New tires on rear...why?

[rpn453]

Originally Posted By: yonyon
I'm going to guess those cars aren't exactly easy to control and don't have a lot of deep tread grooves on the tires.


They were driving on grooved slicks in 2007 when that race happened. Similar to a street tire at the wear bars, though these are much wider relative to the weight of the car.

The point is that these are the best drivers in the world, and are used to driving rear-heavy cars with neutral handling; something the vast majority of people have never done. Yet they are unable to keep the back end from spinning out while driving at very low speeds when the wide rear tires hydroplane.

They would normally be on rain tires in that situation, but it started raining heavily on the first lap and almost all the drivers were caught out on the track with the grooved slicks.

http://en.wikipedia.org/wiki/2007_European_Grand_Prix

 

[rpn453]

Originally Posted By: Garak
Absolutely. For me, when I did a two tire replacement, they always wound up in the front, RWD or otherwise. That's especially important in the winter. I'd rather have a bit of oversteer, which is easier to control as you mentioned, than have no steering at all.

A bit of occasional oversteer is fine. That's not what will happen if only the back end is floating on water or snow while the front is still digging in and making contact with the road.

Next time you buy winter tires, get a set of studdable tires with two studded and two unstudded. For the first half of the winter, run the studded ones in back and enjoy the stability and traction on ice and snow. For the second half, put the studded ones on the front and you'll probably figure out why that's illegal in some provinces!

 

[rpn453]

Originally Posted By: SteveSRT8
I thought I knew how to drive also, and FWD completely took me by surprise one day.

Most people here talking about how much they love oversteer have obviously not had the pleasure of a snap spin in a fwd vehicle.

They can come around so hard and fast you will NOT simply catch it and drive out of it.


It sounds like there must have been something unusual going on with the tires or the car setup. FWD is normally the most stable drivetrain configuration, all else being equal. Obviously you have to intentionally make a FWD car unstable to get it to go around a track properly though.

 

[yonyon]

Grooved slicks in the rain? I would expect that with those tires there isn't much you can do once the rear tires lift off the pavement regardless of who's driving. Moses excepted, of course. I mean the first Moses, not Browning. Those tires have nothing to dig with.

 

[rpn453]

Originally Posted By: Jarlaxle
Just one reason I loathe wrong wheel drive!


I've been driving them to the limit all winter - 3 to 4 months of icy/snowy roads every day - for many years now. Plenty of oversteer moments involved when coming off the throttle but all the FWD cars I've driven are very stable and predictable on four studded tires. I even use cruise on straight-ish highways no matter what the road conditions. A highway covered in ice is a lot of fun because of how you feel the car constantly slipping around in a stable manner. Good AWD is fine for that too but I'd never even consider using cruise on ice at highway speeds with RWD.

My favorite article on the subject:

http://www.thetruthaboutcars.com/2012/02...nt-wheel-drive/

 

[rpn453]

Originally Posted By: IndyIan
Here's a run of one of my silly oversteer autocross setups on too fast a course for it... This was our clubs first setup on the oval and it was not too safe! We have since learned how to set it up to be fun but not so fast between concrete walls...


Good catch! Those are the most memorable driving experiences!

 

[rpn453]

Originally Posted By: yonyon
Grooved slicks in the rain? I would expect that with those tires there isn't much you can do once the rear tires lift off the pavement regardless of who's driving. Moses excepted, of course. I mean the first Moses, not Browning. Those tires have nothing to dig with.


Just like the illegal or barely legal tires that many people drive around on. That's what it's all about. A tire shop doesn't want to put new tires on the front with 3/32" tires on the back. Or 4/32". Or maybe even 5/32". It's a gray area, so they take the safest route.

 

[Jarlaxle]

Originally Posted By: HollowEyes
Originally Posted By: bigmike
I want good tires on the front so I can steer. I don't think any amount of convincing can change my mind.


And least you can admit you're being close minded.


But this issue is moot for me. AWD means I HAVE to have 4 matching tires. No more of the just replacing 2 of my RWD days.


Replacing two tires on an AWD car happens every day. Long as they are the same size, I wouldn't worry about it. I work with a guy who has been running 2 different brands of tires (IIRC, two each Kumho Solus and Hankook Optimo) on a Subaru for at least 2 years. Over 150,000 miles, zero problems.

 

[bigmike]

Originally Posted By: HollowEyes
Originally Posted By: bigmike
I want good tires on the front so I can steer. I don't think any amount of convincing can change my mind.


And least you can admit you're being close minded.


But this issue is moot for me. AWD means I HAVE to have 4 matching tires. No more of the just replacing 2 of my RWD days.


Yes, I can. I take no joy in it.

I probably wouldn't recommend others do the same as me. I think it's invariably up to the driver whether they prefer a certain setup. I'd prefer 4 brand new (slightly broken in) tires any day, but reality keeps us from that being an option.

I've driven in alot of rain here in Florida. Only once have I had any issue. When it was raining, I lost control in a RWD long bed truck taking a corner, right when I shifted into 2nd gear the rear snapped around on me. I had a chance to correct it before any damage, but I still smacked a curb pretty good. Other than that, hundreds of thousands of all types of miles later, I'm not overly concerned about having worn tires on the rear.

Drive the conditions is really the best advice I have for anyone.

 

[hattaresguy]

Originally Posted By: Tim H.
Why do tire installers recommend putting new tires on the rear if you only need two new tires? I was looking at tires and saw a poster showing a car skidding around a curve (animated drawing) with old tires on rear and new in front, and below that was the car going around same curve normally with new tires on rear and older on front. Seems to me with only two new tires in back, you would be just as easy to have under steer with new in back, VS oversteer with new in front. What's the logic in this?


Under steer is safer because the average driver will simply lose it if the rear comes around and lacks the skill to stop it.

 

[hattaresguy]

Originally Posted By: Astro14
Originally Posted By: dparm
Oversteer is easier to control, in my opinion.


You mean...like in an old 911??

Sure, lots of those wrapped around trees when they had that "controllable" lift-throttle oversteer...

And understeer is felt through the wheel...more warning = safer...


No that was a design defect that only 911 and Tatra T87 owners can properly enjoy.

Good tires or bad if you lift that rear end is coming around.

 

[Astro14]

Originally Posted By: hattaresguy
Originally Posted By: Astro14
Originally Posted By: dparm
Oversteer is easier to control, in my opinion.


You mean...like in an old 911??

Sure, lots of those wrapped around trees when they had that "controllable" lift-throttle oversteer...

And understeer is felt through the wheel...more warning = safer...


No that was a design defect that only 911 and Tatra T87 owners can properly enjoy.

Good tires or bad if you lift that rear end is coming around.


By putting the good tires on the front, you build that same design defect into your new car, regardless of FWD or RWD...and it will be just as uncontrollable...you simply have to experience it.

Only those who have felt a car swap ends too fast for them to react have the experience to believe it can happen to them...all others believe that they are superior enough drivers to be able to control the oversteer.

But they can't.

And the testing proves it. Watch the Tire Rack video...the guy knows it's coming, he knows that the car is going to oversteer, he's ready...and it still swaps ends on him. What good is having the front tires planted when the car spins? Not a fun bit of oversteer as the car slides, it swaps ends...and you're still completely out of control.

People who refuse to believe basic advice like this, people who think their driving skills are superior, are the reason I bought my wife a Volvo...at least she'll walk away from the crash caused by the unbelieving driver who loses control of their car....

 

[d00df00d]

Originally Posted By: Astro14
By putting the good tires on the front, you build that same design defect into your new car, regardless of FWD or RWD...and it will be just as uncontrollable...you simply have to experience it.

The previous owner of my car commuted several times in heavy snow with good front tires and BALD rear tires. It was white-knuckle driving at times but he was okay. I never tried the same thing and I would strongly advise against doing so, but it seems clear to me that not all cars immediately turn into old 911s just because their rear tires are worse than their fronts.

I can see bad rear tires being problematic on a front-heavy car with a mediocre suspension setup and an inattentive and/or inexperienced driver, and if the tires in question are cheap to begin with. To be fair, that probably accounts for the majority of all vehicles on the road. But I still think the problem is being exaggerated because, again, not all cars behave this way.

 

[d00df00d]

On the point about the video:

Originally Posted By: Astro14
And the testing proves it. Watch the Tire Rack video...the guy knows it's coming, he knows that the car is going to oversteer, he's ready...and it still swaps ends on him. What good is having the front tires planted when the car spins? Not a fun bit of oversteer as the car slides, it swaps ends...and you're still completely out of control.


Did you mean the Uniroyal video?

 

[Garak]

Originally Posted By: IndyIan
I sort of agree with the oversteer thing, a bit is nice! Just not too much... I guess if you are always a bit fearful of the backend and are "ready" for it, you can live with it. But long trips in the snow can wear you down and then, whoops!


Agreed. I certainly wouldn't want perfect, new tires up front and bald ones on the back. That would be a bit much.

Originally Posted By: rpn453
Next time you buy winter tires, get a set of studdable tires with two studded and two unstudded. For the first half of the winter, run the studded ones in back and enjoy the stability and traction on ice and snow. For the second half, put the studded ones on the front and you'll probably figure out why that's illegal in some provinces!


Umm, no. That would be a little too much fun.

As I've stated, my preference would be four new tires, and that's it. If the back is bald enough to be floating and hyroplaning like crazy, then there's a major problem.

Oddly enough, when I had my 1999.5 Lightning with summer tires, it handled quite well on the ice. It had a short enough wheelbase that the back end didn't snap out unpredictably, even with all that power. However, those wide tires were a nightmare on the snow, since they would never sink into it to gain any purchase - they were like snowshoes.

 

[SteveSRT8]

Originally Posted By: Astro14
only those who have felt a car swap ends too fast for them to react have the experience to believe it can happen to them...all others believe that they are superior enough drivers to be able to control the oversteer.

But they can't.

People who refuse to believe basic advice like this, people who think their driving skills are superior, are the reason I bought my wife a Volvo...at least she'll walk away from the crash caused by the unbelieving driver who loses control of their car....


Totally true. And it's a bit sad to hear the folks here telling us all that they can drive out of it. They won't.

Perhaps a Skip Barber course, or some other HPDE to help them understand? When it does happen it'll likely hurt someone else, too.

 

[CapriRacer]

Maybe this will help:

I've conducted demonstrations where we equipped 3 identical cars with tires of different tread depth.

A) 4 new tires
B) New tires on the rear, shaved to 4/32nds on the front
C) New tires on the front, shaved to 4/32nds on the rear

We have people drive around a large paved skid pad at about 45 mph. It's a little harder than most people would drive but it serves the purpose.

There is a section of the skid pad that has a 1/8" deep stream of water running across it - about 50 feet long. Just after that is a large paved recovery area. Nothing to hit for a couple hundred feet.

When folks drive Car A, nothing happens.

When they drive Car B, the front tires hydroplane, and the car takes a decided lurch but once it leaves the wetted area, the driver can recover and continuing driving around the circle.

When they drive Car C, the rear comes around and they have no ability to steer the vehicle. They have to wait for the car to come to a complete stop before they can can do anything. By then they are 50 to 100 feet off the circle.

We have done this with FWD and RWD and short wheelbase FWD works best - the car will turn within the wetted area and continue in a straight, but sideways trajectory.

Lierally thousands of people have been through this exercise. Some didn't believe before they did it - and some had great difficulty reconciling what they experienced with their preconcieved notions. But it is hard to argue when you experience it.

 

[rjundi]

Originally Posted By: Jarlaxle
Originally Posted By: HollowEyes
Originally Posted By: bigmike
I want good tires on the front so I can steer. I don't think any amount of convincing can change my mind.


And least you can admit you're being close minded.


But this issue is moot for me. AWD means I HAVE to have 4 matching tires. No more of the just replacing 2 of my RWD days.


Replacing two tires on an AWD car happens every day. Long as they are the same size, I wouldn't worry about it. I work with a guy who has been running 2 different brands of tires (IIRC, two each Kumho Solus and Hankook Optimo) on a Subaru for at least 2 years. Over 150,000 miles, zero problems.


What matters on a Subaru and AWD is rolling circumference(distance around tires). It differs between brands even for the same size tire but different make or model.

My 25year experienced Subaru indy mechanic said Subaru states 1/4" matters but his experience >1/2" rolling circumference will break the internals of the transmission. He pulled a few and found broken gears. On the Automatics it will burn out the clutch packs.

 

[rjundi]

Back in college I did the extreme of why not to do this.

I ran winter tires on the front of Jetta GLI (FWD) and summer performance tires on the rear. It wagged its tail on snow and at speed would actual go into swaying motions. Stopping I would find the back end swinging around.

On icy roads complete 360 on roads were other drivers going similar speed in town but likely somewhat matched all-seasons fine.

It reset me to always buy in sets.

 

[Garak]

Originally Posted By: CapriRacer
Lierally thousands of people have been through this exercise. Some didn't believe before they did it - and some had great difficulty reconciling what they experienced with their preconcieved notions. But it is hard to argue when you experience it.


I'd believe it. You don't think of wet traction much until you hydroplane, and then it's a bit of a white knuckle experience, to say the least. And it's bad enough up front, let alone letting your tail end swing out frontwards.