karthik_003 wrote:why do drivers go in a zig-zag manner in the warm up lap ?
I heared that it'll increase the grip of the tire ? If so how?
First of all every input you give into the tyre will result in deformation and this will release some energy in the form of heat.
If driving zig-zag on a warmup lap will raise the tyre temps or help to keep them is
in my view negligible.The dedicated applying of braking force that can be seen as well is more useful in creating warm tyres (and brakes ,of course).
It is as well more easy to get the rears up to temps with 700something HP available.. just be a little eager on the throttle and they are there .
To get heat into the fronts ...well understeer seems to heat the tyres very well..
but then we have learned that weaving at speed adds tyre temp s as well .. see Button last year.
Here something from a Bike forum ,makes interesting reading and reflects exactly my experience (of non aero cars):
this is something that I am guilty of doing. It made sense, swerving would create friction on the tires inturn increasing tire temp. Guess I have been wrong. Here is the Linky over at the R1-forum for those interested. But those who don't have the time, here is the main bidy of evidence.
Weaving
Makes For
Good Collisions
By Dave Swarts
Weaving to warm tires is a fiction that just won't die. All sorts of riders who should know better can be seen weaving wildly on warm-up laps, and we've seen plenty of collisions and near-misses caused by one guy weaving into another guy on a warm-up lap. Yet some riders persist in the belief that weaving actually does something other than create a hazard. So, since we had gathered a test bike, a test rider, all sorts of measuring instruments, some extra tires, and had a track to ourselves for our big tire test (Roadracing World, January, 2000), we decided to test the effects of weaving on motorcycle tire temperatures.
We conducted this experiment using Mark Junge and his 1999 Kawasaki ZX-6R, at Oak Hill Raceway. Michelin tires were used for this test, the front a standard Pilot Race, and a Pilot Race "W" on the rear. First, we measured the cold tires' core temperature in the middle and on both sides of the tread, front and rear. We then sent Junge onto the track to ride slowly in a straight line and then measured the tire temperatures. Then we instructed Junge to weave aggressively from turn eight to turn two and back again (approximately one-half mile), and measured the tire temperatures again to see how much heat was produced in the tires.
Next, we let the Michelins cool off. We then heated the tires on warmers for 45 minutes per Michelin's recommendation and took the tire temperatures. Then Junge went out and did the same weaving and temperatures were taken again to see if additional heat was built up or if heat was lost.
Next, Junge was sent on a standard warm-up lap. We then quickly measured the tire temperatures. Then Junge did another 1.8-mile warm-up lap, this time weaving, and we measured the temperatures again to see if weaving built additional heat when compared to a standard warm-up lap, kept the heat in, or lost the heat. Then we did the half-mile of weaving again before taking the tire temperatures yet another time.
To complete our test of tires and temperatures, we sent our rider out on two normal warm-up laps. Once back on the starting grid, we stopped the bike with the tires remaining on the pavement just as you would sit on a grid with the 3-minute board in the air. Then we measured each tire, as quickly as possible, to see how quickly the tires lost the heat built up on the warm-up lap.
The first thing that we discovered while trying to take the temperature of the cold tires was that the sun has a significant effect on a tire's temperature. Our test bike was under a canopy but the front tire was still in direct sunlight on an 88-degree, Texas afternoon. Just from sitting in the sun, the front tire had between 10 to 20 degrees more heat at the tread's core, not the surface.
When Junge rode in a straight line at line at approximately 40 mph for about a half-mile, the shoulder of the tire that was in the shade remained at 85-88 degrees F. The temperature at the center of the tires went up slightly while the shoulder of the tire facing the sun also started picking up heat. Then our rider went on his weaving course and came back. Once again the side of the tire facing away from the sun and the center changed very little. The side of the tire facing the sun continued to gain heat. We attributed this solely to the sun as Junge was careful to weave equally hard on each side of the tires.
Junge went back to his task of learning Oak Hill on his "A-bike" while we took the weaving test bike back under the canopy and applied Tyr Sox tire warmers for 45 minutes. After the warmers, the rear tire had about 129 degrees F across its entire tread while the front held 171 degrees F on the right, 175 degrees F on the left, and 182.4 degrees F in the center. Both warmers were on for the equal amounts of time.
Just as I was organizing a theory into how the tire warmers have equal heating elements but the (120) front tire has less surface than the (180) rear tire, I noticed that the bike had been put back in its original parking spot with the front wheel in the sun. Although I can't rule out my equal tire warmers versus different-sized tires theory, I can't rule out that the strong sunlight increased the effect of the warmers.
As soon as we took the post-warmer temperatures, Junge went out to do the same exact weaving course. The right/away-from-the-sun side of the rear tire lost 12 degrees of heat. The right side of the front lost 45 degrees. The center of the rear lost 5 degrees of heat. The center of the front lost 43 degrees. The left side of the rear tire that was facing the sun stayed steady at 129 degrees while the left front only lost 36 degrees. Once again weaving did not build or hold the temperature. The sun had more effect than weaving.
As soon as these temperatures were taken, Junge was sent off to do a normal hot lap on the twisty, 1.8-mile course. After the hot lap, the heat in the rear remained fairly constant, cooling just a few degrees. The front continued to steadily lose its significant tire warmer heat. However, the left sides of the tires were the warmest parts. We could not attribute this to the sun because throughout our two-day test, tires always recorded higher temperatures on their left sides after doing any laps at speed on the track.
Then, we sent Junge to do an entire lap of weaving. Again, the weaving failed to hold heat anywhere on the tire. Then Junge once again did his straight weaving test, and the tires began cooling rapidly. In fact, during weaving the tires lost heat as rapidly or more rapidly as just standing still.
For our final test, we sent Junge out to do two laps to get some heat in the tires. Then as the bike stood still on the racing surface just as it would on a grid, we measured how quickly the tires lost their heat. I had originally hoped to measure the six spots on the tires every 10-15 seconds. That proved too ambitious. I ended up measuring each spot every 45-60 seconds. Next time, I'll have two pyrometers. This was very interesting, though. While the center and right sides of the tires lost 10-12 degrees over a 4-minute time period, the left side of the rear lost very little heat and the front gained heat from the direct sunlight.
Here are some conclusions. Tire warmers will produce the highest pre-race tire temperatures. During the tire comparison test consisting of 8-10 laps at 100 percent speed, we sometimes did not record temperatures higher then straight off the warmers. So the best way to warm tires is to use tire warmers.
The second-best way to warm tires is to take a hot lap. As powerful as the sun proved to be, a good hot lap produced more heat than time in the strong sun, and it's quicker, too.
The third-best way to warm tires is to leave the tires in strong, direct sunlight. Just don't forget to get both sides.
But weaving, no matter how aggressive your lean angle and your speed or how long the distance covered, does not build any additional heat in a tire!
So now, we will hopefully never see another unfortunate accident from useless weaving on a starting grid or pit lane. Case closed.
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