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Old 12-26-07, 05:28 PM   #1
mtlbob
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Wheel flop

Hi

I have a touring bike (sold by LBS from their specs in Taiwan). The aluminum fork is at the limit of "wheel flop". When riding, it is "twichy", the fork is very bend forward. I measured the distance between the axle and the steering axis and it is 55mm. I'm looking to buy an other fork. What I see is one with 50mm rake. Would this fork make a difference in handling.

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Old 12-26-07, 09:59 PM   #2
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Twitchy when? going slow or fast? Touring bikes traditionaly have less steering trail and will feel more stable at low speeds. Unloaded touring bikes often (IMO they should ) feel "twitchy" at higher speeds since it's intended use is for touring with the weight of panniers and handlebar bags. Sorta like a pickup truck rides better when it is loaded down.

There is a tradeoff, You might reduce the twitchy feeling somewhat by using the 50 mm fork but if you later add 50-70lbs of touring weight for a tour, the steering will likely feel heavier. If you ride the unladen bike enough you will likely get use to the sensitive steering by learning to use less steering input
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Old 12-27-07, 08:20 AM   #3
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Quote:
Originally Posted by velonomad View Post
Twitchy when? going slow or fast? Touring bikes traditionaly have less steering trail and will feel more stable at low speeds. Unloaded touring bikes often (IMO they should ) feel "twitchy" at higher speeds since it's intended use is for touring with the weight of panniers and handlebar bags. Sorta like a pickup truck rides better when it is loaded down.

There is a tradeoff, You might reduce the twitchy feeling somewhat by using the 50 mm fork but if you later add 50-70lbs of touring weight for a tour, the steering will likely feel heavier. If you ride the unladen bike enough you will likely get use to the sensitive steering by learning to use less steering input
My opinion about lower trail (55 mm offset) versus higher trail (50 mm offset) is that stability is affected. I have a few touring-ish bikes, a Trek and a Woodrup, both with lower (45 to 55 mm) trail, and both with sensitivity to crosswinds, road bumps, and fidgety rider actions. I don't ride with heavy loads, so perhaps I don't see the advantages. What I prefer for my riding are '70s and '80s road race style designs, such as my Mondonico and Masi, which each have around 60 mm of trail if not a bit more. The steering on these requires a decent 'bar effort, but the bikes respond fast, well, just because they do.

I would tend toward the 50 mm fork. One side effect will be reduced vertical fork flex, a little more road jitter coming up through the handlebars.

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Old 01-02-08, 11:17 AM   #4
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Thanks for the answers.

My bike is twitchy at low speed.

My fork is a very stiff aluminium one, so changing for 50mm rake one will not change much. I think I'll change the tires for Michelin (more supple tires), and a more absorbant bar wrap (maybe two wrapping).
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Old 01-11-08, 09:55 PM   #5
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Hmm. If you think the problem you have might be improved with fatter tires and spongy bar wrap, then I do not think you were using the word "twitchy" in the way it is usually used in cycling. I think you have a ride that is too harsh for your tastes; that is too much vibration up through the front wheel, through the fork, through the stem and bars, and into your hands.

Are my guesses right? If so, then tires can make a huge difference. Get great big ones if you can. Good bar tape will help some. So will gloves. But, if after all that it is still too harsh, you may consider switching to a non-aluminum fork. Steel perhaps, but carbon fiber will really help.

If this is the problem, then messing with the fork rake is not really the solution.

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Old 01-15-08, 06:25 PM   #6
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Trust me, after riding for over twenty years with an array of bikes, this one is twitchy at slow speed. The aluminium fork is very stiff and, I think, an antiquated design with a steep curve in it.

A straight blade steel fork with 50 mm of rake (offset) would diffuse the vibrations in all of the fork instead of only at the curve. I was just weary of the weight of such a fork. A carbon fork for a touring bike? Maybe.

But then, this bike is not my primary bike. I bought it more as a reminder of travels I made in Europe, self-supported with all the camping gear... I use it sometimes with my girlfriend.
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