Tyre Fitting Plonker?

[parapaul]

I'm far from an expert, but I think that when new tyres are fitted, the yellow dot should line up with the valve.

The yellow dot is put there by the manufacturer to indicate the lightest point on the tyre, so when lined up with the valve which is obviously the heaviest point on the wheel, it means the least weight will be required to balance the wheel.

There's also a red dot on new tyres but I can't remember what it's for - something to do with brand new wheels IIRC.

I had a new set of alloys a couple of weeks ago, and they came fitted with tyres. Fitting was done by a mobile guy, who is used regularly by the shop supplying the alloys. But not one of the 4 wheels has the yellow dot anywhere near the valve, and as a result every wheel has loads of balancing weights, and I STILL get wheel wobble

Am I right about the yellow dot? I've given it a couple of weeks for the tyres to scrub in, but the balancing is still not right.

Can I take them back after this long and ask for it to be done right?

Grrrrrrr

[plasma]

Did a bit of digging. Yellow spots are indeed the lightest point on the tyre but it isnt necessarily true that the valve stem will be the heaviest point of the rim, it only applies if its a brand new rim as they drill and mount the valve stem at the lightest point. After use on a vehicle with slight knocks/wear etc this point then isnt valid any longer.. Still not found out about the red dots yet..

Found this bit of info..

Makes no difference as the theory is usually not true. The idea that the valve stem will be the heavy part of the rim usually isn’t the case (at least on every bike I’ve owned). The only way to really do it right is to: take the old tire off, remove all the weights, clean the rim, put the core and cap back on the stem, put it on the balancer, mark the heavy spot, balance the rim, mount the new tire (air it up to the correct PSI), put it on the balancer, mark the light spot on the tire, break the bead, align the heavy spot of the rim with the light spot on the tire and re-balance. Mark P. balancer is what I use and it works great.

[plasma]

Just seen something about the red dot being the proper place to take tread wear readings from?

[67688c]

Yes... I always thought this too, but I noticed that none of the 4 new tyres I had fitted recently have the paint dot anywhere near the valve. Dont think they bother at all these days, mine has quite large counter balance weights on the wheels, on 2 of them anyway.... probably why.

[VauxVeteran]

I thought the dots were to indicate the tyre rating easily.

[V6 JDT]

From Tony - founder of wheelsinmotion forum
"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. " or

[67688c]

Thanks for that informative read matey....
There's information on a few of the tyre companies sites which explains it too. Just a shame the tyre fitters dont know what they are for. A couple of the weights on 2 of my wheels are like bricks.

[markd3925]

i used to fit tyres not all the time but when was required sort of thing.
i was never told about the yellow dot, but was told to put the red dot to the outside if the tyre didnt say the word dot on it.
i always found better quality tyres balenced up better than the budgets


could be something else causing the wobble maybe?

[vectragsi3.2]

i would take them somewhere else to be balenced paul. i bought a brand new set of alloys for my old golf and i had a horrible wobble but as soon as i had them re balenced they were spot on wheres the pic with the new wheels on?

[parapaul]

Haven't had a chance to take one yet - I'll get round to it eventually!