Trust me, I know the math.
Originally Posted by
cny-bikeman
Let's take the OP's 110mm stem and reduce it all the way down to 80mm, and assume fairly narrow bars - 40cm or 200mm per side. ... the rider is gripping the bars about 50mm forward ...
The original turning radius is 269 mm
The reduced turning radius is 256 mm
First off, your math is wrong.
At a stem length of 110 mm: r = sqrt[200[SUP]2[/SUP] + (110 + 50)[sup]2[/sup]] = 256.12496 mm
The arc length traversed for a 10[sup]o[/sup] turn: l = (pi/180)*10*256.12496 = 44.70224 mm
For a stem length of 80 mm: r = sqrt[200[SUP]2[/SUP] + (80 + 50)[sup]2[/sup]] = 238.53721 mm
And the arc length for the 10[sup]o[/sup] turn: l = (pi/180)*10*238.53721 = 41.63259 mm
The difference in achieving a ten degree turn of the bars is 2.2mm, or less than a 5% increase in "twitchiness."
That's a difference of 3.0659 mm or a 6.86688% increase in "twitchiness."
I have an old steel bike fitted with a "short" 60 mm quill stem, and had a "narrow" 38 cm bar. Disregarding the bar in this case and just using the stem length for this argument:
The turning radius becomes: r = 228.25424 mm
And the arc length is: l = 39.83788 mm
Increasing the "twitchiness" to 10.88167%.
I very much doubt most riders would notice that difference.
The nearly 11% increase in response is generally regarded as perceptible to most people.
It may or may not be the case for the OP, but even without the math I can "feel" the difference. Thus the reason for the quotation marks on term
twitchier in my original post.