Tips | RandoTips

How To Choose The Perfect Stem

The wild west. A small and dusty town. A bar. A derivative walks into the bar. All the functions scatter. In a dark corner, a lone function dares to stand his ground. The derivative walks up to the lone function and asks, “Who the hell do you think you are?” Without skipping a beat, the function, with eyes barely visible from under the brim of his hat, replies “I’m ex.” The derivative gives a small, knowing grin and says, “Today is not your lucky day, I’m d/dy.” – Original source unknown

So it’s been a while since whipping out the high school math books. I mean who needs that kind of grief in the real world?

Well, ladies and gents, for the first time ever, I’m going to show you a practical use for your trigonometry classes.

But fear not, I’ll be holding your hand through this, you just need to plug in the numbers.

Why This Is Useful

The best option for choosing a stem is to have yourself measured on your bike and get a stem that matches the angle and length of the one used for measurement. There is no guessing here, and it’s all worked out well.

But what if your bike is not quite right, or if you didn’t have it fitted, or after some time the “correct” fit just doesn’t quite cut it?

Amongst other things, the stem will need to be adjusted.

Simple?

No.

Doable?

Yes.

Because of the angles, every adjustment of the stem affects not only the height, but the distance from the top of the saddle to the handlebars.

How My Dilemma Helps You

I am 6’1″ (185mm) and my build gives me legs that are quite long, but not long arms. I’m like a Tyrannosaurus on wheels.

Ideally I’d be riding a custom built frame that’s just right for me, but I don’t have deep pockets for that kinda stuff, so standard consumer bikes is the only option. Fitting my body on a standard, production bike takes a bit of work, thought and adjustment.

My current mountain bike setup puts the handlebars about 79cm in front of the saddle (measured from where my sitting bones would rest). This is a position I have had on my bikes for over 10 years already, but after riding a small, folding bike that is only 72cm from seat to handlebar, and finding it quite comfortable, I need to make some adjustments to my bigger bike. The vertical difference between saddle and handlebar currently puts the handlebar 2cm below the saddle.

There is one other sure giveaway of being too stretched out. When riding for over three hours I often place the middle of my fingers on the handlebars, rather than the palm. This position eases strain in my back and just feels right.

Target: move handlebars 4cm closer to seat, and raise them by up to 2cm.

Ready?

Let’s go.

Preparation

First, some abbreviations:

hl = horizontal length, the length of your stem measured directly forward, parallel to level ground (we’ll calculate this number)
vh = vertical height, the height of your stem as measured directly upwards (we’ll calculate this number)
sa = stem angle, the angle marked on the stem
sl = stem length, the length marked on the stem
hta = head tube angle, the angle of your head tube (we’ll measure this)

To measure the head tube angle:

Take angle from manufacturers specifications (I did)

Stand bike securely (lean against something, tie rubber bands around brake levers and handlebars to stop sliding)
Find something long and straight (broom, etc)
Drop line straight down the head tube to the floor
Measure the head tube angle as shown in the diagram, between the floor and that line (you’ll need a protractor for this)

To measure the stem length:

Check specifications (often written on the underside of the stem)

Measure from the center of the head tube to the center of the handlebar.

The Math Part

You’ll need the online scientific calculator (or a real one) for these.

Calculate horizontal length and vertical height.

bignum = 90 – head tube angle + stem angle

horizontal length = cos(bignum) x stem length

vertical height = sin(bignum) x stem length

Original Stem Figures

My current figures are…

stem angle = 25
stem length = 120mm
head tube angle = 72

so…

bignum = 90 – 72 + 25 = 43

horizontal length = cos(43) x 120 = 87mm

vertical height = sin(43) x 120 = 81mm

Find A New Stem

Now you just need to plug in the numbers of a new stem to find the one that is closest to your requirements.

To get 4cm extra height is quite a rise, so I’ll try out a 45 degree stem first. These are available in a range of lengths, this angle is probably right, but the length will make a big difference.

120mm stem with 45 degree rise:

bignum = 90 – 72 + 45 = 63

horizontal length = cos(63) x 120 = 54mm

vertical height = sin(63) x 120 = 106mm

So I’ve moved back 33mm, but moved up by 25mm.

I was hoping to move further back and don’t need that much more height.

Next…

100mm stem with 45 degree rise:

bignum = 90 – 72 + 45 = 63

horizontal length = cos(63) x 100 = 45mm

vertical height = sin(63) x 100 = 89mm

Overall, for my bike, they work out as shown in the table below.

Stem	Horizontal Length	Vertical Height
120mm, 25 degree	87mm	81mm
120mm, 45 degree	54mm	106mm
100mm, 45 degree	45mm	89mm

Conclusion

Taking the time to get the right stem is worth it. However, this isn’t really needed any more and there are plenty of shops with adjustable stems in their stock. It’s much easier to use one of those to determine the right length, etc.

If you are in the market for a very expensive stem, I’d recommend just buying an adjustable one (not that expensive), and then spend a little less on the full stem when you’ve determined the right size and length.

Pedaling for Greatest Efficiency

“Just hop on and enjoy the ride” – a mantra I can appreciate.

Throw all concerns to the wind, just get on with it, cut to the heart of a great ride.

But…

If you want to go that little bit further, save that little bit more energy and make your long efforts feel that much easier, then a slight change in riding style is probably called for.

The reality is that any ride is directly affected by how effectively you pedal. When going for distance or going for speed, or anything beyond a quick spin around the block, how fast you pedal has a direct effect on your overall energy usage and power output.

Usually…

People will hop on a bike and start to pedal at a pace that feels comfortable. And surely being comfortable is a major concern, right?

Or course.

But what we find comfortable is actually more accurately described as “what you’re used to”. Pedaling in the same way as you always have is just falling back on your experience, and chances are that your experience has probably taught you some bad habits.

To break those bad habits you’ll need to bring a bit of science and timing into your pedaling action. So here’s the background information.

What is Cadence?

Cadence is how fast your pedals are turning around while you’re pedaling.

Thanks to the invention of gears you end up turning your legs around at about the same cadence all the time. You adjust the gears to be easier when you are climbing a hill and you adjust them to be harder when you are descending or on a flat.

Low cadences require you to put more pressure on the pedals to maintain the same speed. This puts stress on your muscles for hard strength. Spinning as low as 60 puts most of the strain on these parts of your muscles.

Higher cadences require you to put downward pressure on your muscles but require you legs to turn over very quickly. Racers will typically keep their cadence over 90, while spin at up to 120 during time trials and such speed events.

What Is The Best Cadence?

This article on Cycling Performance suggests that the perfect cadence is somewhere from 85-100 RPM.

It varies depending on the terrain, but a smooth, fast cadence will increase your overall efficiency.

How do you work out your cadence?

Many bike computers/speedometers and fancy bike gadgets work this out for you. They will have a sensor mounted by the crank.

But if you don’t have one you can get a general idea of how fast you are pedaling.

You’ll need:

An easily visible timer (preferably on the handlebar, a watch can be wrapped around the handlebar for this purpose too, if necessary)
A clear road (because your focus will not be entirely on the road for up to 15 seconds)
You math hat

Counting cadence:

1 revolution = right side pedal movement from bottom position (6 o’clock), all the way around, past 12 o’clock, and back to the 6 o’clock position

Timing (best shown by example):

6 seconds = every stroke from the moment the clock shows :00 to the last moment it shows :05 (stop counting once the clock shows :06)
12 seconds = every stroke from the moment the clock shows :00 to the last moment it shows :11 (stop counting once the clock shows :12)

The process:

Start riding
Settle into a single gear at a constant speed
Start counting pedal strokes when the timer hits :00 (first stroke is the second time the right pedal is at the bottom)
Stop counting as soon as the timer hits :06 (or :12)
Multiply the result by 10 (or 5) to get your cadence

Because you’re multiplying by 10, it’s important to start and stop counting at the right time.

If your cadence is too low, change to an easier gear (bigger cog at the rear or small chainring at the front). If it’s too high, change to a bigger chainring at the front or a smaller cog at the back.

How Will This Help Anything?

There is a useful test you can do which is outlined at the link above.

The test goes like this:

Thorough warm-up (20 minutes, with a few fast efforts)
Rest for 5 minutes
Pick your usual gears with slower cadence
Go flat out for 15 minutes and time it
15 minutes rest
Change to an easier gear
do 15 minutes hard again

Try the same two days later, with the higher cadence part first and you will be able to feel the difference.

Panda Portraits – You, Your Bike and Your Camera

If you ride a bike much you’ve probably taken a picture like this. Raw, on the go, just you, just for fun.

Well, sometimes you just wander into things that you don’t know and don’t expect.

For some reason I was on Flickr and I wondered into a picture in the same style as the one above, either captioned or titled as “Panda”. Now to set the obvious aside, there were no big black and white animals in the shot.

So, dutifully following the rabbit trail of digital knowledge I discovered the Panda Portrait Flickr group.

As it turns out, the panda portrait is a very specific kind of cycling photo.

It’s a photo taken of yourself, by yourself, on your bike, while moving. The only exception to these rules is shooting the aftermath if you crash while doing it.

Here are a few tips (from a non-photographer who uses his cellphone to take pictures most of the time):

Set the camera to take the picture faster (set the ISO to 400 or higher, higher is faster, compensates for wobbly arms)
Try a few first to get an idea of where to aim (or just forget it and see what happens, just as fun)
If you really want a decent shot, check the image after taking (take again if your head is half cut off etc.)
Watch the road! Quieter roads without too many cars are better. You’ve been warned!
Capture yourself, bike and… something else. Getting a friend in the shot, or something interesting in the background adds a little something to the basic panda.

In the end, just have fun. Be aware that although you probably won’t get fined for using a cellphone on your bicycle, that you still need to pay attention to the road and where you’re going.

Here are some interesting ones for your viewing pleasure. Big, happy smiles were my main criteria when picking. (Photos that are not mine are linked to their pages on Flickr)