jlk16188

Well I was bored at work today so I figured I would do some research and start a discussion based around traction achieved and benefits of wider vs. narrower tires on your DD, drag or autocross car.

First…. Your contact patch will remain the same if you run a 175mm wide tire or a 235mm wide tire IF, and this is a big if, you use the same make and model tire and same tire pressure in this comparison.

Now if you would run a wider tire with lower tire pressure, your contact patch would increase also increasing your static traction.

Now before all of you either start arguing with me or go out and buy super wide rubbers and stuff them under your Hondas, hear me out further.

Narrow tires will not roll as well as wider tires. Wider tires will distribute your vehicles weight across the wider contact patch, deforming the tire less. The more tire deformation will result in more rolling resistance of the tire. But, wider tires are less aerodynamically efficient at high speeds and add extra drag to the overall vehicle.

Taller tires have more affect on tire traction than wider tires in pure lateral movement (i.e. drag racing). But as a result of running taller tires, you increase the torque on your entire suspension and drive train systems, causing potential for component failure.

In the case of tires, although traction increases with load, it increases less than linearly, and coefficient of friction decreases with load. A larger contact area reduces the load per unit area, resulting in more grip. There is a point of diminishing returns, such as weight and aerodynamic drag. It's also true that a larger tire dissipates heat and with a lighter load involved, it wears less. Another reason for a larger contact area is to compensate for debris or track imperfections interfering with the tire and pavement contact.

Note that load sensitivity is commonly used to adjust the understeer or oversteer of car. When a car turns, the downforce on the outside tires is increased and the downforce on the inside tires is decreased. The body of a car also rolls a bit, and the suspension can be used to unequally distribute the load between the front and rear tires. If the front end is relatively stiffer, then more of the downforce is exerted on the outside front tire, and the relative grip is reduced because of tire load sensitive. A stiffer front end causes the front end to lose some grip in turns, resulting in understeer. A relatively stiffer rear ends results in oversteer. Street cars are generally setup with understeer, while race cars are setup with a small amount of oversteer.

For a variety of reasons, such as deformations, molecular bonding type reactions as well as surface roughness, real world friction isn't the simple thing described in physics books.
Now to sum up everything rather than starting an endless rant…
Going wider will not always give better traction.

If you want an all sweeping statement that is roughly true. Wider contact patch sacrifices linear traction for lateral, narrow tires sacrifices lateral for longitudinal traction. And the most important thing about tires is not contact patch area but that they are at correct working temperature.
Wider tires are not always better. They dont always give better traction. It depends on the car, the situation, the conditions.

Eg. Rally cars use wider tires when on tarmac rallys, and use (surprisingly) very thin tires on ice rallys.
F1 cars used to use narrow tires until aero began to be used in the 60's.
Drag racers actually want tall tires, width is there to stop the tire being destroyed.


An example I can think of is formula student cars, they used to use 8 inch tires but couldnt get them up to temperature. They switched to 6.5 inch and got more grip because they can get them up to temp.

So before you go out and buy some super wide meats and cut the crap out of your fenders to stuff them in there…. Sit back and consider some factors.
What temperatures are you going to be driving in?
Are you only accelerating in straight lines like drag racing or are you autocross racing and need more lateral stability?
How long do you want your tires to last? Obviously sticky tires don’t last as long as hard compound tires, but have a much higher coefficient of friction. And running tires with lower tire pressure can put too much heat into the tire.
Lastly, if you are using your car as a DD, running 235mm wide tires when the stock size is 195mm, probably isnt helping you at all. Instead of modifying your car to fit these tires and paying higher prices for these wide tires, really isnt worth anything to you unless you plan on whipping it through your local neighbor hoods like a rally driver on a daily basis (which I will never encourage or think is “cool” to drive like an idiot on public roads)

The point is though the mentality that wider always = better is wrong. There is an optimum limit even on drag racers
Wow, that is by far the longest post I have ever written, lets hear some comments honda-tech.

d15b7inEF

Really good information wow i'm almost convinced not to buy wide tires. I have a question though. I just recently bought some 1986 crx wheels and the rims call for 185/60-14, but then they give me other options for tire sizes.

165/65-14
175/65-14
195/55-14
195/60-14
205/55-14

My question is will all these tires fit my rims. I want a lower profiled tire then the stock tire is. But i don't want fitment issues. Some insite on this would be good you seem like you know about tires lol. Oh BTW my car is only a DD maybe once a year i take it down the 1/8 mile.

jlk16188

id like to tell you what size to buy but thats all up to you. BUy the size that is closest to your stock size diameter to keep your speedometer from reading high or low. the 195/55/14 and 195/60/14 looks suspicious to me, I would personally just buy the 185/60/14 if its your DD

chi town brat

Suspension set up and how you drive is the first thing that comes to mind. I autocross and I like my car feeling like a rail as compared to another driver who prefers a softer feel. So I dial in my suspension and tire pressure to have the car grip for less load on the tires in quick movement areas.

I can agree also with the width not being the biggest factor of winning a race. I have 205/50/15 Hoosiers and came within 7/10ths of my competitors who were on 10" wide Hoosiers.

As far as tire temps and conditions many use tire warmers as an option to overcome the varying factors. If you are not that serious of a competitor then it is something to consider.

I also just found an equation about the weight of a vehicle and how many hp it takes to move that weight. So some may consider this when trying to find more bhp to get down the track.

jlk16188

actually cutting 1lb of rotating mass is about equal to 10 lbs of vehicle weight when you are driving

d15b7inEF

you know i concidered the diameter and it only makes a difference of 2-3 MPH so im not too concerned about that. My thing is I want a lower profile tire. Money might overall win the debate but i would like something a little lower profile.

jlk16188

Diameter doesnt affect speedo speed by 2-3 mph, its a percentage, so it will be a lot more at high speeds compared to low

Todd00

Remember that the most important thing is tire compound, period. After that, then select the appropriate size for what it is you are doing.

If you are autoxing your EF, then a 225/45/13 Hoosier will be a faster tire than a 205/50/13 Hoosier. The wider contact patch will allow you to pull more g's. This is just one instance, however.

Basically though, there are just so many factors to consider when choosing a tire that one post cannot cover all of them. Gearing, suspension setup, driver preference, car classing rules, car style/powertrain layout, car weight, wheelbase, wheel width/diameter, compound, heat generated, tire aspect size, power of car, overall width of setup, ...the list goes on.

A good rule of thumb though is that once you find the best compound, the wider tire will enhance lap times and cornering grip. Obviously there is always a law of diminishing return, but this should be somewhat obvious (especially on an EF).

d15b7inEF

Ok even if its a percent I don't Speed or much less drive more than 55 MPH so it is still only going to change it by 2-3 MPH

nineohnine

i have run 195/60/14 185/60/14 and 185/65/14 and i can tell you the difference in MPH that your speedo reads is almost not noticeable. with that being said out of the three in imo the 185/65 is the tallest looking (because it is). if u want a low pro look.. go with the 185/60. the 195/60 looks good too it just looks like a little wider low pro... hope this helps.

also edit:
the difference between the O.D. of the the three tires are as follows

195/60/14 = 23.2 in
185/65/14 = 23.4 in
185/60/14 = 22.7 in

so the difference in height isn't much. .7 inches max

d15b7inEF

Thanks it helps alot but what about the 165/65-14, 175/65-14, 205/55-14 any insite on these wheels. I know they are a little extreme at least frmo the numbers they look extreme.

nineohnine

22.4 O.D =165/65-14
22.9 O.D =175/65-14
22.8 O.D =205/55-14

again not much difference in O.D. but they do start to get a little smaller than the 3 that i have used...

but i dont see why they would have a problem fitting the difference in width between a 185 and a 205 is 20mm (or .7 in.) at its wides point

also on a side note the trans/speedo are tuned to a specific tire size. so if you have done an engine swap/ trans swap it is best to stay within the range of the tire size required for the car the trans came from in my case i have a B18a1 swap and trans from a 92 teg.. the recomended tire size is 195/60-14 for that car so thats teh range i liek to stay in.

d15b7inEF

Good info thanks. I look at them and sometimes the difference if 50 a tire and sometimes its 2 dollars a tires so money will have to do with my choice and .7 inches is not alot at all so its really a coin toss when your talking about a DD and tire choice is alot more important when you go to motox or drag/straight line racing

efjones9

When u start gettn down to the technical aspect of contact patch and all that jargon I remeber my convo with a former f1 driver. He told me that I should find a tire size that my application(suspension) and use, will work best and get u around the track faster. After 3 months of testing we shaved 3 secs off a e36 2002 just by changing the wheel tire size. Plus the driver getting better lol

Stinkycheezmonky

All that theory is well and good, but you could've summed up that enormous post with this:

"Sometimes a narrower tire will be faster than a wider tire for a variety of reasons. Only proper back-to-back testing will show what the best option is."

In the real world, most Honda drivers (hell, most track drivers PERIOD) don't have the means temporally, financially, or logistically to pull that off. If you happen to find one setup that is faster than another, kudos! Don't let the theory consume the real practice though.

As a technical aside, try not to compare 20-year old tire technology with current tire technology (Ex: 1981 F1 tires with 2009 F1 tires) because there is much more that has changed than simply width or outer diameter (such as compound and internal construction for starters).

VTECIntegra9

Stinkycheezmonkey for president.

descartesfool

That is an old wife's tale, repeated endlessly by people who should do some math and actually calculate the benefit of lower rotational inertia. It is not remotely close to a 10 to 1 factor. First, such a statement could never be true as a generalization, since moment of inertia varies as radius^2, and thus the effect of tires with a 12" radius is completely different than wheels with a 7.5" radius which is completely different than rotors with a 5.5-6" radius which is completely different than hubs and axles with a radius of 3" or less.

tire relative importance is 12^2 = 144
wheel relative importance is 7.5^2 = 56
rotor relative importance is 5.75^2 = 30
hub/axle relative importance is is 3^2 = 9

And then you have to compute the energy used to accelerate the non rotational mass vs the rotational mass to see the benefit.

And as for why wider tires are better than narrow tires, you have to first consider weight and HP. You could try to fit some 205/50/15's on a Corvette Z06 and see how long they last. Tires get hot, and they have to be kept below a certain temperature for optimal grip, and the total outer surface area is the prime determinant in the tire shedding that heat energy generated as the carcass deforms to meet the tarmac.

redzcstandardhatch

i read the initial post a few times...

good theory, and a very long way to say "unless your adding weight or downforce, there is diminishing returns on adding more tire width."

obviously there is a cure to not having enought weight per square inch of tire, and thats downforce..

its a tricky balance, made trickier by budgets, lack of proper testing equipment (especially by budget guys like us), and different driver preferences.

autoluder

Here is different thought, neg camber can allow you to use wider tires and not lose straight line speed cause there is less tire on the road when driving in straight lines...but when turning you can maximize with the wider tire's contact patch.

Stinkycheezmonky

This is a two-lane road. On high-horsepower cars, this can adversely affect traction on corner exit or (with enough power) straights. For a practical test, try drag-launching/racing a car with something like -3* camber on the drive wheels. It also only addresses the potential frictional drag increase of a wider tire in a straight line, not the aerodynamic drag or weight increase.


P.S. I LOVE all you critical thinkers so much

Egezzy

iTrader: (2)

also too some wider tires are also shorter tires compared to some skinnier/taller tires. so would it take less energy to get them around? plus easier/quicker for the car to accelerate if so??

Todd00

A short tire basically changes your gear ratio, so...what do you think?

Egezzy

iTrader: (2)

i know what i think. im just trying to stir the pot.

EdoMoto

I run 245/45/16 tires compared to others with 225/45/15 and I am way faster.
In H2.

Thank You
Edo.

jdm_AE86

owned

lol seriously tho although like some are saying, its all about the setup of the car IMO. There are so many different variables.