Not enough bike...

[tch]

in front of me. At least that's what it feels like. Situ: I have been riding my 56 Ramboulliet a lot during the early spring and have gotten used to it. Now, when I get on my 54 Concours, it somehow feels like it is "short" up front. Especially, I have noticed that when I stand up to rest my butt periodically, I get front wheel shimmy -- almost as if when I stand on the pedals at 3 and 9 I am over-weighting the front wheel and causing it to shake underneath me. Questions:
Is it possible that my bike's front end/front center is short and is responsible for this behavior?
If this were the case, could I get a fork with a larger rake and stretch out the geometry a bit (would it be noticeable?). I know it would affect trail (and hence stability), but it seems like I might have some extra. Do I?
Some numbers for the Concours:
overall wheelbase: 96.13 cm (is this short?)
front center: 55.98 cm
HTA: 72*
trail: 6.53 cm
fork rake: 4.3 cm
I am riding a 110 mm stem with three cm of spacers to get the bars fairly close to same height as saddle because I am long-legged and short-torso'ed for my height.
Any bike fit gurus out there?

[Smiley]

With a 6.53 trail and a 72 degree head angle , its sounds to me that Serotta was trying to minimize toe over lap with your frame . Also since they were using a 43 mm rake fork my guess again is its an older frame with an F 1 fork and at the time Serotta did not have the fork rake choices they have today . What your frame is designed to do is have WEIGHT on the front wheel where as your Rambo was designed more as an up-right bike . There were inherent design decisions made to the Rambo to make for a stable ride while riding almost up-right and no hands , Not with the Serotta , you must put some weight on the bars so you distribute the ratio across the wheel base to 45 / 55 % , so when you get up-right you are de-weighting your front wheel and hence causing it to lift a tad from contact with the pavement . People forget that when moving forward with a bike your frontal area of wind resistance will act like a chute and will tend to be a sail to help this process along , especially during high speed decents , thats why the pro's get low and weigh that front wheel . My take on your problem . And no if you shorten the rake the front end will slow down and you don't want to do this with your already slow or large trail .
Will you be at the Open House ?

[tch]

With a 6.53 trail and a 72 degree head angle , its sounds to me that Serotta was trying to minimize toe over lap with your frame . Also since they were using a 43 mm rake fork my guess again is its an older frame with an F 1 fork and at the time Serotta did not have the fork rake choices they have today . What your frame is designed to do is have WEIGHT on the front wheel where as your Rambo was designed more as an up-right bike . There were inherent design decisions made to the Rambo to make for a stable ride while riding almost up-right and no hands , Not with the Serotta , you must put some weight on the bars so you distribute the ratio across the wheel base to 45 / 55 % , so when you get up-right you are de-weighting your front wheel and hence causing it to lift a tad from contact with the pavement . People forget that when moving forward with a bike your frontal area of wind resistance will act like a chute and will tend to be a sail to help this process along , especially during high speed decents , thats why the pro's get low and weigh that front wheel . My take on your problem . And no if you shorten the rake the front end will slow down and you don't want to do this with your already slow or large trail .
Will you be at the Open House ?

Thanks so far :). Unfortunately, I don't think I'll be able to make it to Open House; that's too bad and I'll miss riding/talking/drinking/drinking/drinking... with all.
But, I got a question: it seems like when I stand up, in fact I am OVER-weighting the front wheel, not unweighting it. You say that when I stand up, I am deweighting my front wheel, but I am moving my body off seat and forward, not back.
And, I was thinking about going with MORE, not less fork rake, to lengthen front center. As you say, I have a fair bit of trail, so I thought I could give up some (as I would if I went to a 4.5 cm fork).

[Smiley]

tch , if your going forward that much are you not lifting the rear wheel ?

[tch]

I'm still wondering if a change in fork rake (to a 4.5) would make the bike feel more stretched out or if it would even be noticeable... And would it reduce the sense of short front center?
thanks,