IMO frame priorities are to get the seat forward and over the BB and to be

as aero as possible (lower on the front). Weight distribution and thus

handling are minor considerations in a TT because, for the most part,

you're riding on your own. Just as well because riding on the aerobars far

overshadows an other handling characteristic.

I'm curious about tri bike geometry.

It seems that putting an aerobar on a regular road bike ends up

putting more rider weight forward. This likely changes bike handling

quite a bit.

When I ride with an aerobar I move my seat up a half inch and forward

an inch. I also tilt the nose down. --This also indicates that my

weight has moved forward.

So how do tri-specific bikes deal with this?

Do they change the bike geometry to move the rider rearward for a

given wheelbase to make up for the forward-weight? (How do they do

that? Shorter stays, curved seat-tube, LONGER top tube, shorter stem?)

I see that at least the Cervelo offers a steeper seat-tube---which

would put rider weight more forward unless other changes offset it.

(What is the ideal weight ratio on the wheels anyway? I recall that

it's 50-50 but who knows.)

Weight ratio and C of G would also affect how a bike responds to

braking. --It would seem that aerobars put weight forward AND raise

the CoG causing a bike that would do an endo if braked hard.

Also, does the front geometry change? I would think that if a position

had more weight forward that one might want a low-trail fork. Long-

trail is often associated with fork-flop which is increased with added

weight on the front-end. --This means that small changes in body

position on an aerobar would cause a bike to wobble going down the

road. But long-trail is also associated with race bikes. While low-

trail is known mostly in French long distance touring circles---for

bikes with loaded handlebar bags, especially.

Do tri-bikes have longer wheelbase? --They don't have fast handling

needs.

Here's a webpage for the geometry of a Cervelo:

http://www.cervelo.­com/bikes.aspx?bike=­P2C2008#G

Offhand, it looks like they don't do much special for geometry other

than throwing rider weight forward. It looks like they have a slack

head-tube angle---which would really increase fork flop with a long-

trail fork

Just wondering...

--JP

allbikemag.com

outyourbackdoor.com­

On May 27, 6:47 pm, "Tom Kunich" <cyclintom@yahoo. com> wrote:

I'm not convinced. I suggest looking into this further. People who

spend big bux on bix should get great handling no matter what position

they're in.

That's how I'd sell my pricey bikes anyway if I was

buildin' 'em. There's probably a way to have an aero/forward position

while still having great handling. Handling is CRITICAL ALWAYS in my

view. Emergencies come up ALL THE TIME on race courses. Courses are

tricky. "Stuff" happens while out training. ZERO excuse for not having

a great-handling bike. Anyway, if you wanted a great handling aerobar

bike, what would you do?

On May 27, 6:47 pm, "Tom Kunich" <cyclintom@yahoo. com> wrote:

I'm not convinced. I suggest looking into this further. People who

spend big bux on bix should get great handling no matter what position

they're in. That's how I'd sell my pricey bikes anyway if I was

buildin' 'em. There's probably a way to have an aero/forward position

while still having great handling. Handling is CRITICAL ALWAYS in my

view. Emergencies come up ALL THE TIME on race courses. Courses are

tricky. "Stuff" happens while out training. ZERO excuse for not having

a great-handling bike. Anyway, if you wanted a great handling aerobar

bike, what would you do?

When I say my TT frame bike is better handling, I mean it is more

stable and just feels more balanced. It isn't nimble or anything, but

I do feel better riding fast with it for example down hill. And around

turns. So I can stay in the aero bars through more stuff than I was

comfortable doing with ethe road bike frame.

(Yikes. --Nothing I wrote suggests a desire for TT bikes that are like

crit bikes. , stable and steady would be fine. --I doubt that

torsional stiffness is the culprit behind most bad TT handling. --

Remove aerobars...good one, Ryan! ...Not a TT rider, I gather.)

So, does anyone here have a sense (based on knowledge and experience)

for how changing the design of a TT frame might affect handling? I

suggest changes that lower the CoG and move it rearward. Also changes

that might improve handling---and ability to ride a straight line when

in aerobars. I wonder what those changes might be? Any thoughts

(based on knowledge/experienc­e, that is) on fork trail in this regard?

I'm wondering if short stays, lower BB (lower saddle), curved/steep

ST, long TT, short stem, handlebar with elbow rests as low as comfy,

and a low-trail fork might add up up to something interesting...

Anyone ever see a bike like that?

To keep it simpler: Anyone know of a low-trail TT bike?

Anyone know of a curved/steep ST TT bike with long TT?

On May 28, 4:36 pm, "joseph.santanie...­@gmail.com"

<joseph.santanie...­@gmail.com> wrote:

[ ]

The thing is, to have "neutral" handling with a bike that has a

forward position might require a low trail fork. The common race bike

has a long trail fork which makes a bike sensitive to front-end weight

shifts as might happen often when riding on aerobars.

Sounds like a good start!

I'm no fork-trail expert but I think it's part of the equation to give

a stable bike. Different-use bikes need different trails but my

impression is that modern race-bike trail is somewhat of an ignored

issue.

Kind of one size fits all.

--JP

allbikemag.com

(Yikes. --Nothing I wrote suggests a desire for TT bikes that are like

crit bikes. , stable and steady would be fine. --I doubt that

torsional stiffness is the culprit behind most bad TT handling. --

Remove aerobars...good one, Ryan! ...Not a TT rider, I gather.)

So, does anyone here have a sense (based on knowledge and experience)

for how changing the design of a TT frame might affect handling? I

suggest changes that lower the CoG and move it rearward. Also changes

that might improve handling---and ability to ride a straight line when

in aerobars. I wonder what those changes might be? Any thoughts

(based on knowledge/experienc­e, that is) on fork trail in this regard?

I'm wondering if short stays, lower BB (lower saddle), curved/steep

ST, long TT, short stem, handlebar with elbow rests as low as comfy,

and a low-trail fork might add up up to something interesting...

Anyone ever see a bike like that?

To keep it simpler: Anyone know of a low-trail TT bike?

Anyone know of a curved/steep ST TT bike with long TT?

In article

<a64b97dc-9728-458­f-af55-cacc11e81082@­x41g2000hsb.googlegr­oups.com>,

"Jeff Potter (of OutYourBackdoor.com­)" <JeffOYB@hotmail.co­m> wrote:

Further requesting that said aero position offer stable handling is

trying to make a bakfiets out of a sow's ear.

In my experience, TT bikes are good enough. They're probably close to

being as good as possible, given the number of professionals with an

incentive to make them better.

In article <rcousine-162BCF.08­331229052008@[74.223.­185.199.nw.nuvox.net­]>,

Ryan Cousineau <rcousine@gmail.com­> wrote:

I think "as good as the rules allow" would be closer to the

facts. See Chris Boardman and the superman position.