MX-TECH's MXA 2006 KTM 250SXF Mods Evaluation.
Reprint courtesy of MX-Tech Inc U.S.A.
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Project development
Managers: Jeremy Wilkey, John Curea.
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Component Set-up Information: |
- Forks:
SXS Twin Chamber units with MX-TECH Valving.
Fork Springs: .45kg/mm spring.
Oil level: 350cc Motorex 2.5 wt.
Gas Charge: 1.1 bar
MX-TECH component list:
- MX-TECH Works Piston and proprietary solid clamp
midvalve design.
The twin chambers were used to improve the overall
handling package. We modified the stock forks and
improved them significantly. For the stock forks we
recommend revalving, and Enzo subtanks. However, after
much testing, we decided that the SXS twin chamber fork
is a much better match for the new MX-TECH valved shock.
Also we decided to use this fork because it will be the
same design that will compliment the 2007 SX models. It
also makes for a much better handling bike, and it will
put the technology at the same level with the Japanese
Showa and KYB designs. |
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Shock:
Production shock with MX-TECH Internals and valving.
Progressive Shock Spring PDS #7 (7.6-9.5)
Fluid: MX-TECH WP fluid. Full synthetic.
Gas: 150 PSIMX-TECH component list:
- MX-TECH new one piece 88mm shock needle. Shock shaft with all new internals
including nut, rebound adjuster, jet, tube and seat.
- MX-TECH Works Piston in position
#1. Modified stock piston in position
#2. MX-TECH Progressive shock spring
- Works Piston and proprietary solid clamp midvalve design.
Supporting Technical data.
MX-TECH has developed an 88mm long needle, small bypass, with constant damping
overlap of the two pistons, which results in linear progression from full extension
to full bottom. The design was optimized to best duplicate the feel of a linkage.
Interestingly a PDS shock does this through volume change, whereas a linkage does it
through speed change. As we have worked through the PDS project this point has again
and again been the design feature and crux, as we have maintained that prospective and
focus, the shock has yielded substantial improvements.
The major point of the modifications can be summed up by viewing the following Rhoerig
computerized shock dyno files.
Note the Dyno runs of the stock shock are at 10mm increments. The dyno compresses the
shock at 15in/s for these tests and has a 50mm stroke. So Zero displacement tests
from full extension to 50mm of stroke. When the test is at 10mm it is testing to
50mm + 10mm = 60mm stroke, until full stroke is attained with
50mm + 50mm = 100mm or maximum stroke.
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The stock PDS system with its short needle high volume change (large needle diameter)
produces a massive change in damping force at the end of the stroke. Note that damping
force is fairly constant at subsequent points in the stroke. Finally at just over 60mm 3/5 of
total travel the damping force doubles. The result is the rider notices an inconsistent or
unpredictable feel, and substantial harshness. |
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With the MX-TECH needle system the shock is much softer at any given point
and with each increment of travel produces a measured increase in damping force. Since damping force
equates to stiffness, which bike would you rather hit bumps with?
The Stock WP design uses a very stiff valving initially to control swingarm movement and reduce the KTM hinge feeling; whereas, the rider feels
the softer part of the shock stroke slamming into a harsh wall of damping.
The MX-TECH valving uses progression like a linkage, making the shock more
predictable, plush, and yet controlled.
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MX-TECH Suspension Inc would like to acknowledge the following
for their contributions:
John Lakovich and Boeing project Engineer Marcus Erickson.
Additionally the entire worldwide MX-TECH family has been involved in MX-TECH product
and technical developments.
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MX-Tech Project Evalutation
© MX-TECH 2007 |
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