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CARBON-BARS
CENTER OF
CONTROL
You can see the glimmer in many bikers’ eyes at the
sight of carbon-fiber bikes. But with carbon-fiber bars,
some people’s foreheads are drenched in sweat. Our
lab test attempts to uncover whether it is wise to trust
the black luxury material even with the most delicate
parts.
A bar's life in time-lapse: the testing machine
“VR-3” squeezes ten years into nine hours.
CARBON-BARS
After passing the test many
bars still look great but already
have ten years of hard riding
under their belt.
tace. These two manufacturers cover the
bases from light to strong very well.
Text Stephan Ottmar Pictures Daniel Simon
---- And again the cell phone of BIKE tester Martin Peukert rings. At the other end
the testing machine “VR-3” is beeping
loudly. A tested bar broke – that much is
clear. Now there is no time to waste. The
breakage has to be evaluated, a new bar
has to be put onto the machine and the
machine needs to be started anew. Martin
starts off running. Time is of the essence
since all in all 60 precious handlebars are
being put through the test cycle on the
testing machine. Every single one will be
bent, compressed and pulled for eight
hours.
Fifteen models from eleven different manufacturers are being put to the test. We
test four samples of every bar. That's a
world premiere. Never before has anyone taken such a comprehensive sample.
The balance is excellent. Nine models receive all points possible. If you compare
this result with past tests, you will see that
carbon fiber is first choice as a material
for handlebars.
Normally these kinds of tests are limited to
a maximum of three samples. With such
an important part we wanted to be on the
safe side. There's a good reason for it:
Carbon-fiber problem: spread
The main problem of composites is centered in manufacturing methods. Currently, there is no cost-effective way to mechanize manufacturing of the black fiber.
That‘s why the bars are being laminated
by hand. By doing so, small irregularities
can lead to capital weaknesses. And what
worker puts out constant results day after
day? Proof can be found in the weights of
the products. A spread of five percent is
not unusual.
Horror scenario: bar failure
The big danger for users: slightly damaged carbon fiber will fail suddenly – similar
to aluminum. A weakened bar can break
apart with a sudden crack during a descent. The results are open for your imagination.
Neither a cracked frame nor brake failure
is as scary as bar failure. Handlebars are
safety-relevant parts of outmost priority.
That is why we leave no stone unturned
during testing. The weakest of the four
samples is the deciding factor for the test
result. Only if all four samples are yielding
good results will the grade be positive.
FSA, Easton and Truvative all had one
weakling on their team. Even big-name
manufacturers, who invest lots of time
and know-how in their development, apparently have problems in manufacturing.
After less than one-tenth of testing time, a
Truvative “Team Carbon” said good-bye.
One Easton and one FSA followed suit
relatively soon after. This is why buying a
bar can be like playing the lottery.
Much worse are Control Tech and Ritchey. Of the models “WCS Carbon Riser”,
“WCS Carbon Flat” and “Crossbow”, none
of the tested samples reached significant
runtime. Just one “WCS Flatbar” finished
the test. We strongly discourage buying
those products.
Significant is the thin midfield. The bars
either break early or never. Therefore the
list of “Best of Class” is fairly long. Weightconscious racers use Race Face and Syn-
The Test
The testing machine demands everything of the bars. In less than nine
hours a full life of a handle bar is simulated. For this, a complex of loads is used.
Through real-life riding the loads acting
on a bar have been measured. The testing machine transfers those loads from
real-life into the lab. Since simulating a
test track is not yet possible, the most
important loads are being picked. That
is how the complex of loads has been
created (page 38).
Six different loads are created. Naturally, different events happen with different frequency. What biker rides only
standing or drops every few yards over
high steps? In addition, light crashes are
simulated. Everyone falls off of the bike
occasionally. After a big crash, though,
there is only one thing to do: replace the
bar and stem. Neither aluminum nor carbon fiber offers enough margin for safety. Whether a bar has already been damaged is not always evident, so always
take the safe route and replace it.
Appropriately, all bars are clamped on
the testing machine with a suitable stem.
For technical reasons we had to use a
substitute stem because the vibrations of
the machine loosened bolts. After eight
hours of run time the machine stops the
test. Many bars survived the time without damage and withstood 150,000
load changes. About such samples, Jo
Klieber, Syntace boss and developer of
the testing machine “VR-3” says, “Experience shows that
Blind trust: At high speed you have to
be able to trust your material.
Carbon fiber material: processing, strengths and risks
Production process
Even today manufacturing of carbon-fiber products requires lots of manual labor. Layers of
material are added by hand. For bars, so-called
prepregs made of unidirectional fibers are used.
The individual fiber mats are already drenched in
resin so the right combination of resin and fibers
is ensured.
A bar consists of a base, middle and top sheet.
Each sheet is made of several layers of prepregs.
Those layers are glued to a flexible rod. For greater strength, more layers are used. An interesting
note: Only the top sheet is end-to-end for optical
reasons. Below the top layer the sheets are quite
often criss-crossed.
After the last sheet has been glued, the rod is
pulled out and substituted by an inflatable bladder. Now the bar will get its final shape: It is
placed in a negative mold. In an oven the bladder
is inflated and pressed to the mold. This autoclave method is very laborious, but its advantage is
the production of highest quality parts. After molding, the bars are cut to size and lacquered in
several layers.
Material properties
Carbon fiber is anisotropic, which means it can
bear loads only in one direction. Perpendicularly
to the strands it can bear only a fragment of the
load. As a result we have the interwoven structure
with its carbon-fiber typical looks. Fiber strands
are run in all directions and make the material
stronger in all directions.
Comparison of carbon fiber and
aluminum
Everywhere you read how much better the material properties of carbon fiber are in comparison
to aluminum. If only tensile strength were of importance, a bar made of carbon fiber would only
weigh one-tenth of an aluminum bar. But tensile
strength is not the only important property. Aluminum has advantages in many other areas that
outdo carbon fiber. So in fact, the weights of bars
made of one or the other material barely differ.
As soon as manufacturers get a handle on the
variants that occur in production, they can start
making composite bars lighter. While aluminum
has reached its limits, carbon fiber still has lots
of potential.
CARBON-BARS
bars reaching this number of load changes do not break in the real world.”
Carbon fiber beats aluminum
While frames made of the high-tech material are widely accepted, there is still a
lot of skepticism about handlebars, but
without reason. The carbon bars tested
break all the records: 75 percent of all
tested samples pass every hurdle easily. During the bar test in BIKE 10/02, we
tested almost exclusively aluminum bars
and the number of bars that passed the
test was below 30 percent.
A few rules have to be observed however.
Always install the bar exactly as specified in the manual. Use the stated torque
values when installing, not only for clamping the bar to the stem but also for the
fastening the controls. Only cut the bars
as far as the manufacturer specifies. The
manufacturer must also state that mounting bar ends is admissible. After small
crashes and at the end of the season,
you should inspect the bar and replace it
if you see damage. After bigger crashes
replace the bar and stem – safety first.
Bike tester Martin Peukert now can savor his leisure time. The testing machine
won’t be calling him at ten at night anymore. Now it is time for manufacturers to
react to the results of his tests and take
action. A few can relax, though.
Dipl. Engineer Dirk Zedler, BIKE contributor and bicycle technical expert: www.zedler.de
Installation influences riding
pleasure and breakage
The analysis of many broken bars yielded a clear picture: the majority of breakages have been caused either by a
bad combination of parts or poor installation. So observe these tips: Always
use bar and stem from the same manufacturer and with the same quality.
Stay within the recommended torque
values by using a suitable torque
wrench and check frequently. Contact
the manufacturer of the stem to check
whether the stated values are good for
carbon-fiber bars. The torque values
stated for controls are usually too high
for carbon. Use carbon-fiber mounting
paste for controls and bar ends. The
paste increases friction and a lot less
torque is needed for the same result.
If you want to cut the bar, contact the
manufacturer to check on where the reinforcements for the bar ends and controls are located. If you install controls
outside the reinforced areas, breakage
is imminent.
DH
Testing cycle: completeStem
life &
ofHandlebar
a bar 2002.4
in time-lapse
Test Machine VR-3
Test procedure
(Load collective)
500 N
0N
500 N
Push
1 sequence = 1000Lc = 2:30 Min (24000 Lc/h)
Pull
1000 N
1000 N
1500 N
1
500 load cycles
200
250
50
1
Repeated until failure of specimen
Load parameters
Offset Impact
Climbing
Alternate phase
Alternate phase
Cross Country
Simultaneous phase
(Effective forces per side)
Hard Climbing
Alternate phase
Jump / Impact
Downhill
Simultaneous phase
Simultaneous Phase
Push 1000 N
Pull
450 N
x Angle
2°
y Angle
22°
Frequency
7 Hz
Push
Pull
x Angle
y Angle
Frequency
1600 N
900 N
2°
22°
4 Hz
Each 4000 Lc
4 times
40mm
Push 1100 N
Pull
300 N
x Angle
2°
y Angle
22°
Frequency
3 Hz
Offset 70 ms
4 times
Each 4000 Lc
Push
Pull
x Angle
y Angle
Frequency
Offset
Cycles
400 N
250 N
2°
22°
6 Hz
20 ms
200
Push
Pull
x Angle
y Angle
Frequency
Cycles
600 N
250 N
2°
22°
10 Hz
500
Push
Pull
x Angle
y Angle
Frequency
Offset
Cycles
300 N
550 N
2°
22°
2,5 Hz
0 ms
50
Cycles
250
17. May 2006
A: Loadpoint: 40 mm from bar end. B: Top distance between cylinders = Bar width -100 mm. C: Headtube angle: 72°. D: If no manufacturer restriction, standard test w/ MTB-stem block ID #256#.
E: Rod end w/ clamp: 500g +-125 g. F: Grip clamp width: 50mm. G: Temperature: 18°-28°C. H: Random specimen of 3+1 required. I: Tighten all screws w. 150% of recommended max. torque.
© Jo Klieber / Germany
I:\TESTMASCHINE\
TESTSTANDARDS DH
+ RC (Artworks &
Texte)\DH Standard\
VR3 DH 2002.4 v01.ai
Lab test: 480 hours permanent operation
Lab test
Since it does not make any sense to make a
real-life test, we rented space at Syntace in Tacherting, Germany, where the VR-3 is located.
The VR-3 is a bar testing machine developed by
Syntace in conjunction with several testing institutes and BIKE. The machine is connected to a
huge compressor and is able to apply its force in
well-controlled doses. It can exert either push or
pull forces on both bar ends.
The testing cycle is stored in the machine’s brain
(page 38). Every bar goes through this cycle either
until it breaks or 210,000 changes of loads have
been reached. After that, the machine stops. The
bar has done its due. The run time equals a life
span of about ten years. But be aware: weather
influences are not part of the simulation. This test
focuses on mechanical forces.
The testing cycle
The offset impact at the beginning (0) and the
drop/hit (5) are special events that don’t happen
very often. The events simulate very hard riding
or light drops. Steps 1 and 3 simulate riding while
standing. In those events the rider pushes down
one side of the bar and pulls up on the other.
Steps 2 and 4 simulate bumps and rough ground
as they occur in real rides under varying conditions. Exact testing forces can be read in these
“load situations.”
All in all, the test runs through 1002 changes of
loads with varying loads and force transmissions.
After one cycle runs its course, the game starts
anew. A good bar runs through the cycle 210 times for a period of about 9 hours.
The meaning of it all
Every type of bar is tested four times. This way
we are able to uncover variance in the production
process. If the numbers of successful cycles for
one type and model are close to each other, it is
possible to make a prognosis about life expectancy. If there are mavericks, it is a sign of variances
during the production process. We bolted all bars
with recommended torque values.
Installation and maintenance: torque values are decisive
Torque wrench
To install an expensive and delicate carbon
fiber bar you need a torque wrench. Normally,
if bolts are tightened by feel only, the disparity
between it and the correct value is too high.
If the stem plate is tightened too much, there
is too much stress in the clamping area. The
fibers don’t have enough room to move and
can break. The same holds true for all controls
like brake levers, shifters, lights and screw-on
grips.
Mounting paste
Torque values, instructions for installing bar ends
and cutting the bar should be part of a good manual. Please read the manual before installation.
Mounting paste disperses the pressure onto the
material and improves clamping of the bar onto
the stem. The paste is infused with plastic particles. They roughen the surface of the clamping
areas of bar and stem without damaging them.
The effect: Even at low torque values the bar is
tight and the strain on the material is lower.
Routine checks
After a long period of use, the stem works its
way into the material of the bar. Damage can
also occur at shifters and brake levers. Winter
tune-up is the perfect time to perform a complete check including dismantling the bar. Carefully
inspect the clamping areas. In case of irregularities such as cracks, nicks, or chips, replace
the bar.
CARBON-BARS
Pictures of breakage
Breakage in the clamping area
Forced breakage
This is the classic of carbon fiber materials. Through permanent pressure
on the underside of the bar, the structure becomes waved. If the radius of
the wave gets too small, the bar breaks.
This form of damage only occurs under extreme forces, like the appearance of a bar after a huge drop. The fibers are torn in the direction of
force pull. (This damage did not occur on the testing machine, we created
it on purpose.)
Breakage at a bend
Bad design
The bend is a critical area for carbon fiber bars. High pressure on the Abrupt transitions are a bad design for any material, and this holds true
fibers is responsible for failure at this location. Under pressure, fibers rip for carbon fiber as well. The “Crossbow” has many abrupt transitions. A
off.
testing sample shows ruptures in five different places.
Overview of all 15 carbon fiber bars
Four of eight bars did a great job and are fully within the green area. Bars
that constantly manage to withstand more than 80,000 changes of force are
suited for mountain biking.
Changes of force
A flat bar has two bends fewer than other bars and is easier to manufacture.
Five models can be recommended without limitation. They are fully raceready.
Changes of force
CARBON-BARS
Statement from the Control Tech regarding the test results of the “Crossbow”:
“We inspected the Crossbow extensively and tested
it according to the Euronorm and DINPlus. It passed
those tests. The Crossbow
is no downhill bar, therefore
we think the requirements
(...in this test...) were too
high.”
Technical and other info
Statement of Ritchey about the test
results of the “WCS Carbon”:
Within the two years of selling the carbon fiber bars
we never had any breakage
in the clamping area. Nevertheless, we will refine our
internal testing procedure
that is already beyond the
CEN-Norm. Particularly, we
will integrate more abrupt
hits. We owe this to our customers.”
Technical and other info
Distribution
Technical and other info
Distribution
Technical and other info
Distribution
Distribution
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Conclusion: The Trek brand Bontrager can
take quite a bit of abuse. Sure, the “Race X
Lite” is not especially light but a reliable partner
for all riding situations.
Conclusion: The distinctive design is the
problem of the stem/bar unit. Too many transitions make the part susceptible to breakage. The
weight is too high for racers.
Conclusion: Three out of four bars are
great? Smells like variance. The design is OK,
but there is a problem in manufacturing.
BIKE says *
BIKE says* has weaknesses
BIKE says *
super
Technical and other info
Technical and other info
Distribution
acceptable
Technical and other info
Distribution
Distribution
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Conclusion: FSA has the same problem as
Easton, one maverick on an otherwise great
team. The weight of the bar is the highest in this
test. Too bad.
Conclusion: Apparently FSA is better at
making flat bars. Four bars survived the test
without damage. That is a sign of quality.
Interesting design.
Conclusion: Race Face shows how it’s
done: light, sturdy and affordable. Three arguments for the “Next XC’. The oversize design
saves another 10 grams according to BIKE
measurements.
Conclusion: The narrow 25.4 mm diameter
between bar and stem does its job as well as
the oversized version. This product has only
strengths. Nice surface.
BIKE says *
BIKE says *
BIKE says *
BIKE says *
acceptable
*The BIKE evaluation reflects the subjective impression of the test ride�
**Because of bolts on the sta�
super
super
super
Technical and other info
Technical and other info
Technical and other info
Distribution
Distribution
Distribution
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Conclusion: The definite loser of this test.
Not a single bar made it through. The “WCS
Carbon Riser” is full of safety risks. Not suited
for a mountain bike.
Conclusion: The only bar to present four
vastly different values. The first 2 are especially
too low to use this bar on a mountain bike.
Conclusion:Many racers already swear by
the “Duraflite.” For good reason, it is the lightest
bar in this test. Exemplary: The clearly stated
torque values next to the clamping area.
Conclusion: If you shell out 159 Euros for a
bar, you expect quality. It is what you get with
the “Lowrider Carbon.” Light and sturdy are its
attributes. The bar can be shortened as much
as you like.
BIKE says* has weaknesses
BIKE says * has weaknesses
BIKE says *
BIKE says *
Technical and other info
Technical and other info
Technical and other info
Technical and other info
Distribution
Distribution
Distribution
Width
Rise (height)
Bend
Weight
Price
super
super
Technical and other info
Distribution
Distribution
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Width
Rise (height)
Bend
Weight
Price
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Test result: change of loads until breakage
Bar 1
Bar 2
Bar 3
Bar 4
Conclusion: All four samples cruise through
the test and achieve great results. Weakness:
Because of its high weight it is not suitable for
weight weenies.
Conclusion: The new Syncros “Factory
Carbon” has a 31.8 mm diameter. It can be recommended without limitations for competition.
Conclusion: After only half an hour one
sample broke. This spread holds an inherent
danger. Could be the bar holds up, could be
it fails.
Conclusion: “Atom Flattie” from Use is a
really hot item. The part has been designed with
the help of modern technology and it pays off.
Recommended without limitation.
BIKE says *
BIKE says *
BIKE says* has weaknesses
BIKE says *
*The BIKE eval�
**Because of bolts on the sta�
super
super
super