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TI_roadracer said:
Would you choose a 130 with a 56cm frame over a 110 with a 58cm frame?
Its hard to make that call because other factors come into play, such as heat tube length in relationship to saddle to handlebar drop. Lots of info missing; you really need to fill in the blanks in order to get a meaningful response.
 

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No!

A change froma 120 to a 130mm stem is trivial. Even a change from an 80mm to a 120 only changes the length of the steering arm by 15%.

At high speeds you don't turn the wheel more than a degree or two, even to make a tight turn. Most people don't even realize that the bars have to be turned in the opposite direction of the turn at high speed. It's called countersteering. The first thing you learn in motorcycle training is to push on the right side of the bars (turn left) to make the bike lean to the right and turn right. Everyone who rides a bike does it, but few think about what they are doing. Negotiate enough high speed hairpins on a mountain descent and you'll either figure this out or crash.
 

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People usually figure out countersteering unconsciously without even knowing it. The problem comes when a car pulls out in front of you or you have to make a quick direction change at speed. If you haven't mastered countersteering your lizard brain may actually cause you to steer right into the obstacle.

Countsteering is a good thing to consciously practice every time you ride. When you are at speed (above 20mph) consciously push forward on the right-side handlebar to lean right. Push the left bar to lean left. You are basically turning the bars in the wrong direction. Sounds crazy but it works.
 

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I don't think so..

I've logged plenty miles on a motorcycle on mountian roads and hundreds of hairpin turns on a bicycle. Either one wants to go in a straight line without some help. If you don't keep applying a constant pressure to the right side of the bars in a hairpin, you'll find yourself over the centerline in a hurry. This is a common crach scenario. The rider comes into a corner too fast and instead of applying heavy prressure to stay in the right lane, he panics and quits pushing, crossing the centerline into oncoming traffic.
 

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I'll come back on topic sooner or later.....


C-40 said:
I've logged plenty miles on a motorcycle on mountian roads and hundreds of hairpin turns on a bicycle. Either one wants to go in a straight line without some help. If you don't keep applying a constant pressure to the right side of the bars in a hairpin, you'll find yourself over the centerline in a hurry. This is a common crach scenario. The rider comes into a corner too fast and instead of applying heavy prressure to stay in the right lane, he panics and quits pushing, crossing the centerline into oncoming traffic.
Motorcycles and bicycles work a tiny bit differently here, because of the location of weight and the application of greater power. IMO, C-40 is right in that you have to keep applying pressure to the inside bar, but it doesn't necessarily follow that it's pushing to the extent that the steering is turned past the centerline of the bike in the outboard direction.

Countersteering works to initiate a turn by moving the wheel track 'out from under' the center of gravity of the bike/rider, and so initiating the lean in the proper direction for the turn. From there, the geometry of the steering angle and trail work to keep the bike in balance, and since it's leaned, that balance necessarily means turning. The force vector of gravity and of the centrifugal (OK, centripetal for the engineers and physics majors amongst us) force have to combine to point thru the wheel patch, or physics wins and elbows lose.

If all is going as ideally designed, no steering pressure is required in either direction to continue the turn. However, most designs have "excess" trail, which helps to bring the bike back upright (making it far easier to handle and balance.) This means that continued 'outward' force is required to maintain the turn, even though it's not crossing the bike's center line - it's just keeping the front wheel on the natural line of the balanced turn, resisting it's natural desire (courtesy of the trail) to move to the inside and upright the bike.

A continued outward pressure to the extent of steering over the centerline (truly "crossed") would result in the bike laying over to the inside of the intended turn. It's rare that it happens on either type of bike, unless the rear is scrubbing out, or the turn was entered waaaaay too fast. Either way, it's not a stable situation. There can also be additional countersteering if the rider (particularly on a motorcycle) has grabbed a bunch of brake, as the nosedive from the suspension changes the geometry.

It's something our muscles know, if our brains do not - we maintain balance with the handlebars, and steer by shifting weight. And because of the excess weight of a motorcycle relative to the rider, a lot of that balancing happens by shifting the wheels out from under the weight. So, 'countersteering' is even more evident. But it's rare that it's actually 'crossed' steering, other than in the first instant of a turn.



Back on topic:

A 130 on a 56 won't be a problem as such, but it's not the choice I'd personally be likely to make. As compared to a 110 on a 58 (as your example), the more obvious changes (rather than steering moment) would be that you'd effectively be shortening the head tube. That would tend to create more saddle-bar drop, which you might or might not want. It would also move your center of gravity forward (relatively speaking, and in relation to the front wheel contact patch), which would tend to make the steering a bit more 'immediate' if you like it, 'twitchy' if you don't. The changes would be small, and you might be happy either way - you'd really have to try both to be sure. I personally value comfort and ergonomics over an ideal aero position, believing that for me it's more important to be able to consistently apply power than to use that power most efficiently. Different levels of strength, flexibility, and style of riding can make that equation flip.
 

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yeah choose the 110 58 over 130 56 unless your going for a crit or sprint bike. If you race and are a sprinter of sorts you'll like the setup on the 56 better but for general riding you find the 110 58 to probably work better for you. Stems always look best as parallel to the ground as possible.
 

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What Dan1 said. Normal steering only works on a bike at very low speeds. Any steering input used after the turn is initiated is the result of unbalanced forces for which compensation must be made.

Countersteering on a bicycle is less dramatic than it is on a motorcycle 'cuz the gyroscopic forces aren't nearly as large. Motorcycles exhibit a range of midturn behavior: some need pressure on the bars to the inside of the turn to keep the bike from standing up and running wide; some need the opposite to keep 'em from "falling" into the turn; and there are some that once in the turn are dead neutral. Bikes are the same....just more difficult to notice the effects mid turn on a bicycle.
 

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from my experience

shorter stems make for better crit bikes. maybe it's psych. but I find my bikes with short stems to be a tad quicker handling, on another note I find longer stems seem to stabilize the front end at high speed.
 
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