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Old 11-18-08, 08:51 PM   #1
spray2020
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Tight Clearances: serve a purpose or more for looks?

A while ago when I got interested in fixed gear riding and track bicycles- I was more interested in the fixed gear styling, crazy colors and trendy stuff.

I have gradually stopped liking all of that stuff, and for appearance reasons have been attracted to simple track bikes with super close clearances-

I find that out of all the pictures on this website, its hard to come by a lot of track frames that have these tight clearances.

Do they serve a true purpose, or is the actual purpose so minimal that its more for an appearance thing?

I might not know what the hell I'm saying, forgive me if I sound like an idiot.

A frame like this, specially the front wheel to the down tube clearance

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Old 11-20-08, 04:32 PM   #2
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My uneducated guess would be that a shorter wheel base would give better power transfer and aerodynamics for more speed. Plus, the upright geometry which leads to tighter clearances would give better handling when navigating through other riders (also uneducated). As I have never ridden on a track, take what I say with a grain of salt.
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Old 11-20-08, 06:34 PM   #3
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Minimally tighter wheelbase, minimally stiffer/lighter chainstay since it's a tad shorter... back when the only building material was steel and tubing diameters were relatively close, you had to work more closely with geometry to achieve a certain stiffness/feel. But it's aesthetics as well...
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Old 11-20-08, 10:13 PM   #4
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thanks for the comments-

looks wise, I like the tight clearance all around (rear wheel to seat tube, front wheel to top of fork and front wheel to down tube-

but it seems very hard to find frames like this?

usually its only the rear wheel to seat tube is always tight (which is of course adjustable)

but rarely do I see a frame like that yamaguchi, where everything is tight-

maybe its just that it was a style of the past?
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Old 11-21-08, 01:40 AM   #5
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I've seen old cinellis that have tight clearances all around like that. Obviously they are meant to be ridden on the track. Imagine the toe overlap on those, esp while trying to make sharp turns. I think on the track its more leaning and going sideways into the ramps for turns so toe overlap isn't an issue. But yea I dont think riding an extremely tight clearance bike is safe on the street.

I was wondering if this tight clearance applies to road bikes too. Like if I buy a fork that is straighter (less rake) and slide the rear wheel closer to the seattube, I would achieve a shorter wheelbase. Would this also improve the handling of the road bike?
My guess is that I would get alot of toe overlap (more than the track bike), since road bikes have slacker seat and headtube angles.
But this would be interesting to try to how the handling changes.
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Old 11-21-08, 11:43 AM   #6
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my friend was explaining this to me.. i think bikes are kinda complicated because if you reduce rake, you increase trail and your bike handles "slower" but then i think that counters the way you would steer, because leaning turns and actual more upright steerer turns are different. I am not sure which feels 'twitchier', however I was told that increasing trail, reduces twitchiness.

and all this is directly related to head-tube-angle.

i wanted to replace my 40 rake fork for something like a 35 or 38, but figured i'll wait until i can understand what i wrote, above.

that yamaguchi is incredible and that the straightest fork i have seen on an NJS frame. prob a 35 rake fork with a 74* or 75* hta?

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Old 11-25-08, 05:56 PM   #7
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Originally Posted by sunv View Post
I was wondering if this tight clearance applies to road bikes too. Like if I buy a fork that is straighter (less rake) and slide the rear wheel closer to the seattube, I would achieve a shorter wheelbase. Would this also improve the handling of the road bike?
My guess is that I would get alot of toe overlap (more than the track bike), since road bikes have slacker seat and headtube angles.
But this would be interesting to try to how the handling changes.
It depends what you mean by "improve." It will make the bike twitchier and more responsive but less stable, which is desirable for a criterium or track bike but undesirable for a touring bike. On a road bike, you would be more likely to have toe overlap but not because of the slack headtube angle (a slacker HT angle would increase the wheelbase and move the front wheel away from the BB) but because road bikes have longer crank arms compared to track bikes.
Criterium-specific road bikes (do they even make these any more?) have tight rear triangles, steep HT and ST angles and low-rake forks because they are designed to be responsive and maneuverable in close racing formation around fast, winding criterium courses. In essence, they are track bikes for the road. Pursuit track bikes, on the other hand, have longer wheelbases and shallower angles (the question of rake is complicated because they use 24" front wheels), which makes them more stable and allows the rider to stretch forward into an aerodynamic position. Pursuit bikes aren't meant to be ridden in close formation, so they don't need to be maneuverable. In essence, they are time-trial bikes for the track.

Sorry that none of this addresses the question of frame clearances. As for the rear wheel, a tight rear wheel clearance will also get an aerodynamic "draft" effect from the seat tube, which is also achieved in some Al/CF track frames by using a teardrop shaped seat tube to get closer to the wheel. Tight front wheel clearances allow for reduced wheelbase and trail which makes handling more responsive, but there's another reason the clearances are so small on track bikes: When you apply the front brake on any bike, the braking forces cause the front triangle and fork to bend (more or less depending on the stiffness of the frame, weight of the rider, etc) which causes the front wheel to approach the downtube. Hard braking on a tight bike with oversize tires could cause the front tire to touch the downtube, which would apply an additional braking force, and cause the frame to bend more, force the wheel harder into the downtube, etc. etc. positive feedback loop, which would immediately lock the front wheel and probably cause you to have a pretty bad crash. Track bikes can afford to be built with tighter clearances because (a) they're stiffer anyway and (b) they don't have brakes- although the rider's weight still moves forward in a deceleration, the deceleration is more gradual and limited by the fact that the rear wheel would probably become unweighted before the braking force flexed the front wheel into the downtube. OTOH, has anybody seen those bolt-on keirin brakes being used on super-tight NJS frames? I am pretty concerned that sooner or later one of those riders is going to hurt themselves pretty badly when their front wheel gets jammed up during a panic stop.

... was that long enough?
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Old 11-25-08, 06:36 PM   #8
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^thanks for the response-

I totally understand what you are saying-

I am a car enthusiast at heart- specifically hondas- so I love "tight wheel clearance" and lowered stances

so when I got really into bicycles a year and a half ago-

I could help but to be obsessed with these track bikes that are so tight and awesome looking

but similar to cars-

driving a civic on the street with racing wheels and a really low stance is not meant for the street- and all the potholes arent in your favor!
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Old 11-25-08, 06:42 PM   #9
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Originally Posted by trueno92 View Post

that yamaguchi is incredible and that the straightest fork i have seen on an NJS frame.
Yamaguchi is a U.S. frame maker--builds cx, track, road etc.
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Old 11-25-08, 09:19 PM   #10
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Originally Posted by kaiju-velo View Post
Yamaguchi is a U.S. frame maker--builds cx, track, road etc.
It's an understandable mistake, Yamaguchi used to work for 3Rensho so his designs are all rooted in keirin framebuilding.
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Old 11-25-08, 10:40 PM   #11
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It's an understandable mistake, Yamaguchi used to work for 3Rensho so his designs are all rooted in keirin framebuilding.
I thought that might be the case--I was just clarifying it wasn't a keirin frame--
but it looks influenced by that style of frame--nice in any event.
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Old 12-18-08, 01:18 PM   #12
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tight clearances are an effect of exactly what the frame builder wants the bike to do.
a steep head angle will make the bike turn quicker but if it's counteracted with less rake you get a bike that turns real quick but the front end will still be stable.

rear wheel, uhh, shorter chainstays are stiffer so better power transfer on the track bikes and road bikes deisgned for racing. touring bikes use the same principle but they lengthen them to reduce vibration transferred to the rider, they also are longer so that the riders feet don't have clearnace probelms with bags.

a smaller frame will have worse toe overlap because the top tube is shorter so the front center is also shorter.
i like the feel of a steep head angle and a short rake fork myself, i don't really care whether the clearances are tight or not as long as it rides good.

somebody up there got their trail and rake mixed up in their post.
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Old 12-18-08, 01:22 PM   #13
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oh yeah. i'd guess that yamaguchi up there is a 74.5* head angle with around 28mm rake.
ask the owner he should know.
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