If I put wider tires on my car, that will give me more rubber on the road and better handling. That sounds good. Are there any disadvantages?
WelllâŚmaybe.
If you put wider tires, on the skinny OE wheels, you may actually decrease the handling advantages a wider tire can provide.
Then, there are suspension settings: the E suspension has limited adjustability to take advantage of a wider tire.
I used 6" center-laced wheels, plus I set as much negative camber as was possible, to better utilize the 205/70s I had on it. At the carâs limit, they did indeed provide a higher performance envelope, but in 99% of the driving I did, they provided little advantage.
My main goal wasnât ultimate handling, but a betterâIMOâlook, with the wider wheels and tires.
Many on here report perfectly good handling with the 185-70 Vredestein tires, on either 5- or 6-inch rims.
EDIT: when Tweety did his race car service, back in the 60s, he sported 6- inch Borranis and wider Goodyear Blue Streak tires: to accommodate that rubber, his rear fender lips were flattened, and the bump stops and brackets removed.
The only rubbing he had in the front was a slight scuffing on the headlight diaphragm, but it was at full lock, and minimal.
My series 3 appears to have little to no room for anything bigger than stock. Rubbing on the front inner fender wells in the turns. The car I bought came with the next size up and it had this problem.
wider tires are worse for traction in winter/snow because of less pressure per square inch. I would imagine the same principle holds in dry weather. I once read, donât know if true, there is more pressure under a womanâs high heel tip than under an elephantâs foot.
Apples and the color red: wider tires, on dry ground, will provide more traction, due to greater contact patch area.
Check out any road race car, for confirmation.
In snow, you are correct: skinny tires generally do better.
IIRC, S3s had 6-inch rims and 205s, did they not?
Racers use wide tires to spread out the heat in their tires because they use softer compounds that can overheat. For street cars on all season tires, wider is just for looks.
No: racers use wider tires to gain traction, by utilizing a greater contact patch, among other factors.
As for the heat thing? Maybe.
I once went for new tires and the salesman said that specific tires were great in rain or snow. I told him I never take my car out in rain or snow. I love my wide tires on 6 inch wheels, but added electric PS since parking was a bear.
At low speeds, the 205s greatly increased steering effort.
However from 5 mph-up, it wasnât bad.
I have a distinct memory of Tweety, with four studded snow tires on itâŚ! I figured in my time, I wasnât going to use it in the winter, as did my parents!
This subject is interesting from the âphysicsâ point of view. To a first approximation, the traction (or frictional force resisting acceleration including lateral acceleration) depends for each tyre on corner weight alone and not contact area. To a second approximation (true at least for old fashioned pneumatic tyres) the contact patch area doesnât depend at all on tyre widthâonly corner weight and tyre pressure. But those points are out the window because the âfrictionâ is due to a unique mechanismâthe intercalation of rubber into irregularities in the pavement, sometimes with the rubber shearing off.
The contact patch does change shape as the tyre is made widerâa rectangle oriented parallel to the road with thin tyres and perpendicular with wide tyres. But the physics lesson IMO is that one needs to forget theory and bank on the experience of owners, particularly racers. IMHO.
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Yes, 205/70/r15 is the equivalent of the tires size used in the old system, the correct tire for the series 3.
I thought so, but wasnât sure: without a fair amount of surgery, and expensive wheels with exact offset and backspacing, thatâs about as much tire as the car can accept.
You make good points, and letâs go further into the physics!
The second link is more correct. The tire / road coefficient of friction varies with temperature. Too cold slippery, so racers warm their tires. Too hot, blister or tread failures. Wider tires have the same contact patch size but more total surface area. This spreads and dissipates the heat.
Yes, the only reason for me. Bolt on rims also allow a wider track (hard to get rears off the wire hub with some off sets). It was widening the track for looks that was a big deal for us. Would have been happy with 185R 15âs if they were cheaper. The 205/70âs I thought looked a bit better and were easily available. The sidewalls donât look so hot, however. If we could get modern construction and reasonable cost in the 185R 15âs Iâd guess they were the best - you need the diameter. The Pirellis look too narrow for me (the âoriginalâ looking ones).
I know people say âWhy be cheap on an expensive carâ, but 'âA man has to know his limitationsâ. At some point it just gets too expensive.
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many tire choicesâŚdealt with massively on forum topics on tires in archives/search. Tire Grip, adhesion, friction on pavement, how the tire behaves with cold, with heat, ride comfort, and yes appearance all factors to considerâŚfor meâŚI just canât put Sumho a on JaguarâŚno matter other features., Radial Pirelli Cinturato âre-makesâ look nice at a price, AvonâŚnice at a price, Michelin have been availableâŚDunlop used to have a 205-70-15 SPâŚvery classic look, now discontinued. Pirelli recently had a nice appearance a P4 in that size also nice look, âŚI found some with recent date code last year. The oft used Vredestein has a âsummer tire designation and warningâ about use in very cold tempsâŚAs to performanceâŚF1 for example has 3 Pirelli tire compoundsâcarefully controlled via rulesâŚa soft, medium and hardâŚjust watch any F1 race to see the diff in lap timesâŚand how long they lastâŚif they want to have fastest lap,âŚthey put on the soft. For appearanceâŚpick what you like that will fit both rim and carâŚdone. But for performanceâŚthen suspension, alignment, camber etc adjustments all come into play., The improved rip of modern tires changes the prior classic handling a lotâŚto the point where rip is so goodâŚit is scary to find the limit which often happens âsnapâ suddenlyâŚnot like the ol classic driftâŚor hang the rear end out oversteer,. I donât buy tires based on how they feel when parking. Nick
Robert, thank you, that is what I had understood. I believe the common thought often is that a wider tire puts more rubber on the road, that a wider tire gives more contact area between the tire and the road. What I have understood is that the contact area of a tire is not a direct function of tire width. But of the weight on the tire. For example, if a tire has a load of 900 lbs on it, and the tire has 30 psi of air pressure in it, the tire will squash down until it has a contact patch of 30 sq in. 30 sq in time 30 psi will hold up 900 lbs. As you said, the width of the tire only changes the pattern of the contact area, not the total area. One can note that contact area does not equal handling. Many other factors do.
On your second point, I believe if the theory does not match the facts (of racing) then the theory needs adjusted, or maybe the facts are not being observed properly.
Tom
Wider tires donât put any more ârubber on the groundâ.
Your car rides on air, not on rubber. If you have a wide tire, the contact patch is wide and short. If you have a skinny tire, the patch is thin and long. Allowing some fudge for varying sidewall stiffness, the amount of rubber on the road is the same, but the shape of the patch differs. If you really want more rubber on the road, lower your air pressure.
More rubber in the line of travel gives you more starting and stopping traction. More rubber transverse to the line of travel helps with handling and stability.
That is close to my understanding of wider tires.