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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 12-07-03, 05:57 PM   #1
extomesm
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track frame geometry

ive heard that track frames have a steeper geometry than the standard road frame but i dont really know what that means. what makes its geometry steeper? ive noticed on a few track bikes that the top tube slants downward going from seat post to the head tube. whats that about? thanx austin
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Old 12-07-03, 11:29 PM   #2
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track geometry will also have a less sloping head tube and the forks will have 0 rake to them. it makes the bike very twitchy on the road, but this responsiveness is neccessary to shoot up the walls and manuever, etc. track bikes will typically have very short stays. the bottom bracket is higher as well for clearance issues.

edit: that sloping toptube you are referring to may be a pursuit bike. those will usually run a small fork with a 650c front wheel.
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Old 12-07-03, 11:40 PM   #3
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whats the benefit of running smaller front fork and wheel? (forgive me, im new :-) )

Last edited by extomesm; 12-07-03 at 11:47 PM.
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Old 12-07-03, 11:48 PM   #4
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Quote:
Originally Posted by extomesm
whats the benefit of running smaller fork and wheel? (forgive me, im new :-) )
Smaller and lower frontal area for improved aerodynamics.
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Old 12-07-03, 11:53 PM   #5
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Originally Posted by isotopesope
track geometry will also have a less sloping head tube and the forks will have 0 rake to them.

now, i haven't been into this track thing for that long (a year or so), but i've never, ever, ever seen a bike with a 0 rake fork.
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Old 12-08-03, 12:16 AM   #6
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a guy here in town builds track frames and forks and all of his track forks are totally straight. in 0 rake i mean they don't slope forward more than the angle of the head tube. i don't mean the fork is perpendicular to the ground or anything. his site is sort of out of date and doesn't have any pictures of his track forks, but it's worth a gander:

http://www.groundupdesigns.com/

0 is sort of a blanket statement though. very little rake...

Last edited by isotopesope; 12-08-03 at 12:24 AM.
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Old 12-08-03, 02:31 AM   #7
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zero rake, sloping top tube, AND 650c!!

edited so as not to break things.
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Old 12-08-03, 01:39 PM   #8
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with a zero rake fork is there more chance of pedal overlap since it seems to bring the front wheel closer to the frame? also how do people ride with pedal overlap? isnt that unsafe?
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Old 12-08-03, 02:06 PM   #9
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I have toe overlap on my Kogswell. Not a lot but yea, it can be tricky. You'd have to ride a bike with overlap to understand that whenvever you're turned far enough to hit your toes you can't be going very fast anyway. You just get used to tapping your feet every now and again and you learn how hard you can turn, no big deal really.
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Old 12-08-03, 02:11 PM   #10
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If you don't have a huge overlap, you can tip your foot down on the down stroke during a slow, tight turn too.
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Old 12-08-03, 03:17 PM   #11
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or you can tip it up.

my bike has quite a bit of overlap, though not as much as i've seen on other frames (*cough*KHS aero track*cough*). it also makes the steering quite twitchy. but i'll never go back to the original fork for that bike. i'm too used to being able to zip through traffic and change lanes pretty much just by shifting my hips to one side or the other. that bike is so dangerously quick.
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Old 12-09-03, 12:53 PM   #12
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comparing my track bike to my old road frame fixie, it takes off faster, sprints better, swerves quicker and feels "tight". On the other hand, it's not as comfy on the arms & hands for long trips, it's harder to slow down, and I do sometimes hit my toe on the front tire. It also doesn't soak up as much of the bumps in the road.
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Old 12-22-03, 07:06 AM   #13
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frame geometry

The term steeper geometry refers to the head tube angle which moves the forks into a more vertical alignment than a standard road or touring frame. The rear triangle is shorter due to the seat tube being a slightly different angle than the other type also. The combination of those factors makes for a quicker handling bike that is an advantage in a velodrome setting. It also makes for a harsher ride, but that is not of concern in the short races that take place on a velodrome.


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Old 05-14-07, 12:53 PM   #14
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Quote:
Originally Posted by isotopesope
a guy here in town builds track frames and forks and all of his track forks are totally straight. in 0 rake i mean they don't slope forward more than the angle of the head tube. i don't mean the fork is perpendicular to the ground or anything. his site is sort of out of date and doesn't have any pictures of his track forks, but it's worth a gander:

http://www.groundupdesigns.com/

0 is sort of a blanket statement though. very little rake...
youre confusing the appearance of straight blades with rake. all forks have rake, and the rake in combination with the headtube angle determine the trail (which is the important thing which determines stability). that builder uses straight blades, the rake is still there, but its at the crown vs the taper in the forks as with curved blades.
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Old 05-14-07, 01:04 PM   #15
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You're confused Isotope: adding rake gives a bike quicker handling by decreasing trail, and vice versa. A "zero rake" fork actually increases trail compared to a positive rake fork, making the bike more stable. Bikes meant to go very fast inside a motorycle draft (they hit speeds in excess of 130 miles an hour) generally have negative rake forks for even more stability.

Sheldon links to a great article on this of course, I recommend it.

http://www.phred.org/~josh/bike/trail.html

Does anyone know why bikes use rake? Why not slacken the ht angle and have no rake at all?

Last edited by mander; 05-14-07 at 01:10 PM.
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Old 05-14-07, 01:08 PM   #16
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Quote:
Originally Posted by misterherman
youre confusing the appearance of straight blades with rake. all forks have rake, and the rake in combination with the headtube angle determine the trail (which is the important thing which determines stability). that builder uses straight blades, the rake is still there, but its at the crown vs the taper in the forks as with curved blades.
right on.
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Old 05-14-07, 01:16 PM   #17
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Quote:
Originally Posted by extomesm
whats the benefit of running smaller front fork and wheel? (forgive me, im new :-) )

extomesm, bikes like that are meant for races where you aren't allowed or able to draft your opponents, such as a pursuit where two people start on opposite sides of a track and the first person to get passed loses; or an hour record where you see how many laps of a track you can do alone in an hour. Basically you sacrifice some ergonomics for aerodynamics. For the same sort of reason, triathlon bikes look really weird---triathletes aren't allowed to draft each other and so they set their bikes up to fight the wind.
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Old 05-14-07, 01:21 PM   #18
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Originally Posted by extomesm
with a zero rake fork is there more chance of pedal overlap since it seems to bring the front wheel closer to the frame? also how do people ride with pedal overlap? isnt that unsafe?
Toe overlap doesn't matter on the track because your not going to turn your handlebar that much
edti: damn didn't know i was answering a question from 4 years ago!

Last edited by rodny71; 05-14-07 at 01:37 PM.
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Old 05-14-07, 01:30 PM   #19
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holy thread necromancy!
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Old 05-14-07, 01:37 PM   #20
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whoa, i didnt catch that. I was hoodwinked!
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Old 05-14-07, 01:38 PM   #21
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extomesm is probably an ol' track pro by now
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Old 05-14-07, 02:12 PM   #22
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extomesm is probably an ol' track pro by now
lmao, i ddint' even notice that...holy****.
brought the thread back just to tell isotopesope he was wrong, ****ing awesome.
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Old 05-14-07, 03:05 PM   #23
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hahaha yeah, this thread is super old; i was still learning or mistaken i guess. me, for the lose.
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Old 05-14-07, 03:08 PM   #24
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Maybe pictures will help?

Note that the track frame has 75° head tube and seat tube angles, whereas the road frame has a more relaxed 72° head tube and seat tube angle. The track frame has shorter chainstays (440 mm vs 460 mm for the road frame), and less fork rake (20 mm vs 35 mm for the road frame) resulting in a shorter wheelbase for the track bike.

The steeper head tube and seat tube angles, shorter chainstays, and reduced fork rake of the track bike make the handling quicker and steering a little less stable than the road bike.

These Nervex frame designs are from the late 1950s, but today's traditional geometry frame designs haven't changed much.

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Old 11-25-07, 04:50 PM   #25
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so, what is the 'standard' point that distinguishes track frame geometry.... 75 deg. 74 deg? how steep do they go.. 80?

I'm curious as to what my headtube/seattube angle is, but I don't have a protractor and am too lazy to pull out the makeshift geometry contraptions right now...oh well
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