DJ

What we have here in this thread is a bunch of people who made poor decisions. That's ok, everyone has made bad decisions at one time or another (some more often than others). But the point where it all goes wrong is when instead of admitting that that was a bad decision, the writers go on to attempt to justify why it was ok. Then, to compound the problem, not only are they justifying this bad decision to themselves, but now they want to convince others to make the same bad decision.

If we were talking about house paint, or where to eat dinner, none of this would matter much at all. But we're talking about tires for high-performance sports cars, arguably the single most important safety item on your car.

Don't compromise your safety because you want to save money. Don't pretend that it's ok. Don't be a dope.

TheOtherEric

So if mixing tires is so controversial, why isn't it just as controversial to deviate from the stock tire widths? It seems that we do this all the time on our 993s with the full knowledge that it will affect handling characteristics. Yet no controversy (or is there?). Aren't we thus assuming that a moderate change in tire width has less effect on rolling resistance (or whatever form of tire performance is appropriate) than installing a different brand tire? Is sidewall stiffness an issue as well?

The answer is probably that none of us knows enough about tire performance to say if switching brands has more or less effect than changing widths. Hence the rule-of-thumb about not mixing brands.

Can anyone post some objective analysis without being insulting??

waybrig

So, I'm supposed to admit I made a poor decision when that decision has worked our perfectly fine for me? I guess I don't get it.

"The point where it all goes wrong" is when people start adding intent to other's posts. I didn't try to convince anybody that one way is better than another for them. I simply am relating my own experiences (the experiences of a dope) and everyone is free to take from that what they will.

adsc4s

I believe there are some quantifiable changes some have experienced with differing widths.

Generally, wider in the front will reduce understeer/increase oversteer. Wider in the rear will increase understeer. Stiffer sidewalls, lower aspect ratio will generally result in increased responsiveness at the expense of ride comfort.

As I have no experience with mixing brands, all I can surmise is that there would not be a general pattern of changes.

To some, it works, to others, it doesn't. All I know is Porsche spends a lot of time testing tires and having them certified for their cars. They don't mix brands, even if they are approved, so I won't.

In the end, aap, there is not a huge price difference in getting 2 matching rear SO2's instead of a "cheaper" non-matching brand.

Dirt Track Racer

No.

The people who post here and actually know a thing or two know enough that they are only insulting when they have to be. Then they stop posting and allow the users to go out and kill themselves during their self-administered engineering tests.

DTR

TheOtherEric

Good point Adsc4s. We generally can predict what will happen when we change tire widths. But we can't predict what will happen when we change brands, since we don't know comparative coefficients of dry friction, coefficients of wet friction, sidewall stiffness, etc. So even if (for example) we WANT a slightly harder compound in the rear and WANT less sidewall stiffness there, most of us just don't know how to get it. Hence the rule-of-thumb.

Franklin229

More interesting reading:
http://www.aceinsuranceltd.co.nz/doc...ber%202002.pdf
http://search.netscape.com/ns/boomfr...re_safety.html
http://www.goodyeartires.com/kyt/FAQ/
http://www.pulse24.com/News_Features...7-001/page.asp

Hopefully you can open these-

waybrig

Franklin: Thanks for the links. I checked all those out but didn't see anything very different from what everybody else was already posting.

One was a lawsuit regarding mixing radial and non-radial tires which seems quite a bit different than what we're talking about. Another talks about an accident with a car equipped with snow tires in the front and only all-season in the back. Again, very different in my opinion.

The other links that I could open all had generic statements about mixing tires not being recommended and degrading vehicle stability.

Nothing I disagree with there. No argument that mixing tires would degrade handling versus having a matched set. The question is how much is handling degraded, and how much of a safety risk is this? To take it to the point of being ridiculous one could argue that using racing slicks is the most stable, safest option on dry pavement, so anybody not doing this is risking their safety. Of course we weigh the cost/convenience/legality, etc... of running racing slicks on the street, and decide to use street tires even though they degrade vehicle handling versus slicks.

I think it's interesting to note that I don't recall ever reading a post from anyone that actually had a big problem driving with mixed tires under normal street conditions. The worst I've seen is comments about having more or less understeer than the person would like. I've never read about a car spinning wildly out of control under hard braking or avoidance maneuvers, etc... Maybe people are out there that we haven't heard from. The only person's we seem to hear from are one's that did mix and didn't have a problem, or one's who wouldn't ever think of doing such a reckless thing. Where are all the people who have mixed and had problems? If this is so outrageously dangerous, they must be out there. Or maybe they're all dead?.............

aap

OK fellas...I m the poster and have no idea what I will do next. perhaps I'll just sell it...? ; )
Safety has got to be #1 and since I have no idea how old the fronts are I'll probably replace all 4 (they are in good shape and the car has 37K on it so I doubt they are original, but have no idea of knowing). Thanks for all the suggestions although the infighting reminds me of home!
aap

adsc4s

aap, the tire will have a "date code" of the month and year the tire was manufactured. It is usually on the sidewall.

DJF1

Aap, don't be dishearted by the "infighting". Once a year or so, sparks are going to fly around here but they are all in good faith and we are generally a friendly bunch with the best interest in mind. I guess this is the key to the whole matter, the fights are good if they are to keep in line the principals that this forum was founded on ,the reputation that it has and arguably this alone needs to be preserved.
Rennlist is and should be a place that an enthousiast or simply a person that needs to find a realiable source of information goes to. We, the members have the obligation to safeguard the forums from becoming a bunch of useless information, how fast did you go today types, things in general you find in other useless forums about Porsche cars. Most of us and the people before me have spend a ton of money to find out and try things. We have to pass and receive this information responsibly for the benefit of the community. Not only the members will then benefit from the mutual exchange of info in saving a ton of $$$ , but also can benefit in matters of safety, resale value, maintenance etc. So a fight here and there if it means that the values of the community are kept is not an unhealthy thing although I don't like it myself either. What matters is that ALL the members here have good intentions and noone here wants anything bad to happen to each other.
Sometimes in a pub things happen, well things always come back to normal and we have a couple of cold ones

In your case, i guess do what your mom always told you: Better be safe than sorry

EricGT3

Wow, what a post about tires! I just have one thought to pass along. We all bought Porsches, one of the most expensive and finest high performance sports cars available. We didn't skimp on the car, we could've bought Hondas, Mazdas, Corvettes, BMWs, etc. and spent less money with less maintenance cost. So it is somewhat puzzling why we wouldn't go just a bit extra when we look at something as important as tires. I can't imagine why anyone would spent $50k-$100k on the car and then put crappy tires on it. It just doesn't make sense. Do you also put regular unleaded in it? Do you bring it to Aamco for transmission work? Midas for your exhaust work? No offense intended to these fine places, but they're not for Porsche performance work.

I understand that most of us will never drive our cars 10/10th on the street. That is exactly the point, we only drive our cars 5/10ths and still we have bought the best machine available. It only makes sense to provide the best solution for the car and that's to replace all 4 tires with the best possible tire.

Franklin229

DJF1-absolutely. Some people take other's passion personally.
Eric-Could not have said it better.

waybrig-
Your welcome regarding the links-I just skimmed the surface there-I'm sure if one were to actually dig-there would be more.
If there is nothing you disagree with, then what's the point of questioning "degrees of safety"?
It is already been mentioned that it is not safe to do. Fire is fire, regardless of whether it's on the tip of a match or the roof of a house-you can still get burned from both.

Ran

aap,

I noticed that you were in the area. I have not seen Ocean Blue up close and would love to take a look sometime.

As regards my 911 turbo (993), I have always used:-
a) Only Porsche recommended tyres;
b) Porsche authorised dealers to mount tyres; and
c) Pirelli PZero Asimmetrico tyres (currently N3 version on ALL four corners though I have used other versions of N but always the same version on all four corners at any given point of time - originally, car came to me with N0).

I have had relatively fair to good experiences with four of the local dealers in our general area - no idea about dealers or independents other than those visited. I always inquire about equipment used to mount tyres AND supervise the job, or person doing the job, where possible.

All the best. Hope to see you and your C2S around (we do not necessarily have to discuss tyres )

Speedraser

Waybrig,

FWIW, I don't agree with your comments that the safest vehicles are large SUVs or that our Porsches are relatively unsafe. There is no question about the relative ACTIVE safety of these two vehicle types (especially with four matching tyres). Interestingly, the insurance company crash records, as compiled by the HLDI (see the hwysafety.org site) show that the 993 has a better crash record (injuries/mile) than virtually all of the large SUVs, and nearly all other vehicles on the road. Obviously, this combines the active and passive safety aspects of the vehicles. And no, I wouldn't want to be hit by a large SUV (in the Porsche or any other vehicle).

Sorry if this is a little ot.