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Old 07-15-2004, 06:59 AM   #16
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Quote:
Originally posted by TryHard
That final line is wrong, the wider the tyre you have the more grip you have, due to the larger contact patch of the tyre. (think of using just one finger to grip something instead of 4 [plus thuumb ], much easier with five due to increased grip)

However with an increase of contact patch also comes an increase in rolling resistance, and also a reduction in track width (distance between centre position of the tyre).

Ever wondered why the narrow (22mm) tyres seem more stable? Is mainly because the track of the car is wider, which helps aid stability and hence direction change.

This is something i have a fair bit of experience with, in that when i was running indoor on polished wood, the narrower tyres were faster, despite giving less ultimate grip, due to them being more stable, and being more consistant over a run, than the equivilant 26mm ones. I now never use wide tyres when in low grip situations, unless the rules say so. (In the wet I always run narrow, but thats a different reason [cuts through standing water better])

However I will agree that you are more likely to overwork a narrower tyre more quickly than a wider one, due to the amount of weight spread over the tyre. i.e. More pressure on the narrower contact area = more work to be done by less rubber = excesss heat generated in tyre, reducing grip. But then again this can be an advantage in some situations, as it will allow the tyres to get up to temperature faster.

Personally, I feel that the manufactuers have hit the sweet spot with the tyres at the moment, with the compromise between grip and rolling resistance begin at it's least in the 24mm tyres.

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Try HARDER. You're totally wrong, what have been stated before is right : narrower tire gives more pressure on the rubber, which provides more grip. Moreover, this also leads to a faster and higher rise in temperature, which can provide better grip in cold conditions, but also overheat in hot conditions.

You talk about dronfield (polished floor) and wet surface, it's exactly the same. A narrower tires provides better grip because the pressure is higher. On the wet, it's not that narrower tires cuts trough standing water better, it's that the higher pressure cuts trough standing water better and allows for more grip on a very low grip surface.

Also, nothing to do with track width, as when you're turning, the track width depends only in the offset of your rims as the patch of rubber in contact moves to the outside of the tire.

Don't forget one thing, tire adherence is not only a matter of coefficient of friction, because it's not flat surfaces moving relatively one from another. The tire adapts its shape to the surface which it sits on, which creates adherence by the ground being an obstacle to the movement of the tire (on a microscopic scale). So a higher pressure equates to more and bigger obstacles and thus more adherence.
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Old 07-15-2004, 07:02 AM   #17
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Quote:
Originally posted by pheyhoe
at my local club we run on polished wood. we use schumacher minin pins. 20mm tires have noticeably more grip than 24. at first i thought the reason for this was the same as on ice where cars use a really skinny tire, but then i realised the reason they do that was to get to the harder stuff under the top layer of snow/ice. why do skinny mini pins work better than wider ones?

Edit: Did not see the previos posts bit about polished wood.
Even on polished wood, the grip is not totally provided by friction. However, there also is the factor of the rubber itself, some might work better with narrow rims and some with wide rims.
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Old 07-15-2004, 01:06 PM   #18
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Umm, there's also one overriding thing that I think most everyone hasn't thought of, be far the biggest reason to use 24mm rubber tires is because the tire manfacturers are only selling their best compounds in that size. Regardless of this argument or that, the COMPOUND is the most important thing in what tire is best, & that's the only fact that truly matters...
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Old 07-15-2004, 01:35 PM   #19
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Cobra I believe we have two situations here that are in fact, both correct.

However the over riding factor in tyre performance is the caontact area, NOT the amount of pressure going through the tyre. This is mainly because if you think about it, this pressure relies ON the contact area! To get the pressure, you have to have a contact area first!

Indeed it is highly possible to get a narrow tyre with the same contact area as a wide one (running a softer insert for example), but these will provide different characteristics. The wider will provide the greater forward traction, the narrow the greater sideways (this is to do with contact area shape, as well as the way they tyre would slip)

What I believe our problem is here is, we are confusing forward traction with sideways traction. A wider tyre will provide more forwards traction, as it presents the greater area in that direction, whereas the narrower will provide better sideways traction (ie resistance to slip) due to the way the contact area is orientated, and the greater pressure running through the tyre.

Also on another point, you'll find with the mini pins work well becuase the pins themsleves deform to increase the contact patch (also why rally blocks work as well), whereas this doesn't happen with cut slicks (carpet dragons etc). Also the deformed pins have a better chance of finding grip versus the slicks, because the contact area is not fully conected (lots of small contact areas), compared to the slicks.

Also narrower tyres DO cut through water better (in adition to what you say), as there is less resistance to the water, provided by less aera of tyre. Why else would Rally cars run narrower tyres on a rally such as monte carlo? Because it cuts through ice, snow, standing water better. Now that is a low grip situation.

Track width will have an effect on your car.
You measure the distance between the centre of the tyre's, and they will be on a wide compared to a narrow tyre. what your talking about would only affect the front, and even then your contact will be in a different position as the wheels turn due to the position of the front wheels contact patch being closer to the outside edge of the tyre, and hence the outside edge of the car. On the rear, as the wheels don't turn, your track will be wider.
Also, technically the outside contact patch moves to the outside of the tyre (away from the car centerline), the inside one will move too the inside (towards the car centerline).

I think it might be best to agree to disagree on this topic....
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Old 07-16-2004, 05:44 AM   #20
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Yup, anyway from what alex just told me about you, I can't wait to meet you.

I was considering the fact that during a corner the car rolls, and depending on the amount of roll and camber change, the contact patch will move to the outside of the outer wheel (and the inside of the inner whel, but that wheel does have less influence, doesn't it ?).

Also, I agree that tires with pins are a totally different understanding, so that should not really be discussed here.

Anyway, gotta go, see you tonight...
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Old 07-16-2004, 01:16 PM   #21
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Traction IS friction. Friction is generated between the racing surface and the tire surface. Friction creates heat. There is tire adhesion, and mechanical traction. Knobs/pins or treads is an example of mechanical traction. Adhesion is the natural tendency for rubber to stick, which gets better with some heat, and worse with alot of heat. You can chime on all day about contact patch and its relation to rim width and its affect on overall stability of the car. The fact remains, you overheat the tire, you lose traction. Are you guys familiar with a "friction circle"? (type "friction circle" into your browsers search bar and read what you find) There is concrete, wood, asphalt, and carpet for us to race on. Each racing surface is going to have an optimum tire and temperature range. This range is different with supported tires, than it is with unsupported tires. Supported would be tires with inserts. These actually heat up faster than unsupported, such as foams. The amount of rubber is the key. The surface temperature, tire temperature, and your driving style, makes for a tire combination that works. If you have a set of tires that are good to 120 degrees F, the racing surface is 95 degrees F, and you drive the car HARD, you will exceed the temperature range of the tire and the car will be slower. (unless there is additional downforce) The rubber begins to breakdown and tear away excessively from the surface of the tire. Some of this is necessary for traction. Too much is too slow. If you take the insert into consideration, NO tire gives you a totally flat contact patch throughout the range of suspension travel. The tire actually bunches up on the inside sidewall, which is why the tire always wears there first, giving you that nasty "groove of death". This would also tell us that the tire is never really heated evenly. Rolling resistance is a definite consideration for low-powered racing classes. But nothing beats a larger contact patch, and a properly tuned car to utilize it. The larger the patch, the slower the heating time... and cooling time, the wear is more even, and gives you a more consistent tire lap after lap. How many F1 racers do you see on 70 series tires? The more rubber, the wider the tire, the faster the car goes. Its simplistic math. (At the Snowbirds this year, we ran double pink/double pink-orange compound tires in TC... the traction available on the track was similar to low tack masking tape. You would think you would run a harder tire to keep the car "on top" of the carpet for a faster car (rolling resistance mentioned earlier)... WRONG. The more grip, the faster we went.) For you guys that run on wood surfaces, have you ever tried to run soft foams with grooves cut in them? Cut them on a tire lathe similar to F1 tires. Try 1mm of depth to start. Treat the tires with traction compound the day before racing... several times. Place them in ziplock bags until use. Make sure your car is set up to give you even tire wear. Start with -2 degrees of camber... move it a bit each run taking note of tire wear. See how the car handles, check laptimes, is it faster? Does it feel like your car is on four oiled icecubes? Sometimes extremes is the only way to learn. The sad thing is, to go fast, you always end up shelling out $$$. Speed is never cheap. Experiment = experience. Speed is a byproduct of this effort.

I didnt reply here to disagree with anyone. I actually enjoy threads like this. I am glad there are people out there that are into the "depth" of this hobby as i am. These cars are just as, if not more, sensitive to tuning than the full scale counterparts. The smaller the scale, the finer the detail, the more work it takes to go fast. Now if we only practiced racing as much as we thought about this stuff.

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Old 07-16-2004, 09:46 PM   #22
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Good job DaveW... I just learned something

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Old 07-17-2004, 09:25 AM   #23
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ya Dave's post is good.

In short, grip allows you to keep your corner speed up, thus lower lap times.

If low rolling resistance is all you cared for, just run your car with your alloy setting wheels. Nothing beats o-rings for minimum rolling resistance!!



Dave missed out one thing but... you also need enough rubber width to put down your power. Too narrow and you'll not be able to lay it down well enough.

Am old enough to remember racing with 22mm supernarrows on HPI "PRO" compound. These worked great on electrics and gave enough grip to corner well for these light cars. But put the same on a nitro tourer and the horsepower just smoked them at takeoff, whilst they couldn't wrestle a heavier chassis around a corner. Had to stick with 26mm on nitro.
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Old 07-18-2004, 07:33 PM   #24
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Your point about Formula 1 cars, is why I asked this question in the first place.
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Old 07-18-2004, 11:36 PM   #25
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Yokomo introduced the narrow tires (22mm) in 1997. At that time we all ran 26mm. Turns out that the 22mm tires were way faster but they looked like bicycle tires on a car. In 1998 ROAR made the min tire width 24mm because any narrower didn't look scale and we have stayed with that.

As far as I know no one makes competitive racing rubber tires wider than 24mm.
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Old 07-19-2004, 07:20 AM   #26
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Thanks guys. Did any of you read any information on the friction circle, and slip angles? Its amazing the detail of information people afford us on the web. I will mention an annoyance of mine with rubber tires on asphalt. Surface temperature of the track in relation to the tire is critical. Almost TOO critical. You BASICALLY have to have three temperature ranges of tire (and i say... of the tire and insert combo that you found out even works... so you have more than three sets in the long run) to run on asphalt. Now there are really only a few manufacturers that make tires we normally use, although there is a large amount to choose from. This "natural selection" has made it a little cost effective to run asphalt, but there is still an added expense in the short term experimentation process. This is, to me, the only advantage of foams on asphalt... the lack of an insert. The insert can make or break a tire on the track. With foams, its just the selection of a few tires that work well on the surface you are running on. Foams will wear (accelerated) as rubbers do, if you overdrive the car, or if your setup is off. It just depends on the type of asphalt you run on. Is it really abrasive/smooth? Dusty? However, the greatest thing, to me, about rubber tires, is the car can go out of control... controllably. Sounds silly but, when foams let loose, it is ALOT harder to regain the control, when compared to a set of rubber tires. This comes back to the friction circle, slip angles, and the composition of the tire being used. You can actually toss a TC sideways with rubber tires and drift that puppy through a sweeper, feel the tires grab, and countersteer/counterthrottle (gotta love 4wd) the car back into shape. Try that with foams. Im sure Barry Baker can do it, but i cant. LOL

As far as rim width goes. I still prefer 26mm. Occasionally, when the grip is high on a smooth blacktop asphalt track with good heat in it, ill stretch a set of 24mm tires over a set of 26mm inserts and rims. The car actually feels like it has less overall grip. But the "illusion" of more stability is there. Usually the car can be faster per lap like this. (ill usually add another - .5 degree of camber too) Setup sheets are critical for fast repetitive setups from track to track. Take the tire temp after your run... track temp... air temp... etc. Write all that down for comparitive purposes. When the clouds come out on your otherwise sunny day at the track, the track temp drops 20 degrees, air temp drops 5, then you know what tire you need to goto for your car to be dialed in the main.

Alright, i got to go for a bike ride. See you guys later.

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Old 07-19-2004, 07:39 AM   #27
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DaveW, good post but you're partly wrong.

Make some easy calculations and you'll find that you have a coefficient of friction superior to 1, which is impossible as you must know. This is because we are not dealing with friction alone. Friction alone is only involved when two perfectly FLAT surfaces (and i mean perfectly) slip one from the other. With tires, it's not the case as I explained above as there is also (and mostly) mechanical traction.
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Old 07-19-2004, 08:50 AM   #28
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dude cobra you guys are way over the top. the guy made his point and we know it is not a perfectly flat surface! who cares we know what he is talking about!
We dont need to breek it down and disect it. shoot for all I care the molecules in the tire could be making love! Most of the guys you race dont know this stuff and probly beat you most off the time.

Look I use to race dirt oval back in the 80's when it was popular here in the states.
Everyone was using shumacher mini pin spike tires narrow front and wide rear.
I ran narrows front and rear the car accelerated better and didnt bogg down in the corners. I knew why but everybody said hey whats the deal! I am nuts! but when I started winning races then it became the norm.
I Raced full scale cars for a while and have been an auto tech for 12 years.
I have done a lot of reading in the bosch blue book and well tell you that people dont care they will run what ever the fast guy is running regardless of slip angles, lateral adhesion, or contact patches.

do you know that 90% of full scale cars have a contact patch no bigger then a six cell stick pack.

Most of you guys even forgot that the tires where smaller diam in the bigging and know they are taller.

I rather have a narrow tire and a taller wheel tire combo.

Most racing bodies limit tire width but not hieght which is what they did in full size touring car thats why they were running 18 to 20 inch wheels. they made the contact patch longer thus more grip.
On acceleration and decel, aswell as latteral!

But doesnt matter most people only race what the winner is running and aslong as its the case there will always be the leaders and the followers.
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Old 07-19-2004, 10:36 AM   #29
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I believe it was the JEMCA(japan) which set the minium width to 24mm first. Don't forget major touring car tyre manufacturers are from Japan,e.g, take off, sorex, pit & yokomo. They then started making 24mm tyre, other organisations just followed the rules, ROAR, EFRA, etc. Narrower tyres are faster in most situations, thats why 24mm has became the standard.
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Old 07-19-2004, 01:08 PM   #30
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for aslong as I remember here state side running touring cars they have been using 24mm since 1999.
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