Bad Vibrations - After Excessive High Speeds

[xmateo]

I took a trip recently that spanned a desert; very few cars on the road. Anyway, It was difficult to keep the car (Y33) under 105 even if I wanted to. Since then, I've noticed a steady increase in vibration. It feels like the wheel is out of round, but they were balanced 3 mos ago. The vibration occurs more pronounced at 50-60 mph, less at around 80. Will driving fast throw the wheel out of balance?

[Jesda]

What is the brand/age of the tires?

[elwesso]

Thats what id like to know... also when was the last rotor resurface...

[maxnix]

If you didn't hit anything, speed should have nothing to do with it. Check wheels for missing weights. If it has been over 5K miles, might be time to spin them up again.

[xmateo]

What is the brand/age of the tires?

They are Pirelli Centuro - must be about 4 years old. New brakes on rear - front rotors need to be turned, but the vibration seems to be coming from the rear. There is a small leak in one of the rear shocks, but not ready to replace yet - just 87k on my Q. I've ordered some Conti Extreme Contacts to replace the tires. Hopefully that will iron out the prob if its tire/wheel related. Otherwise I will replace the front rotor/brakes soon. Its funny because the vibration came on all of a sudden. Maybe I did lose a wheel weight. I guess I'll go check that too. The Pirelli's have never given me a prob yet and handle quite well for a T rated tire.

[szh]

They are Pirelli Centuro - must be about 4 years old

...

The Pirelli's have never given me a prob yet and handle quite well for a T rated tire.

Both of these facts scare me!

Tires start vulcanizing and developing micro-cracks after a few years. Although not extreme, four is a bit too long to go without changing them, almost no matter what the wear. I would certainly not do 105mph on them at all ... frankly, driving around town may cause premature failure.

Secondly, T-rated tires also implies (but not certain) that they do not have the load index for a Q - even the Y33 years - and the speed limits for these tires is lower than suitable for a Q. You definitely need to change the tires for at least an H rated (preferably V or W or Y or Z) tire as soon as you can do so.

BTW, I am fairly sure that your vibration and problems are due to tire failure inside the treads ... maybe some belt has broken. Please be safe and do not drive at highway speeds on them, if you can avoid it, and change them asap.

Z

[maxnix]

Four year old T rated Cinturatos???? Ack!!!! Waht Z says. Don't even go on the highway with these things. you have used your 9 lives for sure!

Get the Conti or other top tire ASAP for safety's sake. >94 load rating, >H speed rating if you are going to drive in the desert at speed.

[bigjimmy]

Speed ratings and load indexes are completely different. Many truck tires are rated for massive loads, but very low speeds.

Tire shops will try to tell you that a higher speed rated tire is a better, higher performance tire, but this is absolutely not true. Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at increasing speeds. They run the tire for a specified amount of time and if it doesn’t blow, it becomes a speed rated tire period.

Obviously the tire on the car has to support the load. If you never drive over 105 mph a T rated tire is just fine. A touring sedan benefits greatly from a T or H rated tire compared to a Z rated tire. No more vibrations when cold and a much smoother, quieter ride. A tire capable of running at high speeds requires stiffer construction, in order to provide the necessary high speed stability & durability, and this comes at a cost. T and H rated tires generally last longer, ride better, and cost less.

Every tire has a Traction rating, Speed rating and a maximum load. Out of those three speed is usually the one everyone focuses on, but in the real world it is the most meaningless. I drive fast and an H rated tire has never disappointed me. Would I drive a 4 year old T rated tire 105mph? Maybe for money. Just my 02.

[maxnix]

A touring sedan benefits greatly from a T or H rated tire compared to a Z rated tire. No more vibrations when cold and a much smoother, quieter ride. A tire capable of running at high speeds requires stiffer construction, in order to provide the necessary high speed stability & durability, and this comes at a cost. T and H rated tires generally last longer, ride better, and cost less.

While most of what you say is true and generally known in depth by the members of this board, the above is abosolutely FALSE. You don't understand the minimal sufficiency of speed rating test, you don't understand what happens to tires as they degrade over their lifespan, and you don't understand that tire life and safety performance have an inverse correlation.

Obviously you have never run a properly set up maximum performance summer tire on a well set up suspension. And you have no clue about how load rating affects tire performance.

Other than these misconceptions, great post!

[elwesso]

I would say that, YES if you never exceed 100MPH a BRAND NEW T rated tire will be sufficient... After a year or so, who knows!

Its probably safe to say that a mid-quality Z rated tire is going to have better quality than most really good T rated tires after 15k miles... At the beginning of their life, they will probably be very similar, assuming you dont go really fast... but after a year or 2 the T rated tire is going to be wasted... Smaller cars can get away with this...

Quote »Obviously you have never run a properly set up maximum performance summer tire on a well set up suspension. And you have no clue about how load rating affects tire performance.[/quote]So true... While I really like the ride and quietness that my 15in tires give me (im running on my winter wheels right now), the handling and overall stability of my summer wheels (michelin pilot sports) is worth it....

There is a difference between doing what is best and doing what you can get away with....

[Q45tech]

Speed ratings apply to BRAND NEW TIRES and are meaningless after 8,000 miles.

No tire company [maybe Michelin] would dare test a worn out [HALF WORN] tire with more than 20,000 miles on it to the speed explosion point by allowing an employee to drive at the speed rating inwarm conditions.

Arizona is ground zero for heat and tire destruction.

I suspect your rear tires told you something when the vibrations began! Sustained near rating destruction typically shows up first as new vibrations.

[Q45tech]

Speaking of tires note Michelin's Chris Bakers use of Q45 [he has 2] on the proving grounds. Unfortunately the VLSD is worn in the 94 as I remember.Excellant article about mixing and matching and real tires vs wantabees.

http://www.sportcompactcarweb....patch/

[Q45tech]

Speaking of tires note Michelin's Chris Bakers use of Q45 [he has 2] on the proving grounds. Unfortunately the VLSD is worn in the 94 as I remember.Excellant article about mixing and matching and real tires vs wantabees.

http://www.sportcompactcarweb....patch/

http://69.63.136.213/documents/177047_web.pdf

"""The ECE test requires a tire to be tested at increasing speeds in a stepwise manner at 77F on a smooth wheel and sustain the rating speed without structural failure for 10 minutes. Yup, 10 minutes!

But as most engineers will tell you, you should "over-design and under-utilize". This applies to every product including tires. So vehicle manufacturers will specify a tire that exceeds the maximum speed of the vehicle.

Tire manufacturers want ALL their tires to pass the speed rating, so they'll specify that all their production tires exceed the test by some margin. Does this mean 20 minutes? Does this mean 100F (The SAE version!), Does this mean one additional step up in speed? Depends on the manufacturer.

This "over-design / under-utilize" credo is important as it has a basis in reality. It's been found that barely meeting the conditions - load capability, speed capability, etc. - results in a certain rate of failure in the real world. And while we can talk about underinflation, road hazards, etc., the reality is that over-specifying a tire results in reduced failure rates.

But there is one aspect that deserves additional comment.

Pretty much every tire will pass an S rating. (Please note that I'm limiting the discussion to regular passenger car tires. Winter tires and light truck tires are a different story - similar, but different.) And T ratings are not much of a stretch.

So an S rating would - on the surface - seem to be adequate for use in the US where there are speed limits everywhere.

But, in order to pass an H speed rating, a tire more or less has to have a cap ply. This change has a profound effect on failure rates, way beyond what the increase in speed rating suggests. The failures rates are so low for tires with cap plies that court room "experts" claim that tire manufacturers are negligent for not using cap plies even in their S rated products. (My response to that is that these "experts" must also be saying that tires ought to have a minimum of an H speed rating - and if that is true, the "experts" ought to be lobbying NHTSA to specify H rated tires for any tire sold in the US.)

But the point I want to make is that the step between T and H is enormous from a tire durability point of view. And I don't recommend anyone use anything less than an H rated tire. Considering that the risk of a tire failure includes fatality, the cost / benefit seems to be there."""""

[Q45tech]

The 10 minute 77F speed test is in a lab on a machine the CAMBER IS SET AT ZERO.

ANY NEGATIVE CAMBER will increase the tread and thus the tire temperature increasing the failure rate compared to a LAB TEST.

[maxnix]

Pretty much every tire will pass an S rating. (Please note that I'm limiting the discussion to regular passenger car tires. Winter tires and light truck tires are a different story - similar, but different.) And T ratings are not much of a stretch.

So an S rating would - on the surface - seem to be adequate for use in the US where there are speed limits everywhere.

My wife's 2000 FY33 standard was delivered with new oversized S rated tires. I cannot convey how poorly they handled and how bad the ride was. Very, very scarey. Dealer even drove the car for a week or so!

Immediatley mounted 245/50-16 Firstone SZ50EP for a real world revelation. Why did they ever quit manufacturing them (except for two runflat sizes, for Corvettes?)? The replacement Wide Ovals are have less technology and don't cut it.

[bigjimmy]

"1.You don't understand the minimal sufficiency of speed rating test, 2.you don't understand what happens to tires as they degrade over their lifespan, 3.and you don't understand that tire life and safety performance have an inverse correlation."

My point was speed ratings do not mean a better tire.1. I believe I understood it better than you, they take a tire and spin it against a bar with a load for a set amount of time and if it doesn't blow it gets a rating.2. From my post, how could any sane person derive this?3. See #2.

I respect everyone on this board, and everyone’s opinion except MAXNIX.Go bag on someone who just signed up.

[maxnix]

1. My point was speed ratings do not mean a better tire. I believe I understood it better than you, they take a tire and spin it against a bar with a load for a set amount of time and if it doesn't blow it gets a rating.2. From my post, how could any sane person derive this?3. See #2.

I respect everyone on this board, and everyone’s opinion except MAXNIX.Go bag on someone who just signed up.

1.) You are WRONG and ignorant of tire construction - i.e., why does one tire merit a higher speed rating than another? Duh?

2.) How could any conscious person with a room teperature IQ not?

3.) See #2 above. Works for me.

It ain't about the love (that's the Ann Landers Forum), it's about the truth. Even long time members (and there are few longer time members) get called for spreading false and inaccurate information.

Didn't call out Q45tech, did we? Because his information is correct. Read it and learn.

[bigjimmy]

"You are WRONG and ignorant of tire construction - i.e., why does one tire merit a higher speed rating than another? Duh? "

Please pay attention. It receives a higher rating because it can spin against a bar for a set amount of time without blowing out. Period, end of story.

Would you rather have a Z rated tire with a traction grade of C and a Temperature grade of B that costs $150Or an H rated tire with a traction grade of AA and a Temperature grade of A that costs $150

My guess is you would go for the Z tire and impress your friend.

[szh]

It receives a higher rating because it can spin against a bar for a set amount of time without blowing out. Period, end of story.

This is simply not true, unfortunately!

Frequently, the exact same model tire with different speed ratings and different load indexes will have very different construction inside them. The number of belts, the material, often the type of rubber used during the manufacturing, etc., are quite different.

I have spent quite a bit time researching tires and tire technology and this is a well-known fact. On some tire mftr web sites, they even describe the construction details of the various speed rated tires (for the same model). This used to be more common practice but has been abandoned now by many of them .

By the way, there is legislation pending that may require after-market tire changers (if different from the OEM requirements for a given car) to put a sticker on the car that has been "altered" in this manner. The logistics for this are horrible, of course, but the issue is very, very clear and important.

Feel free to search my posts for the spreadsheet I put together on tires for the Q45 and M45 (and also, to a lesser degree, the G35) to make sure that people here make proper decisions about tires. This is where it "all happens". Good tires will give you good performance, mileage and safety. Bad ones will not. Period.

Z

[Q45tech]

In the EU and Japan it is illegal to try to renew annual registration [car inspected] to make sure the oem load and speed rating are on the car!

In the field the car can be confiscated [towed off the street] if an officer find improper fitment and then you must supply tires to impound lot and pay them to mount then after paying a big fine you might get your car in a few days.

I do believe insurance companies should require their policy holders to adhere to speed and load rating minimums. And sign a statement [send copies of work order] that their tires exceed minimum tread depth and brakes have been checked on every 6 month renewal.

Probably more valuable than side air bags?

[maxnix]

Probably more valuable than side air bags?

Certainly in that they are used every day! Hopefully the airbags are not.

[maxnix]

Would you rather have a Z rated tire with a traction grade of C and a Temperature grade of B that costs $150Or an H rated tire with a traction grade of AA and a Temperature grade of A that costs $150?

You really don't understand tires at all, do you? Care to name a Z or higher rated maximum performance summer tire with a "traction grade of c" or a "temperature grade of b"?

End of story. Dismissed.

[xmateo]

Both of these facts scare me!

Tires start vulcanizing and developing micro-cracks after a few years. Although not extreme, four is a bit too long to go without changing them, almost no matter what the wear. I would certainly not do 105mph on them at all ... frankly, driving around town may cause premature failure.

Secondly, T-rated tires also implies (but not certain) that they do not have the load index for a Q - even the Y33 years - and the speed limits for these tires is lower than suitable for a Q. You definitely need to change the tires for at least an H rated (preferably V or W or Y or Z) tire as soon as you can do so.

BTW, I am fairly sure that your vibration and problems are due to tire failure inside the treads ... maybe some belt has broken. Please be safe and do not drive at highway speeds on them, if you can avoid it, and change them asap.

Z

Thanks to all for all the info. For the ugly banter, enough is enough!! I bought my Q with the T rated tires on it. I was later surprised to see this rating as I have always worn at least H rated tires, and these Pirelli's handled surprisingly good. The tires may be newer than 4 years (just a guess since I don't see them on the market anymore and I can't find the repair history at this time. Nevertheless, I did proceed to buy the V rated Conti's even before I felt the vibrations. I knew it was time! They will be in any day. Pray nothing bad happens in the mean time. I have slowed way down for now.

[bigjimmy]

That proves you are a moron. A simple question, and you are not able to answer.

[Jesda]

There are no low-rated Z-speed tires for inherent reasons.

Brian isn't the nicest guy on earth (LOL, an understatement) but he's making a good point here.

[bullittandy]

Another new member-another tongue lashing by Maxnix. How can anyone tolerate this?

Bigjimmy- Unfortunately, Maxnix knows alot about tires and is likely correct in this instance. You should take consolation in that it has been my experience that most of his non-tire posts are not very helpful. In addition, he only insults new members.

Maxnix, would it kill you to pass along your information without insults and being condescending??

[DrewQ45]

You could also try rotating your tires back to front. If tire related, things should change. If not already felt, you should feel the vibration in the steering wheel. If nothing changes....read on...

I know everyone is focusing on your tries but your issue may be drive-shaft related. To zone in, take your car to a shop and run it while on a lift. If the vibration still occurs at 50-60 with wheels off the ground, then it's probably your drive shaft. If you neutral it while at that speed and it disappears, then it's most likely transmission related.

....Drew...

[bigjimmy]

"05-05-2005, 10:23 AM 1995Q45 Senior Member Join Date: May 2002Location: Austin, TXiTrader: (0)Posts: 1,087 Re: How fast can you go!! The X50 is the best. Early G50 were reputed to be able to reach 160 or 165 mph. Later were limited electronically to 150 mph. Now that I am running XGTH on my 15" rims, will never know what it is like over 130 mph."

So maxnix runs H rated tires. What a hypocrite.

[szh]

"Now that I am running XGTH on my 15" rims, will never know what it is like over 130 mph."

So maxnix runs H rated tires. What a hypocrite.

He has them on his Q for the simple reason that Michelin Pilot XGT H-rated tires are probably stronger in internal construction, and after many miles, than most other companies V-rated tires and also, he does not reach or exceed 130mph in his Q as he is saying.

Michelin does a better job than other tire manufacturers at meeting the stated load index and speed ratings, with more margins, etc. Look at the posts above (and in other threads) by Dennis (Q45tech) on Michelin's quality. In a 15" tire size, the Pilot XGTH 235/60-15 is highly recommended by Q45tech and others.

The point is that Brian and I (among others) have done a lot of research and real-world use about tires. While his lack-of-patience approach in his posts may not be appreciated by everybody here, his facts in this post are accurate.

So, I will ask you nicely: stop flaming and slinging mud, please, okay?

Z

[maxnix]

There are no low-rated Z-speed tires for inherent reasons.

Brian isn't the nicest guy on earth (LOL, an understatement) but he's making a good point here.

Geez, Jesda, I thought you were my friend!?? I mean, ever since the sauna.......

The slow FY33 has the PS2 on the OZ wheels, the others will follow when the XGTH on the G50s expire. Unfortunately, Texas in my area is highly populated, so like Atlanta, must find a track to top out over 100mph.

The PS2 are enormously expensive, but they are a superior tire to the XGTH, especially in the rain. Haven't really found their limits after installing the Eibachs and SR Specials. With a 99Y load rating, I bet it can hang with some G35 pretty well in the curves. And they are quiet and comfortable and so far wearing very well, which is good as they are directional and asymmetrical . Truly incredible.

Curious people might go to TireRack and read owner's ratings. While not the be all and end all, no other tire I have read about has recieved so many 10 or even 9.9 and 9.8 from owners.