

Ooops! 46.3 should have read 76.3, sorry.

Mate, I hated maths & physics at school and I just put my tryes on, pump and go.

I have two 23"x700 on a 48x19

Do want my inside leg measurement too? ;-)

That's a bit too personal ;)

Ha Ha Ha! Just for fun...

I've been thinking about this one, because a day at the office can be less interesting without a bit of maths to keep you busy.

Get this:

700c 23mm tyres at 48x17 = approx 74.3 gi.
With 170mm cranks, has a gain ratio (google for this) of 74.3 / (170 x 2 / 25.4) = 5.55

If you use a different crank - 165mm - and try to get same gain ratio, gear inches changes!
With 165mm cranks, 5.55 x (165 x 2 / 25.4) = 72.1 gi

If the gain ratio is the same, so is the amount of force on the pedals. So for the same amount of continuous force at the pedals, you'll go quicker or further for one revolution of the pedals with longer cranks and the same amount of force.

Conversely, if you reduce the crank length and keep the same gearing, from 170 to 165 with 48x17, you will feel the same difference as increasing the number of teeth on the chainring by about 1.5 teeth, or the equivalent of going from 74.3gi to 76.6gi in terms of pedalling difficulty.

Okay, I know there are other factors here too. people with shorter legs get better use out of 165mm cranks because of the working range of their muscles, but when you're standing on the pedals - working the legs vertically - 170mm cranks have a longer vertical range in which the vertical effort has more effect (something to do with angles and vectors, blah, blah, blah...).

Have a nice day!

Thank you Chris. Having read that through four times I get it. I think. But where does the 25.4 come from?
Your aptitude for maths is wasted... unless you're doing some sort of maths based job, in which case it isn't.

Cheers