On Tue, Dec 30, 2008 at 10:11, Doug Shaker <[email protected]> wrote: > > At 05:54 AM 12/30/2008, you wrote: >>I am interested in what design >>considerations go into making a frame more rear-weight than front- >>weight friendly. > > Wheel flop/trail are the main considerations that I know of. > > As I understand it, trail (the distance between the tire-ground > contact patch and where the headset turning axis would hit the > ground) effects handling in that the larger the trail, the more > the front wheel wants to go straight. High trail is, in that > sense, stabilizing. > > However, the more trail you have, the more wheel flop you have. > Wheel flop comes from the way that the wheel lowers itself slightly > when you turn it any direction from straight. Gravity pulls the bike > into wheel flops, so wheel flop tends to de-stabilize bikes. > > At high speed, the stabilizing effects of high trail dominate. At low > speeds and high front loads (more weight, more flop) the de-stabilizing > effects of wheel flop dominate. Since high trail and wheel flop go > together, a bike that tracks beautifully at high speed may be very > difficult to control at low speed. > > I have one bike with high trail that is perfectly fine 99% of the time, > and pleasant 95% of the time. But with a front load and going up hill, > it just wheel flops all over the place - I have to get off and walk it > rather than risk driving into traffic. > > At least this is my understanding. This understanding might be completely > wrong. If so, I would love to be corrected. > > > > - Doug "Anonymous" Shaker
Doug's answer matches my experience. I have one of the original Kogswell P/R with the low trail fork (30mm trail). I've configured it with a large front rack, and have carried loads in excess of 50 pounds with very little loss of handling: it doesn't require me to manhandle the handlebars to keep the bike on track, even when I am just starting from a stop. This has never been my experience with high heavy front loads on any other sort of bike. I have a Heron with more typical high trail that would probably be hard to handle with that same sort of load. Instead, it has a pair of panniers on a low-rider rack, and seems to handle that just fine. I got a low-trail replacement fork for an older Kogswell G, and find that it too handles heavy front loads well. The increased rake on that fork also eliminated my toe-clip overlap. Rivendells are spec'd with high trail, because that's the way Grant likes it. I suspect that there are a number of reasons for his preference, but I would like to say first and foremost that he probably considers trail to be insignificant in comparison to other design considerations; in fact, I've heard him say as much. That said, some of what I think might be informing that is his preference for rear loading (the proportion of rear/front load does indeed affect the way the bike handles), his feeling that toe-clip overlap is not significant, the speeds he likes on downhills, and that he prefers stability and the ability of a bike to hold a line well. -- How often have I lain beneath rain on a strange roof, thinking of home. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en -~----------~----~----~----~------~----~------~--~---
