I have recently had a new pair of tyres fitted, 2weeks later I find one of them has a red spot on the side wall about the size of a ten pence piece, are there any tyre fitters out there? or someone who can tell me what this means, could it mean red for danger, or for short term use only or even keep your speed down?? or does it not matter, maybe I'm worrying over nothing
The dots on the sidewall typically denote unformity and weight. It's impossible to manufacture a tyre which is perfectly balanced and perfectly manufactured in the belts. As a result, all tyres have a point on the tread which is lighter than the rest of the tyre - a thin spot if you like. It's fractional - you'd never notice it unless you used tyre manufacturing equipment to find it, but its there. When the tyre is manufactured, this point is found and a coloured dot is put on the sidewall of the tyre corresponding to the light spot. Typically this is a yellow dot (although some manufacturers use different colours just to confuse us) and is known as the weight mark. Typically the yellow dot should end up aligned to the valve stem on your wheel and tyre combo. This is because you can help minimize the amount of weight needed to balance the tyre and wheel combo by mounting the tire so that its light point is matched up with the wheel's heavy balance point. Every wheel has a valve stem which cannot be moved so that is considered to be the heavy balance point for the wheel.
As well as not being able to manufacture perfectly weighted tyres, it's also nearly impossible to make a tyre which is perfectly circular. By perfectly circular, I mean down to some nauseating number of decimal places. Again, you'd be hard pushed to actually be able to tell that a tyre wasn't round without specialist equipment. Every tyre has a high and a low spot, the difference of which is called radial runout. Using sophisticated computer analysis, tyre manufacturers spin each tyre and look for the 'wobble' in the tyre at certain RPMs. It's all about harmonic frequency (you know - the frequency at which something vibrates, like the Tacoma Narrows bridge collapse). Where the first harmonic curve from the tyre wobble hits its high point, that's where the tyre's high spot is. Manufacturers typically mark this point with a red dot on the tyre sidewall, although again, some tyres have no marks, and others use different colours. This is called the uniformity mark. Correspondingly, most wheel rims are also not 100% circular, and will have a notch or a dimple stamped into the wheel rim somewhere indicating their low point. It makes sense then, that the high point of the tyre should be matched with the low point of the wheel rim to balance out the radial runout.
Copied from elsewhere Ya learn something new everyday
So we have a light point that should be aligned with the valve stem.
We then have a high spot that should be aligned with a low spot on the wheel.
As these are two different defects was the a suggestion as to which alignment should take priority?
High point to low point or light point to valve stem?
it is as said an alignment marker to aid easier wheel balancing on car and lorry tyres, nothing to worry about and is ignored on most standard car fitment.
only really helps on 4x4 / high performance or commercial vehicles where the balance tolerance is either more sensative (sports) or if you need large amounts of weight ( commercial and 4x4 ) aligning the spots in theory would mean you would need to use less balance weights on cars and none at all on commercial (lorrys) but even then some lorrys require there front wheels balancing and suffer from vibration
Quote: Originally posted by Bob61 on 13/4/2012
Now I know why they can never seem to balance my wheels correctly...all the coloured dots are in the wrong places
most balancing issues actually come from the wheels not being mounted onto the balancing machine properly and not the dot placement, sometimes you need special clamps/adapters that actually bolt the wheel to the machine using the stud holes in the wheels the same as it fits too your car and not through the centre of the wheel like most balancing machines..
if its clamped to the machine through the centre of the wheel and that centre is not true then you will get a diffrent reading everytime you put the wheel on the balancer and will never balnce the wheel properly, 4x4 wheels and mercedes vans and suzuki 4x4's had this problem alot, find a garage with the correct clamps and you will remove the problem.
unfortunatly most tyre depots dont like to use them because you have to dismantle the balancer to fit the correct adapter and the adapters are expensive and are not universal.. so you need a different attachment for different cars
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.
Topic: Tyres/tyre fitters
