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Question about bicycle handling and trail(6 posts)

Question about bicycle handling and trailcyclopathic
Jan 27, 2004 11:13 AM
modern industry views 56mm trail as "ideal", giving "neutral" handling (amount of input required to rotate bike is independent from speed). What actually constitutes 5.6cm as "ideal"? Wouldn't ideal depend on some bike design properties such as wheelbase, stem length, front wheel, etc? any insides are welcome
not ideal....C-40
Jan 27, 2004 1:14 PM
It's Tom Kellogs opinion of ideal, but not Ernesto Colnago's. All Colnagos have a lot more trail and the amount decreases as the frame size and wheelbase increase. It's makes perfect sense to use less trail on larger frames and more on the small sizes.

Since I've been riding a Fondriest with a lot less trail and shorter front-center than my Colnago, I see the main disadvantage of less trail being less stability in gusty winds. The Fondriest can be a handful in severe gusts. I rarely ride in such nasty conditions, but did so recently. In all other conditions, including high speed mountain descents, I like the quick steering.
re: not ideal....cyclopathic
Jan 27, 2004 7:28 PM
actually Tom is not alone; Cdales, Treks, LS are all designed around 5.6cm trail.
re: not ideal....divve
Jan 27, 2004 10:57 PM
With Cannondale it's as C-40 explained. The smallest road frames have as much as 63mm trail with the largest ones having 53mm (all using a 45mm rake fork).
correction smallest is 62mm. nmdivve
Jan 27, 2004 11:02 PM
yeah, butcyclopathic
Jan 28, 2004 4:39 AM
you can hardly call their charts correct. http://www.cannondale.com/bikes/04/geo-14.html

Sizes 54,55,56 and 58-64 listed with the same HTA, however first have trail 5.6 and later 5.3, using the same fork rake. Generally with 45mm fork you get 5.6 on 73 HTA and 5.3 on 73.5.

In smaller sizes trail is longer b/c of design compromise, to avoid excessive toe overlap, common for many mfg. Maybe more for Colnago due to shorter TT. In longer sizes compromise is made to keep wheelbase in check. With those two minor exceptions, they aim at 56mm. No real science behind involving radius of gyration, weight distribution, etc, just fixed castor angle design. In days before, when most forks were steel and it was easy to bend blades to specific size, smaller sizes were commonly treated with 2" (or 50/51mm metric) rake.

One of the few mfg who consistently has longer trail is Look, at least in smaller sizes. 65mm in sizes 54cm and under and 52mm in 55cm and up.