Wider is better?

[Angelo]

Hi!
I would like to hear your opinions on this:
Will wider tire result better handling? It seems like few people here think that it's not true. However, every time I go auto x I see some old Vette with really meaty tires getting some quick times. And old Vettes are boats! I know for sure that wider tires help to achieve higher G's in corners, how about overall performance? What are pros and cons? Thanks guys!

Angelo

[Raymund]

IMHO, get the widest you can fit on your car.

I'm running 225s for track use and have no plans on ever switching back to 205s. I've even considered running 245s if only I can find the correct rim off-set to eliminate or minimize binding.

pros: definitely more grip. its obvious and someone who doesn't notice the different probably isn't running hard enough. braking distance should also improve.

cons: some said it takes longer to heat up. If you're autoX it probably won't work to your advantage. It should weight more than a comparable 205 and your acceliration and top speed will suffer. However, its a compromise i have no problem accepting for more lateral G's.

[autxr]

Wider ins't necessarily any better, more contact patch is better (see the difference there).

The old vette is probably modded to some degree? If so they probably have put some new rear end gears in it. It also probably weighs about 800 pounds more than your Celica (and has a lot more power).

Wider tires weigh more. Con.
Wider tires usually come with a larger diameter. Con

That larger diameter slows acceleration. I guaranty a car with 205/50-15 tires will out accelerate a car with 225/50-15 tires.

Many of us run in a stock autocross class, so we are restricted by the rules. We can only run a 6.5 inch width rim. With that restriction, wider doesn

[nxracer]

Ok here's one to ponder.....
Currently the fastest ES (now GS) car in the country is a 85 Honda CRX Si. Rob runs 225/45R13's on the stock 5.5(?) Honda wheel.

I sure hope he doesn't change to a 205 or 185 and go faster.

[Raymund]

Originally posted by nxracer
Ok here's one to ponder.....
Currently the fastest ES (now GS) car in the country is a 85 Honda CRX Si. Rob runs 225/45R13's on the stock 5.5(?) Honda wheel.

I sure hope he doesn't change to a 205 or 185 and go faster.

hmm.. the fastest huh?? maybe its due to the 225s

[Angelo]

NXRACER: Good point.
Scott: That's the exact responce I expected from you:) However please note that I didn't specify autox. It could be a road course too. Oval. Track. Canyon. Please mention some pros! Don't be so negative.
Raymund: I already got the widest tire I could fit on the car. There is no way you could fit 245 tire without fender flares (or just roll them) I don't care how long it takes to warm them up, or real race cource you always get enough time. They are definetely heavier than narrower ones, but not by too much to make it noticable. Especially once you get it up to speed, we're not a drag racers. So I say there are more advantages. Once thing to consider: never get wider wheels on narrow rims, it won't make a difference.

[autxr]

Angelo-

You want Yes and no answers, then don't ask open ended questions. I speak form my experience running STOCK autocrossing. I know that that isn't ideal for everyone.

nxracer-

What size tires was the fastest 7th gen Celica at the 2001 Nationals running?

Scott

[afghan]

Scott, I'm pretty sure they were running 225s.

[nxracer]

Scott: The only car I know that was on 205's was Ken Rupp in third.

Of course yuo need to remember it is Ken that is driving.

He runs the 205 BFG R1 until his supply runs out.

[preparedcivic]

Count me in on running 205's. Kumho's even. Yes, Ken Rupp was the fastest on 205 (BFG brand). In 2000 The faster 7th gens were on 205 Hoosiers. I was fifth this year. Y2K I was on 225 Hoosiers, and waaaaaaay back. You can figure which size I think is faster. Better turn in due to better sidewall support. More contact patch because the tire is stretched across the rim. Not to mention being ableto get heat in the tire, particularly in the rear where it is critical.

Having intimate knowledge of the 3rd gen Civic/CRX like Carpenter's (see my username), I still own a DP/EP one that started out as a DS car (good enough for 4th in 93), and ran another one earlier from 1990 to 1992 with some success. His car works on those funky 225/45-13 Hoosiers for a few reasons. They are:

1. An 85 CRX is the absolute lightest 3rd gen there is. I would guesstimate his car is under 1700 lbs in race trim. That bulged sidewall doesn't have to support a whole lot. By the way, those wheels are 13x5.0!

2. The torsion bar front suspension is ride height adjustable. So while there is no camber adjustment in the front, other than loosening bits and pieces up and taking out the tolerance slop, with the camber curve dropping the car gets a good amount of static negative camber.

3. If it ever rains, I hope he has Dirt Stockers, because I guarantee the car is almost undriveable with those tires on in sloppy stuff with how it is set up.

4. In the dry, they are exceptionally easy cars to drive. The gas pedal is an on-off switch. Celicas, especially without shocks, are diabolical by comparison.

YMMV

[B1mmer]

After owning a '86 Civic Si, he's right on all accounts. The car is very easy to drive, especially when prepped correctly. The rims are 13"x5", yet a lot of people squeeze 225's on them. I ran 205's and thought it was a pretty tight squeeze. I can remember running against Rob in the 2000 24 heures du mall in Charlotte, and I was convinced he was illegal when he beat me by over 2 seconds in a 40 second course... After a little research, I was happy to only be that far back. - Aaron

[nxracer]

Your not alone a whole bunch of people (even out of the class) thought Rob's car was illegal last year (I was not one of them). Locally I run (well ran) against two very well driven but not as well prepared 8x CRX's so I know how fast those little bastards can be. Actually fast is probably not the right term, they're just so damn small they can drive through just about any maneuver.

I say ran because Zeisler's car now lives in the Chicago region. It will be driven by a very good x CRX driver. Paul is keeping his CRX (like it's worth a lot) just incase he can stop hitting cones in the longer, wider Celica. He loves the power and the fact that it actually turns but does not think his "never lift" driving style (like Rob's) will work in the Celica. Will it?

GS in the Chicago area will be fun in 2002
(2) 00 GT's (Chrt/Hirt)
(1) Neon ACR (Collins/Vandermey)
(1) 85 CRX (now with 225 Hoosiers)
(1) Cashmore (?)

Ps: After my current set of 225's are toast (about 20 runs left) I am actually going to try a set of 205's

[Mas]

My .02

Here

[B1mmer]

I don't know if it was just me, but I don't buy into Alex Tziortzis analysis on Kuhmo vs. Hoosier. I've run both tires, and in all sizes. I've had 205 and 225 Kumho's, 225 Hoosiers, etc. Of all the tires, Hoosiers, with temps above 65 degrees, grip the best on concrete and asphalt. The ideal is flat, unbroken asphalt, but if you look at my times from the 2001 Petersburg Pro, you can see that new Hoosiers do a lot, even on a bumper asphalt lot. When it's cold, there's no better tire than a Kumho, but when it's warm, the Hoosier is the best tire - Aaron

[nxracer]

Looking at the "actual" Nationals results
2001
2 Zimmerman on 2?? Hoosier
3 Rupp on a 205 BFG
4 Brown on a 2?? Kumho
5 Foley on Kumho ?
6 Reinhardt (P2 co-driver)
8 Joyce (P4 co-driver)

2000
4 Burns on a 205 BFG
5 Cone on a 225 Hoosier
6 Rupp on a 205 BFG
7 McDaniel on a 2?? BFG

[preparedcivic]

Its too bad I tossed all my shredded y2k 225/45 Hoosiers back in September, but tonight I'll measure the worn tread width my used up 2001 Kumho V700 205's and post tomorrow. They were never flipped, so it will be easy to measure what actually got used from the outside sidewall to the inside edge.

From what I remember eyeballing the 225 H's to these tires during the year, I was using more total rubber width with the narrower Kumho's, and had a much more drivable car. Maybe not with the same ultimate limits, but one that could stay at 99% much longer more often.

On the subject of bogus vintage Hondas, don't forget Mr. C was found illegal at the Pro, with the the wrong travel length shocks in the car. He was extremely lucky only getting Saturday times tossed. Prior precedent for similar infractions has typically resulted in points being revoked for the year at a minimum, also with potential prize/contingency money paybacks. There also was a potentially bogus time in his Sunday am runs that gave him the win for the event and the championship over me. Besides being late to Pre-Grid, which should have cost runs. Next year I won't be on the SEB, and won't be so politically correct with what I will do if similar shenanigans occur.

[B1mmer]

I have no doubt that other tires can be driven fast, but at 2001 Nationals, of the 51 classes that were run in stock, street prepared, and mod, 44 were won by a driver using Hoosiers, those exceptions being CSL, GSL, BSP, BPL, EP, CM, and CML. Granted it was concrete, which I believe is a bigger advantage for the Hoosiers. I know tires don't make the driver, but it's hard to deny the #'s. - Aaron

[preparedcivic]

Zimmerman/Reinhart were on 225/45 Hoosiers.

Brown/Joyce were on relatively new 225/50 Kumho V700's.

I was on thin tread 205 V700's. They corded the 1st event after Nationals. Great turn-in and lateral grip. Sucky longitudinal. Mega wheelspin everywhere. Also no co-driver, which would have helped for heat in tires. Course then they would have corded during Nationals. I maybe had .20-.25 left on the table. On my last and fastest run I was a little late into the slow left hand sweeper in the middle of the course, and had to wait a little for the car to take a set, and pinched the offset-in-the-middle of the right hand sweeper off a little too much, leaving about 3 feet between the car and the outside cone. Besides the putting the power down problem, those were the only things that weren't pretty close to perfect on that run.

Rupp was on 205 Biffs out of his special stash.

Remember, this course was basically a g loading test. The place to make time was in all the sweepers. Not hard to figure why the lightest car on the biggest tires won.

[preparedcivic]

As promised, I measured the 205 Kumhos and used 8.1" of rubber, from outside to inside. I'm curious what a similar measurement on 225/45 Hoosier would show.

[B1mmer]

I'll measure my 225/45 Hoosiers this afternoon and post. I just pulled them off a set of rims, and I was going to chuck them. - Aaron

[Joshua Clarke]

Just to elucidate a couple of points that have been misrepresented in this thread...the size of a tire's contact patch depends almost entirely on the weight of the vehicle and the air pressure in the tires. Sidewall stiffness may or may not come into play, depending on how accurate you want to be, but the point is that a wider tire with the same construction and air pressure does NOT create a larger tire contact patch. A wider tire will have the same contact area, but it will be longer laterally and shorter longitudinally. It's this change in contact patch shape (not increase in area) that creates greater grip from a wider tire. Also, on a less important side note, Mason said to look at the Camaro as an example of what big tires can do for a car with a poorly designed suspension, but Camaros actually have surprisingly good suspensions from the factory...SLA's up front, Torque Arm and Panhard in the rear, I believe. If you want an example of a crappy suspension that can be hidden by good tires, look no further than the Ford Mustang.

[B1mmer]

Josh... you need to point out that the aspect ratio of the wider tire is important too on contact patch, for two tires (identical construction) of differing widths that are supporting identical amounts of weight and equal air pressure, yet have different sidewall heights (affecting the overall circumference) will have different shape contact patches.

I have a tough time believing that the two contact patches in your example will be of equal size, just different shapes. Your example forgets that with equal pressure, the larger tire will still have more flex across it's longer width (disregarding sidewall flex) and thus would create a truly larger patch. It's been a few years since I got my minor in Physics, but from what I remember, there wouldn't be a direct one to one relationship of increased lateral to decreased longitudinal. - Aaron

[Joshua Clarke]

If you have a minor in physics, this'll also be too elementary for you, but it may help others.

Drawing a free body diagram of one wheel on a car, you'll have the weight of that corner of the car pushing down, and the ground pushing back up with equal force (Normal Force). Now, the tire is the only part of the car in contact with the ground, so it supports the normal force. Clearly, the force it applies to the ground is equal to the air pressure in the tire multiplied with the area of that tire's contact patch. This is accurate because the only other manner in which the tire could support the weight of the vehicle is through the compressive force in the sidewalls, and I'm sure you've seen a car sitting on a flat tire...the sidewalls don't do anything to hold the car up (that's not their job). Clearly, this argument falls away for run-flat tires. Anyway, if you change the tires on a car, the weight on that corner of the car doesn't change (except for the tiny change in tire weight), and thusly the force supported by the tire doesn't change. Ergo, if the air pressure in the tire doesn't change, the area with which it contacts the ground cannot change. Like I said previously, what does change is the shape of the contact patch. Assuming the contact patch goes from shoulder to shoulder on the tire as it should, and we've mounted wider tires, it's gotten longer in that dimension. To keep the same contact area, it gets shorter in the perpindicular dimension. You're right, it's not a 1-1 relationship in dimensional change (if the contact patch gets 1 cm longer, it doesn't get 1 cm thinner) but that's not really of consequence. What matters is that the shape of the contact patch has changed into one more suited to handling loads. Let's look at the case of lateral loading. With tire A (thinner tire), the contact patch is a square. With tire B(wider tire), the contact patch is a rectangle with its longer dimension oriented along the lateral axis (axis of loading). Now think about laying a rectangular piece of rubber on the ground. If you push it on its long side, it moves and deforms easily (bad). If you push it on its short side (along its long axis), it holds its shape and counteracts the force much better. This is how the contact patch shape change increases the grip of a wider tire.
Now, if you put a tire on a rim that's way too wide or way too thin, all you're doing is making the shape of the contact patch worse, and there's no sense in trying to compare two tires of differing widths if one or both of them is flexing or bowing excessively, as you can't really guess how the contact patch is going to look or behave.

Anyway, this is long enough. Some of you guys are going to be at the AutoX in Dinwiddie Sunday, right? I'll be there in my red GTS. Unfortunately, I'll be pimpin' the street tires, as the R1's (from Ken Rupp's "secret stash") won't fit in the car for my trip up there from Atlanta on Saturday. See you there!

[B1mmer]

:D

[B1mmer]

Hey Josh... that's a good analysis, that makes me realize it's been too long since my physics days (6 years and counting). I'll be up there on Saturday. Scott Johnson (autxr) will be co-driving my car in the Prokhana, for his car isn't out of the shop yet. The intersting thing is I'll be running BFG G-force R1's for the 1st time. I found a guy who had a set of 225/50's and 205/50 (pair of each) that are brand new. (just heat cycled on the road). I've never ridden them so, it'll be interesting to feel the difference of the BFG's as compared to the Hoosiers and Kuhmo's I've been running. Stop by when you get a chance. I'm running #74, but Nationally I tend to run #47, so hopefully we won't be at any events that coincide.:D Looking forward to meeting you. - Aaron

[autxr]

While I agree 100% with Joshua's analysis, there is one other thing to consider.

If the tire pressure changes, then the contact patch does change.

So, if you can run one of the tires at a lower pressure than the other, then you do get an advantage.

Not sure which way the pressures would need to go depending on the tire size.

I kind of think that you might be able to run a lower pressure on the skinnier tire. A vertical sidewall should support the load better than an angled one.

Scott

[Raymund]

Bimmer

I recomend you run lower psi on those R1s than you would normally. they're special tires.

[Joshua Clarke]

Aaron,
I have some notes about R1's that Ken gave me when he gave me the tires. I'll share them with you on Sunday...I figure if anyone knows how to run a Celica with BFG's, it's Ken Rupp. See you there.

-Josh

[nxracer]

So Jim Z sold Aaron the rest of the "secret stash" of BFG's. I believe Jim was Ken's source for 205's, Jim bought out TireRack's stock of 225's and 205's when they discontinued the tires. When Jim sold his car to Paul he offered me "the stash" but I didn't want to end up with a tire that is now unavailable. I think you'll like them, in my opinion they are the best tire for a 00 Celica.

Joshua: There is plenty of room inside the car for 4 Tires. I have carried 8 with the passenger seat still open.

[NoCones]

Thanks, Joshua for explaining about the contact patch...I've made the same statement about a wider tire not necessarily putting more rubber on the road, but never explained why.

My additional thoughts:
1. The wider contact patch is probably better for acceleration and braking...if you spread that longitudinal force out wider, the the tire should grip better...see the massively wide rear tires on a dragster...they ain't there for handling.
2. By the same token, the longer contact patch of a narrower tire should support a (purely) lateral load better than the wider...same argument.
3. Of course, it's pretty rare to get a purely longitudinal or purely lateral load on an autox course, but I think it's helpful to think about it that way anyway.
4. All that being said, I think the best setup may be 225 up front and 205 in the rear. 225 should be better at combating wheelspin...and, I haven't heard anyone complain of much understeer with 225's, so there's no real reason to try to help lateral grip up front. The 205's in the rear should help the rear hold better...heat up quicker, better contact patch for lateral loads, more vertical sidewall.