Correlation between Tire Pressure and Acceleration of a Motorbike

  • #1
bagasme
75
9
I have asked this question on Stack Exchange: SE question.

I often encountered this sticker on most motorbikes (especially matic ones) [credit: cintamobil.com]:
245804


There, when the tire pressure was measured from cold condition, the tire pressure are same regardless of loadout (29 psi and 33 psi for front and rear tire respectively).

According to SE:
The acceleration of the bike is given by the torque of the engine and the mass of the bike plus passengers - so when you have a passenger, there is greater inertia to overcome and your acceleration will be less
The force of friction is typically (naively) modeled by Ff∝μN
, whether static or kinetic (while both of these forces are vectors, the normal force acts perpendicular to the surface while friction acts in some direction parallel to the surface). If engine/gearbox can put enough torque on the axle to spin the wheels out, then the acceleration is capped not by the drive-train, but by the friction between the drive wheel(s) and the road.

Most tire manufacturers recommend a tire pressure which balances the durability of the tire's sidewall and the increased gas mileage of an over-inflated tire with the added comfort, acceleration and braking of a slightly less inflated tire (see rolling resistance). Obviously, tires either too flat or too full are a safety hazard.
If the engine/gearbox are powerful enough, the center mass hasn't moved too high and the connection between the road and the wheels exceptionally tight, one could see greater acceleration with a passenger.

Is it true that tire pressure and loadout (e.g. riders) correlate with acceleration of motorbike? Are there any papers that explain about it?

Regards, Bagas
 

Answers and Replies

  • #2
jbriggs444
Science Advisor
Homework Helper
11,572
6,220
Is it true that tire pressure and loadout (e.g. riders) correlate with acceleration of motorbike? Are there any papers that explain about it?
Tire pressure will figure into load sensitivity.

As indicated above, for power-limited acceleration, total rider mass is crucially important.

The passenger will be toward the rear of the bike. Adding the passenger could thereby increase rear wheel loading proportionally more than front wheel loading, gaining more through traction than is lost due to the extra mass. On some surfaces, (snow, slush, water sufficient to hydroplane), the weight of the passenger could help the wheels "cut through" and get some purchase on the road beneath.
 
  • #3
cjl
Science Advisor
1,980
569
For most motorcycles, acceleration isn't grip limited anyways, so all of those factors are irrelevant. Acceleration is limited by rear swingarm geometry, suspension, and CG location, since the limiting factor is the acceleration at which the bike will wheelie and flip over backwards.
 

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