We’ve designated 2014 as the year of testing here at Fair Wheel. This year we have several tests planned and we’re going to kick them off with the first of the series, stems. The stem testing includes both road and mtb.

We’ve also once again brought back our favorite engineer, Jason Krantz. Jason’s a mechanical engineer whose graduate work focused on the intersection of composite materials and finite element analysis. Jason has worked for several companies in the bicycle industry and never fails to amaze me with the depth of his cycling related knowledge. He adds real value to all of the tests we perform.

Disclaimer: A lot of typing and numbers have gone into this article and we apologize in advance for any typos, but would warn that the possibility of mistakes is present.

Some Initial Notes on Testing

Testing Method: During preliminary testing we determined that the first run of each stem in the fixture produced results that varied significantly from tests 2 and 3 (which produced consistent results each time). We attribute this to a settling of pieces in the fixture. Each stem was mounted in the fixture and the testing performed 3 times. The first test was tossed out and tests 2 and 3 we’re recorded and then averaged. All stems tested were 11cm with the exception of a few which are not available in those lengths. Each stem was mounted with it’s recommend torque specs and preloaded with 20 pounds of force applied 10 inches from the stem (about half way between a road bar and mtb bar) Once preloaded the equipment was zeroed and another 100 pounds of force was added and a measurement recorded. The measurement was taken at the point of load, again 10 inches from the stem.

Loads Tested: While the actual load doesn’t matter because the response of the structure is linear. [That is, a stem with a s stiffness of 150-foot pounds per degree will deflect one degree with a torque of 150 foot-pounds and two degrees with a torque of 300 foot-pounds.] Jason selected a load of 100 pounds because it’s a nice round number, and pretty realistic to what some riders may experience. For a sprinting rider, let’s say he is pushing on the left pedal with 300 lbf (in other words, he can squat 600 lbs). The pedal is about half as far from the frame centerline as the handlebar is, so it would take a reaction force of 150 lbs at the right-hand bar to counteract the pedaling force. This is the same as applying 75 lbf up on the one side of the bar and 75 lbf down on the other; the moment at the stem is the same.

Normalizing for Stem Length: In theory, it’s possible to measure a particular stem of one length and extrapolate its results to longer or shorter versions of the same stem model. In technical terms, this is “normalizing for stem length.” We can do this because torsional displacement is directly proportional to length for a tube of a given cross section. It’s true that a good engineer will use thinner walls on shorter stems (which see lower stresses) and thicker walls on longer stems (which see higher stresses). Still, normalizing to length within a single stem make and model is valid to a first approximation, at least with metal stems. A composite stems is a different beast, because layups (AKA laminate schedules) can vary significantly with length.

While torsional displacement is directly proportional to stem length, bending displacement is proportional to the cube of the length. Our first pass at a stem test setup measures combined bending and torsional displacement, so it would not be valid to extrapolate to longer or shorter stems, even within the same model, at least if you’re looking for absolute values.

If you’re interested in relative values–for example, if you want to know whether stem A is stiffer than stem B–then these results should be quite useful regardless of the actual length you intend to use.

For this test we used 11cm stems in every case except 2 (Pro Vibe Sprint Carbon and Syntace F119) which are both 10.5cm. The stems were similar enough in length that we did not normalize any stems in this test, but in the future we may test some stems that need to be normalized for a fair comparison.

Stiffness to Weight Ratio: This was calculated using =((1/avg. defl) / weight) * 1000

Bolt Material: One question we wanted to answer was if there was a noticeable difference between stems with titanium and steel bolts. We selected a few random stems and tested them both with titanium and steel bolts and found no meaningful difference in deflection in stems with one material over the other.

Mounting Direction: We also wanted to see if mounting a stem with a rise vs a drop made a difference in the deflection. While we were able to measure a difference, less than 0.1 mm at 100 pounds, it was not enough to say that there is a meaningful difference, and was likely within margin of error of the testing.

Notes about Stem Angles. One other item we wanted to test was the difference in like stems with different angles. We tested a couple of stems that are available in both 7 and 17 degree angles and found that 17 degree stems deflected an average of 7% less. The tested stems vary from 5 to 10 degrees which should result in deflection variations of up to about 3%, so keep that in mind when comparing two stems of different angles.

Carbon Fiber vs. Aluminum: – Carbon fiber stems don’t offer the weight savings that, say, carbon fiber rims do. There’s a reason for this: stems are regularly stressed in three ways: bending, torsion and shear. In other words, the stresses in a stem are nearly isotropic (uniform in all directions). Carbon fiber is highly anisotropic (stiffer/stronger in one direction than in the others). When you try to lay up anisotropic carbon to deal with isotropic stresses, you end up with what engineers refer to as “black aluminum,” or pseudoisotropic carbon–and a weight that’s very close to an aluminum stem.

There may be other advantages to a carbon stem; vibration damping is one that is often put to the forefront of the debate. It’s true that composite structures generally damp vibration better than metallic ones, and there may be real-world damping benefits to a carbon stem. One way to test stem damping would be to wire an accelerometer to the stem and then strike it gently with a hammer, reading the accelerometer data to see how quickly the vibrations dissipated. This ring-down test may be on the Fairwheel menu for a future article, but is outside the scope of this test.

Mixed materials. Hybrid stems, a carbon overlay on an alloy stem. We tested only a couple of these but neither did well, we’ll do more testing on others in the future to develop out thoughts on this medium further.

We tested two similar stems one in full alloy (7s) and one in hybrid (vibe carbon) to see if there was an advantage to the hybrid stems. Both are the same weight and same dimensions with the same puzzle lock clamp. The difference being that the Carbon has thinner alloy, reinforced with carbon. Deflection was noticeably different, the full alloy was significantly stiffer than alloy/carbon.

To speculate on why tests put carbon/aluminum stems on the flexible end of the spectrum, one might consider two competing design constraints. First is galvanic corrosion. When aluminum and carbon touch each other, they’ve made a weak battery. The electron-swapping that goes on will cause an aluminum/carbon part to fail in short order. To avoid this, manufacturers use a layer of insulating material. This layer is often a fiberglass/epoxy composite but could be plain epoxy. Neither material is as stiff as aluminum, so you’re taking a stiffness loss right away.

Secondly, the market won’t tolerate a carbon-wrapped aluminum stem that is both more expensive and heavier than its plain-aluminum counterpart. So manufacturers are forced to use thinner-walled aluminum forgings for their carbon-wrapped stems than they do for their straight-up aluminum stems. Effectively, they’re replacing relatively stiff aluminum with relatively compliant fiberglass and/or epoxy.

Making matters worse, some carbon-wrapped aluminum stems use a 0°/90° weave for aesthetic reasons. This weave’s stiffness reflects the dreaded pseudoisotropy referred to earlier, and is particularly compliant in shear–which, in a stem, determines torsional stiffness.

The net result is a carbon-look stem that has adequate strength but more compliance (and possibly better vibration damping) than a “pure” aluminum stem.

To be clear, the above is what engineers call a SWAG: a Scientific Wild-Ass Guess. It’s a reasonable first pass, but there may be other factors at play that we haven’t considered and which will be further explored in future tests.

Now on to the results

*You’re viewing a truncated table since we can’t fit all the data on a cell phone screen. The data is listed out below under each stem, just no in an easy to compare table. To see all 9 columns and seven data points we collected on every stem please re-visit our site on a desktop or laptop
Model Weight (g) Stiffness to Weight
Arx Team 129.4 2.033
Carbon 120.1 2.07
OC Road 87.7 2.25
S1 144 1.77
Arrow 138.6 1.68
Flyride 127.3 1.72
Evo 110.8 1.7
Vibe 7S 137.3 1.79
Vibe Carbon 138.4 1.38
Vibe Sprint Carbon* 199.4 1.87
Vibe Track Carbon 186.9 1.96
XCR 117.6 1.58
Turbine 144 1.59
260 113.5 1.83
4-Axis Carbon 120.2 1.45
F119* 132.2 1.66
X2 146.8 1.62
X4 168.2 1.74
4 109.4 2.04
* Stems measured at 10.5cm vs the standard 11cm effecting stiffness results.

Thoughts on Each Stem

3T Arx Team

3t Arx Team Stem
The 3T arx did quite well in testing making it one of the most well rounded stems we tested. Minimal deflection with
a good weight gave this a high stiffness to weight ratio. Available in a couple of finishes and a full range of
sizes. It includes ti bolts for a near $100 price tag which make it a top choice for all around performance value.

  • Manufacturer: 3t
  • Model: Arx Team
  • Stack Height: 40mm
  • Avg: Def: 3.8
  • Weight: 129.4 gr.
  • SxW: 2.033
  • Material: 7075
  • Bolt Material: Titanium
  • Angle: 6 degree
  • Price: $110

ENVE Carbon

Enve Carbon Stem
Full carbon stem which had the 2nd highest stiffness to weight ratio of all tested stems. Good looking and available
in a full range of sizes. Full carbon construction should provide additional vibration damping over alloy stems.
Textured face plate adds to it’s ability to hold a bar in place with lower torque which reduces the chance of
damaging a lightweight carbon bar. Includes ti bolts but is a bit more expensive than alloy counterparts.

  • Manufacturer: Enve
  • Model: Carbon
  • Stack Height: 41mm
  • Avg: Def: 4 mm
  • Weight: 120.1 gr.
  • SxW: 2.07
  • Material: Carbon Fiber
  • Bolt Material: Titanium
  • Angle: 6 degree
  • Price: $265

Extralite OC Road

Extralite Road OC Stem
The lightest (by a significant margin) stem that we tested. In spite of being near the bottom in terms of deflection
it still has the highest stiffness to weight ratio thanks to it’s super light weight. Extralite lists the stem as
being reversible but logos printed in only one direction make us think nobody would run it in a rise position. It’s
more expensive than all the other alloy stems in the test, but it is exquisitely made and has very nice attention to
detail with items such as the custom torx head titanium bolts. We would like to see some sort of gnurling on the
inside of the face plate to help with bar slippage issues that have occasionally been reported.

  • Manufacturer: Extralite
  • Model: OC Road
  • Stack Height: 40mm
  • Avg: Def: 5.06
  • Weight: 87.7 gr.
  • SxW: 2.25
  • Material: 7075
  • Bolt Material: Titanium
  • Angle: 8 degree
  • Price: $230

Far and Near Sl

Far and Near S1 Stem
This stem was a surprise to us. Scoring 5th in deflection gives it a well balanced stiffness to weight ratio, which
could be improved upon with the addition of some titanium bolts. It is available in a full range of lengths in both
white or black with a range of colored faceplates.

  • Manufacturer: Far and Near
  • Model: S1
  • Stack Height: 38mm
  • Avg: Def: 3.92
  • Weight: 144.0 gr.
  • SxW: 1.77
  • Material: 6061
  • Bolt Material: Steel
  • Angle: 6 degree
  • Price: $85

KCNC Arrow

Kcnc Arrow Stem
Available in both 7 and 17 degree this stem offers more choices in fit than most stems in the test. The small
titanium bolts do tend to strip in the head fairly easy. It falls right into the middle of the spectrum in terms of
deflection making it a pretty good all around stem.

  • Manufacturer: Kcnc
  • Model: Arrow
  • Stack Height: 38mm
  • Avg: Def: 4.28
  • Weight: 138.6 gr.
  • SxW: 1.68
  • Material: 7050
  • Bolt Material: Titanium
  • Angle: 7 degree
  • Price: $90

KCNC Flyride

Kcnc Flyride Stem
The Flyride is the least expensive stem we tested in this round. It’s available in several clamp sizes for different
road and mtb handlebars. Even with it’s steel bolts it’s on the lighter side of the stems in the test and falls
right in the middle of stiffness to weight ratios.

  • Manufacturer: Kcnc
  • Model: Flyride
  • Stack Height: 38mm
  • Avg: Def: 4.55
  • Weight: 127.3gr
  • SxW: 1.72
  • Material: 6061
  • Bolt Material: Steel
  • Angle: 5 degree
  • Price: $45

New Ultimate Evo

New Ultimate Evo Stem
The New Ultimate Evo is on the lighter end of stems in the test, 3rd lightest tested. Deflection is higher than most
stems which puts it just short of middle position in terms of stiffness to weight ratios. The New Ultimate does
however have a 90kgs rider weight limit. It includes titanium bolts and has a unique face plate attachment method
that is claimed to significantly reduce stress on a carbon bar. Available in a full range of sizes from 7cm to 13cm
and in both black and white.

  • Manufacturer: New Ultimate
  • Model: Evo
  • Stack Height: 40mm
  • Avg: Def: 5.3
  • >Weight: 110.8gr
  • SxW: 1.70
  • Material: 7050
  • Bolt Material: Titanium
  • Angle: 6 degree
  • Price: $115

Pro Vibe 7s

Pro Vibe 7s Stem
Most of the Pro stems tested fell to one extreme or the other, the 7s is definitely the most well balanced of all of
them. Falling right in the middle in terms of weight and deflection it ends up a little better than middle (8th out
of 19) in terms of stiffness to weight ratio making it one of the most well rounded stems in the test. Has a unique
puzzle lock faceplate attachment method and is available in a full range of sizes in both black and white.

  • Manufacturer: Pro
  • Model: Vibe 7S
  • Stack Height: 44mm
  • Avg: Def: 4.06
  • Weight: 137.3gr
  • SxW: 1.79
  • Material: 7075
  • Bolt Material: Steel
  • Angle: 10 degree
  • Price: $100

Pro Vibe Carbon

Pro Vibe Carbon Stem
As far as we can tell the Vibe carbon is a 7s with some material removed and replaced with carbon, which does not
seem to work in it’s favor. In terms of weight it’s almost identical to the 7s but in terms of deflection it scores
on the low side, being 4th from bottom. That drags it’s stiffness to weight ratio down to the bottom position in the
test. Available in full range of sizes from 8cm to 14cm.

  • Manufacturer: Pro
  • Model: Vibe Carbon
  • Stack Height: 39mm
  • Avg: Def: 5.24
  • Weight: 138.4gr
  • SxW: 1.38
  • Material: Alloy/Carbon
  • Bolt Material: Titanium
  • Angle: 10 degree
  • Price: $180

Pro Vibe Sprint Carbon

Pro Vibe Sprint Stem
This was the stiffest stem tested by a large margin. (not considering the very similar Pro Vibe Track) This was the
2nd heaviest stem in the test though, beating only the Pro Vibe Track. It should be noted that this stem was a 10.5
when almost all others in the test were 11cm. Obviously this stem wasn’t built for the rider concerned with weight,
only the one concerned with absolute stiffness, and still it managed to snag 6th spot in terms of stiffness to
weight.. Available only in a few sizes.

  • Manufacturer: Pro
  • Model: Vibe Sprint Carbon* (10.5cm)
  • >Stack Height: 39mm
  • Avg: Def: 2.69
  • Weight: 199.4gr
  • SxW: 1.87
  • Material: Carbon Fiber
  • Bolt Material: Steel
  • Angle: 10 degree
  • Price: $270

Pro Vibe Track Carbon

Pro Vibe Track Stem
This stem is not a current model but being so similar to the Vibe Sprint Carbon we wanted to see how they compared.
The two tested very similarly in every aspect with the track being a couple grams heavier and the Spring being
slightly more stiff. (though to be fair if both were 11cm instead of the sprint being a 10.5 we expect they’d be
almost identical. Overall this stem was extremely stiff and being slightly lighter than the Spring it bettered it by
one spot in terms of stiffness to weight sitting in the 5th spot.

  • Manufacturer: Pro
  • Model: Vibe Track Carbon
  • Stack Height: 40mm
  • Avg: Def: 2.73
  • Weight: 186.9gr
  • SxW: 1.96
  • Material: Carbon Fiber
  • Bolt Material: Steel
  • Angle: 10 degree
  • Price: $280

Pro XCR

Pro Xcr Stem
The Pro XCR was the 2nd from the bottom in terms of deflection of all the stems tested. It is one of the lighter
stems, being the 5th lightest in the test, but the poor deflection test pushed it’s stiffness to weight ratio down
to 3rd from the bottom. Being that it’s not that different from the 7s We have to wonder if the a big part of that
was caused by the difference in the upper attachment point for the face plate. Available in a full range of sizes.

  • Manufacturer: Pro
  • Model: XCR
  • Stack Height: 39mm
  • Avg: Def: 5.38
  • Weight: 117.6gr
  • SxW: 1.58
  • Material: 7075
  • Bolt Material: Steel
  • Angle: 5 degree
  • Price: $100

Race Face Turbine

Race Face Turbine Stem
The Race Face Turbine posted average deflections, right in the middle of the field. However it was a little bit
heavier than average which dragged down it’s stiffness to weight ratio to 4th from bottom.

  • Manufacturer: Race Face
  • Model: Turbine
  • Stack Height: 39mm
  • Avg: Def: 4.38
  • Weight: 144.0gr
  • SxW: 1.59
  • Material: 7075
  • Bolt Material: Steel
  • Angle: 6 degree
  • Price: $95

Ritchey 260

Ritchey 260 Stem
The clamp on the 260 looks different than most, and is said to dramatically reduce stress on the bar. The drawback
to the clamp is that it does make bar changes a little bit more difficult, though certainly not unmanageable. The
260 was the 4th lightest stem in the test and just a couple spots below middle in terms of deflection which balance
it’s stiffness to weight ratio quite nicely, 7th out of 19 makes it a couple spots better than middle. Available in
full range of sizes, not only in length but rise as well as finish.

  • Manufacturer: Ritchey
  • Model: 260
  • Stack Height: 42mm
  • Avg: Def: 4.81
  • Weight: 113.5gr
  • SxW: 1.83
  • Material: 7075
  • Bolt Material: Steel
  • Angle: 6 degree
  • Price: $130

Ritchey 4-Axis Carbon

Ritchey 4-Axis Carbon Stem
Unlike the 260, the Ritchey 4Axis carbon did not test well. This was the highest deflecting stem of all tested
stems. Combined with it’s near average weight and the stiffness to weight ratio was the 2nd worst in the test. This
is an older design by Ritchey and seems to be on it’s way out with the 260 looking like the logical replacement.

  • Manufacturer: Ritchey
  • Model: 4axis carbon
  • Stack Height: 42mm
  • Avg: Def: 5.73
  • Weight: 120.2
  • SxW: 1.45
  • Material: Alloy/Carbon
  • Bolt Material: Titanium
  • Angle: 6 degree
  • Price: $100

Syntace F119

Syntace F119 Stem
Like some of the other tested stems, the Syntace has a unique feature which is said to reduce stress on the bar. The
front opening is less than 180 degrees which should give more support to the bar. In terms of weight it hit the
middle of the pack. Deflection was just below the middle of the pack which when combined pushed it’s stiffness to
weight ratio down to 5th from bottom. The Syntace does have a very clean and underlogo’d look which appeals to many
and is available in a near full range of sizes (though 11cm is not one of them so a 10.5 was used in this test.)

  • Manufacturer: Syntace
  • Model: F119* (10.5cm)
  • Stack Height: 40mm
  • Avg: Def: 4.55
  • Weight: 132.2
  • SxW: 1.66
  • Material: 7075
  • Bolt Material: Steel
  • Angle: 6 degree
  • Price: $110

Thomson X2

Thomson X2 stem
Thomson has long been thought to be a top contender by many for one of the stiffest stems. The x4 definitely hit
that mark, but the lighter x2 should not be expected to finish the same. 4th heaviest in terms of weight but with a
good, slightly better than middle deflection, it has a stiffness to weight ratio of 5th from bottom. Available in a
wide range of sizes including 10 and 17 degree and two finishes so there are a lot of fit options.

  • Manufacturer: Thomson
  • Model: X2
  • Stack Height: 36mm
  • Avg: Def: 4.2
  • Weight: 146.8gr
  • SxW: 1.62
  • Material: 7000 Series
  • Bolt Material: Steel
  • Angle: 10 degree
  • Price: $100

Thomson X4

Thomson X2 stem
The x4 has long been talked about as stiffest stem available, if not for the Pro Vibe sprint and track, this would
have been the stiffest stem in the test but ended up being 3rd overall and the first stiffest of the alloy stems.
However when looking at the numbers that should have been expected since only the Pro Vibe sprint and track are
heavier than this stem and only those stems are stiffer. Stiffness to weight came in mid pack, 10th out of 19. So
that does indeed make this a well rounded super stiff stem, but at a weight penalty. Available in a full range of
sizes, both 0 and 10 degree.

  • Manufacturer: Thomson
  • Model: X4
  • Stack Height: 41mm
  • Avg: Def: 3.41
  • Weight: 168.2gr
  • SxW: 1.74
  • Material: 7000 series
  • Bolt Material: Steel
  • Angle: 10 degree
  • Price: $100

Tune 4.0

Tune 4.0 stem
Like the Extralite the Tune is one of the most expensive alloy stems in the test, but also features fine attention
to detail. It’s also one of the lightest with only the Extralite beating it in terms of weight. It finished
mid-field in terms of deflection putting it into 3rd for overall stiffness to weight ratio. The biggest draw for
this stem is perhaps the number of options. It’s available in 8 and 17 degree with 3 bar clamp diameters and with
more colors than you can shake a stick at, 10 to be exact.

  • Manufacturer: Tune
  • Model: 4.0
  • Stack Height: 39mm
  • Avg: Def: 4.47
  • Weight: 109.4gr
  • SxW: 2.04
  • Material: 7075
  • Bolt Material: Titanium
  • Angle: 8 degree
  • Price: $230

A Few Graphs

Closing Thoughts

That’s as far as we go with the first instalment of our stem testing. We do have future installments planned with more models being tested as well as other variations such as different lengths and materials. We’ll also be posting handlebar tests for both road and mtb as well as some other tests we’ve devised.