21 replies to this topic

[wawawa]

Could someone please explain the difference between graining and blistering? How do these two differ in the way they effect the car's handling? Which is more severe while it lasts? Which is easier to "wear away"? What can drivers do to avoid these phenomena?

Thanks!

[Ross Stonefeld]

I know graining when I see it, but ive never been really sure what the heck it is. Blistering is just that. The tire has gotten so hot the chemicals inside it overheat and boil and it puts holes in the tire from within.

[wawawa]

Originally posted by Ross Stonefeld
I know graining when I see it, but ive never been really sure what the heck it is.

Sounds like Traction Control So what's it like handling-wise?

[Marlowe]

I was watching speedvision and the commentators said that graining is when very small rubber pieces loosely form on the surface of the tyres and causes the tyres to be slippery when turning.

I don't know if that's correct.

[Mosquito]

What I understand from it is that a tyre doesn't work optimally or isn't on the right temp for the track, and the rubber sort of deteriorates under high stress. The surface in contact with the road 'breaks off' from the underlying layers in small pieces.

Michelin's (at least last year's) suffer from this more than Brickstones, and that's one of the reasons you probably see the Michelin drivers often opt for rubbed in tyres.

Something like that.

[benn5325]

Some clues can be found here

[karlth]

Graining occurs mostly in the softer compounds and with understeer as rubber particles get stuck to the tyre causing it to lose grip.

Blistering is caused by oils inside the tyre overheating.

Graining usually occurs at the start of the GP with fresh tyres while blistering usually happens when the tyres are under too much stress.

[maclaren]

I have only heard about graining when Michelin is concerned and blistering when it's Bridgestone. Also, if I understand correctly blistering happens more and more towards the end of stint and the rubber melting, where as graining happens early and the pieces of tyre somehow fall apart. This shows how different philosophies the two tyre makers have for compounds.

[Todd]

Originally posted by maclaren
I have only heard about graining when Michelin is concerned and blistering when it's Bridgestone. Also, if I understand correctly blistering happens more and more towards the end of stint and the rubber melting, where as graining happens early and the pieces of tyre somehow fall apart. This shows how different philosophies the two tyre makers have for compounds.

Bridgestones have been described as graining, and either condition can happen at any time in a tire's life. Blistering is more likely to happen to a new tire, as that is when the tread is thickest, so that is when it distorts and builds heat the most. Remember the 1997 season?

[Deeq]

Originally posted by maclaren
I have only heard about graining when Michelin is concerned and blistering when it's Bridgestone. Also, if I understand correctly blistering happens more and more towards the end of stint and the rubber melting, where as graining happens early and the pieces of tyre somehow fall apart. This shows how different philosophies the two tyre makers have for compounds.

No that is not entirely correct, RS suffered Blistering during Monoca GP last year so has JPM N-ring same year. But graining I havent heard associated with BS yet they may have suffered but I didn't heard of so there you can be right.

[Todd]

Originally posted by karlth
Graining occurs mostly in the softer compounds and with understeer as rubber particles get stuck to the tyre causing it to lose grip.

Blistering is caused by oils inside the tyre overheating.

Graining usually occurs at the start of the GP with fresh tyres while blistering usually happens when the tyres are under too much stress.

You should look at the Avon link. It describes graining not as pickking up rubber, but as a separation of the outer tread layer.

[wegmann]

Yes, the Avon link is an excellent description of graining. It causes a visual rippling effect across the tire perpendicular to the direction of sliding. If you need good pictures and more detailed info, I recommend the book "The Racing & High-Performance Tire" by Paul Haney.

I don't know about the handling differences, but I would suspect that since graining is most often very directional, it may affect lateral vs. longitudinal grip. On the other hand, blistering probably affects both equally. Just a guess.

[karlth]

Originally posted by Todd


You should look at the Avon link. It describes graining not as pickking up rubber, but as a separation of the outer tread layer.

My comments on graining were based on this quote:

"It is said, on pit road, that the Michelin fronts are
prone to 'graining' -- little bits of rubber, like shards from
an eraser -- sticking to the tread. Acceleration, and the
resulting bit of wheelspin which occurs even with traction
control, takes care of the problem on the rear tires, ..."

While this BMW quote contradicts the one above:

The other crucial factor relates to the tyres. Michelin
fine-tunes its tyre compounds according to certain asphalt
temperatures. As a general rule of thumb, the hotter the
asphalt, the more grip a tyre can develop. If the track surface
is too cool for the selected compound, the asphalt and the
tyre tread don't connect well with each other. The rubber
develops small pellets that detach themselves - an
effect known as graining, which can turn a race into a slippery
business.

[Todd]

Originally posted by karlth


My comments on graining were based on this quote:

"It is said, on pit road, that the Michelin fronts are
prone to 'graining' -- little bits of rubber, like shards from
an eraser -- sticking to the tread. Acceleration, and the
resulting bit of wheelspin which occurs even with traction
control, takes care of the problem on the rear tires, ..."

While this BMW quote contradicts the one above:

The other crucial factor relates to the tyres. Michelin
fine-tunes its tyre compounds according to certain asphalt
temperatures. As a general rule of thumb, the hotter the
asphalt, the more grip a tyre can develop. If the track surface
is too cool for the selected compound, the asphalt and the
tyre tread don't connect well with each other. The rubber
develops small pellets that detach themselves - an
effect known as graining, which can turn a race into a slippery
business.

I tend to believe the latter explanation. For one thing, a racing tire supplier corroborates it.

[baddog]

Originally posted by karlth


My comments on graining were based on this quote:

"It is said, on pit road, that the Michelin fronts are
prone to 'graining' -- little bits of rubber, like shards from
an eraser -- sticking to the tread. Acceleration, and the
resulting bit of wheelspin which occurs even with traction
control, takes care of the problem on the rear tires, ..."

While this BMW quote contradicts the one above:

The other crucial factor relates to the tyres. Michelin
fine-tunes its tyre compounds according to certain asphalt
temperatures. As a general rule of thumb, the hotter the
asphalt, the more grip a tyre can develop. If the track surface
is too cool for the selected compound, the asphalt and the
tyre tread don't connect well with each other. The rubber
develops small pellets that detach themselves - an
effect known as graining, which can turn a race into a slippery
business.

the two quotes dont contradict.. the first quote, while referring to bits sticking to the tread, doesnt refer to bits bieng picked up from the road, but to what the second refers to as 'small pellets' detaching themselves from the compound and then covering the nearest sticky surface (the tyre) in themselves, hence 'graining', the tyre forms 'grains' of rubber which coat it

Shaun

[djned]

to paraphrase the bmw quote: if we're talking about pellets of rubber detaching themselves and making the track slippery - isn't that what has been referred to ever since i started watching f1 as 'marbles'?

i would tend to think that a grained tyre is one whose surface is...well...grainy. not as a result of picking up something. yes or no?

are there any pictures of this graining phenomenon around?

[wegmann]

Originally posted by djned

are there any pictures of this graining phenomenon around?

This seems to be a general article about rubber in general, whether it's on tires or not, but you'll find some graining pictures on page 128-129:

Evaluation of the durability of elastometric easy-release coatings

Note that I found this by searching for "abrasion pattern" rather than "graining pattern." According to Paul Haney's book (which I mentioned above), these are pretty much equivalent terms.

[Mox]

Blistering is typically caused by overheating, causing the oils in the compound to "boil" (as it has already been mentioned).

Graining is typically caused by the tyre not getting up to the ideal working temperature (often the result of wrong tyre pressure, which is why this problem is often eliminated - or at least reduced - after a pitstop, when the new set of tyres have had the pressure set better).

[prettyface]

I think of blistering as the phenomenom where a road car tire develops, in its terminal phase, a tit .

Graining should be similar to what you get by rubbing or brushing leather the wrong way, tiny pieces of leather sticking up but still atached, giving a rough surface. Think baseball glove rubbing on asphalt when you reach for a bad throw from your brother, fall and slide a bit.

[kenjafield]

Watching the French Grand Prix, Martin Brundle described graining as little balls of rubber detatching from the tyre and you drive on them "like driving on ball bearings". Makes for understeer, wheelspins, etc. etc.

Blistering - not so sure, but when a tyre blisters it is ready to go 'pop'!

[Peter]

Graining is a Michelin technique for hampering the Bridgestone runners

Little bits of rubber rub off the tyres and can be picked up on other cars' tyres.

Blistering is what causes Bridgestones to be less effective than Michelins. When a compound picks up bits of itself, they a reabsorbed (so Michelins are not affected). When a different compound picks up these, there is an allergic reaction which leads to blistering.

[Yelnats]

One thing graining isn't is that gross malformation of the tire surface caused by running over the marbles left off the racing line.

Driving through marbles causes a gross clumpy texture on the tire whereas graining is a much subtler undulation across the face of the tire and is caused by material from the tire it's self flowing by lateral deformation across the tire (usually the front) to form an uneven surface in both texture and profile. It's suspected appearance is often commented on by Steve Machete (F1 mechanic/commentator SpeedVision) and appears as a darker circumfrential band on the rotating tire face and dissappears rapidy after the corner is passed only to reappear at the next turn.

Running a tire too fast on a cold tire accentuates this problem but it can happen any time and obviously is a not completely understood phenomonon (or Bridgestone would have solved it by now).

Blistering is a mechanical separation between compond layers caused by a failure of the bond between the layers (usually due to overheating due to overstress under lateral loading). It can develop at any stage of wear but is most serious on a new tire new because the layers are thicker and may begin to detach to cause serious imbalance or complete tread separation.