trail question

[eddief]

steering geo is still hard for me to figure. all things being equal, just considering wheel diameter, would installing a smaller diameter wheel increase or decrease the trail measurement?

[Ray]

decrease

[Dave]

Trail = (R/tanH) - (offset/sinH). R is the tires radius, so smaller tires have less trail. The equation also shows that all (positive or forward) fork offset works to reduce trail. The first half of the equation would be the very large trail, if there was no fork offset (rake).

[Tobias]

Trail = (R/tanH) - (offset/sinH). R is the tires radius, so smaller tires have less trail. The equation also shows that all fork offset works to reduce trail. The first half of the equation would be the very large trail, if there was no fork offset (rake).
Not always. ;)

Sorry, but since you love exactness (to the point of often being nit picky …. as do I some times) I thought I’d end 2009 right. :beer:

[eddief]

my two nearly identical long wheel base Easy Racers recumbents. one has a 406 front wheel and the other has a 451 front wheel. think the geometry factors are all identical except for the wheel size. the 451 seems to have quite a bit of wheel flop especially as compared to the 406....and it is causing me some consternation trying to understand the differences.

[Dave]

It would not make sense to me to use the same HTA and fork offset with a much smaller wheel. Since the smaller wheel would have less trail and quicker steering, the HTA might be more shallow on the bike with the smaller wheel, to increase the trail to a value more like the bike with the larger tire. That might explain the flop.