It’s been over 10 years since Honest Wheel Bikes in Tucson, AZ first shared with us their impartial bar & stem testing, however they’re again at it, measuring actual stiffness in a brand new crop of 15 trendy highway & gravel bike stems. What do you like: absolute lightest weight, most stiffness, the best stiffness:weight ratio, or possibly some pleased medium that may not break the financial institution. Honest Wheel does the testing so we will all make extra knowledgeable shopping for selections.
Honest Wheel Bikes assessments actual highway & gravel bike stem stiffness
So why did Honest Wheel mud off their check rig? We spoke to long-time head of the store Jason Woznick, and he mentioned merely that, “it has been a couple of decade since we did testing…. [and] we needed to re-test, bars, stems and cranks and see how issues have modified.”
Sounds good to us.
I’ve personally recognized Honest Wheel since round 2001 or so. That’s once I was first launched to the store and their weight-weenie methods by a buddy who’d labored in there earlier than transferring to the East Coast. After which, quickly after I headed to fulfill them in Tucson in individual when touring out to race the 24 Hours within the Outdated Pueblo. Honest Wheel bikes has catered to each native on the lookout for trusted service, and bike nerds from far & large looking essentially the most unique parts and a number of the world’s lightest bike builds.
Though we didn’t get to it then, Honest Wheel not too long ago celebrated their Fiftieth-anniversary final yr by updating their highway crankarm and handlebar stiffness assessments with some extra of the most recent & best trendy fashions. You possibly can try that Might 2023 highway crank check right here or their up to date November 2023 highway bar check right here.
However now let’s get again to stems.
Why can we belief Honest Wheel Bike’s impartial part testing?
The great thing about Honest Wheel Bikes testing parts is three-fold. First, they’ve been round for greater than half a century, they usually saved the identical check rig at the back of the store simply ready. Secondly, they’re tremendous analytical however sensible, in order that they preserve their assessments easy and use the very same check protocol right now as after they began testing parts.
And lastly, they’re form of a bunch of nerds. OK, undoubtedly fellow bike nerds… our favourite kind.
Try their authentic 2014 stem assessments, right here.
Stem deflection testing methodology
Their stem stiffness testing is simply measuring stem deflection – how far a stem bends below a repeatable load. Once more, Honest Wheel introduced again their “favourite engineer” Jason Krantz to run the assessments. He’s now a mechanical engineer at a world firm growing testing & measurement tools. However he additionally labored within the biking business over his profession, for instance designing bikes at Titus and sharing our journalistic focus at Bicycle Retailer and Trade Information again within the 90s.
The stem deflection testing protocol he developed fixes the stem in a inflexible body, then applies a uniform 100lb (~45kg) load 10″ (~25cm) away from the centerline of the stem. The check simulates an inexpensive approximation of the power when a rider is sprinting, pulling towards the bar – up on one aspect, down on the opposite – as they attempt to pedal as laborious as potential. However the actual power/load/weight doesn’t actually matter, as deflection is linear, and they’re evaluating all stems with the identical forces.
Honest Wheel has tried to attenuate variables as a lot as potential. Their methodology says all stems ought to be 110mm lengthy and -6° of rise, with a 1.125″ steerer clamp and 31.8mm bar clamp. However some stems examined weren’t out there in that actual measurement, so there’s +1° variability in angle and -5mm variability for simply two stems (105mm Professional Vibe Dash Carbon & Syntace F119). However they clarify why which will or could not matter.
What’s stiffness?
One thing of a disclaimer… neither Honest Wheel nor us at Bikerumor are essentially saying that better stiffness really means a greater stem.
Possibly some lighter and even all-road & gravel riders would possibly like a little bit of compliance of their stem?
And the Honest Wheel check doesn’t even contact on the potential vibration damping that some supplies can present, independently of stiffness.
However if you’re on the lookout for cockpit rigidity for some discount of vitality loss or improved dealing with efficiency advantages, stem stiffness is actually a superb place to begin in comparisons. And so, we’re fairly psyched that Honest Wheel is there out crunching these numbers for everybody to see.
Scroll right down to the underside of this text if you wish to learn Honest Wheel’s personal detailed description.
2024 Honest Wheel stem stiffness assessments’ outcomes
High 5 Stiffest
FSA SL-Ok at simply 3.7mm deflection, fabricated from 2014 aluminum with metal bolts
FWB machined Ti prototype at simply 3.7mm deflection, fabricated from titanium with ti bolts
Ritchey Superlogic C260 at simply 3.7mm deflection, fabricated from 2024 aluminum with metal bolts
ENVE Carbon at simply 4.2mm deflection, fabricated from carbon with ti bolts
Uno Stealth at simply 4.5mm deflection, fabricated from 2024 aluminum with stainless-steel bolts
High 5 Lightest
Extralite Hyperstem at 82.5g from 7075 aluminum with titanium bolts
THM Tibia at 91g from carbon with titanium bolts
MCFK Carbon at 92.3g from carbon with titanium bolts
Schmolke TLO (ICR) at 94.5g from carbon with titanium bolts
Uno Stealth at 104.7g from aluminum with stainless-steel bolts
High 5 Stiffness:Weight Ratio
Extralite Hyperstem with 5.6mm deflection at 82.5g for a 2.16 S/W ratio
Uno Stealth with 4.5mm deflection at 104.7g for a 2.12 S/W ratio
Ritchey WCS C260 with 4.7mm deflection at 108.1g for a 1.97 S/W ratio
Ritchey Superlogic C260 with 4.1mm deflection at 128g for a 1.91S/W ratio
FSA SL-Ok with 3.7mm deflection at 144g for a 1.88 S/W ratio
Full 2024 Take a look at Knowledge
Mixed 2014 & 2024 Take a look at Knowledge
Bonus stem stiffness content material
Quoting Woznick once more, “In case you’ve made it this far, you’re in all probability fairly within the subject basically. For some bonus content material we determined to run a check of the identical stem in 8 completely different lengths. It’s possible you’ll be stunned how predictable the variations within the outcomes actually are.“
My Bikerumor Takeaways from Honest Wheel’s stem assessments
My first impression when wanting on the new information and evaluating it to the previous was that on common the brand new stems are 7.1% lighter however 8.9% much less stiff, giving them a mean 2.7% lower in stiffness:weight. Honest Wheel clarified a bit that we in all probability can’t so simply evaluate the figures total, as the person stems principally fell in comparable ranges. However they did notice that new to the 2024 testing have been some prototype titanium stems, that are stiffer, but in addition heavier, skewing the averages a bit.
It’s laborious although for me to miss that there have been already 8 stems in 2014 (out of 25) with ~4mm or much less deflection, whereas solely 2 have been so stiff within the new 2024 batch (of 15). I take that to counsel that the business as an entire would possibly probably not be making an attempt laborious to make stems stiffer, as a lot as they’re making an attempt to enhance aerodynamics & integration.
Then again, wanting carefully although at like stems (Ritchey & FSA, for instance the place there are basically the identical fashions in 2014 & 2024), it appears the newer iterations are both a bit lighter or a bit stiffer. That matches with the concept that part engineers try to incrementally enhance efficiency, even on primary parts like stems.
Honest Wheel’s Takeaways
Jason Woznick of Honest Wheel Bikes did say that he sees, “that as an business development, stems have gotten disproportionally heavier than they’ve stiffer. That is probably because of extra trendy stems accommodating inside cabling. We plan on doing extra testing with extra internally routed stems to bear this out a bit extra.“
Of notice exterior of simply wanting on the numbers, Honest Wheel additionally provides that their testing reveals for highway parts “the extra aero a bar or stem is the extra compliant will probably be since flat surfaces deflect greater than a spherical one“. In order that’s additionally a bit extra context on deciphering their information.
Lastly, let’s all thank Honest Wheel for doing the work to assist us choose what parts we would like on our bikes!
FairWheelBikes.com
Full Honest Wheel Bikes description of their stem testing course of, in their very own phrases…
Stem Deflection Testing:
We’ve as soon as once more introduced again our favourite engineer, Jason Krantz. Jason’s a mechanical engineer whose graduate work centered on the intersection of composite supplies and finite aspect evaluation. Jason has labored for a number of firms within the bicycle business and by no means fails to amaze us with the depth of his biking associated information.
Disclaimer: A variety of typing and numbers have gone into this text and we apologize prematurely for any typos ought to they occur, however would warn that the potential for errors is current.
Some Preliminary Notes on Testing
Testing Methodology:
Every stem was mounted within the fixture and the testing carried out 3 occasions after which averaged. All stems examined have been 11cm aside from just a few which aren’t out there in these lengths. Every stem was mounted with its beneficial torque specs and preloaded with 20 kilos of power utilized 10 inches from the stem (about half means between a highway bar and mtb bar) As soon as preloaded the tools was zeroed and one other 100 kilos of power was added and a measurement recorded. The measurement was taken on the level of load, once more 10 inches from the stem centerline.
Hundreds Examined:
Whereas the precise load doesn’t matter as a result of the response of the construction is linear. [That is, a stem with a 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 chosen a load of 100 kilos as a result of it’s a pleasant spherical quantity, and fairly real looking to what some riders could expertise.
For a sprinting rider, let’s say he’s pushing on the left pedal with 300lbf (in different phrases, he can squat 600lbs). The pedal is about half as removed from the body centerline because the handlebar is, so it might take a response power of 150lbs on the right-hand bar to counteract the pedaling power. This is similar as making use of 75lbf up on the one aspect of the bar and 75lbf down on the opposite; the second on the stem is similar.
Normalizing for Stem Size:
In concept, it’s potential to measure a selected stem of 1 size and extrapolate its outcomes to longer or shorter variations of the identical stem mannequin. In technical phrases, that is “normalizing for stem size.” We are able to do that as a result of torsional displacement is instantly proportional to size for a tube of a given cross part. It’s true {that a} good engineer will use thinner partitions on shorter stems (which see decrease stresses) and thicker partitions on longer stems (which see greater stresses). Nonetheless, normalizing to size inside a single stem make and mannequin is legitimate to a primary approximation, at the very least with metallic stems. A composite stem is a distinct beast, as a result of layups (AKA laminate schedules) can fluctuate considerably with size.
Whereas torsional displacement is instantly proportional to stem size, bending displacement is proportional to the dice of the size. Our first move at a stem check setup measures mixed bending and torsional displacement, so it might not be legitimate to extrapolate to longer or shorter stems, even throughout the similar mannequin, at the very least when you’re on the lookout for absolute values.
In case you’re taken with relative values–for instance, if you wish to know whether or not stem A is stiffer than stem B–then these outcomes ought to be fairly helpful whatever the precise size you propose to make use of.
For this check we used 11cm stems in each case besides 2 (Professional Vibe Dash Carbon and Syntace F119) that are each 10.5cm. The stems have been comparable sufficient in size that we didn’t normalize any stems on this check, however sooner or later we could check some stems that should be normalized for a good comparability.
Stiffness to Weight Ratio:
This was calculated utilizing =((1/avg. defl) / weight) * 1000
Bolt Materials:
One query we needed to reply was if there was a noticeable distinction between stems with titanium and metal bolts. We chosen just a few random stems and examined them each with titanium and metal bolts and located no significant distinction in deflection in stems with one materials over the opposite.
Mounting Course:
We additionally needed to see if mounting a stem with an increase vs a drop made a distinction within the deflection. Whereas we have been capable of measure a distinction, lower than 0.1 mm at 100 kilos, it was not sufficient to say that there’s a significant distinction, and was probably throughout the margin of error of the testing.
Notes about Stem Angles:
One different merchandise we needed to check was the distinction in like stems with completely different angles. We examined a few stems which might be out there in each 7 and 17 diploma angles and located that 17 diploma stems deflected a mean of seven% much less. The examined stems fluctuate from 5 to 10 levels which ought to lead to deflection variations of as much as about 3%, so preserve that in thoughts when evaluating two stems of various angles.
Carbon Fiber vs. Aluminum:
Carbon fiber stems don’t supply the burden financial savings that, say, carbon fiber rims do. There’s a cause for this: stems are recurrently careworn in 3 ways: bending, torsion and shear. In different phrases, the stresses in a stem are almost isotropic (uniform in all instructions). Carbon fiber is very anisotropic (stiffer/stronger in a single path than within the others). While you attempt to lay up anisotropic carbon to cope with isotropic stresses, you find yourself with what engineers check with as “black aluminum,” or pseudo isotropic carbon–and a weight that’s very near an aluminum stem.
There could also be different benefits to a carbon stem; vibration damping is one that’s typically put to the forefront of the controversy. It’s true that composite constructions typically damp vibration higher than metallic ones, and there could also be real-world damping advantages to a carbon stem. One approach to check stem damping could be to wire an accelerometer to the stem after which strike it gently with a hammer, studying the accelerometer information to see how shortly the vibrations dissipated. This ring-down check could also be on the Honest Wheel menu for a future article, however is exterior the scope of this check.
Combined supplies:
Hybrid stems, a carbon overlay on an alloy stem. We examined solely a few these however neither did properly, we’ll do extra testing on others sooner or later to develop our ideas on this medium additional.
We examined two comparable stems one in full alloy (7s) and one in hybrid (vibe carbon) to see if there was a bonus to the hybrid stems. Each are the identical weight and similar dimensions with the identical puzzle lock clamp. The distinction being that the Carbon has thinner alloy, strengthened with carbon. Deflection was noticeably completely different, the total alloy was considerably stiffer than alloy/carbon.
To invest on why assessments put carbon/aluminum stems on the versatile finish of the spectrum, one would possibly think about two competing design constraints. First is galvanic corrosion. When aluminum and carbon contact one another, they’ve made a weak battery. The electron-swapping that goes on will trigger an aluminum/carbon half to fail briefly order. To keep away from this, producers use a layer of insulating materials. This layer is usually a fiberglass/epoxy composite however could possibly be plain epoxy. Neither materials is as stiff as aluminum, so that you’re taking a stiffness loss straight away.
Secondly, the market gained’t tolerate a carbon-wrapped aluminum stem that’s each dearer and heavier than its plain-aluminum counterpart. So producers are compelled to make use of thinner-walled aluminum forgings for his or her carbon-wrapped stems than they do for his or her straight-up aluminum stems. Successfully, they’re changing comparatively stiff aluminum with comparatively compliant fiberglass and/or epoxy.
Making issues worse, some carbon-wrapped aluminum stems use a 0°/90° weave for aesthetic causes. This weave’s stiffness displays the dreaded pseudo isotropy referred to earlier, and is especially compliant in shear–which, in a stem, determines torsional stiffness.
The online result’s a carbon-look stem that has ample energy however extra compliance (and presumably higher vibration damping) than a “pure” aluminum stem.
To be clear, the above is what engineers name a SWAG: a Scientific Wild-Ass Guess. It’s an inexpensive first move, however there could also be different components at play that we haven’t thought-about and which can be additional explored in future assessments.
