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How much fork trail is enough trail?

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How much fork trail is enough trail?

Old 03-31-18, 05:45 PM
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Ladel
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How much fork trail is enough trail?

I'm looking for a range of trail lengths that make a bike more stable and easier to ride no-handed. My current bike is a little twitchy at low speeds. I'd like to be able to compare my trail with other trail lengths. While this is very subjective, it would be nice to see the length of trails people consider very stable.
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Old 03-31-18, 06:53 PM
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Quickly throwing published numbers into a trail calculator, the bike I find easiest to ride no-hands has a trail figure of 61mm

That's a 2014/15 New Albion Privateer with a 72 head angle, 50mm rake, and 700x35 tires
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Old 03-31-18, 07:06 PM
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Originally Posted by agmetal
Quickly throwing published numbers into a trail calculator, the bike I find easiest to ride no-hands has a trail figure of 61mm

That's a 2014/15 New Albion Privateer with a 72 head angle, 50mm rake, and 700x35 tires
Very nice! Using an online calculator, my trail is 76mm. It has a head tube angle of 71; a fork offset of 40mm; and a 26x2.35" MTB wheel. That's quite the difference in trail, and I find it hard to keep a straight line at low speeds with no hands.

The calculator also lists my wheel flop at 23mm. Given your geometry, your wheel flop is 18mm. Wikipedia states that "a bike with too much wheel flop will tend to veer off its line at low and moderate speeds." It seems like there needs to be a good balance between trail and wheel flop.
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Old 03-31-18, 07:08 PM
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How low is low, in terms of speed?
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Old 03-31-18, 07:21 PM
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Originally Posted by agmetal
How low is low, in terms of speed?
Around 10mph.
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Old 03-31-18, 07:23 PM
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I've never bothered to check my actual speed when riding no-hands, but I know I can't do it super slow. 10mph or close to it is probably my low limit
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Old 03-31-18, 07:25 PM
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Originally Posted by Ladel
Very nice! Using an online calculator, my trail is 76mm. It has a head tube angle of 71; a fork offset of 40mm; and a 26x2.35" MTB wheel. That's quite the difference in trail, and I find it hard to keep a straight line at low speeds with no hands.

The calculator also lists my wheel flop at 23mm. Given your geometry, your wheel flop is 18mm. Wikipedia states that "a bike with too much wheel flop will tend to veer off its line at low and moderate speeds." It seems like there needs to be a good balance between trail and wheel flop.
More trail generally coincides with more wheel flop.

High trail stiffens a bike up with speed, it doesn't do much to stabilize things when you're going slow.

If you want a bike to handle stably at low speeds, it's usually beneficial to have quite low trail.
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Old 03-31-18, 07:35 PM
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Originally Posted by HTupolev
More trail generally coincides with more wheel flop.

High trail stiffens a bike up with speed, it doesn't do much to stabilize things when you're going slow.

If you want a bike to handle stably at low speeds, it's usually beneficial to have quite low trail.
Excellent, thanks for all the responses. This is really helpful in understanding how various fork geometries will affect the handling.

Cheers!
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Old 03-31-18, 09:34 PM
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A cheap way to make a bike less stevie is to play with the wheels & tires. Toss a larger dia wheel & tire up front to increase rear sag & it should limit the wondering. It'll impact steering with increased understeering.
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Old 04-01-18, 09:01 AM
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Originally Posted by Troul
A cheap way to make a bike less stevie is to play with the wheels & tires. Toss a larger dia wheel & tire up front to increase rear sag & it should limit the wondering. It'll impact steering with increased understeering.

Don't I want to smaller diameter front wheel and smaller tire width? That would increase the head tube angle, which will decrease the trail, thus yielding a more stable bike at low speeds.
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Old 04-01-18, 12:50 PM
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Originally Posted by Ladel
Don't I want to smaller diameter front wheel and smaller tire width? That would increase the head tube angle, which will decrease the trail, thus yielding a more stable bike at low speeds.
yes
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Old 04-01-18, 05:29 PM
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Originally Posted by Ladel
Don't I want to smaller diameter front wheel and smaller tire width? That would increase the head tube angle, which will decrease the trail, thus yielding a more stable bike at low speeds.
Decreasing the trail will make it harder to ride no-handed at higher speeds. I'm not sure that any bike is easy to ride no-handed at slow speeds. A high trail bike will tend to wander more at low speeds but a low trail bike will tend to have more responsive steering but will also be more twitchy, and might not be easy to ride no-handed. I typically ride no-handed (on a bike with high trail and a long wheelbase) at a moderate speed - I don't think I would try it at a low speed or at high speed. Dave Moulton has some interesting blog posts on trail.

Last edited by GailT; 04-01-18 at 05:32 PM.
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