Scraping a tyre?

[gato azul]

I agree, it's done/was done in quite a few series, which specify "road/street legal" tyres.
And as Marcus said some manufacturer "offered" shaved tyres to their customers, after seeing/lerning what they did with the tyres, to "get around the rules" and gain performance.

on another note: some teams/race series do the same with "rain tyres" to make
something more similar to an "Intermediate" tyre, when the rules only specify
one "rain" and one "dry" tyre.

[Scootin159]

There's two elements being confused a bit here, but both are equally common.

The picture above shows someone cleaning off used tires. As mentioned above, this is very common in nearly any racing series that uses race tires. If you go at all offline (and even still if you don't) you will pick up plenty of what is called "OPR", or "other people's rubber". In series that use street tires this is less of an issue because the tires just aren't grippy enough to pick it up.

In amateur racing circles this is normally handled with a torch, putty knife and a beer at the end of the day.

The other item mentioned here is tire shaving. This is used only when street tires are required, and is done using a specialized machine, not normally by hand. The advantage of shaving street tires depends largely on the tire you start with, but generally it is to avoid overheating the tire (tread blocks flex under load, adding too much heat) or to improve the 'feel' of the tire (addressing tread 'squirm' mentioned above). In either case, the tires in these series normally need 3/32nds of tread depth BEFORE the race to be considered legal. Much less than this doesn't really add performance anyways, and just shortens the life of the tire.

Other interesting notes:
1) A lot of series will have one spec tire that is used either shaved in the dry, or at full-depth in the wet (the Toyo RA1 is a prime example - it looks a lot like F1 grooved tires when shaved)
2) Some racers will also hand-cut a rain pattern into a racing slick to use as an intermediate tire
3) Some racers will also hand-cut sipes (basically very narrow grooves) into their tires to cause them to warm up faster. The small cuts allow the tires to flex more internally, adding to the heat generated. You'll see these tires used on either cold days or for qualifying laps.

[Jersey Tom]

In amateur racing circles this is normally handled with a torch, putty knife and a beer at the end of the day.

Oh do tell what elaborate tools the 'professionals' use for removing pickup...

[hardingfv32]

How long to clear this 'pickup' if you simply just go back onto the track to scrub them? Say on your out lap.

Brian

[marcush.]

How long to clear this 'pickup' if you simply just go back onto the track to scrub them? Say on your out lap.

Brian

I think detecting damage of the tyre by scews ,nails cuts is not to be underestimated in this process of tyre cleaning.Some drivers and cars seem to have a hard time getting rid of pickup .and as i said before it really depends on the track ,how much rubber is out there to be collected plus where your driver is going at which speed on his inlap...if you have more important things to perform after your FP or qualy you may haave no choice but leave the tyres as is...

[Jersey Tom]

How long to clear this 'pickup' if you simply just go back onto the track to scrub them? Say on your out lap.

Brian

All you're doing it scraping off one little strip of the stuff so you can measure the wear pins. Not trying to clean the whole tire.

[alelanza]

...(one of the reasons why drivers are weaving in pace car periods!) ...

Marcush, not sure i understand what you mean here? My understanding has always been that it's done to keep heat in the tyres, which in itself is another hotly debated topic

A friend of mine told me that in some series, street tires are 'lathed' and the tread cut down to make them 'slicks'.

AFAIK that was the 'origin' of slicks. At some point the threaded tyres started to exhibit better performance under certain conditions as they wore down.

[strad]

Located on the tread surface of the tires are small divots or holes. These divots are called tread depth holes and are used to measure the wear of tread. Tread depth is usually referred to in 32nds of an inch. A brand new tire should measure 4/32 of depth in each of the holes.

Back to topic..Ya gotta scrape the crap off to find the wear holes to measure how worn they are,,,there are other reasons but that the gist of it.

[andylaurence]

Many people in British hillclimb and sprinting circles scrape the tyres between runs. The idea is to scrape off all the old rubber (yours and other people's) from the surface so that when you leave the line, all you're laying on the track is fresh, virgin rubber. I don't have the patience for it, so I just leave a very tall 11 at the start line!

[Mystery Steve]

I have a random, somewhat on topic question for anyone who may know: do any race engineers perform some form of hardness testing across the tread of the tires to evaluate if there may have been thermal inconsistencies at the end of the run? Does rubber show trends similar to metals (i.e. heating and then quickly cooling results in harder and more brittle material, etc) when it is heated and cooled, or would that information be useless?

Or are the tires such a relatively small surface/volume for the amount of work being put into the material, that any potential gradient would be imperceptible?

[strad]

I'm not sure if the teams can measure the change in hardness resulting from heat cycles if that is what you mean, but I'm pretty sure the tire company does.

[munks]

Does rubber show trends similar to metals (i.e. heating and then quickly cooling results in harder and more brittle material, etc) when it is heated and cooled, or would that information be useless?

Rubber has all kinds of trends, some beyond what metal exhibits. Absolutely the hardness and other properties can change after a heat cycle. Also you can simply stress rubber a bit to permanently change its properties.

[olefud]

Rubber is different than metal. Greatly oversimplified, metal (steel) has changing properties depending on the rate of cooling because rapid cooling doesn’t allow carbon to drop out of solution in the iron. Rubber continues to vulcanize (crosslink) and does so faster at higher temps. If you don’t relieve the load on a tire after a heat, the rubber can take a set at the flat spot. Particularly race tires get harder and harder with time.

[marcush.]

there is the possibility of measuring shore hardness in the field but you don´t get the full picture with that as the tyre characteristic -histeresis in rebound after being comressed .
But there is a french company around supplying tools to measure tyre characteristic as well as track surface charecteristics .i think at least some teams rely on this .

[raymondu999]

From the Bahraini race thread:

What are they trying to do here? Scrubbing?