Originally Posted by
engineerbob
About a month ago, we bought a used Burley Duet. After I changed its gearing, it is working out pretty well. However, at low speeds, I have noticed that it is very sensitive to any movement in the handlebars. At higher speeds it is extremely stable, much more so than my Trek road bike. I assume that this is a function of the amount of trail in the front-end geometry.
If I were to change the fork to one with less trail, I would expect less h/s stability, but less sensitive steering when climbing at very low speeds. Like many things, there is a trade-off.
Is my analysis correct? How would I go about finding a fork that would reduce my tendency to weave all over the road at low speeds?
Thanks.
Bob
I did exactly what you are thinking about and it worked out well. Bilenky uses low trail geometry on its standard tandems. There standard unicrown forks for their small sized tandems has 60mm rake and he made me one painted in black for a reasonable price. The axle to crown height needs to be considered because a change there will change the HT angle. Most all steel tandem forks are about the same height so that was not a problem for me with the Comotion or with a Santana. Now I can ride with one finger tip on the bars climbing at 10 mph. Also it allows for a front bag if you want to go that route.
I do not know about the Burly but most major makers use a 73 degree head tube angle. When I bought the fork I owned a Comotion speedster and the substituted fork worked well. Trail went to the low forties. Very stable at high speed and much less flop at very low speed. The only downside is that it takes very little effort to turn the bars and so a light touch is needed. This is with 28-30mm tires. The bike tracks very straight and needs little steering correction at low speed but id you are in the habit of correcting then you end up moving the bars when it is not needed and then you have to move them back. It may take a little getting used to. If you have a long stem and wide bars this will be less of an issue.
Another benefit for me about the lower trail is that it does not feel locked in when cornering at high speeds. Some like the "cornering on rails" feeling of high trial bikes but the low trail really does allow for changing your line in mid corner. That ability is great when faced with an unexpected pot hole mid corner. On the other hand not being locked in means you have to steer actively thru the corner rather than set the bike up entering the corner and just let it roll through. It is a different mind set but once I became used to it I find I can take corners faster and tighter than I could on higher trail bikes.
Overall I loved it and when I sold my Speedster I kept the 60mm fork and moved it over to a Santana. I have now converted the Santana to 650B and the wider tires also reduce the sensitivity at low speeds. If you ride with a light touch on the bars then it should be fine. The nice thing about the fork change is that if you do not like it then you can easily change the fork back.