| Author |
Message |
Dennis (Bighead)
Junior Member
Username: Bighead
Post Number: 59
Registered: 2-2003
| | Posted on Tuesday, March 25, 2003 - 11:38 pm: | |
A few comments, gentlemen:
1. I sincerely doubt any car you can get at a rental counter in the US is able to achieve a sustained speed in excess of the maximum speed rating on its tires. Too much liability. On some cars sold with lower-speed-rated tires, it comes with a limiter to prevent any excess.
2. Dave, most of this board's tire advice relates to automobile tires, and probably OEM-ish truck/suv tires and not the monster 4x4 offroad tires you're apparently thinking off.
3. Mitch, when Bart wrote: "ZR tires last only for about 10 to 15,000 miles as against 50 - 75,000 miles for normal tires", I think he wasn't talking about "normal" tires for a Ferrari, he was talking about normal tires for normal street cars. And it's certainly not unusual for crappy, no-grip $48 tires available at your local tire center to last 75k miles on your Taurus or Explorer.
4. I totally agree with Jon, DO NOT run above the tire's speed rating. But... I think there is more to the story about the Ferrari wreck at the Silver State Classic. I dimly recall that he fixed a puncture in the tire that later delaminated. Could be with a plug or a patch, or it could have been with a car of instant-sealer. Autoweek covered it, I think?!? If someone else has a source, or more details, I'm curious.
5. Jon, I just got back from two track days in my wife's Porsche 996, running Michelin Pilots. That makes, oh, 9k street miles and at least 6-8 track days on the tires. They're worn, but still quite serviceable, maybe 40-50% tread depth? Grip is perfectly acceptable, and handling at the threshold is exemplary. I liked them well enough to put a set on the 355 too.
vty,
--Dennis
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PSk (Psk)
Member
Username: Psk
Post Number: 287
Registered: 11-2002
| | Posted on Tuesday, March 25, 2003 - 9:17 pm: | |
How deep are the tread blocks on the Pirelli PZero's?
If the tread blocks are too deep they will flex and walk all over the place and cause massive wear. The solution to this is to machine the tread off until the tread blocks are only 3mm deep. You have to do this to Bridgestone RE71R's to get them to last on the race track ... and to handle. Once done they are a fantastic tyre and will last a lot longer.
Yokohama A008Rs make great club track tyres also. Note these tyres have very large tread blocks and also shallow tread and thus are perfect for serious track abuse.
Just a thought.
Pete
ps: Are you also running your tyres too low in pressure and thus over heating them?, and causing premature wear. What Ferrari and Pirelli recommend for the road won't equate to the track. You need to get some temperature equipment and work out what temp they are running at and make adjustments based on this and feel, etc. |
Jon P. Kofod (95f355c)
Member
Username: 95f355c
Post Number: 536
Registered: 8-2001
| | Posted on Tuesday, March 25, 2003 - 9:09 pm: | |
Solly,
Despite all the claims from Pirelli about their "performance" tires the PZero's are horrible at the track. On my street 355 they would last two days before getting rock hard and losing all grip. They looked fine with plenty of tread but the heat cycles made them useless.
I am not sure if any of the so-called "maximum" performance tires would do any better. A set of Michelin's lasted a day longer. I have heard that the Good Year tire last a bit longer.
Regards,
Jon P. Kofod
1995 F355 Challenge #23 |
Steven J. Solomon (Solly)
Member
Username: Solly
Post Number: 455
Registered: 6-2001
| | Posted on Tuesday, March 25, 2003 - 8:23 pm: | |
Put on a new set of 4 Pirelli P-Zeros on the 360 in October 2002. Used them on the road for 2,000 miles. Did 6 days of track events and the rears were shot. going very fast wipes these tires out in no time. |
Dave Wapinski (Davewapinski)
Member
Username: Davewapinski
Post Number: 525
Registered: 8-2001
| | Posted on Tuesday, March 25, 2003 - 7:41 pm: | |
Thanks for the input. That answered the questions.
Will NOT run them over the rated.
Also this gives me a feeling for how often I will have to replace tires.
Happy Motoring! |
Jon P. Kofod (95f355c)
Member
Username: 95f355c
Post Number: 531
Registered: 8-2001
| | Posted on Tuesday, March 25, 2003 - 3:10 pm: | |
Dave,
Would not recommend doing this even if the tire in question is a low speed rated tire and you are only going over a bit.
Anyone ever see that video from the Silver State Classic? The guy was driving a TR at 170+ with tires only rated up to 149 mph if I remember correctly. Car was totalled and one of the occupants was killed.
No way I would run a tire above the recommended rating.
Regards,
Jon P. Kofod
1995 F355 Challenge #23 |
Mitch Alsup (Mitch_alsup)
Member
Username: Mitch_alsup
Post Number: 417
Registered: 4-2002
| | Posted on Tuesday, March 25, 2003 - 3:04 pm: | |
"ZR tires last only for about 10 to 15,000 miles as against 50 - 75,000 miles for normal tires. "
I seriously doubt that anyone could get that kind of millage on a set of normal tires--UNLESS they decambered the suspension so that the tires are standing straight up on the road. Then the car wouldn't handle worth crap; and wouldn't be stable at high speed.....
BTW I get around 12K on a set of rears and change the fronts after two set of rears. I haven't actually worn out a set of fronts. |
Dave Wapinski (Davewapinski)
Member
Username: Davewapinski
Post Number: 524
Registered: 8-2001
| | Posted on Tuesday, March 25, 2003 - 9:11 am: | |
Two reasons for the questions:
Sometimes I rent cars - they do not normally have the best of tires. On one rental ran it continuous 120 to 140 (indicated - do not know true speed). Car felt rock steady, but I am sure it was over the rating. Was wandering about the risks.
Also risks when get a used car that does not have Z rated tires. How safe at speeds?
On a 4x4, want to put off road/road radials on it and then run it faster than its speed rating. Was concerned about the safety and its risks. Some have told me that it is normally safe. Others have told me to expect blow outs, but they know of noone who has had such a blow out. So this has lead me to question this.
Vibration does not appear to be an issue.
The 4x4 tires are expensive - about $500 each (I believe). These tires appear to be the best for the application. Believe they are Michelin 14.5 x 20 XM 47. Big, almost a yard tall tires, weigh about 200 lbs each.
Any insight is appreciated. |
Bart Duesler (The_bart)
New member
Username: The_bart
Post Number: 24
Registered: 1-2003
| | Posted on Monday, March 24, 2003 - 11:55 pm: | |
ZR tires last only for about 10 to 15,000 miles as against 50 - 75,000 miles for normal tires. Buy normal tires if you wish to go normal speeds.
Me, I need ZR tires which are rated for 200+ mph.
Thank you.
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PSk (Psk)
Member
Username: Psk
Post Number: 283
Registered: 11-2002
| | Posted on Monday, March 24, 2003 - 11:45 pm: | |
Hmmmm ... tyres those ever so important things that are the only contact with the road. You buy an expensive car and now we are worrying about saving a few dollars (and yes I am aware that those high speed tyres are expensive) ... ???
Yes they are speed rated for continous use, but I for one would not want to take a risk like that ... think of the consequences, the massive damage you could do to yourself and your Ferrari and the other road users. Just not worth it.
Dave, I really respectively think you should stick with the recommendations here. What happens if you lend the car to somebody, or sell the car and they have an accident?
If you were tracking the car only, then playing with tyres is cool ... but not for road use when other road users expect you do be maintaining your car correctly and safely.
Pete
ps: The other thing is that lower priced tyres will not work as well with the Ferrari and thus grip and stability, etc. will be compromised. After all why make a low speed limit tyre that has all the qualities of a high speed tyre, that will never get put on a car that needs them ... ie. Mums people mover is what they are designed for. Thus you could end up wasting your Ferrari experience. |
Mike Fisher (Mikef)
Junior Member
Username: Mikef
Post Number: 182
Registered: 11-2001
| | Posted on Monday, March 24, 2003 - 9:06 pm: | |
One thing to remember. Speed ratings are for sustained speed. |
Mitch Alsup (Mitch_alsup)
Member
Username: Mitch_alsup
Post Number: 410
Registered: 4-2002
| | Posted on Monday, March 24, 2003 - 9:54 am: | |
There are two issues here: 1) heat 2) mechanical stress. Either can cause a tire to a) come apart, or b) to come off the wheel. Neither is a good idea 'at speed'.
Is there a reason you want to run a tire of less than Z rating? |
Lawrence Coppari (Lawrence)
Member
Username: Lawrence
Post Number: 541
Registered: 4-2002
| | Posted on Monday, March 24, 2003 - 5:57 am: | |
Generally, there is a heat build up that can lead to a blow out. I suspect that high speed (beyond the rating) can overstress the tire or cause layer separation and tire failure.
I, for one, would not do it on a sustained basis. |
Dave Wapinski (Davewapinski)
Member
Username: Davewapinski
Post Number: 522
Registered: 8-2001
| | Posted on Monday, March 24, 2003 - 5:36 am: | |
Tires have speed ratings.
Many times things have a large safety margin built in.
Sometimes things are just not put through the cost of rating it higher.
What happens when a tire is driven faster than its rating?
Does it normally become unstable in turns? But that would also seem to be a function of car design.
Does it normally become unstable driven straight? But that would also seem to be a function of car design.
Is there a heat buildup and increased chance of blow out?
Where are the dangers? |