To put it another way, what makes a person think that a shorter stem might be a better fit? I'm 6'2" riding a 61 cm 2012 Bianchi Infinito. I try to ride for exercise and more for distance than speed. I rarely ride with hands on the drops. Mostly my hands are on the bars behind the hoods (fingers touching the hoods but palms not on the hoods). I'm looking for comfort mainly. If I stretch out too far or get too low, I get kind of a sore neck.
Currently I've got a 110mm stem. I'm building a back up bike so will put this bar and stem on the new bike and want to get a new stem for the Bianchi. I feel like the fact that I'm more comfortable sitting higher up and with my hands on the top bars or behind the hoods suggests that maybe a 100mm might be a better choice. The 110 is in the ballpark, don't get me wrong.

Are there decent "rules of thumb" about stem length (such as if you can see your front skewer behind your bar etc)?
Thanks

Use a shorter stem if you want a more upright position while riding. A longer stem will put your body more forward on the bike.

Remember that stem length also affects handling. A shorter stem will make steering "twitchier".

If you cannot easily bend your elbows when on the hoods, or your hands, shoulders or neck gets sore then your stem is probably too long and possibly too low. A shorter stem redistributes your weight off shoulders and arm and toward saddle as well as making you slightly more upright - although the ability to bend your arms more compensates a bit. Stem length should be considered before height, but if you can get a stem that is a bit longer to allow more vertical adjustment that may help as well.

You should make sure saddle height, tilt and fore-aft are proper first, as all can affect distance to the bars and weight distribution. If there are resources near you for proper fitting of your bicycle that would be helpful. Often if a shop is not available a local bike club has someone who is good at it. You need to be clear about your style of riding so that you are not set up too aggressively.

If you are on your own try Google (bicycle + fit, stem length, or saddle position). Be prepared to be overwhelmed – it’s not as simple as some say. Bars should hide the hub axle, knee over pedal axle, and leg straight with heel on pedal are all common guidelines for stem length, fore-aft and seat height, and each has it’s weaknesses. One fairly solid guideline though is to not tilt the saddle forward.

I would not worry about twitchier handling. The stem and bar form two legs of a triangle on each side. The hypotenuse (imaginary line between outer edge of bar and stem bolt) determines responsiveness (degrees of wheel rotation obtained by moving the outside of the handlebars a given distance). Reducing stem length only affects the short side of that triangle, changing the hypotenuse by a very small amount.

+1 No easy answer, spend some time on google, an endless number of opinions out there.

Ihorn, Many threadless stems can be mounted two different ways (right side up or upside down) so that if the stem is isn't 90 degrees from the steerer tube can offer slightly different handlebar height. Flip it on the Bianchi if the stem angles downward for a test before buying a stem.

Brad

No. It won't.

How are you positioning your back and pelvis when you ride? If you make a conscious effort to rotate your hips forward and flatten your back, you won't need to crane your neck as badly to look up. I know that when I started riding road bikes, I got into the habit of planting my rear as if I were riding an upright bike and then bending my lower back in order to get my hands to the handlebars... it sucked. Everything would hurt unless I took frequent breaks.

Yes, there are multiple benefits to riding with a flatter back. Part of fitting a bike is evaluating your riding position.

I have read mention of the handlebars at least partially obscuring the front axle, when you are on the bike, as being a good rule of thumb indicator of correct stem length. Top tube, and upper body/arm length obviously will play a part!

You may want to check out a local bike shop or two, most around here have a bin of various stems. They are more than happy to let you swap them out and ride with a few different sizes, and when you get one you like you keep that one and they'll keep theirs : ) I got a deal on some stems at jenson recently for 2 or 3 bucks a piece so I threw them a few extras and they were thrilled.

If you're uncomfortable, keep adjusting the bike. : ) Some people are more willing than others to sacrifice comfort for speed, or just don't care about comfort because of a short ride. I personally think they're silly.

Thanks for the advice. Largely I'm already pretty comfortable but after a while feel the need to sit more upright and put my hands on the top bars so that I can stretch my neck and back a bit. I've noticed that when I'm in my comfortable position (hands just behind the hoods) I can see the hub clearly behind the bars so I might try a 100mm stem. Thanks for the advice. I'll have to check out some sites on the internet and re-examine my riding position.

Google sucks, go find a helpful LBS that will allow you try different lengths and raises.

To me your body is giving a clear indication that you need less reach to the hoods. Again, you have to approach your entire position starting with the saddle, but if you end up changing only the stem 10mm may not be enough, as that's only 3/8 of an inch. It sounds to me like a 90 may be the better choice. Also, make sure at your size that the bars are wide enough for you. Bar shape varies as well. I know to some that's going too far but making sure everything is right can make a big difference. Here's what I consider a very good treatment of the handlebar issue. \

https://www.bikerumor.com/2010/12/28/...ar-size-shape/

Oh, but it does. Depends on how "short" you define short to be. Agreed it may not be much but it's there.

It's too small to consider in any typical reduction in stem length. 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. If you draw a straight line from the stem bolt towhere the rider is gripping the bars that is the turning radius, which determines how far you have to move the bars to achieve a given angle.

Assuming the rider is gripping the bars about 50mm forward of the straight portion of the bars:
The original turning radius is 269 mm
The reduced turning radius is 256 mm
The difference in achieving a ten degree turn of the bars is 2.2mm, or less than a 5% increase in "twitchiness." I very much doubt most riders would notice that difference.

Trust me, I know the math.

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

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%.

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.

Used 6 cm stem, no problems. Didn't feel anythign twitchier. Now have 12 cm stem. Also no problems. Experimented with reach, but didn't feel any handling difference.

Don't know what your stem looks like, but I'm nearly certain it's not a perfect 0-degree stem. if it's angled down, try flipping it up (so it angles up away from the tire) before you start spending money on new stems. Also, if you have spacers, try playing around with the stack of them (all below the stem, some above and some below, all above the stem) while you're at it. These adjustments won't cost you anything and will give you a better sense of what to be looking for. Also, if you have one 20mm spacer, head to the LBS and 'make change'- get a 10mm, a 5mm, and two 2.5mm (3mm will work if 2.5mm can't be found) spacers.

Yes, I see I made a math error. I was trying out different scenarios and must not have recorded the right numbers at the end. However in my post I said it was small in a "typical" reduction in stem length, so your 50 mm difference does not really apply. Very few people will reduce stem length even as much as 30 mm, and as you were giving advice/info to the OP one would assume you would be addressing his situation, not a theoretical one. As for knowing the math, it would have helped if you had given some backup for your stance in the 1st place.

Cheers.

Also consider your saddle position. If your saddle is too far back that may be contributing to your feeling too stretched out.
Try KOPS, knee tibia tubercle over pedal spindle (if you haven't already). You can make a plum line with a string and a metal washer.

KOPS is popular but does not give a correct position. Google KOPS myth - the video is especially instructive about how KOPS can result in a poor position.

We both agree that there is a change in [theoretical] response with a change in stem length. Also agree that a lot of people will not be able to notice the change due to the reduction. But there are some people, albeit a very few, that do. I have some riders in my group that tell us about how "responsive" his bike became going from a 110 mm to a 90 mm stem. I don't know whether it was real or just perceived.

Granted mine was quite an extreme case, but the argument still holds true.

As for the OP "noticing" the difference if he changes stems, I really don't know. He may actually feel it, or just perceive something has changed.

It's hard to quantify a "perceived feeling". Though there is a science (psychophysics) that deals with that, a lot of the observations cannot be directly translated into an empirical formula. And I didn't really want to bore people with math (no offense meant) so I just tried to keep it simple in my original post by using the perception factor.


I appreciate the intellectual discussion, especially coming from a person who understands both the math and the real-world implications.

No harm, no foul man.

Cheers.