2021 YAMAHA YFM90R tire size

3-3
3
technique described in this manual on level
ground. Avoid crossing the side of a steep hill if
possible.
 Always use proper procedures if you stall or roll
backwards when climbing a hill. To avoid stall-
ing, use the proper gear and maintain a steady
speed when climbing a hill. If you stall or roll
backwards, follow the special procedure for
braking described in this manual. Dismount on
the uphill side or to a side if pointed straight up-
hill. Turn the ATV around and remount, following
the procedure described in this manual.
 Always check for obstacles before operating in
a new area.
 Never attempt to operate over large obstacles,
such as large rocks or fallen trees. Always follow
proper procedures when operating over obsta-
cles as described in this manual.
 Always be careful when skidding or sliding.
Learn to safely control skidding or sliding by
practicing at low speeds and on level, smooth
terrain. On extremely slippery surfaces, such as
ice, go slowly and be very cautious in order to
reduce the chance of skidding or sliding out of
control. 
Never operate an ATV in fast flowing water or in
water deeper than that recommended in this
manual. Remember that wet brakes may have
reduced stopping ability. Test your brakes after
leaving water. If necessary, apply them several
times to let friction dry out the linings.
 Always be sure there are no obstacles or people
behind you when you operate in reverse. When
it is safe to proceed in reverse, go slowly.
 Always use the size and type of tires specified in
this manual.
 Always maintain proper tire pressure as de-
scribed in this manual.
 Never exceed the stated load capacity for an
ATV. Cargo should be properly distributed and
securely attached. Reduce speed and follow in-
structions in this manual for carrying cargo or
pulling a trailer. Allow greater distance for brak-
ing.
 Do not operate your ATV during darkness un-
less it is equipped with a properly functioning
headlight. Off-road riding is inherently danger-
ous and additionally, off-road trails do not have
streetlights to guide you.
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6-5
6Tire information
This ATV is equipped with tubeless tires and tire
air valves. After extensive tests, only the tires list-
ed below are approved for this model by Yamaha. Aftermarket tires and rims
The tires and rims that came with your ATV were
designed to match the performance capabilities
and to provide the best combination of handling,
braking, and comfort. Other tires, rims, sizes, and
combinations may not be appropriate.
WARNING
EWB02552Use of improper tires on this ATV may cause
loss of control, increasing your risk of an acci-
dent.
1. Tire tread depth
Front:
Manufacturer/model:DURO/DI2017
Size: AT18 x 7-8
Rear: Manufacturer/model:DURO/DI2016
Size: AT18 x 9-8
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11
Transmission type:CVT automatic with reverse
Gear ratio: Transmission ratio: 2.570–0.851 : 1
Forward gear: 8.292 (49/15 x 33/13)
Reverse gear:
25.395 (49/15 x 49/16 x 33/13)Front tire:Size:AT18 x 7-8
Manufacturer/model:
DURO/DI2017Rear tire:Size:AT18 x 9-8
Manufacturer/model:
DURO/DI2016Tire air pressure (measured on cold tires):Vehicle load:0.0–82.0 kg (0–181 lb)
Recommended:
Front: 25.0 kPa (0.250 kgf/cm², 3.6 psi)
Rear:
25.0 kPa (0.250 kgf/cm², 3.6 psi)
Minimum: Front:
22.0 kPa (0.220 kgf/cm², 3.2 psi)
Rear: 22.0 kPa (0.220 kgf/cm², 3.2 psi)
Front wheel:Rim size:8 x 5.5ATRear wheel:Rim size:8 x 5.5ATFront brake:Type:
Mechanical leading, trailing drum brakeRear brake:Type:Mechanical leading, trailing drum brakeFront suspension:Type:Swing axle
Spring: Coil spring
Shock absorber:
Gas-hydraulic damper
Wheel travel: 126 mm (5.0 in)Rear suspension:Type:
Swingarm
Spring: Coil spring
Shock absorber: Gas-hydraulic damper
Wheel travel:
145 mm (5.7 in)
UBD365E0.book Page 3 Monday, January 27, 2020 9:05 AM