KB Article - Trust Your Motorcycle Tyres

How to trust your motorcycle tyres!

If you ride at the speed set out by posted speed signs, ALL road legal motorcycles can complete corners at posted sign speeds with the following items taken into consideration.

1. Adjust your speed, ride to the conditions and ride to your own ability.

2. The posted yellow chevron arrow with speed signs posted and other yellow diamonds with speeds posted are the recommended speeds for corners in adverse or poor weather conditions, set your speed before entering a corner.

3. There are no races to win when you are starting out your motorcycle self-discovery path as a new rider.

Keep your tyres inflated to the correct pressures

If you do not know this information, visit a motorcycle shop or ask a trusted friend to assist you.

Tyres actually change air pressure over time, the pressures change with hot and cold weather and all tyres loose a fair amount of air pressure through the tyre itself within a week or two!

Having the correct tyre pressure warms up the tyre effectively so you have optimal tyre grip available when you ride a motorcycle.

Best to use a screw-on tyre pump as there is less stress on the tyre valve and many screw-on tyre pumps can fit much easier onto motorcycle tyre valves due to the funny angles needed to reach the valve and attach the air pump as brake rotors can get in the way!

Car pumps and bicycle pumps are easy to find but getting a battery pump like the Xiaomi Tyre Pump with a measurement gauge and screw-on valve hose is much simpler to use and easy to carry in a bag or under seat storage.

Understanding lean angle

The curved profile of any motorcycle tyre is what does the cornering for you on two wheels and the lean angle the rider feels is a direct result of any motorcycle tyre using its tyre profile through the corner.

For every rotation of any motorcycle tyre and wheel, the middle or center of the tyre tread has the longest path to travel while the tyre’s profile edge or sidewall has the shortest distance to travel.

When we ask a tyre to get a motorcycle around a corner, it will always be using the tyre’s profile rotational differences in distance traveled that allows you to corner while moving.

How to initiate a motorcycle to corner or turn? See video item 6 in the YouTube playlist here: https://youtu.be/0mbaVJvfxFg?si=7rvfw2J9JCpGHog_&t=18

How to demonstrate with words? Place a Trumpet or Cornetto ice-cream on your desk or table (keep it in the wrapper people!)… What happens when you roll this item forward? It will turn in one direction in a circle and the smallest section being the skinny tip is always on the inside of the corner radius while the bigger end is on the outside of the corner radius as it has to travel a longer distance per rotation of that ice-cream object. Once the motorcycle is using the tyre’s profile to turn in a corner it has the same effect.

Larger arrows represent longer distances traveled due to circumference differences on the same object, As a tyre has a curved profile, your turning radius is adaptive and changes based on rider input and is not one constant turning radius like the waffle cone as shown below. (Waffle cone without a curved profile is similar to “V” front tyres after a track day - read further down about tyre wear!)

How much lean angle is available?

The amount of tyre profile used is directly related to the speed you are travelling at through any corner radius (how tight a corner is). If you choose to go a little slower, less lean angle is required to complete the corner. If you go faster, you will need more lean angle to complete the same corner.

Typically a motorcycle has foot peg “feelers” or knobs that are consumable items, they scrape the ground when that lean angle limitation is close approaching to make a sharp sound that alerts the rider to the fact you are near the intended design limits of the motorcycle you are riding.

Not every rider has the same state of mind, or has same motorcycle model but the same the physics we all depend to go down a road will apply to all riders and their motorcycles.

Below are some samples of recommended speeds in shown in blue arrows vs hot or aggressive riding shown with red arrows, the difference in tyre profiles are evident.

Note where “!!” is shown in red on the tyre profile below = Expect your foot peg feelers to scrape loudly before you exceed the tyre’s tread/grip area. If you are scraping foot pegs mid corner, you may not be able to complete the corner on your side of the road if the corner tightens more and you may fall victim to rider survival reactions which can make things worse (running wide, aggressive braking or throttle chop etc).
If you wish to learn more about your own limitations and rider ability, enrol for some track time with a motorcycle school near you - A much safer place to learn more about yourself, your motorcycle and have some fun without other vehicles coming towards you!

Touring or mixed tyre profile

Cruiser tyre profile

Sports tyre profile

Mixed 50/50 profile

Can tyre wear affect motorcycle cornering?

When you have new tyres installed on the motorcycle, the tyre profile is operating at it’s optimised design and will make all corners and related steering tasks feel amazing until signs of heavy wear and replacement start to show.

No matter your riding style and distances traveled you need to observe tyre shape over time. The handling of the motorcycle is affected by the following common issues (not including flat tyres and accident damage!)

Tyres when over-inflated above the recommended air pressure for a tyre can make the tyre too hot when used and wear prematurely and under-inflated tyres can prevent the tyre from staying adequately warm loosing valuable grip as all tyre rubber has a operating temperature range they work best in. Under-inflated tyres will also cause uneven wear patterns that look wavy across the tyre side profile.

Tyres need road friction to warm up and a tyre’s air pressure affects the amount of friction generated, that heat generated by friction creates the tyre grip needed when riding a motorcycle.

Result of under-inflated tyre with wavy wear pattern

Under-inflated tyre result, shows wavy in-out wear pattern

Front Tyre - Long distances without aggressive riding?

The tyre may flat top and simply wear down tread, turning into corners may feel more delayed and slow turning will be less “willing” to enter the corner or exit the corner smoothly, it won’t be smooth in corners until the lean angle is past the flat top area of the tyre.

Front Tyre - Aggressive or charging into corners and scrubbing speed off using front tyre grip?

Most front tyres start to flatten the tyre profile sides into a “V” instead of the “U” shape needed to complete corners smoothly at different speeds.

If the handlebar is pulling against your steering input or changing your intended path of direction into an overly tighter turn when doing low speed corners it is time to replace the tyre.

Once this “V” has occurred on a front tyre, while the days are warm and sunny you can compensate the steering as the dry warm grip provided by the road allows you to exercise a little more input to over correct the steering issue caused by “V” tyres, but once you get rain or cold weather that spare grip you had is no longer available to add that extra steering input and you risk having a accident when you need to ask the front tyre to turn when in lower grip areas (Bare tar, road imperfections, water pooling, cooler evenings etc).

Once a tyre has less than 1.5mm of tread is remaining or tyre profile is “V”d flat on the tyre profile sides, you should replace the tyre.

“V” tyre profile due to high speed cornering

Rear tyre - Long distances or aggressive riding?

Flat topping rear tyre tread is the most common issue with rear tyres, this is when the rear tyre has done a lot of long distance travels or high power motorbikes used on many straight road areas without an equal amount of cornering done within the distance travelled to keep the tyre profile rounded or a “U”. (high torque, tyre abuse etc) - “V” tyre wear on a rear tyre is not that common, mainly seen on a race track motorcycles where corners and straights are mixed well and corner speeds are maximised everywhere.

The rear tyre also does a lot of work to steer a motorcycle (50% and more of a motorcycles ability to steer comes from the rear tyre!), the front and rear work together to complete a turning radius.

Once a rear tyre has flat topped substantially, when the days are warm and sunny you can compensate the steering as the dry warm grip provided by the road allows you to exercise a little more input to over correct the steering issue caused by a flat topped tyre but once you get rain or cold weather that spare grip you had is no longer available to add that extra steering input and turning into corners in normal situations and typical speeds zones becomes much harder.

This is because the rear tyre profile is not ready to turn in the corner until a higher speed is reached to overcome the flat topped section of the tyre as you have essentially worn off the lower speed cornering profile of the tyre. This can make the front tyre feel like its fighting the rider’s input at any normal posted speeds and when entering any corners and that can create rider confidence issues, an accident and other additional issues as you are trying to force/change the front tyre turning radius that is different to its natural turning radius mid corner with forced steering actions while riding in not so ideal weather or road conditions.

Tyre flat-topped profile showing next to new tyre, see profile differences.

Tyre flat-topped profile showing. This removes low speed corner smoothness and feel.