Long Distance Competition/Ultracycling, Randonneuring and Endurance Cycling - Weight distribution and handling

I do not know whenre to post this, but I figured you all will most likely have the most experience.

I recently got an '86 Bianchi Sport SX and converted it to 650B. I chose it for a variety of reasons, but primarily because it was cheap, my size, and the 700C wheel clearence was very tight such that 650B fint very nicely without extreem brake reach. It is 'sport touring' geometry with shorter trail, 42cm chainstays, and 57cm top and down tubes. Picture:

http://i136.photobucket.com/albums/q184/balindamood/IMG_0042.jpg

The bike fits, and I really like it and want to commute on it. I regularly use a Jandd computer/pannier bag which weighs about 25 lbs when loaded with laptop, tools, papers, etc. Specs are here:

http://www.jandd.com/detail.asp?PRODUCT_ID=FCBP

The I am using a Benno (Betto?) rack, of which I have several and really like them, but I am not sure if they were designed for 26-inch wheels, 700C, or "one size fits all". The tend to be a tight fit on the larger wheels. To keep my foot from hitting the panniers, I use the connection hardware to off-set the lower connection about 1-2 cm farther back. I have done this on several bikes without problem. Pictures:

http://i136.photobucket.com/albums/q184/balindamood/IMG00028.jpg

http://i136.photobucket.com/albums/q184/balindamood/IMG00029.jpg

The problem is when I put the bag on the bike. Yes, it is alot of weight off one side of the rear rack, but I have not had a probelm with my other bikes. However, on this bike, the front end becomes VERY twitchy. Not I-am-going-to-crash-at-any-minute, but it certianly requires all of my attention, and the bike is very sensative to shifts in weight...more so than any other I have ridden.

My thoughts are that the bike may be better suited towards front loading, but this does not work well for a brief case sort of thing. Is it possible a different rack would help. I really do not know where to start trouble shooting.

Thanks.

The key phrase that caught my eye in your post was "shorter trail". Many bikes with low trail geometry do well with front loads, especially if you can keep the load down low as much as possible... like you get with a low-rider front rack.

Someone with more experience with frame geometry needs to chime in here... but I'd imagine that the combo of low trail and heavy load concentrated on the rear would make for twitchy handling.

but I'd imagine that the combo of low trail and heavy load concentrated on the rear would make for twitchy handling. Yeah, actually much of the loss of handling stems from having the load so far back.

Realistically, you could actually correct the problem by putting as much of the "heavy" gear as you can on the front rack. Of course "low-riders" would be even better. I'm kind of surprised that the "650" mod would cause handling to "go to hell"- but in this case I guess so.

25# isn't a huge load for a rear rack even if it is off-center.

By reducing the tire size the trail has been reduced. Perhaps you have crossed a boundary in terms of handling stability with this trail reduction. Can you put a set of 700Cs on to see if the handling is still spooky with the load?

Later,
HB

nice bike!

(sorry, can't help you with the loading Q's tho)

commuting? why not post in commuting section?