What’s the deal with those tyre dots?
The humble dot: the coloured circle of a million uses. Whether its polka, separating website names from www and com or providing a nickname for Dorothys everywhere, the dot is hot.
You may have noticed (possibly during your last DIY tyre check) that there are yellow or red dots painted on the sidewall of your tyre.
So why are they there, what’s the difference and what do they mean? The answer is actually surprising.
We grabbed our main man Technical Manager Steve Burke to find out what the deal is with dots.
Known to the tyre industry as ‘balance dots’, the dots are there to guide tyre technicians as they mount fresh rubber to wheels. When matching a tyre with a wheel, the chance of perfect weight distribution is very, very rare (though our NanoEnergy3 and Proxes C100 plus tyres normally require minimal weight to balance).
This means tyres and wheels need to be balanced. Correct balance prevents vibration which is the major culprit behind a range of issues, not least increased noise, driving discomfort and uneven tyre wear.
The yellow dot indicates the lightest part of the tyre sidewall.
On a wheel or rim, the heaviest part is generally the valve stem. During fitting the yellow dot is aligned with the valve stem of the wheel. Having the dot and valve stem in alignment means technicians won’t need to use as many balancing weights.
Fewer weights and a more balanced wheel mean a quieter, more comfortable ride and a longer-lasting tyre.
It might not change the world, but we bet you’ll check if your dots line up to your valves next time you get in the car.
The red dot follows the same concept as yellow, but it’s a little more complex. Applying to original equipment (the wheels and tyres the factory fitted your car with) the red dot indicates the radial force variation (RFV) high point of the tyre.
Tyres have high and low spots, differences in thickness and joins in the carcass and inner liner. These cause variations in the how each section of the tyre flexes up and down when running. Where sections of the tyre flex considerably more than other sections of the tyre during running, this can cause a vibration similar to an out-of round tyre.
Unaddressed, RFV means more force against the road at high point spots as the tyre rolls, causing the tyre to flex, a symptom called ‘radial runout’. This causes vibration and worsens tread wear.
The red dot indicates the tyre’s high point for RFV. During fitting the red dot is matched to a drill mark or dot sticker on a wheel which indicates the wheel’s low point for radial runout.
Matching the two provides the minimum road force to prevent what tyre boffins call ‘ride disturbance’, or vibration noticeable when driving.
So there you have it, the mystery of yellow and red put to bed. Remember, don’t panic if your dots don’t line up. Wheels are carefully balanced by technicians, and sometimes the valve stem or other indicator marks need to be adjusted.