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Old 07-13-2004, 09:50 AM   #1
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Default why 24mm rubber touring car when rules allow wider.

I was reading the Official Roar Rule book, the section on 1/10 electrictouring car is pretty lear that rubber tires can be up to 31mm wide. Is their a reason everyone run 24mm. Does the extra rubber on the road not help? Are there other reasons?
Do they even sell rubber tires and wheels which are wider and will fit 1/10 electric Touring Cars?
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Old 07-13-2004, 09:53 AM   #2
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It's difficult to run wider tires at events that have controlled tires which are 24mm.
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Old 07-13-2004, 10:00 AM   #3
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i do believe there's 26mm tires out there and rims , the offset might in 26mm rims will either cause some drag in the hubs or the tires might drag on the body in the front depending on body used .. unless a 200mm body is used .. i think 24mm is just the norm ... maybe try 26 rim and 24mm tire ...
just 2 cents worth..
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Old 07-13-2004, 10:40 AM   #4
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Default its all about traction

You can get the same grib with a 24 mm wheel as a 31 mm. With a 31mm you get more resistance becouse its wider.

so in the end. runing a 24 mm gives you = grip as a 31 mm tire(or better grib) but less resistance (more speed)

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Old 07-13-2004, 10:46 AM   #5
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ROAR doesn't differentiate between foam and rubber - foam is available in wider widths. I have seen rubber tires up to 28 mm.
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Old 07-13-2004, 01:29 PM   #6
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Right, 26mm tires used to be all the rage, but then they started playing around with different widths(including 24 & even 22mm), & found that a narrower tire has considerably less rolling resistance, & as long as it's still wide enough(as in a 24mm tire), it can produce plenty of grip, so that's what became the new standard, which is still used today.....
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Old 07-13-2004, 06:40 PM   #7
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I'm just starting out racing, so all this drag, resistance, more weight talk is irrelevant to me at this point. The only technical stuff I worry about is tuning and setting up my chassis. I run both widths when I race, and you know what... I'M STILL SLOW AS A TURTLE W/ AN ATTITUDE PROBLEM

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Old 07-13-2004, 08:15 PM   #8
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Jaybee,maybe you should start taking a closer look at these factors you say are irrellevant.All these things are important and play a role in the cars overall performance.Tires are a huge percentage of how well the car handles.There is no getting around it.Rolling resistance and drag are a stock class killer.If your ok with the speed your going,then ignore this suggestion.Ever little bit counts especially in stock class.
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Old 07-13-2004, 09:17 PM   #9
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True, that....
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Old 07-13-2004, 09:47 PM   #10
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You guys have all not thought about *weight*.

Weight of car (and downforce) pushes down on the 4 rubber patches. This produces grip (= stiction + friction).

A wider tyre makes a larger contact patch, so the same weight=force is more spread out over that larger surface (eg difference between a stiletto heel and a flat heel)... = less grip.

However if your tyre is too narrow (eg ppl used to run 22mm)... there is excessive force on the small contact patch. Great grip but the rubber is easily overworked and starts going off quickly.


With modern rubber compounds, the sweetspot is 24-26mm. Current fashion makes most good rubber in 24mm so that's what we use today.

Who knows what tomorrow will bring?
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Old 07-13-2004, 11:04 PM   #11
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Quote:
Originally posted by WC
You guys have all not thought about *weight*.

Weight of car (and downforce) pushes down on the 4 rubber patches. This produces grip (= stiction + friction).

A wider tyre makes a larger contact patch, so the same weight=force is more spread out over that larger surface (eg difference between a stiletto heel and a flat heel)... = less grip.

However if your tyre is too narrow (eg ppl used to run 22mm)... there is excessive force on the small contact patch. Great grip but the rubber is easily overworked and starts going off quickly.


With modern rubber compounds, the sweetspot is 24-26mm. Current fashion makes most good rubber in 24mm so that's what we use today.

Who knows what tomorrow will bring?
I totally agree with this analogy; that's why it doesn't bother me to use both.
24mm has the cars weight on a smaller contact patch, has less rotating mass, good grip but possible excessive wear of the contact patch.
26mm has the same cars weight on a slightly wider contact patch, more rotating mass, good grip also and the wear on the contact patch is minimal.
TO ME , the difference between these two set-ups can only really be noticed by TOP DRIVERS and don't really mean a hill a beans to me-- YET
But I do recognize the importance of understanding these factors for having the ultimate ride on race day.

Look-- it's just a simple thought, from the simple mind, of a simple man.

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Old 07-13-2004, 11:28 PM   #12
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btw "Excessive Wear" is not a big concern to electric racers, the top guys only re-use their tyres for very few races anyway.

Overstressed overheated rubber has LESS grip than when they're at their optimum operating temperature. Wider rubber solves this.
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Old 07-15-2004, 03:15 AM   #13
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Try this one out.
Tires contact patch is in the middle of the tire.
The thinner the tire is the farther apart the contact patches are, with the same total width of the car.
So thinner tires bluffs the car into behaving like it's wider than it is.
Don't ask me why it works, a fellow racer spent whole hour to explain it to me and I still don't understand it.

Thinner tire has also has less rotating weight.
So you use as thin tire as you can before it starts to seriously affect grip.
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Old 07-15-2004, 06:17 AM   #14
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Quote:
Originally posted by WC
You guys have all not thought about *weight*.

Weight of car (and downforce) pushes down on the 4 rubber patches. This produces grip (= stiction + friction).

A wider tyre makes a larger contact patch, so the same weight=force is more spread out over that larger surface (eg difference between a stiletto heel and a flat heel)... = less grip.
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.

Regards
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Old 07-15-2004, 06:46 AM   #15
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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.
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