TT bike handling vs. road bike handling

I used TT and tri bike interchangeably, figured they were the same. Whats the difference?

Also, definitely needing a new saddle. even tilted up and down and so forth its still a lot of pressure in the nether regions. Its not the fit, either :p

Firstly, let's sort out the difference in nomenclature between a "TT" or time trial bike and a triathlon bike, especially since the gap between the two is really growing now at the manufacturer level:

Time Trial Bike: UCI compliant with saddle setback. Used for time trials as in stage race individual timed events, team time trials where drafting is used and in individual (stand alone) time trials. Used by bicycle racers in time trial events. Not intended or configured to run off of. Responsive, not stable. Optimized to comply with UCI rules.

Triathlon bike: Designed around aero, elbow rest handlebars. Designed "from the handlebars back" (Dan Empfield). NOT UCI compliant. Steeper effective seat tube angle, more relaxed, open angle between femur and torso than time trial bike. Some studies suggest better run performance off bike, some do not. Longer "front/center" dimension than TT bike and more relaxed ehad tube angle than TT bike. Optimized to run off of. Not for bicycle time trials, for triathlons and duathlons where athlete will not draft other bikes but will run following bike. Stable, not responsive.

Now, handling:

Most people report poor handling on a triathlon bike because of less than optimal fit and position.

When a triathlon bike is fitted and positoned correctly (you have the optimal bike for you in the optimal frame size and the bike is then optimally positionied for you) the darn thing about rides itself. You could go to sleep on it. All you do is sit there and turn the pedals. It holds your upper body up quite nicely, doesn't kill your crotch, makes your back feel OK and is very stable, stable enough so you can look behind you, reach for a water bottle without affecting your steering. It feels stable.

If a triathlon bike doesn't feel stable it may be because of a few reasons, or any combination of a few reasons:

1. It may not have optimal geometry for triathlons, but may have optimal geometry for time trials. Specifically, the head tube angle is too steep, closer to 73 degrees than 72. Empfield experimented with triathlon bikes with 69 degree head tube angles. The industry has settled on about 72 as a good head tube angle for well designed triathlon bikes. Bikes that do "double duty" as a Tt and triathlon bike usually head back toward 73 degree head angle but may have a fork design with more rake and trail to induce more stable handling.

2. Your fit and position may be off. A very common issue with triathlon bike sizing is buying a frame size too small. I've done it, and I was corrected by both Dan Empfield and Gerard Vroomen of Cervelo. They both moved me up a frame size so I could get a steeper effective seat tube angle and more open angle between femur and torso for a more relaxed posture at the top of the pedal stroke. This also resulted in more wheelbase and more front/center for better bike handling stability.

I hope those ideas help.

Definitely, thanks Tom! Its a QR Kilo and the head tube angle is 72.5. I tried spinning on a medium frame but I was too compressed on it so the shop owner bumped me up to a large. I'll bring up the "twitchy" feel when I go back for a follow-up fit. Turning left and right is where I feel a notable difference, but as far as stability goes I'm definitely more than comfortable staying upright.

I'll keep everything in mind when I go for a few more rides. I'm basing everything I felt off of a 40 minute trial.

Just curious if anyone recommends getting a new fit as you become more agressive.

I bought my Felt B16 in June and over time have made a few adjustments for comfort and to get more aggressive.  I don't think they are too dramatic, basically just removing spacers under the elbow pads and a few minor adjustments to the aero bars and seat height/angle for comfort.

Is a fit meant to be that "precise" or can it generally tolerate these comfort tweeks without going back for a re-fit (the LBS where I bought the bike is about 2 hours drive away)?

By slowly dropping the spacers, though, you're subjecting yourself to a hip angle that'll also slowly become more closed off than before. So yes, if you're gonna be dropping spacers its recommended to get it checked with the bike shop.

At first, I found that when I dropped my stem 1 notch, I could really feel it in the hamstrings.  Also, my neck was mad at me.  I road for a few weeks and was able to get more comfortable.

You know what to do.  Just ride more and make minor adjustments.  Ride for a couple of weeks before making another adjustment.

Tri bikes tend to be stable and comfortable, rather than 'twitchy'.

A likely cause is that you may be positioned too far forward with your fit. 

I haven't ridden a Kilo, but the bike has been around for a few years and I've never heard anything bad about it.  if it were a 'twitchy' bike- people would complain.

your new bike should NOT feel like this.  If it takes more than 10 miles to get used to the handling, something is wrong.