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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 12-29-04, 01:17 PM   #1
salmonchild
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forks and geometry

right, so now i hace my track frame, with fork ends and a track fork. one problem is that i want to run a front brake, and with the fork not being drilled i don't know what to do.

if i swap out the fork for a carbon one or those very sweet straight bladed chrome forks will i mess up the goemetry of the bike?

another option is to have it drilled, but, is there a minimum thickness you have to have to make sure it'll be safe? also if i can get the fork drilled, what would be the alignment issues of the brake pad and rim?

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Old 12-29-04, 01:26 PM   #2
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DO NOT DRILL IT. you don't need a front brake.
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Old 12-29-04, 01:34 PM   #3
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my face would beg to differ! as my first fix i don't wanna learn everything the hard way (hospital trips are not on my list of things to do in 2005).
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Old 12-29-04, 01:40 PM   #4
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it will change the geometry (unless you're able to find a fork that has the same geometry as your current one), but probably not that much.
you probably don't want to drill your track fork, just on general principals. (it's one of those things that's pretty hard to undo )
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Old 12-29-04, 04:23 PM   #5
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Track forks are generaly 38mm rake...so if you get another fork try to approach that degree of rake. 38mm is hard to find, but 40mm rake is common and I doubt 2mm will matter all that much...you'll likely find the axle to crown measurement is slightly longer on a drilled (normal) fork, too, but I'm not sure how much longer and it's probably not that noticable when riding as long as the rake is close.
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Old 12-29-04, 04:28 PM   #6
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By the way, and I wish I'd thought about this when I had my frame/fork built, the more rake you have then the quicker the bike will feel...so even though the wheelbase grows a bit with more rake, the trail decreases and, all other things being equal, the bike will feel more nimble. If your present fork is 38mm and you move to a 40, you'll prob notice little difference...but move to a 45 from 38 and I'm sure it would be night & day. So if you like nimble, get more rake - if you like stable, get less rake.
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Old 12-29-04, 05:18 PM   #7
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I assume someone here has had a fork drilled before but there really isn't any info if you do a search. How much does this usually cost? Any info would be much appreciated. Also, if anyone in Boston knows a shop that would be willing to do this I would love to know.
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Old 12-29-04, 05:56 PM   #8
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If it helps any, Condor has supplied me with a few 'used' steel forks, drilled, immaculate condition...
Altho each time was immediately after a run-in with an automobile and I was trying to get back on the road ASAP.
What size steerer do you need? If the one I have doesn't fit the frame enroute to me, I could sell/trade them to you.

Here's a pic of the first ones I got from them, after I was hit side-on by a whitevan, and the one I currently have sitting around...
http://bettybitty.users.btopenworld....e/DSCF0367.JPG
http://bettybitty.users.btopenworld....e/DSCF1094.JPG
http://bettybitty.users.btopenworld....e/DSCF1096.JPG

Last edited by techone; 12-29-04 at 06:02 PM.
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Old 12-29-04, 07:14 PM   #9
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you can get a brake that mounts with some sort of clamps on the forks. I've seen them on a Japanese web site that I think some one here posted.
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Old 12-29-04, 08:24 PM   #10
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I've drilled my fork (due to an inability to get a new one).

My LBS did it for free (there's a fab shop just behind the LBS), but anyone with a drill press can do it (e.g. any machine shop).

I haven't had any problems thus far, but I only use my front brake for emergencies, and REALLY REALLY REALLY STEEP HILLS.
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Old 12-29-04, 11:34 PM   #11
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Quote:
Originally Posted by dabern
So if you like nimble, get more rake - if you like stable, get less rake.
you got that backwards. the less rake you have, the quicker the steering.
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Old 12-30-04, 03:24 AM   #12
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cheers all. the issue that dabern brought up about the axel to crown length was my main concern- i lined the fork up against an almost identical one which is on a road frame i have lying around and the rake looked the same to the naked eye but there is a noticable difference in length. if the steerer tube on that one was long enough i would do a straight swap and just see how the thing feels, but as it doesn't i'm gonna have to splurge on summat new(ish) and it needs to be right as this bike is going to cost me too much as it is.

jinx_removing- if i go the drilled route i will post how it went.
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Old 12-30-04, 07:34 AM   #13
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jitensha, take a look at this link. I believe you're confusing headtube angle with rake and I stand my statement...
http://www.velonews.com/tech/report/...es/7322.0.html
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Old 12-30-04, 01:51 PM   #14
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dabern is right.
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Old 12-30-04, 04:30 PM   #15
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Quote:
Originally Posted by jitensha_de_go!
you got that backwards. the less rake you have, the quicker the steering.
Quote:
Originally Posted by baxtefer
dabern is right.
Actually both are right. There are may factors that come into play with regard to 'twitchiness' and rake/trail etc. Not the least of which is speed. We discussed this last June and this was my response then for what it's worth:

jimv wrote in June:

Track bikes tend to have alot of trail (and little rake). I think that 'large trail' bikes tend to be more stable the faster you go. In the Jan. 2004 Rivendell Reader there is a short and somewhat cryptic article about Marc Muller's (Waterford) ideas on the subject. While working for Schwinn, he was tasked with creating bikes with a consistent steering feel regardless of head tube angle, tire size and rake. His efforts led him to conclude that there was another factor which he termed 'steering angle'. This is the angle formed by a line drawn from the front axle to the point on the ground where the steering axis is projected and is measured relative to the line dropped straight down from the front axle. It's hard to explain so I added it to the drawing. See below.

Anyway I found it interesting and as a point of reference, he says that a steering angle less than 9.5 degrees results in a twitchy bike. The upshot is that it may be a mistake to place too much stock in rake and trail. Anyone else read this article?

Jim
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