Advantages and disadvantages of 48x18 vs. 48x17?

What are your experiences please?

Errr, what do you mean?

The only advantage I can think of is skid patches:

48:18 simplifies to 8:3 therefore 3 skid patches
48:17 doesn't simplify any further therefore 17 skid patches

adv: can get you up to a decent speed
disadv: you wont win rollapaluza cos you dont spin as much as those on 44x18!

Sorry, yes - to clarify. I ride mainly around central London, but I also do some longer rides outside - 30/40 miles, and potentially want to do longer ones (I used to ride a lot a few years ago and am quite fit now, but do not have much experience of fixed- although I rode three Winters off-season on 67 when I used to race). I have used 72" and am now using 76", I am interested in hearing experiences from others about which they enjoy most. I find 72 too low for faster flat/and downhills but also 76 is a bit of a grind up say West Hill in Highgate. Am I just being lazy and not spinning 72 enough? Is it an illusion that on longer rides the 76 seems lots better for cruising along? Just any general thoughts would be gratefully received (thanks for the skid patch calculations but I do - and will continue - to have brakes).

I'd suggest dropping down a bit further, and ride spinning, like you used to.
Its more comfortable in the long run (46:17). or 44:17 or 48:19.
and you can learn to skid!

Don't forget spinning is better for your knees.

I prefer lower spinny gears, myself. I find a lower gear is easier when filtering through traffic, and then I just spin on the flats.

just get a lockring tool, 2 sprockets, change them and see how you feel like. or get a double fixed hub.

only you can decide what gear you want to use.

edmundane

only you can decide what gear you want to use.

I chose my gear by asking people to pull numbers from a hat.

I'm running 525x8.

Well I came across a friend of mine tonight on 72" and I am glad I am on 76", the suffering on the hills is a small payment for tnot having to twiddle around on the flat (just a subjective experience, from an inflexible cranker).

I ride 48/17 now, first started riding fixed on 48/19.

I don't find 48/17 to be any strain on the knees now. They did hurt a little at first when I was mashing, but I did some leg work at the gym and once I was riding with my muscles instead of trying to use gravity to force the pedal down the knee strain went away. In my very unscientific opinion I think one of the quickest ways to get knee problems is to push a gear bigger than your muscles can handle - you're always going to get the muscle burn when you're tired, but it shouldn't hurt to push.

Anyway, most hills in London I'm quicker up than roadies with gears. That said, there are hills I know I couldn't do. I don't know which one West Hill is (I can find it on a map, I just can't picture it), but some hills around Highgate I can manage okay, and one or two are difficult. Last time I went up there I lost momentum near the top thanks to someone pulling out of a side road, and couldn't get started again and had to walk the last 100 yards or so to the crest.

Along similar lines - I went out on my new (to me...) road bike for a big ride with a roadie friend's club couple of months ago, and there were hills that I was struggling even with a granny gear to fall back on. Some were short and very very sharp, but there were a couple of killers that were several miles long. I think I'd fare better the next time - first long ride I'd done, really - but I didn't see me making the whole 50 on a fixie up and down those hills. Apparently the guys in the club who ride fixed have a separate route to follow to avoid the worst hills, so it's not just me who thinks that...

is this a serious question?
IMHO the difference of something like 4GI is entirely about preference and personal strength/feeling

edmundane just get a lockring tool, 2 sprockets, change them and see how you feel like. or get a double fixed hub.

only you can decide what gear you want to use.

kilgore_trout is this a serious question?
IMHO the difference of something like 4GI is entirely about preference and personal strength/feeling

that's exactly why i said the above

you are killing the internets

Am I the only one who finds this thread title an embarassment? :-/

17 it's prime and prime numbers are the building blocks of all other numbers and hence really really cool. You should base your decision solely on this fact alone. Do not be swayed by how easy / hard it is to pedal.

TheBrick(Tommy) 17 it's prime and prime numbers are the building blocks of all other numbers and hence really really cool. You should base your decision solely on this fact alone. Do not be swayed by how easy / hard it is to pedal.

On that basis run a 47 on the front and 17 on the back. Works out about 74.6GI

thats with a 27" wheel

((622 + 23 + 23) / 25.4) * (47 / 17) = 72.7095878 GI

for a 700 with 23 tyres.

I was going the quick and dirty route :]

oooh dirty!

Gotta love teh dirt.

Object17 [quote]TheBrick(Tommy) 17 it's prime and prime numbers are the building blocks of all other numbers and hence really really cool. You should base your decision solely on this fact alone. Do not be swayed by how easy / hard it is to pedal.

On that basis run a 47 on the front and 17 on the back. Works out about 74.6GI[/quote]

or 51x19 for 72.5 inches (Tommy - this also quick and dirty so don't send a number storm my way!)

thats number wang!

kilgore_trout is this a serious question?
IMHO the difference of something like 4GI is entirely about preference and personal strength/feeling

to be fair, if i had a double fixed hub I'd run 17 on one side and 19 on the other, because although the difference is smallish around London it's the difference between spinning out and making it up steeper hills. i suspect the OP is thinking about 18 because it's a compromise between the two but is unsure because of the skid patches? though i'm just speculating.

that's Wanganum...

I ran 17 and 19 sprockets on a flip flop hub for a while. On a 48t chainring. Then i realised that I never used the 17. So I took it off and felt happy.

Spin to Win, Spin to Win.