Simply sliding the seat forward won't generate that much in the way of handling problems. The problems come from the fact that you will need to keep the cockpit length the same so you will also need to get a longer stem which will push the handlebars and aerobars further forward. Now you have a potential handling problem.

It may be that the bike has a long top tube for you at 75 degrees, in which case you won't need an excessively long stem.

If you know you want a steep seat angle all the time, I think you should buy a bike with that geometry. If you want one bike with different setups at different times, expect to have to make compromises. I can not deal with those compromises, but more flexible people sometimes can.

I had my P3 set up with my weight way too far forward at one time. It is a wonder I didn't kill myself. You can easily lose two minutes on one long hill if you can't handle your bike confidently. No aero advantage will ever make up that much time. Been there, done that.

You have to try - the different bikes and sizes are totally different. While others are talking about serios problems, my ScottUSA road raced with 73.5 geometry works perfect when I move the seat forvard to 78 degrees.

Good question! Take a road geometry bike, put a profile fast forward seatpost on it (or any forward bending seatpost) and crank the saddle forward. "Induce" a 78-82 degree seat angle on a bike built with a 73.5 degree seat angle: Your weight is shifted forward on the bike causing, among other effects, your steering to become more responsive feeling. Weight is coming off your rear wheel. The bike becomes less stable. The effects are worth talking about. In 2000 and 2001 I spent many weekends on the back of a camera motorcycle photographing bike positions for our website in local triathlons. I learned a lot. Ride behind a guy with a well-fitted tri geomtry bike at 22 m.p.h. and watch his bike handling: The bike remains stable and "quiet", not a lot of superfluous side to side movement. When the guy reaches for a water bottle, the bike remains straight and stable. When he looks behind him because he hears the camera motorcycle approaching (or draft marshall)he stays stable. This even applies to new riders (I know they're new becasue I sold them their bikes). Now, get behind a guy on a standard road geometry frame but with the seat pushed forward substantially to 78-82 degrees. Almost regardless of riding expereince they are experiencing substantially less stability and side to side movement on the road. It is easy to see. When they reach for the water bottle they often have to put the opposite hand on their base bars to remain nder control. Many times these riders are good road riders who owned a road bike, were reasonably fit, and then decided to "make their road bike into a tri bike". My opinion is this just doesn't work. It is a big compromise. The effects are there to see.

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Tom Demerly
The Tri Shop.com

luntzy. first off do not think in terms of " forward", but rather "rotating". the more forward post is ALSO higher from the ground, as you rotate around the bb. more impotantly, you are not so much moving forward at the bars as you are down, again ROTATING around the bb. in this view the impact of forward weight shift is lessened somewhat.

as for a rule of thumb - consider that the widely used thompson zero setback post will move the average rider close to or more than 2 degrees from the even more widely used 1" setback post, at a given position on the rails. even with this 2 degrees nobody ever speaks of handling being an issue - in fact the posts are often switched without riders knowing it - moreover there is no such thing as a specific geometry for either. now consider, the difference to a "steep" 77 degrees or so is no different from a 1" setback to a zero setback ! granted it is more forward on the front, but if the differnce for the first inch on handling was essentially nill, why would another inch cause the end of the world ?? answer : it probably won't.

also consider guys routinely strap a liter of water sloshing back and forth to their aerobars cantilevered out over the front wheel and never bat an eyelash.

finally - there is far more to the equation - where you fit on the bike to begin with, the head tube height, the bb drop, frame stiffness, what fork you use, etc etc will play a role. this is why we have mailorder ( apologies to lbs guys) - get a post ( i really think the profile is overkill, btw - get a simple reversable 1" or zero setback ) and do some carefull planning on where and how far you should rotate your front controls down and slightly forward. get the right stem and risers and check it out. go down some hills and ride the thing on some rollers - you will know in short order where you stand. if it doesn't work send it back and consider yourself a wiser man.

Tom, I think I understand what you are saying, but what makes the cervelo soloist or the Kestrel Talon different. Is the geometry (chain stay length, head tube length, Rake?) of these bikes a little different than say a typical road bike. I realize that the handling of these bikes changes when the forward seat post positions are used but it seems as though it is acceptable. What gives?

I found that my Giant TCR-1 felt quite stable at 75/76 degrees. When at a full 78 degrees with a forward seat post it was acceptable in a strait line on a flat, but otherwise I didn't like it.

The Soloist is a compact design very similiar to the TCR. Because of a shorter chainstay than a regular road frame, these bikes seem to lend themselves a little bit better to being set up with a forward seat angle.

IMHO the Talon is an excellent road bike with very limited multisport capabilities. The Soloist is more versatile because (I think....) the rear wheel is shoved farther forward and something is going o with the front end geometry I don't fully understand but seems to work right up to 78 degrees. It is still a road bike first though. I'm riding mine as a standard road bike.

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Tom Demerly
The Tri Shop.com