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Old 05-05-06, 10:31 AM   #1
Sigurdd50
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Theoretical Question: NEw Fork to make tour bike more Stable

Hey... this is just a theoretical question (which means... instead of biking around town and picking the brains of dealers and repair shops I ask the question to the general community)

I know that touring/commuting bikes generally have slacker geometry and longer wheel base. This makes them more stable over the long haul and with loads. Less rake on the fork makes a twitchier, more responsive bike (racer, etc) I assume degree of angle on the rear triangle adds to this ( and to the overall wheel base size)

I have a Jamis Aurora (2002 frame I believe). I like it. Steel is real. Brooks Saddle, EAston EA70 post, NItto Stem, Nitton Randonneur bars... I've customized it to my liking. it's working. Solid. Commuter and ready for some touring.

At times it seems a tad twitchy... I haven't measured the exact degrees of rake and tube lengths, but...

Theoretical Question

How feasible is it (at some point, likely not this season) to improve the stability by going to a different fork? Are decent touring steel forks available and, assuming standard diameters on the head tube, is it easy to do? HAve you done it?

Also, another theoretical question:
How much does one gain with each degree of change... etc
don't know if I said this correctly... just tossing it out there for discussion.
I'm not unhappy with my ride... just wondering
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Old 05-05-06, 11:04 AM   #2
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Less rake = bigger trail = more stable
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Old 05-05-06, 11:10 AM   #3
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There are other forks available. Surly sells the LHT fork seperately, for example. You may also use a cyclocross fork if you don't intend to use the low-rider rack mounts. Most cyclo-X forks have the canti brake bosses you will want. This may give you more choices to look at as far as geometry of the fork itself.

Having said that;
If the fork on your bike is the same geometry as this year's Aurora, the geometry is pretty average for a touring rig. The head tube angle on the frame along with the fork offset determines the rake, which affects how "twitchy" the bike is. You might be able to find a different fork that is enough longer to effectively change this angle, but I doubt it. The forks I have looked at are all pretty close to 400mm from axle to crown race. The offset of the forks is also pretty consistant at around 44 - 50mm offset.

A cheaper way to experiment could be to try some different sizes and brands of tires, bars, maybe stem rises.

Last edited by Old_Fart; 05-05-06 at 11:16 AM.
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Old 05-05-06, 12:21 PM   #4
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Having said that;
If the fork on your bike is the same geometry as this year's Aurora, the geometry is pretty average for a touring rig.
this is what I'm thinking.
A good new fork is gonna cost me... 300 bucks? NOt sure it justifies the gain
It is a 2002, which I bought at a good deal, not from a Jamis dealer, but as a NOS frame-bike put together with some different-than standard components from the usual Aurora. But the frame/fork look like the stock thing. The one thing that I don't like, but it was part of the deal (and part of the package that year) are the caliper brakes (and, as such, LACK OF bosses for canti's) Canti's ain't gonna happen as this would require brazing on bosses, and I just don't see spending that sorta time/$$ on this frame.

I run 700/28 tires, have considered trying 32's

The calipers limit the tire size (the fenders make things tricky as well), but I may spring for some 32's maybe some day and see if I can shoe horn them in there.
I have a technomics stem, so that can come up pretty high. Average reach

heck, maybe I need to load the front wheels to stabilize
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Old 05-05-06, 12:46 PM   #5
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If you are thinking that 300 bucks, though a chunk, is a possible budget to improve your ride, why not go whole hog and buy a new frame. The nashbar is 150-200 depending on the offer, and the LHT regularly sells for 350.

The problem with new forks is they are generally set up for a specific headtube angle. If your headtube angle is more upright, as one would expect at you lower offset, then the fork with 50 mm will actually slightly raise your front end height. Wouldn't be great, but it sounds like a bit of a kluge.

Nashbar makes carbon and steel unicrown forks for cyclocross that some seem to like for touring.

http://www.nashbar.com/profile.cfm?c...eid=&pagename=

http://www.nashbar.com/profile.cfm?c...eid=&pagename=
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Old 05-05-06, 12:52 PM   #6
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Quote:
Originally Posted by Sigurdd50
this is what I'm thinking.
A good new fork is gonna cost me... 300 bucks? NOt sure it justifies the gain
No, if you go for Surly Trucker Fork, between $64 and $75.

http://aebike.com/page.cfm?action=de...=30&SKU=FK0905

http://www.universalcycles.com/shopp...7001&category=

Tange forks are under $50.

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Old 05-05-06, 01:08 PM   #7
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No, if you go for Surly Trucker Fork, between $64 and $75.
hmmm would this be cool:

silver gray frame
black or sage green fork
and a cantilever brake on the front?
and the words 'Surly' painted on the forks
eyelets for whatever

the possibilities (to spend money) are endless

1 1/8th inch steerer tube; would that mean a 1" threadless stem fits?
ahh I'd need the type fork for 700C wheels
(uh oh...talking to myself again)
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Old 05-05-06, 01:27 PM   #8
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If you curently have a 1" threadless stem, this means you will have to stay with 1" everything to match your frame/head tube. So, a current LHT fork would seem to be out of the picture. However, Surly does have a 1" Cross-Check fork for available with 1" steerer tube.
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Old 05-05-06, 01:51 PM   #9
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No, the steering tube and the stem are the same part. If your have a 1" fork then you can't use the surly stuff as a replacement, they use the heavier MTB parts for their head tube and steering tube.

Nashbar used to have a 1" stem option in their steel fork, but they are sold out.

The new Surly colours are candy red and blue.

The Nashbar cyclocross carbon fork is still available, but it doesn't have rack mounts, there are several ways aorund that.
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Old 05-05-06, 02:24 PM   #10
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Thanks for all the suggestions

i think I'll have to figure out some of my current geometry... (this is where I'm a bit at a loss)
angle of head tube
rake angle of current fork

compare to what is available (like the Cross Check fork or whatever)
and see if there is much net gain before I go spending money
Since I can't change the head tube, the rake angle would have to be an improvement

red and blue?
even with a silver-gray speckled frame, they might be a bit ugh
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