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View Full Version : How important is it for all 4 tires to match?


Nars Glinley
04-03-2012, 01:33 PM
I drive a Ford Focus Coupe that absolutely devours rear tires. From the Google results that I've seen, it's a common problem that Ford thinks isn't a problem. The alignment guy tells me that there's no problem with my alignment.

So, after the latest round of wearing out rear tires, I decided to only replace the back 2 since the front 2 are still in very good condition and I'll have to start rotating my tires with every oil change. :mad:

Obviously I don't want different tread patterns on tires on the same axle. How important is it to have all 4 match? Am I taking my life into my own hands? My googling leads to mixed results so I'm turning to the smartest people on the planet.

Dag Otto
04-03-2012, 01:44 PM
I've never had any problem with doing exactly what you propose. I've done it on three different vehicles, with both road tread, and in the case of my 4x4, full mud tires. The mud tires had probably the greatest difference in tread between the two types, but no problems, even at highway speeds.

Of course, the tires are all the same size, and as you note, stay matched per axle.

leahcim
04-03-2012, 02:32 PM
I once had a tire replaced due to a nail, and the guy who replaced it rotated it to the rear wheels. He said that all four the same was ideal, but if not that at least the two front and two back should match, but if not that at least the two on the drive wheels should match (which is why he rotated the new one off the drive wheel).

I didn't have any problems in that configuration.

Thudlow Boink
04-03-2012, 02:41 PM
I've never heard that all four should match. Whenever I've gotten new tires, I've bought them two at a time, and they've never tried to talk me into replacing all four at once.

engineer_comp_geek
04-03-2012, 04:17 PM
Unless it's four wheel drive, I wouldn't worry about all four matching. I would however try to keep the front two matching each other and the rear two matching each other.

On a front wheel car, if the rear tires are shot I would have the new ones put on the front and the still good front tires rotated to the rear.

Nars Glinley
04-03-2012, 04:42 PM
On a front wheel car, if the rear tires are shot I would have the new ones put on the front and the still good front tires rotated to the rear.

The tire manufacturers advise against this because the tires with the lesser tread will hydroplane first. If the front tires hydroplane, the result is understeer which can be controlled fairly easily by taking your foot off of the gas. If the rear tires hydroplane, the resulting oversteer is more difficult to control and can lead to a spin.

Gary T
04-03-2012, 06:49 PM
The tire manufacturers advise against this because the tires with the lesser tread will hydroplane first. If the front tires hydroplane, the result is understeer which can be controlled fairly easily by taking your foot off of the gas. If the rear tires hydroplane, the resulting oversteer is more difficult to control and can lead to a spin.True, however the front tires are going to wear faster; putting new ones on the front allows the wear to even out between front and rear, while putting them on the rear will result in having to buy another pair of tires sooner rather than later. And if those new ones are then put on the rear, the cycle continues. It's a bit of a dilemma. Practically speaking, I think it makes more sense to put new tires on the front of a FWD vehicle. The driver(s) should be advised about the possibility of a rear wheel skid, and cautioned not to push too hard on wet or snowy roads.

JustinC
04-03-2012, 08:01 PM
The tire manufacturers advise against this because the tires with the lesser tread will hydroplane first. If the front tires hydroplane, the result is understeer which can be controlled fairly easily by taking your foot off of the gas. If the rear tires hydroplane, the resulting oversteer is more difficult to control and can lead to a spin.

I have an issue with this statement; surely your steering tires hydroplaning is a much more serious issue than the rear wheels losing traction? For example how do turn into a skid/oversteer if you have no steering? During a hydroplaning incident what if a solid object is in your way - would you rather have your front or rear wheels operational? If you're going around a corner would you prefer to oversteer or head straight on?

Muffin
04-03-2012, 08:18 PM
Next time you get four tires, keep rotating them so that they all wear out at about the same time.

Also, you can get the tread on new tires shaved down so that they match the remaining tires.

Woodenspoon
04-03-2012, 08:48 PM
only matters if you have advanced 4wd, if diameter is not equal then some tires will rotate faster than others, throwing it off?

Rick
04-03-2012, 10:07 PM
I have an issue with this statement; surely your steering tires hydroplaning is a much more serious issue than the rear wheels losing traction? For example how do turn into a skid/oversteer if you have no steering? During a hydroplaning incident what if a solid object is in your way - would you rather have your front or rear wheels operational? If you're going around a corner would you prefer to oversteer or head straight on?
This is what the tire manufactures recommend when mounting new tires.
Forget hydroplaning. As the tire wears it loses grip. When this occurs in the front it is very natural to turn the wheel a bit more to compensate. This also has the effect of moderating your speed a bit as you unconsciously notice that you are having to do this and tend to slow down just a tad.
Put the new on the front and most drivers won't notice anything until their car swaps ends in a corner.
Most people can't drive their way out of a spin.
New on the rear.

Zep Tepi
04-04-2012, 12:24 AM
Greetings.

Just for information, in Spain it is illegal to have different makes and types of tyres on a vehicle.

I do not like the idea of tyre rotation as it implies that your alignment is out and they are getting unequal wear. Secondly if they all wear out together the bill is twice as high as replacing two at a time.

On a rear wheel drive car the rear tyres should wear out before the front ones. That is then the time to put the new tyres on the front and the older ones on the rear. You definitely need better traction on the front than the rear of a car.

On three of my classic cars, the rear tyres are much wider than the front. 235 on the rear and only 195 on the front, so I cannot swap them around anyway as they are designed for one way rotation only, apart from slow moving reverse.

Anaamika
04-04-2012, 08:24 AM
Wow, people actually replace all four tires at once? And it's illegal not to do so somewhere?

Front wheel drive, and I never change all of my tires at once. Never.

cooky173
04-04-2012, 08:46 AM
Little bit of background - about 6 years of experience in the tyre industry, in Australia. So, I know nothing about snow tyres.

As others have noted, two tyres at a time is fine, except for the exceptions...

We like to get people to keep matching axles at a minimum, and haven't come across instances where different tyres front and rear was the cause of a problem. I guess when you think about it, the back and front axles are required to different things anyway, so if anything you might try and find two different treads that complement what each axle is required to do...yes, I know, getting a bit silly now.

Our experience with putting new tyres on the back has usually been negative, and for that reason we like to put the new tread on the front, rotating tyres as required.

If your finding that the inside edge of the tyre is wearing out before anything else, depending on the labor it may be cost effective to have them flipped on the rim partway through their life. Note that its not recommended to do with asymmetrical tyres.

FoieGrasIsEvil
04-04-2012, 08:50 AM
On a side note...does anyone else find it extremely odd that on the OP's Focus, a FWD car, the rear tires are wearing faster than the fronts? There's something just not right there.

engineer_comp_geek
04-04-2012, 08:57 AM
Wow, people actually replace all four tires at once?


I do on my truck, but it is 4 wheel drive and all four tires do tend to wear out fairly evenly (even though it is in 2WD mode most of the time).

I also usually replace all four tires at once on my Cadillac, but it isn't driven very often and the tires tend to dry rot before they wear out.

On our other cars though, I'm with you. I replace them in pairs, front or back, but rarely both front and back at the same time.

pulykamell
04-04-2012, 09:10 AM
I usually do all four because, well, when it's time to change one for me, it's usually time to change them all.

Nars Glinley
04-04-2012, 09:21 AM
On a side note...does anyone else find it extremely odd that on the OP's Focus, a FWD car, the rear tires are wearing faster than the fronts? There's something just not right there.

It's a fairly common problem with the 2 door model. I've read (with a large grain of salt) that the back end isn't heavy enough and that the rear tires don't have the best contact with the road. My awful Oklahoma roads can't be helping the situation either.

Gary T
04-04-2012, 09:36 AM
I do not like the idea of tyre rotation as it implies that your alignment is out and they are getting unequal wear.It implies no such thing, so long as we're talking about normal wear and not the kind of assymetrical wear that misalignment can cause. It is quite normal for the tread to wear down faster on one axle than on the other -- the drive wheel tires tend to wear faster than the non-drive tires, and to a lesser extent the steering tires will wear faster. On a FWD vehicle, these factors combine to make the front tires wear noticeably more quickly. Rotation is recommended by the manufacturers to even out the wear over time, as steering and suspension systems are designed with the assumption of equal tread on all tires.

Secondly if they all wear out together the bill is twice as high as replacing two at a time.True, but over time the same number of tires are going to need replacement. The only cost savings is in not paying for rotation, but that's at the expense of possibly compromised safety.

You definitely need better traction on the front than the rear of a car.I don't know where you got this idea, but it's contrary to industry standards. See the above posts addressing rear wheel skids.

Nars Glinley
04-04-2012, 09:45 AM
Our experience with putting new tyres on the back has usually been negative, and for that reason we like to put the new tread on the front, rotating tyres as required.

Interesting. What has your negative experience been?

Son of a Rich
04-04-2012, 10:01 AM
Also, you can get the tread on new tires shaved down so that they match the remaining tires.

Joking, right? :confused:

Kimballkid
04-04-2012, 10:20 AM
Wow, people actually replace all four tires at once? And it's illegal not to do so somewhere?

Front wheel drive, and I never change all of my tires at once. Never.

I always change all four at once. Always.

LouisB
04-04-2012, 10:46 AM
Joking, right? :confused:

We used to call the process "shaving"; it's not a joke but it was expensive and it was terrifying to watch it done as the new tread you just bought is cut away. It was done to ensure that none of the tires on a car were not out of round. (My experience goes back to the 1950s so take it with large amounts of salt. Tires have come a long way since then.)

pulykamell
04-04-2012, 11:18 AM
We used to call the process "shaving"; it's not a joke but it was expensive and it was terrifying to watch it done as the new tread you just bought is cut away. It was done to ensure that none of the tires on a car were not out of round. (My experience goes back to the 1950s so take it with large amounts of salt. Tires have come a long way since then.)

Good story about it here (http://blog.caranddriver.com/the-lost-art-of-tire-shaving/), with reference to why you still might want to do it.


But shaving still has its uses. Say you have an all-wheel-drive car that started with a full set of fresh rubber ten thousand miles or so ago and suddenly you find yourself needing a new tire as a result of a failure. A mismatched set of tires could force a modern four- or all-wheel-drive system to be constantly working to manage torque, causing undue stress and wear on the components. In order to prevent that type of problem, you could replace all four tires, or replace just the one and have it shaved down to the diameter of the three worn treads. Obviously, the second option would save you a lot of money.

Rick
04-04-2012, 01:07 PM
That is then the time to put the new tyres on the front and the older ones on the rear. You definitely need better traction on the front than the rear of a car.
Glad you know more about it than some of these guys
The Michelin (http://www.michelinman.com/sites/michelincom/tires-101/buying-tires/how-to-choose/mixing-tires.page) mans says:Michelin recommends replacing all four tires at the same time, however if replacing only two new tires, be sure that the new tires are the same size & tire type as the current tires and that the dealer always installs the new tires on the rear axle of the vehicle.
The tire Rack (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=52):However due to a front-wheel drive vehicle’s front tires' responsibility for transmitting acceleration, steering and most of the braking forces, it's normal for them to wear faster than rear tires. Therefore if the tires aren't rotated on a regular basis, tires will typically wear out in pairs rather than in sets. And if the tires aren't rotated at all, it's likely that the rear tires will still have about 1/2 of their original tread depth remaining when the front tires are completely worn out.

Intuition suggests that since the front tires wore out first and because there is still about half of the tread remaining on the rear tires, the new tires should be installed on the front axle. This will provide more wet and wintry traction; and by the time the front tires have worn out for the second time, the rear tires will be worn out, too. However in this case, intuition isn't right...and following it can be downright dangerous.

When tires are replaced in pairs in situations like these, the new tires should always be installed on the rear axle and the partially worn tires moved to the front. New tires on the rear axle help the driver more easily maintain control on wet roads since deeper treaded tires are better at resisting hydroplaning.
Or maybe the Tire Industry Association (http://www.tireindustry.org/default.aspx?id=976&LangType=1033):Q: Why should I install two new tires on the rear axle of my front-wheel-drive vehicle?

A: Because a vehicle with brand-new tires on the front axle and worn tires on the rear has a greater tendency to lose control when turning in wet or slippery conditions. While the new tires on the front may "hug the turn," the worn tires on the rear may slide out and "fishtail." This condition is known as oversteer, and it has been known to cause serious and fatal accidents on front-wheel-drive vehicles with two new tires on the front axle and two worn tires on the rear.

LouisB
04-04-2012, 01:11 PM
Thanks for the link. It's nice to know that I'm not yet completely insane but I am closing in on it. Shaving tires was more of art than a science, probably due to less than optimum equipment for the job.

FoieGrasIsEvil
04-04-2012, 03:15 PM
It's a fairly common problem with the 2 door model. I've read (with a large grain of salt) that the back end isn't heavy enough and that the rear tires don't have the best contact with the road. My awful Oklahoma roads can't be helping the situation either.

That seems really counterintuitive to me. Less weight in the rear end of a FWD vehicle should make the rear tires wear even less, not more. Or so you'd think.

andyleonard
04-04-2012, 03:23 PM
Shaving tires is standard procedure for sedan race classes that have to use a spec tire. About 1/2 original tread depth is where the serious guys start with a new set. Unless I'm out of date, Tire Rack will shave and ship.

Odd sized or mismatched tires, whether on an axle or in a fancy all-wheel-drive setup like BMW's XDrive, will chew the hell out of the transfer case and front and rear diff clutches. A BMW X3 - for example - has a transfer case that holds 1 liter of $80 fluid that only comes from the BMW dealer and said case has no dipstick. Originally the fluid was "lifetime fluid" but BMW changed their mind and now it is to be changed. Point being, this is a fairly delicate unit with a "rebuilt" cost of around $5K. To protect it, the ABS, DSC and tire pressure systems will not accept a tire diameter above or below a certain range without setting off all sorts of alarms. BMW really, really wants all tires to be the same size...a pretty good argument for keeping matched sets on the car.

With 2wd, obviously you are only concerned with one axle at a time being matched, and as stated above, some cars come with staggered sizes anyway. Personally, Tire Rack notwithstanding, I will not be driving in any kind of weather in a FWD car with bad tires on the front and new ones on the rear. I'm guessing way more people have understeered off a wet road than have looped it.

andyleonard
04-04-2012, 03:32 PM
It's a fairly common problem with the 2 door model. I've read (with a large grain of salt) that the back end isn't heavy enough and that the rear tires don't have the best contact with the road. My awful Oklahoma roads can't be helping the situation either.

I ran into a version of this on a 2WD Suburban which had a habit of using up rear brake pads at a rate about 3 times as fast as the front...exactly opposite of what you might expect. Research showed GM had diddled the front-to-rear brake balance to prevent "nosediving" at stoplights and had the back brakes going on first. Is it possible something like this is going on with your car? Either on purpose or by accident?

It seems implausible that the rear tires - aligned and inflated properly - on a FWD car would experience much wear at all compared to the front drive and steering wheels. Maybe you need your proportional valve redone/replaced to have more braking in front and less skidding of unweighted rear tires.

Muffin
04-04-2012, 05:53 PM
Joking, right? :confused:
No joke. (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18)Tire Rack has offered a tire shaving service that has been primarily used for preparing competition tires for racetrack use. This same service can also be used to remove tread rubber from new pairs or individual street tires used on four-wheel drive and all-wheel drive vehicles to allow them to match the remaining tread depth of the other partially worn tires that will remain on the vehicle. In addition to providing equivalent tread depth to eliminate driveline stress, shaved tires will also better match the traction and handling qualities of the remaining worn tires.

Zep Tepi
04-05-2012, 08:46 AM
Not convinced that I have been doing things wrong for the last 50 plus years, I posted the question on a British Classic Car web page asking where would you place the two new tyres and the consensus who replied said definitely on the front.

I feel that I regulate my speed for road conditions and over the last 50 years have never lost control of the rear of a car, but should I have to take avoiding action of say a child running out in front of the car, I would prefer to have the new tyres on the front where the braking pressure is greater and also to be able to take avoiding action.

Rick
04-05-2012, 09:25 AM
So you don't believe the professionals who tell you the facts, but you do agree with other equally misinformed people.
I to have owned LBCs and I participate on a couple of online mailing lists for LBC owners. The lack of technical knowledge on those lists is amazing.
I would not hold up the collective (lack of) wisdom of a bunch of LBC* owners as a reason to do anything.
But hey what do I know, I've only been doing this shit for over 40 years professionally.



* for those playing along at home LBC= Little British Car, think MG Trimuph, Austin Healey etc.

california jobcase
04-05-2012, 09:50 AM
I used to run tires until the cords showed. Yes, I know that's bad, but I was broke back then. I always kept the better tires on the front because getting a blowout on the rear 's a lot less dangerous than on the front. This was generally on RWD no power steering cars, but also on one FWD car. Have a blowout on the front of a manual steering car, and it gets hard to steer real quick. Power steering helps some, but it still pulls hard to the blowout side.

Maybe that's why people stick to the better tires on the front concept.

andyleonard
04-05-2012, 10:24 AM
So you don't believe the professionals who tell you the facts, but you do agree with other equally misinformed people.
I to have owned LBCs and I participate on a couple of online mailing lists for LBC owners. The lack of technical knowledge on those lists is amazing.
I would not hold up the collective (lack of) wisdom of a bunch of LBC* owners as a reason to do anything.
But hey what do I know, I've only been doing this shit for over 40 years professionally.



* for those playing along at home LBC= Little British Car, think MG Trimuph, Austin Healey etc.

My suggestion, Rick, is that you professionally put your new tires on the back and the rest of us who own repair shops, drive race cars and live in the mountains will put them on the front, O.K.?

Zep Tepi
04-05-2012, 11:57 AM
I think I now know why American Cars don't go round corners as well as the European cars do.

Must be something to do with the best tyres on the back.

Gary T
04-05-2012, 12:38 PM
I think I now know why American Cars don't go round corners as well as the European cars do.

Must be something to do with the best tyres on the back.Yeah, that must be it, the factory puts half-worn tires on the front. :rolleyes:

Rick
04-05-2012, 02:22 PM
I think I now know why American Cars don't go round corners as well as the European cars do.

Must be something to do with the best tyres on the back.
:rolleyes:
Yes unlike those great handling British cars (http://www.youtube.com/watch?v=_bIn_ZgHJaE).
Second best selling car with a plastic body after the Corvette.

TurboNuke
04-05-2012, 03:34 PM
I currently have a car with four different tires on it. Doesn't seem to affect the handling at all in normal conditions. Maybe in extreme circumstances it might make a difference. As far as I know the whole matching tires thing started with bias ply and radials. Since almost all tires are radials these days I don't think it makes as much difference as the old days.

Zep Tepi
04-05-2012, 08:52 PM
1963 Corvette. 5358 cc - Top speed 142 mph

1964 Shelby Mustang 4735 cc - Top Speed 119 mph

1962 Jaguar E Type 3781 cc - Top Speed 150 mph.

1962 Aston Martin DB-4 3670 cc - Top Speed 140 mph

1962 Ferrari 250 GTO 2953 cc - Top Speed 185 mph

And the European cars go round corners.

Aestivalis
04-05-2012, 09:18 PM
Here's two times we've discussed it before:
http://boards.straightdope.com/sdmb/showthread.php?t=451141
http://boards.straightdope.com/sdmb/showthread.php?t=490691

But people remain unconvinced. How about video evidence?
http://www.youtube.com/watch?v=gSz7cm6MwH0

You can tell that under the same conditions, the car with the poor rear tires loses control well ahead of the car with the good tires on the rear. How can you argue with that?

Rick
04-05-2012, 10:00 PM
My suggestion, Rick, is that you professionally put your new tires on the back and the rest of us who own repair shops, drive race cars and live in the mountains will put them on the front, O.K.?
OK for shits and giggles we will pretend that my qualifications are inferior to yours. (They probably aren't*, but hey I will humor you) (Aw hell while we are at it we can pretend that I am an 18 year old nympho with DD tits, if that floats your boat)
So we have taken me out of the equation.
Now please explain to us how your qualifications are better than, and how you know more about tires than Michelin tires, The Tire Rack, and the Tire Industry Association. (see post #25)
I'll wait.


*Own repair shop? yup, and managed and managing dealership service departments
Race? SCCA, SCORE, and USAC. You?
Live in the mountains? Got me there.

Nars Glinley
04-05-2012, 10:10 PM
An 18 year old DD nympho? Further proof that you never know where a SDMB thread is going to go.

andyleonard
04-05-2012, 10:20 PM
Here's two times we've discussed it before:
http://boards.straightdope.com/sdmb/showthread.php?t=451141
http://boards.straightdope.com/sdmb/showthread.php?t=490691

But people remain unconvinced. How about video evidence?
http://www.youtube.com/watch?v=gSz7cm6MwH0

You can tell that under the same conditions, the car with the poor rear tires loses control well ahead of the car with the good tires on the rear. How can you argue with that?

I'm not quite sure a wet skidpad slalom is the only situation under discussion. If it is, don't bother with the following. What about dry straight line braking? What about a full-brakes ABS lane change? What about snow? 70% of the work is done by the front tires. My new ones go on the front.

A good fact to check would be that most passenger cars currently made have built-in understeer to keep the melons driving them from looping the rear if anything gets out of balance...in order to eliminate liability lawsuits against the manufacturer. The push allows the melon to scare him/herself witless in a too-fast corner - because the car won't turn any more - so he can slow down and live. The same speed in an early Porsche or VW would have a very different result.

Any decent racecar - especially a FWD one - REQUIRES the ability to get the rear loose before the front washes out and you lose steering input. Let's not equate loose rear with sudden death. That far more frequently occurs with steering loss.

oliversarmy
04-05-2012, 10:32 PM
The only thing I would add is that you should follow the guidelines in your owner's manual about proper tires and tire pressure.

At some point, it could could come down to you and the manufacturer if there is an accident or mechanical problems.

andyleonard
04-05-2012, 10:38 PM
OK for shits and giggles we will pretend that my qualifications are inferior to yours. (They probably aren't*, but hey I will humor you) (Aw hell while we are at it we can pretend that I am an 18 year old nympho with DD tits, if that floats your boat)
So we have taken me out of the equation.
Now please explain to us how your qualifications are better than, and how you know more about tires than Michelin tires, The Tire Rack, and the Tire Industry Association. (see post #25)
I'll wait.


*Own repair shop? yup, and managed and managing dealership service departments
Race? SCCA, SCORE, and USAC. You?
Live in the mountains? Got me there.

I grew up driving snow rallies in New England and opened my first of several BMW race shops in 1975. I'm a licensed car dealer in Los Angeles and I still race. http://www.tamsoldracecarsite.net/MMH0019DDAndyLeonardHustlerSR.html
I just put new tires on the front of my Mini. I well and truly don't care what you do on your rig. It's none of my business.

dontbesojumpy
04-06-2012, 12:04 AM
On a side note...does anyone else find it extremely odd that on the OP's Focus, a FWD car, the rear tires are wearing faster than the fronts? There's something just not right there.

i have an 02 focus ZTS and the same problem.

sucker DEVOURS tires. i have less than 70k miles and i have been through at least 20 tires.

in my case, tho, i'm getting uneven wear. they say i have a slightly bent steering knuckle, but that wheel doesn't wear as poorly as the others.

and if he's got an early-to-mid 00s focus, i can promise you another thing that's gone or is going to go wrong: the window regulators will have the plastic bits rot off and they'll stop working.

all four of mine did. almost every focus i've seen has had that happen, too.

eta:

mine's that burnt orange special mach audio edition that came with Z rated high speed, low profile tires. which were special order and expensive. after the 16th tire, i went to a local ma and pa shop and they said i could just go up to a more standard size. they explained the mechanics of how it all fits and what was more important than the low profile aspect. and once i saw the price break and availability of the tires he proposed, i took the bait.

those tires are about in need of replacing (all four are worn about the same). it's been just around 3 years/12k miles.

dontbesojumpy
04-06-2012, 12:09 AM
this is probably non-applicable to the subject at hand, but something i found interesting about tire rotation: did you know it's imperative to maintain the directional arrows? not because of the tread-grip issues, but because the way the steel belts are laced in production, they are designed to centripetally stress in a specific way. on motorcycle tires in particular, if you get the spin different than the manufacturing method's weave, you can cause them to simply disintegrate with the spin-force.

Woodenspoon
04-06-2012, 12:25 AM
this is probably non-applicable to the subject at hand, but something i found interesting about tire rotation: did you know it's imperative to maintain the directional arrows? not because of the tread-grip issues, but because the way the steel belts are laced in production, they are designed to centripetally stress in a specific way. on motorcycle tires in particular, if you get the spin different than the manufacturing method's weave, you can cause them to simply disintegrate with the spin-force.

Hm don't know about disintegration, they are pretty strong and that kind of failure would be lawsuit bait, more probably the grip would be not optimal, there are some directional tires but I bet most tires on cars out there aren't directional

dontbesojumpy
04-06-2012, 12:44 AM
Hm don't know about disintegration, they are pretty strong and that kind of failure would be lawsuit bait, more probably the grip would be not optimal, there are some directional tires but I bet most tires on cars out there aren't directional

this is a factoid from the q and a section of cycleworld. i believe the author had some anecdotal experience, with points of contention in the forum saying what you just said--a lot of cars don't have directional rotation. that is true--because directional tires are usually only of high performance ilk.

i think the stresses put on bike tires (and high HP cars) are far greater than (normal) cars and that's part of the reason. apparently there's unidirectional and [not unidirectional] tires.

Directional tires have construction and tread designed to rotate in only one direction. They are also called "unidirectional" tires. Directional tires will have an arrow with the word "rotation" on the sidewall showing the proper rotation direction.

i do know my old z-rated tires were unidirectional and it raised a lot of issues when it came to rotation and replacing one or two tires at a go.

they also were rated to "corner at speeds up to 160mph without folding in or under."

because we all know a focus can do that...

dontbesojumpy
04-06-2012, 01:02 AM
not because of the tread-grip issues, but because the way the steel belts are laced in production, they are designed to centripetally stress in a specific way.

i should have said "not ONLY because of the tread-grip issues."

that is a factor, but when you are putting the kind of stresses on a tire that a hi-po vehicle can administer, such as motorcycles, the weave of the belts matter to the over-all structural integrity of the tire.

according to the ten commandments of tires: A tire spinning at a speedometer reading above 35 miles per hour (55 km/h) can in a matter of seconds reach a speed capable of disintegrating a tire with explosive force.
if you also factor in a specialty tire with a belt-weave in a unidirectional pattern and spin it opposite of that, i think you get greater stresses in less time.

back to the op--

i do and will continue to buy as many or few tires as i need, all things considered.
but according to several manufacturers, mismatching tires causes heat imbalances and uneven wear, which can result is premature failure and "tire-pull."

Zep Tepi
04-06-2012, 04:28 AM
Hey Rick.

You know the chap who designed the 64 Corvette was William Mitchell. Well you will never guess what his own personal transport was. One of those LBCs. A Jaguar E Type.

I think that says it all.

Kimballkid
04-06-2012, 09:08 AM
I currently have a car with four different tires on it. Doesn't seem to affect the handling at all in normal conditions. Maybe in extreme circumstances it might make a difference. As far as I know the whole matching tires thing started with bias ply and radials. Since almost all tires are radials these days I don't think it makes as much difference as the old days.

I you're ever in a tire store some time, pull two tires of the same size but different brands off the shelf and stand them side by side and I'll bet there will be a difference. Someone told me that once and I didn't believe them until I did it when I was working at a service station and I'll be damned if it wasn't true. One was a bit taller than the other even though they were marked the same size.

Gary T
04-06-2012, 09:35 AM
Hey Rick.

You know the chap who designed the 64 Corvette was William Mitchell. Well you will never guess what his own personal transport was. One of those LBCs. A Jaguar E Type.

I think that says it all.That's a British car, but not a little British car. It's just not in the same class at all.

From post #32: "LBC= Little British Car, think MG Trimuph, Austin Healey etc."

Then there's the question of what that has to do with the price of wheat, i.e. how does what Mitchell drove in any way relate to the quality of advice available on forums devoted to LBC's?

FoieGrasIsEvil
04-06-2012, 10:56 AM
Hey Rick.

You know the chap who designed the 64 Corvette was William Mitchell. Well you will never guess what his own personal transport was. One of those LBCs. A Jaguar E Type.

I think that says it all.

Corvette ZR1
Ford GT
2013 Shelby Cobra

Rick
04-06-2012, 11:20 AM
That's a British car, but not a little British car. It's just not in the same class at all.

From post #32: "LBC= Little British Car, think MG Trimuph, Austin Healey etc."

Then there's the question of what that has to do with the price of wheat, i.e. how does what Mitchell drove in any way relate to the quality of advice available on forums devoted to LBC's?
Beats the shit out of me what his point is. I think he believes that I don't like British cars when the reverse is actually true. I have owned, driven, raced more than my share of LBCs.
I got done helping a buddy restore a 67 MGB a couple of months back. Not something a guy who hates LBCs would do.
My point was the average car owner on an Internet forum does not nearly as much as they think they do.
AND I doubt that any of them know as much about tires as the guys at Michelin, The Tire Rack, or the Tire Industry Association.
So holding them up as some type of experts on tire mounting is frankly a stupid idea. Not necessarily industrial grade stupid, but stupid nonetheless.

silk1976
04-07-2012, 10:58 PM
I agree with Rick - he's provided multiple cites for his claim, and any simple google search corroborates that the better traction tires should go on the rear.

To be fair, it appears to have only been relatively recently proven via test tracks and so forth that putting them on the rear is better. So for everyone saying they've been putting new tires on the front for 30, 40 or 50 years, and using that as their qualifications - well, science appears has proven that wisdom incorrect since that time.

Another cite (admittedly not as valued as tire rack or the manufacturers, but still):
Popular Mechanics (http://www.popularmechanics.com/cars/how-to/4243992)

Also, if you are hydroplaning on the rear wheels because you put the better tread up front, you have no warning. If you put the better tread up front and start hydroplaning, you feel that and notice it - which is what you want - a signal that you are in a dangerous position.

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