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Do Larger rims give better traction?


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#1 73LJWhiteSL

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Posted 22 June 2006 - 06:11 PM

gday all,

Just a random sort of question. In relation to wheelsize when drag racing, would larger wheels and tyres give better traction for launch?

I am not really super interested in drag racing, but i was thinking if i ever did it more to get like a set of 15" volvo rims with some good rubber on it to see if i could get some better times.

Steve

#2 smeer

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Posted 22 June 2006 - 06:14 PM

Why do you think people tub their performance cars to fit wider tyres? ;D

#3 TORANR AMORE

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Posted 22 June 2006 - 06:51 PM

I think he means diameter.

Well put it this way steve, using smaller diameter rims is like using lower gear ratio in your diff (revvier gear ratio).
Better traction will be attained when you use wider tyres/rims. but as for diameter in relation to traction it depends on your setup, and where it starts to make real power and ultimately it's something you need to experiment with because there are too many factors involved such as the weight of the rear end of the car how it changes gears, RWHP at which rpm, stall converter size etc.

Generally speaking though a larger wheel will provide more surface area on the road (if not fully inflated - ie race setup) than a smaller diameter wheel, but it will require a bit more torque to turn it, yet there will be less likelyhood of wheelspin. Small tyres on V8 Torrys get a lot of wheelspin. But again you have to make the compromise because you are affecting your ratio and for a drag setup you want high effective RPM most of the time accross the 1/4mile from standing point.

Personally, I don't think you'll get better times in you car with 15" rims. I'd try 14's with the widest tread possible (and a NOS bottle, he he).

#4 FastEHHolden

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Posted 22 June 2006 - 08:08 PM

lots of variables here...and you may have to define what you meant by bigger.

205/65 x 13 are damn near the same circumference as 205/55 x 15.....so if you have the same circumference the gearing doesn't change...the perfomance advantage in this case comes in the form of better cornering due to a smaller more rigid sidewall.

by fitting wider tyres you are increasing the contact patch with the road...go too big and you "over tyre" it....the weight of the vehicle is spread over too large an area...less pounds per square inch.

If you get too much wheelspin with your current tyres...let them down a bit....it lengthens the contact patch...more tyre on the road, just the same as fitting wider tyres.

#5 devilsadvocate

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Posted 22 June 2006 - 08:11 PM

The points mentioned ^ are all good, but I think what you want to know steve is whether with the gearing/diff ratio adjusted for the 15in diameter wheels would you be better off? Im leaning to yes.
Would the 15in tyre have a bigger footprint, most likely, though Id expect that not 15/14 times bigger due to the weight of the car remaining the same.

Eh, i wasnt aware of overtyring in the dry though it sounds feasible. Are there some stats one should keep to in relation to vehicle weight and contact size for max adhesion, or simply an ideal contact pressure?

Edited by devilsadvocate, 22 June 2006 - 08:17 PM.


#6 73LJWhiteSL

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Posted 22 June 2006 - 08:27 PM

Sorry guys i should have clarified bigger Diametre rims.

I do understand that bigger rims with smaller rubber does make for better grip on a track (circuit).

Thanks for the replys. :spoton:

Steve

#7 FastEHHolden

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Posted 22 June 2006 - 08:51 PM

Devil..you have me confused with one of those "Has Been Drip Under Pressure" type people.


I don't know of any magic number when it comes to pressure being exerted on the ground....Wet/slippery surfaces will show the problem up much sooner than dry..we should get myth busters to test it...I cant afford 345/35x 13's to test the theory.

NB....I just plucked that size..although it would be interesting to see a set of tyres that big. :rockon:

#8 Shevster

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Posted 22 June 2006 - 08:53 PM

Generally for straight line traction the smaller the sidewall (ie aspect ratio) the less flex in the sidewall. This causes the tyres to break loose traction easier. Bit of side wall flexing say in a larger aspect ratio sidewall should get the torque to the ground abit better. If that makes sense.

#9 devilsadvocate

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Posted 23 June 2006 - 12:23 AM

Devil..you have me confused with one of those "Has Been Drip Under Pressure" type people.


I don't know of any magic number when it comes to pressure being exerted on the ground....Wet/slippery surfaces will show the problem up much sooner than dry..we should get myth busters to test it...

What do you mean by that 1st sentence?

I understand the wet phenomenon, needs to be enough pressure to displace the water from under the tyre to allow rubber and bitumen to make some type of contact, if large area of rubber(or no tread in tyre), film of water trapped between tyre and bitumen...sliding.

The situation with the dry surfaces appears completely non similar, contact area is increased as much as possible, ie slicks etc for maximum adhesion

#10 FastEHHolden

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Posted 23 June 2006 - 07:43 PM

Translation: "You have me confused for an expert"

I wouldn't say completely different. The water lowers the friction.

If the weight of your car stays the same, but you increase the area of the contact patch of the tyre with the road by 2 times (ie you went from a 5 inch wide tyre to a 10) then you have halved the pounds per square inch the tyre exerts on the ground.

We need a physics type person

#11 makka

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Posted 23 June 2006 - 07:58 PM

just say that for the taller wheel the diff ratio is corrected to give the same overall ratio, you will get more traction with a taller wheel.

taller tyre=larger footprint
wider tyre=larger footprint

the higher your sidewall the better (within reason) as it gives you more 'bag' which gives better traction

#12 Struggler

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Posted 23 June 2006 - 09:53 PM

just say that for the taller wheel the diff ratio is corrected to give the same overall ratio, you will get more traction with a taller wheel.

taller tyre=larger footprint
wider tyre=larger footprint

the higher your sidewall the better (within reason) as it gives you more 'bag' which gives better traction

The real bonus is the greater area is in the direction of travel. That is a taller tyre has a greater front to rear footprint, which will gain more traction than a wider footprint of the same area. This is why drag cars with unlimited tyre size usually go for the tallest possible tyre and adjust diff ratio to suit.

#13 Shevster

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Posted 23 June 2006 - 11:55 PM

the higher your sidewall the better (within reason) as it gives you more 'bag' which gives better traction

Thats what I was trying to say :D

#14 devilsadvocate

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Posted 24 June 2006 - 02:20 AM

by fitting wider tyres you are increasing the contact patch with the road...go too big and you "over tyre" it....the weight of the vehicle is spread over too large an area...less pounds per square inch.

Eh: this statement you quoted about overtyring would cause more wheelspin has no real basis and is just your personal theory?

#15 devilsadvocate

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Posted 24 June 2006 - 07:45 AM

Eh: sorry......my post ^ serves no useful purpose, please ignore.

#16 73LJWhiteSL

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Posted 24 June 2006 - 12:54 PM

Looks like i have opened a bit of a can of worms...

I assume from what people are saying is that if I go to 15" rims I probably need to keep the same wheel aspect for dargging, as in not go to low profile.

I understand bigger rims, smaller rubber on a cirucit makes for better handling, but bigger rims and bigger rubber makes for better launch on drag strip right? (Ignoring all other variables like suspension setup etc)

Steve

#17 FastEHHolden

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Posted 24 June 2006 - 01:09 PM

I would have to say it is a theory/opinion.....I'm sure I could find a stack of stuff for and against my view.

I suppose I'm try to say wide is good...Too wide is not

73LJWhiteSL....as you said before that its going to be an occasional folly...i would go low profile to keep your speedo correct and use the same tyre on the street as you do on the strip.

#18 MRLXSS

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Posted 24 June 2006 - 11:13 PM

I Like makka's analagy, very simple....


Bigger Sidewall.... more traction

Bigger Width... More Traction

#19 orangeLJ

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Posted 30 August 2006 - 11:29 AM

sory to bring up a couple month old thread, but i had the same thinking as steve, i had 14 inch hotwires on my VK loved to smoke all day and would spin off the lights all the time, i put 17s on it (same width) and it barely spins em. does this mean its getting better traction?? still acelerates the same..... as i said sorry to open the old can of worms.

#20 shanegtr

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Posted 01 September 2006 - 01:56 PM

sory to bring up a couple month old thread, but i had the same thinking as steve, i had 14 inch hotwires on my VK loved to smoke all day and would spin off the lights all the time, i put 17s on it (same width) and it barely spins em. does this mean its getting better traction?? still acelerates the same..... as i said sorry to open the old can of worms.

pehaps a better compound on the 17"s?

#21 TORANR AMORE

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Posted 01 September 2006 - 02:20 PM

It requires more torque to turn the larger wheel amongst other things. It's just like lowering your gear ratio.

Cheers,
Rick.

#22 TORANR AMORE

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Posted 01 September 2006 - 02:53 PM

Of course when I say that I mean like going from 4:1 to 3:1
Does that mean increasing the gear ratio or lowering it?

Cheers,
Rick.

#23 Toranamat69

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Posted 01 September 2006 - 04:52 PM

I never read this thread previously. I agree with Makka with his original statement.

just say that for the taller wheel the diff ratio is corrected to give the same overall ratio, you will get more traction with a taller wheel.

taller tyre=larger footprint
wider tyre=larger footprint

the higher your sidewall the better (within reason) as it gives you more 'bag' which gives better traction


With regard to 'overtiring', my understanding is that your ultimate grip in ideal conditions between the bitumin and rubber will continue to increase the wider the tire for the same vehicle weight (with any tire you can buy anyway so within reasonable limits) - but that all assumes a perfectly smooth track and an ideal normal force between the two.

It does not account for the fact that you are trying to accelerate as fast as possible, or the fact there is a mass spring damper system above the tire, and 4 of these systems connected and interracting with each other.

Wheel weight is a huge factor in the performance and handling of a car as that weight has to be accellerated linearly and rotationally, as well as being one of the biggest portions of unsprung mass in the suspension system, and the biggest rotating mass on the car, and significant portion of vehicle weight so very significant all round.

The wider the wheel and tire, the heavier it gets.

There is a balance.

A light car with lower HP level would notice this more.
I'm sure there is way more to drag traction than I know though, I tend to look into street and circuit setups.


M@




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