Performance Bikes — March 2018

44 PERFORMANCEBIKES.CO.UK|MARCH 2018

Corner entry dynamics

Thechassisdesigner’sjobistogivetheriderabikewith

excellentbrakingstability,rapidturn-inandlotsoffeel

from the front tyre.

“A lot of longitudinal stiffness in the chassis improves

riderfeelingduringheavybrakingandduringthe

transition into turning,” explains Baumgaertel.

But, of course, too much longitudinal stiffness

reduceslateralflex,sotheengineerscan’tmakethe

metalworkaroundtheheadstockasrigidasthey’dlike

forbrakingstability.Thecompromiseisquitebig:when

the rider is on the brakes the bike bends longitudinally,

with the front contact patch moving up to 10mm in

relationtothechassis,toallowlateralflex.

Oncetheengineerhasconfirmedflex,geometryand

centreofmass,heworksonthesuspension’sset-up.As

always, it’s all down to rider preference.

“Someriderslikeasuper-stifffeelingfromthefront

when they first hit the brakes, others want more

progression; but you want a fair amount of dive to

change the trail, which helps the transition into the

corner,” adds Baumgaertel. “Some riders want to feel

the forks touching the bump rubber; others hate that.

“Teams do a lot of work on suspension at the start of

eachseason,adaptingtonewtyrespecs.Youmayneed

more or less spring rate according to how much you

can dynamically load the tyre.”

Aswellastheframeandswingarm,Kalexalso

producetripleclampsofvaryingstiffness.“Weusually

offer two or three versions. We can make a triple

clampthatissuper-stronginlongitudinalforcesand

only flexes at high lean, but mostly it’s related to what

thefronttyrecantakeinsheerforces.”

Corner exit dynamics

Theengineermustcreateachassisthattakestherear

of the bike through four stages: tyre-contact entry

phase, mid-corner rolling phase, first touch of throttle

Tyres

The bike’s rubbery contact points with the road

are a vital element of race suspension. Tyres lend

more mid-corner cushioning than the flex built

into forks, shock and chassis can offer.

‘WHEELBASEGIVESYOUTYREGRIP

ANDCONTROL–ASHORTERBIKE

SHOULDHAVEMOREGRIP,BUTWHEN

ITLOSESGRIPITWILLDOSOMORE

AGGRESSIVELY,WHILEALONGERBIKE

WILLBEMORECONTROLLABLE’

Cornering dynamics
Theholygrailforachassisengineeristhecreationof
apackagethatcanadequatelytaketherearofthe
bike through four crucial phases of cornering: the
corner entry, mid-corner rolling, the first touch of the
throttle, and giving it full-gas.

Swingarm

Theamountofstiffnessintheswingarmcan

greatly affect the amount of feel a rider has

for the behaviour of the rear tyre. Too stiff and

the rear tyre will snap out of line; any sense of

a progressive slide will be lost.