Alpinist Cockpit -Fit

[flyordie]

I switched from SW Shallow Drop 42cm + -12/100mm stem to the Alpinist cockpit (100/42). The Alpinist should sit 10mm higher (since -6) and otherwise be very close to identical. Weirdly enough the reach feels longer now (unfortunately I didn't measure the "before") and I can't explain it. Bar rotation is within 1 degree.

Does anyone else have a similar experience?

[LanceLegstrong]

Maybe the shifters are slightly lower. Measure the actual stem length, they're not always exact. Other than that, it may just be a position change and all be in your head.

[jmfreeman535]

A change to the stem angle is going to cause a change to the reach, as well. The stem travels in an arch, so a -12 is going to have a shorter reach than a -6.

Then as Lance pointed out, the levers could be in a different position due to the bend shape of the Alpinist.

[mgrl]

Eh? -12 has longer reach than -6

[Johnny Rad]

Love this stem graphical comparison calculator

http://yojimg.net/bike/web_tools/stem.php

[Karvalo]

A change to the stem angle is going to cause a change to the reach, as well. The stem travels in an arc, so a -12 is going to have a shorter reach than a -6.

It's the other way round. A -17 stem (on the average road bike) is horizontal, so the closer you get to that, the longer the effective reach is.

[jmfreeman535]

Yes...and no.

Based on a 100mm stem with a 73 HTA, the -12 will be 1-2mm longer (depending on spacers). On paper. But, when you take the actual seat-to-lever measurment I bet that you will find it longer with the -6 stem.

There is a lot more to it than just the stem angle...bar and lever orientation, back/arm extenstion and wrist angle can all change, thus affecting the actual reach once the bike is set up for a comfortable position.

[alanyu]

Yes...and no.

Based on a 100mm stem with a 73 HTA, the -12 will be 1-2mm longer (depending on spacers). On paper. But, when you take the actual seat-to-lever measurment I bet that you will find it longer with the -6 stem.

You are totally wrong except very few conditions. A -6 stem reduce both dx and dy to your saddle, which is the most cases, and simply results in a shorter seat to lever distance as sqrt(dx^2+dy^2)

[jmfreeman535]

You are totally wrong except very few conditions. A -6 stem reduce both dx and dy to your saddle, which is the most cases, and simply results in a shorter seat to lever distance as sqrt(dx^2+dy^2)

Again, on paper, you are correct. Real world, not always. If the OP had kept the exact same bars, roation angle and lever position, and simply swaped the stem from a -12 to -6, then yes the reach would have been reduced. But that was not the case.

Your math relys on everything besides the stem angle remaining a constant. However the bar rotation and lever position changed, and both of those have an impact on the seat to lever distance.

Bike fitting is not clean and simply math.

[Karvalo]

Yes...and no.

Based on a 100mm stem with a 73 HTA, the -12 will be 1-2mm longer (depending on spacers). On paper. But, when you take the actual seat-to-lever measurment I bet that you will find it longer with the -6 stem.

There is a lot more to it than just the stem angle...bar and lever orientation, back/arm extenstion and wrist angle can all change, thus affecting the actual reach once the bike is set up for a comfortable position.

Lets be clear - in your first post you were specifically talking about the arc of the stem, and you got it wrong.

Now, if you can hypothesise a situation where someone changing a stem goes on to fudge everything else to do with their cockpit setup then sure, the -6 could be longer. But then it becomes equally valid to say a 100mm stem is going to have a longer reach than a 110 because hey, why not? It definitely could do. Not a very useful statement though, is it?

[alanyu]

You are totally wrong except very few conditions. A -6 stem reduce both dx and dy to your saddle, which is the most cases, and simply results in a shorter seat to lever distance as sqrt(dx^2+dy^2)

Again, on paper, you are correct. Real world, not always. If the OP had kept the exact same bars, roation angle and lever position, and simply swaped the stem from a -12 to -6, then yes the reach would have been reduced. But that was not the case.

Your math relys on everything besides the stem angle remaining a constant. However the bar rotation and lever position changed, and both of those have an impact on the seat to lever distance.

Bike fitting is not clean and simply math.

You were talking on stem of changing angle, and got the conclusion that -6 stem has a longer reach, which is wrong

A change to the stem angle is going to cause a change to the reach, as well. The stem travels in an arch, so a -12 is going to have a shorter reach than a -6.

Then you tried to save yourself by cross talking with other cockpits. LMAO

[jmfreeman535]

Yes, my first statement was very incomplete, and thus wrong. I'll own up to that.

But if you two can't agree with me that bar roatation and lever position have a major affect on overall reach, and can lead to a setup with -6 stem having a longer reach than one with a-12, then there is no point in me countiuing this discussion.

[Karvalo]

Yes, my first statement was very incomplete, and thus wrong. I'll own up to that.

But if you two can't agree with me that bar roatation and lever position have a major affect on overall reach, and can lead to a setup with -6 stem having a longer reach than one with a-12, then there is no point in me countiuing this discussion.

Sure, if you agree that a 100mm stem can be longer than a 110 for the same reason.

But then we're not actually discussing which stem is effectively longer, we're just saying that stuff can be setup differently to other stuff.

And it's not that your original statement was incomplete and therefore wrong, it was specifically and explicitly wrong about how stem angles/arcs work.