More information about # of skidding spots with gearing...
#4
Senior Member
Join Date: Jun 2003
Location: Atlanta
Posts: 1,155
Bikes: Zeus (Razesa) tarck, Giant TCR road, Eddy Merckx road, Fuji Touring Series IV for everything else
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
that page seems to make it a lot more complex than it needs to be.
48/16 = 3/1 = 3
so the back wheel goes around three times with each crank rotation and ends up in the same place. so if you always skid with the same foot forward, you always hit the same spot. this is true for all ratios that are whole numbers.
45/18 = 5/2 = 2.5
now the crank has to go around two times to get the rear wheel back in the same position so you have two places on the wheel.
48/15 = 16/5 = 3.2
here, the crank has to go around 5 times to get back to the same spot on the rear wheel so you've got 5 spots to hit.
48/17 = something with a lot of decimals.
it won't reduce so the crank has to go around 17 times to hit the same place on the rear wheel.
easy formula:
reduce your ratio to the smallest denominator (chainring/cog). the denominator will tell you how many places you will skid on the rear wheel. (if you skid with either foot forward, double the number)
much easier right?
a month ago I taught a lesson to a 6th grade math class about ratios using my fix.
tim
48/16 = 3/1 = 3
so the back wheel goes around three times with each crank rotation and ends up in the same place. so if you always skid with the same foot forward, you always hit the same spot. this is true for all ratios that are whole numbers.
45/18 = 5/2 = 2.5
now the crank has to go around two times to get the rear wheel back in the same position so you have two places on the wheel.
48/15 = 16/5 = 3.2
here, the crank has to go around 5 times to get back to the same spot on the rear wheel so you've got 5 spots to hit.
48/17 = something with a lot of decimals.
it won't reduce so the crank has to go around 17 times to hit the same place on the rear wheel.
easy formula:
reduce your ratio to the smallest denominator (chainring/cog). the denominator will tell you how many places you will skid on the rear wheel. (if you skid with either foot forward, double the number)
much easier right?
a month ago I taught a lesson to a 6th grade math class about ratios using my fix.
tim
#6
Senior Member
Join Date: Jun 2003
Location: Atlanta
Posts: 1,155
Bikes: Zeus (Razesa) tarck, Giant TCR road, Eddy Merckx road, Fuji Touring Series IV for everything else
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
yeah, my mentor teacher liked it a lot. I'm teaching high school geometry and algebra next spring. I'm trying to think of lessons using cycling that I can use on them.
tim
tim
#7
無くなった
Join Date: Mar 2004
Location: Sci-Fi Wasabi
Posts: 5,072
Bikes: I built the Bianchi track bike back up today.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
44/14 = 3.1428571428571428571428571428571 - dammit - I almost had the fabled pi gearing!!!!
According to the last paragraph, taking the highest denominator (2) I have 7 patches to skid on...
I don't see how he connects Sheldon with brakeless though...
According to the last paragraph, taking the highest denominator (2) I have 7 patches to skid on...
I don't see how he connects Sheldon with brakeless though...
#8
Iguana Subsystem
Join Date: Nov 2004
Location: san francisco
Posts: 4,016
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
HereNT, he doesn't connect scheldon with brakeless;
<snip>
Though Sheldon Brown, the laws of several states and plain old common sense urge otherwise, many fixed gear riders choose to pilot their machines without brakes.
</snip>
<snip>
Though Sheldon Brown, the laws of several states and plain old common sense urge otherwise, many fixed gear riders choose to pilot their machines without brakes.
</snip>
#9
無くなった
Join Date: Mar 2004
Location: Sci-Fi Wasabi
Posts: 5,072
Bikes: I built the Bianchi track bike back up today.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Dang, losing that contact lens earlier must be affecting my eyesight or something. Found it again, but everythings kind of blurry out of that eye...
#11
Senior Member
Join Date: Jun 2003
Location: Atlanta
Posts: 1,155
Bikes: Zeus (Razesa) tarck, Giant TCR road, Eddy Merckx road, Fuji Touring Series IV for everything else
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
damn...
this thread's been Pi-jacked
this thread's been Pi-jacked
#15
//
Join Date: Feb 2003
Posts: 766
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 2 Times
in
1 Post
yup i think trevor worked all this out for us a while back. totally awesome.
and now as of last week my new chainring is 43t. i also changed to a 3/32" drivetrain. hopefully ill take some pics in a week or so..
and now as of last week my new chainring is 43t. i also changed to a 3/32" drivetrain. hopefully ill take some pics in a week or so..
#16
NACCC 2007 Winner
Join Date: May 2004
Location: Copeland - Denmark
Posts: 135
Bikes: A Lot!
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Originally Posted by BostonFixed
#18
Senior Member
Join Date: Jun 2003
Location: Atlanta
Posts: 1,155
Bikes: Zeus (Razesa) tarck, Giant TCR road, Eddy Merckx road, Fuji Touring Series IV for everything else
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Originally Posted by dolface
you've got 17 patches, since 17 is a prime number.
52/17 indeed gives 17 skid patches, but it's because 52 and 17 are mutually prime.
tim
#19
Retrogrouch in Training
Join Date: Sep 2004
Location: Knee-deep in the day-to-day
Posts: 5,484
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
relatively prime.
edit: hey, lookit that, indeed "mutually prime" is also an acceptable term. I don't think I've ever heard it called thaht.
edit: hey, lookit that, indeed "mutually prime" is also an acceptable term. I don't think I've ever heard it called thaht.
#20
Iguana Subsystem
Join Date: Nov 2004
Location: san francisco
Posts: 4,016
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
heh heh, i was gonna point that out too, nice to know that both are correct.
btw, TimArchy, thanks for correcting my comment. nice catch
btw, TimArchy, thanks for correcting my comment. nice catch
#21
Senior Member
Join Date: Jun 2003
Location: Atlanta
Posts: 1,155
Bikes: Zeus (Razesa) tarck, Giant TCR road, Eddy Merckx road, Fuji Touring Series IV for everything else
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
mutually prime, relatively prime...
I can't remember which is correct.
I took abstract algebra twice, but it was two years ago
I figured that since they were prime relative to each other...
tim
I can't remember which is correct.
I took abstract algebra twice, but it was two years ago
I figured that since they were prime relative to each other...
tim
#22
Direct Hit Not Required
Join Date: Nov 2003
Location: San Bruno, CA
Posts: 6,193
Bikes: Leopard DC1, Ridley X-Fire, GT Zaskar 9r
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
A prime chainring is what you want. Otherwise you'll need to do the calculation at the bottom.
#24
Direct Hit Not Required
Join Date: Nov 2003
Location: San Bruno, CA
Posts: 6,193
Bikes: Leopard DC1, Ridley X-Fire, GT Zaskar 9r
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Yes, but what is most flexible is a prime chainring. Then you can run pretty much any size cog and not have to worry.
#25
troglodyte
Originally Posted by BlastRadius
Yes, but what is most flexible is a prime chainring. Then you can run pretty much any size cog and not have to worry.
Justification of reasonable size: 37 seems a bit small, 61 a bit big. Certainly a good spread though.