when youre picking your next chainring or cog, its important to know how many skid patches the resulting combination will leave u with... ok im assuming two things here: firstly you dont have all the money in the world and enough time to go with it to keep changing your back tire, and secondly that you use your back tire to stop, not your front rim or something similarly silly. so here is a list of relevant prime numbers
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71
currently i ride a 51-19. jees i thought 51 was a prime number..? noddy badge for anyone who can tell me what it is divisible by (other than 1 and itself). apparently it still gives me 19 skid patches (according to the application on my mate's iphone that is). thats kinda cost effective, no?
found this on an irish forum, so im not the only one talking about it:
"You will never get more skid patches than the number of teeth on your sprocket, (you may get less, depending on the chainring) so more teeth is always better in that regard. You can get up to the max skid patches with a non-prime sprocket, you just have a wider range of possible chainrings with a prime sprocket (and vice versa.) A 47T chainring will give you the most possible skid patches with any rear sprocket, so it could be a very good choice."
why do almost all off the shelf fixies come with a 48-18 then? only 3 skid patches, unless ur an ambi-skidder... i guess they also come with brakes
ok, so i did two years of engineering maths and didn't know what you were on about. not even applied maths helped (funny that).
ReplyDeleteso thanks to that irish forum i kinda understand.
James is skid stopping his fixie.
that's for the guys who don't use brakes/technology. i think it involves a nosewheelie, and then holding the cranks straight with your legs and skidding to stop with the backwheel providing the friction.
Due to the vagaries of static and dynamic fiction, no nosewheelie and the bike throws you off(i think?)
anyway, if the crank and sprocket are a divisible ratio, the tyre will skid on the same patch of rubber everytime. Which will result in a useless tyre which is still 95% usable.
prime numbers and stuff help out