Blistering, wear, degradation, graining - Huh?

[raymondu999]

Hey all; given that this year tyres have been a huge talking point; I was thinking about what each term above meant; I think not all people are clear on this matter either; so I'd like some enlightenment from someone who is POSITIVE that they know what they're talking about.

I asked a friend of mine what each term meant; and they gave me some convincing responses, but I just wanted to cross-check. As far as I'm aware, and based on what he has told me,

Blistering - is more structural damage rather than rubber damage; caused by overheating; it's when the rubber kind of "pops" or "erupts" as it were on the side, creating kind of like a "perforated" line and if it gets bad enough, the remaining rubber on that "perforated" line isn't strong enough to keep things together and the tyre fails (structurally)

Wear - Akin to, as my friend explained it to me, when you're using an eraser to rub off some pencil marks on paper. Friction causes some rubber to go off the tyre; so it's literally the tyre "running out" of rubber; For example if the tyre had a 1cm layer of rubber on it, it would wear down to, for example, 7mm. The physical amount of rubber

Degradation - It's when the rubber "degrades" chemically for lack of a better word, due to so many stresses and heat cycles being put through it.

Graining - When you slide across the track, and it physically "rips" strips of rubber away from your tyres.

I'd love any and all guidance that you folks can give on this matter.

Cheers!

[munks]

You might do a search on this site to refine these definitions a bit more, JT among others have discussed some of the terms. But it's not a bad start. I think of blistering as when the belts get so hot that the rubber "boils" off of them, so yes this could be a bit of a structural problem. The description of wear and degradation seem okay. You might note that wear is like abrasion, although there are a few types of abrasion (cut growth, smearing, oxidation, I think).

I still don't quite understand graining, to be honest.

[strad]

I still don't quite understand graining, to be honest.

HAHAHAHA Apparently neither do the tire experts
Personally I agree with the last part of this . except I would add too cool a tire temp..

Steve Matchett, the former Benetton mechanic who is the technical analyst, said, "It's called graining because the rubber rolls off into grains. Laying down more rubber will increase grip and help with graining."

A more accurate description would have been, "It's called graining because the tire surface takes on a grainy texture. The soft, adhesive tread surface digs into the track texture, gets deformed into waves, and as sliding continues the waves turn over wearing rubber off the upstream side of the wave. When the sliding stops the deformed rubber snaps back leaving a peak pointing against the direction of travel. As more rubber is laid down during the race, grip will be reduced and there won't be enough side loading on the tread surface to start the wave formation."

Steve is a smart, very articulate guy with a lot of experience. The basic errors in his description of graining just shows how complicated tires are and how much misinformation exists even, or maybe especially, among experienced racers.

Steve could have added that a poorly balanced car maybe one with excess understeer will grain the front tires more readily than a better balanced car. Since some drivers need more understeer for comfort than others, driver style can also contribute to graining.

I'll bet another factor is the relatively light loading of F1 tires. The contact patch is wide and the cars are light. I don't think you'd see that same type of graining at NASCAR events. Of couse the rubber formlations of Goodyear and Bridgestone are entirely different.

Paul Haney

[Jersey Tom]

Paul Haney...

[strad]

Paul Haney...

I only did the polite thing to supply the source.
Point is I agree with what he says.
While you're here...
Click on this pic for a short video and then explain what appears to be a lot of flex in the McLaren fronts. I check the Ferrari and other onboards and didn't notice the effect. I thought it might be the lettering causing an illusion, but it doesn't do it on other cars as it would if it was optical.
watch the gold stripe..thanks in advance

[xpensive]

Paul Haney...

Really, I never thought about it that way? A most elaborating and enlighting post as usual JT, thanks for sharing.

[strad]

So...Any views on why the tire appears to ripple?

[Jersey Tom]

I'll admit that looks odd given you see it pretty much non-stop. Personally I've never seen anything quite like that except tire chatter but I don't think that's the case.

Bear in mind, the way those Pirelli decals are placed on the tires isn't exact. Could be something funky with it being off center on that particular tire or set, or the video equipment on the McLaren.

[strad]

both McLarens......At first I thought it was the writing..but it's only,,,near as I can tell...on the McLarens.

[Jersey Tom]

Eh, still beats me. Can't think of a reason you'd have standing sidewall waves around the whole circumference, particularly in a straight line.

[Pup]

For what it's worth, there was an article in Auto Motor und Sport a couple of weeks ago that said that McLaren had hired Bridgestone's former chief engineer to have a look at the Pirelli's. Supposedly he made some sort of a breakthrough, though the magazine said that it had to do with keeping brake temps from transferring to the tires.

[marcush.]

What is an imbalance in the tread causing in terms of movement of the tread to rim ?
I´d guess depending on the system it should be possible the imbalance is having a pronounced effect on sidewall squash in certain speed windows ?

[munks]

If that's what we're actually seeing, that seems rather dangerous. Standing waves on tires create quite a bit of heat, IIRC.

[strad]

It just happens that Matchette at the one point in the video,in an unrelated subject, mentions that the
McLaren runs more down-force on the front wing than others. I wondered if that played into it. And yes,I agree that if we are seeing what it looks like we are seeing,,,that might be a tad dangerous. Tire experts...Could it be that it is a combination of large down-force and really low pressures?

[DaveW]

It just happens that Matchette at the one point in the video,in an unrelated subject, mentions that the
McLaren runs more down-force on the front wing than others. I wondered if that played into it. And yes,I agree that if we are seeing what it looks like we are seeing,,,that might be a tad dangerous. Tire experts...Could it be that it is a combination of large down-force and really low pressures?

Interesting video. The apparent tyre instability seems to be maximum in clear air & high speed. It's not possible, I suppose, that you have captured the tyre coupling with the vehicle porpoising mode? The videos captured at Turkey (now been deleted from youtube for some reason) showed clearly that the McL was more unstable than most (certainly RBR). The mode is "powered" by the air, it is an aeroelastic "flutter" mode with a natural frequency of around 7 Hz for an F1 vehicle.