: Tires



lasstss
05-18-06, 07:14 PM
Some next to useless info but might make a difference on your next balance job.

http://www.searsguy.com/Content_Images/dotsandstripes.gifhttp://www.searsguy.com/images/cleardot.gifWhen you're looking for new tires, you'll often see some colored dots on the tire sidewall, and bands of color in the tread. These are all here for a reason, but it's more for the tire fitter than for your benefit.

The dots on the sidewall typically denote uniformity and weight. It's impossible to manufacture a tire which is perfectly balanced and perfectly manufactured in the belts. As a result, all tires have a point on the tread which is lighter than the rest of the tire - a thin spot if you like. It's fractional - you'd never notice it unless you used tire manufacturing equipment to find it, but its there. When the tire is manufactured, this point is found and a colored dot is put on the sidewall of the tire corresponding to the light spot. Typically this is a yellow dot (although some manufacturers use different colors 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 tire combo. This is because you can help minimize the amount of weight needed to balance the tire 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 tires, it's also nearly impossible to make a tire 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 tire wasn't round without specialist equipment. Every tire has a high and a low spot, the difference of which is called radial run out. Using sophisticated computer analysis, tire manufacturers spin each tire and look for the 'wobble' in the tire 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 tire wobble hits its high point, that's where the tire's high spot is. Manufacturers typically mark this point with a red dot on the tire sidewall, although again, some tires have no marks, and others use different colors. 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 tire should be matched with the low point of the wheel rim to balance out the radial run out.

What if both dots are present?

Generally speaking, if you get a tire with both a red and a yellow dot on it, it should be mounted according to the red dot - i.e.. the uniformity mark should line up with the dimple on the wheel rim, and the yellow mark should be ignored.

OldRoadDawg
05-18-06, 07:29 PM
Interesting stuff that I was never aware of. Gotta go straight out to the garage and look at my GSD3s stacked up waiting to be mounted and look for the colored dots.

DILLIGAF
05-18-06, 07:59 PM
Marty rules!

mike041357
05-18-06, 09:45 PM
Wow!:holycrap: I just had my GSD3's mounted and I just ran out there and I just looked and......there they were......2 tires had WHITE DOTS! One was close to the stem, the other a little farther off. I still have a wobble, but was going to drive it some more to see if it goes away after the tires heat up. Now I'm driving it back to the the tire store.

AND.....as I was putting my Mille Miglia's up for the summer, I saw the "dot" drilled into the wheel and thought "what the *#&%?".

Now I feel enlightened. If I learn nothing else this week, I am ahead of the game.

This is something nobody will ever believe at a party.....

Whoever said "all dots are created equal"....

mlg
05-18-06, 10:33 PM
d3s suck!!! most are not round and can NNNNNEEEVVVEEERRR be balanced have it road force tested. perfect is 0, acceptable is 1-25, if it is greater than 25, it needs to be trashed. i had 3 of 4 d3s over 25 . never again , they SUCK.

atdeneve
05-19-06, 06:19 AM
Don't some tires have arrows denoting high/low spots? Remember reading about this somewhere (seems like I always remember some random shit I read from some random shit, if that makes any sense at all). Though, on the F1's, it seems that it has arrow heads spaced evenly around the whole circumference of the tire. Don't really know what they are supposed to mean.

cash
05-19-06, 06:01 PM
Good advice!. I just had my new tires mounted to Fikse rims and asked the guy about this. He said they always try to mount the spot with the valve stem but this is not foolproof. Quite often it does not work out to be best, and with the weight of the pressure sensors it makes it a little less than ideal.

So it the spot is not perfectly lined up it may not be becasue the technician screwed up but that may not have been the ideal balance spot.