"Unsafe" tires at 15K

[HeavyH20]

There is nothing to disagree with. That is the way the tire ratios are calculated. Always have been. The rim has nothing to do with the tires size except to limit the possible width. For example, a 205-50-18 has a much shorter sidewall than a 275-50-18. Or, in our case, the sidewall is almost the exact same height (as is the circumference) on a 255-55-18 as it is on a 235-60-18. Simple math.

http://www.dsm.org/tools/tiresize.htm

Type in a 255-55-18 and it will list every single tire that is the same height. If you look at the 18 inch results, 60 series, you will see a 234 mm result (235).

 

[SuperStretch18]

I disagree. The lower aspect ratio tire has less sidewall height for a given rim diameter.

Heavy's right; the numbers on a tire are as follows:

205-55-18

205 = width of the tread in mm
55 = sidewall height = % of tread width
18 = rim size

Since the sidewall height is a percentage, a wider tire with the same aspect ratio will have a higher sidewall. This explains the calculations well (although a little technical):

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=7

 

[erhayes]

Heavy's right; the numbers on a tire are as follows:

205-55-18

205 = width of the tread in mm
55 = sidewall height = % of tread width
18 = rim size

Since the sidewall height is a percentage, a wider tire with the same aspect ratio will have a higher sidewall. This explains the calculations well (although a little technical):

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=7

Now I understand what you were aluding to. I was wrong as I forgot about the width factor. I consintrated only on the aspect % without reguard to a width increase. Thanks for clearing that up for me. Ed

 

[azcat]

OK, so...

Two new RSAs installed. Four wheel alignment done (almost (and I mean, 0.01 almost)) no adjustments on the alignment. I'm thinking the RSAs aren't all that good.

Two new all-season, high-performance tires are on the market in our size: the Goodyear Eagle F1 and Toyo Versado. The F1 and Toyo Proxies have excellent reps in the Miata world, and I've run Proxies on my Miata for years. The Toyos are gumballs--incredible traction, about 18k-20k miles per set on the Miata. No experience with the Eagles, but other Miata pilots love them. If these RSAs go the way of the first two, I'm going with the Toyos. If they're going to wear fast, I want grey-out cornering.

 

[MrPirelliCX7]

goodyear

I've got the Goodyear RSA OEM tires. I took my AWD GT in for the 15K service today, and my tires are "unsafe" and at least the front two should be replaced. Had them rotated at this dealer at 5k and 10k miles. Tread depth varies from place to place on the tire, but there are no indications of an alignment problem. I'm thinking "belt separation."

To their credit, the dealer is "going to try to" replace all four under warranty. I'll know more Monday.

I expect tread life of 17k-18k miles on my Miata's Toyos--they're gumballs and soft rubber wears quickly. But these? Anyone else checked their tires lately?

 

[MrPirelliCX7]

goodyear RSA are soft compound and have a bad treadwear rating, try a different brand if you have to pay and make sure to do an alignment every 10-12k miles

Front wheel drive vehicles with power also are hard on tires

 

[MrPirelliCX7]

tpms will work regardless of size of tire, 255/55/18 will create more road noise as well, although believe it or not the contact patch will really not change contrary to many beliefs

Try an all season 255/55/18 not a bfg or nitto they will not wear any better

Try a Pirelli scorpion Str, I have 5000 miles on a set of 245/50/20 and they still look new, they will wear at least 30K and are specifically designed for Volvo which are much heavier than mazda and harder on tires

 

[AWmustang]

although believe it or not the contact patch will really not change contrary to many beliefs

I find that hard to believe. Do you have some explanation for why a tire that is 20 cm wider has no more rubber touching the road?

Because I went from 215/65/16 to 235/55/17 on my Mustang and it made a HUGE difference, both in acceleration and cornering. (I realize the difference in cornering was probably partly to do with a shorter side wall.)

 

[HeavyH20]

Contact patch will change based on tire size, vehicle weight and tire to rim width (too wide a tire on a rim forces the lateral belts to round). A wider tire will have shorter, wider contact patch than the stock tire. The square area of contact may be close to the same however. One important aspect is that if you have too wide a tire, the front to rear contact patch may be limited enough to affect stopping ability. There are a number of items to consider when changing tire size.

 

[CX-7owner]

tpms will work regardless of size of tire, 255/55/18 will create more road noise as well, although believe it or not the contact patch will really not change contrary to many beliefs

Try an all season 255/55/18 not a bfg or nitto they will not wear any better

Try a Pirelli scorpion Str, I have 5000 miles on a set of 245/50/20 and they still look new, they will wear at least 30K and are specifically designed for Volvo which are much heavier than mazda and harder on tires

Pirelli tires are prone to blow outs.

 

[5280_CX-7]

The stock rims are 7.5 inches wide. I will go with the 255-55-18 size when it comes time, as well. I will go with the Nitto or the BFG g-Force.

The BFG KDW2's will give you AWSOME dry and wet traction but they are very loud and they suck in snow. I have a set on my Ford Focus and I love them, but I don't drive it in the winter snow. I have a 4 wheel drive truck for that.
We put a set of Pirellli Scorpion Ice and Snow tires on my wifes CX-7 and the traction on ice and snow is phenomenal. Much better then the Truenza's that came on it. But they were not cheap.

 

[AWmustang]

Pirelli tires are prone to blow outs.

Do you have any evidence of this? Cuz I certainly haven't heard anything like that. I beat on my Pirellis. They were OEM on the 17 inch Mustang tires and I'm still on that forum. Not a single person there has had a blowout.

 

[CX-7owner]

Not ALL but some Pirelli's Are known to blow out.
Summary:
I have had 6 blow outs with thses tires. I could not be anymore uphappy.

Strengths:
none

Weaknesses:
run over any normal chuck hole - you will have a blow out. Speed does not matter - I had two blow out at under 20 mph.

Summary:
I drive in the New York City vicinity; this past year I have replaced 5 tires (225/40/17) due to sidewall bulges or tear. The last incident was caused by a small pothole that caused a bulge on the left front, and a sidewall tear on the left rear. Good on wet, but terrible on grooved roadways. On the tire dealer's suggestion I have replaced the front two tires with Pirelli "P-Zeros assymetricals"; I just learned from Audi that this was the wrong thing to do; they tell me that all four tires should be the same thread design due to the all-wheel drive. I welcome any advice!

Summary:
I drive on 5 percent of the distance on gravel /dirt roads and the rest on tar. The average speed is around 140km/h and 180km/h on the the tar. I have done 200 000 km with this car and am surprised to see the tyre degredation after 30 % wear. The tyre is soft at speeds exceeding 160 km/h and the smallest stone chip pierces the inner lining of the tyre. When repairing the tyres (Two) both displayed the same wear. Small air leaks were found over the tyre. At the straight line speed I normally drive this would a high risk. Fortunately the tyre deflates nomally (does not burst)and you can feel the lateral movement. This gives you enough time to reduce speed and stop.

Just some of the Consumer reported issues with blow outs.

 

[AWmustang]

DANG!!!! If I had as much trouble with a tire as that I'd be bashing them as well.

It's good to know, because I always thought Pirrellis were a step above the Goodyear and Bridgestones.

 

[Gray Ghost]

The BFG KDW2's will give you AWSOME dry and wet traction but they are very loud and they suck in snow. I have a set on my Ford Focus and I love them, but I don't drive it in the winter snow. I have a 4 wheel drive truck for that.
We put a set of Pirellli Scorpion Ice and Snow tires on my wifes CX-7 and the traction on ice and snow is phenomenal. Much better then the Truenza's that came on it. But they were not cheap.

They don't make the G-Force in size 255-55-18. Actually, they don't make them in the stock size of 235-60-18 either. The best tire reviews I could find in the CX-7's size were on the Yokohama ADVAN and the GoodYear Response Edge. Both of these come in either size.(2thumbs)

 

[1Sleepy93]

You have to take the reviews of the Response Edge with a grain of salt since not that many people have tried them yet and very few total miles have been reported. When looking on tire rack, I look for tires that have a few million miles reported before I take the ratings seriously.

 

[HeavyH20]

They don't make the G-Force in size 255-55-18. Actually, they don't make them in the stock size of 235-60-18 either. The best tire reviews I could find in the CX-7's size were on the Yokohama ADVAN and the GoodYear Response Edge. Both of these come in either size.(2thumbs)

Are you sure about that? The BF Goodrich g-Force T/A KDW NT is available in 255-55-18 sizing.

http://www.discounttire.com/dtcs/fi...false&cs=255&pc=38474&rd=18&ar=55&ct=&rf=true

http://www.1010tires.com/tire.asp?tirebrand=BFGoodrich&tiremodel=g-Force+T%2FA%AE+KDW+NT

https://www.tiresavings.com/tireSho...=BF+Goodrich&tirename=g-Force+T/A+KDW&season=

And, the Nitto comes with very good reviews.

http://www.discounttire.com/dtcs/fi...false&cs=255&pc=40263&rd=18&ar=55&ct=&rf=true

 

[erhayes]

Just because tirerack does not carry a size doesn't mean it isn't made.

 

[Zoom49]

Check out these General 255/55/18 tires. They have very good reviews.
http://www.tirerack.com/tires/tires.jsp?tireMake=General&tireModel=Grabber+UHP
I put a set of General Exclaim UHP on our Mazda RX8. Good handling with low noise and a competitive price. This grabber is rated number one in its class
on tire rack.(yes)

 

[CX-7owner]

Check out these General 255/55/18 tires. They have very good reviews.
http://www.tirerack.com/tires/tires.jsp?tireMake=General&tireModel=Grabber+UHP
I put a set of General Exclaim UHP on our Mazda RX8. Good handling with low noise and a competitive price. This grabber is rated number one in its class
on tire rack.(yes)

Yeah I was going to get those originally but every store around here had low stock of them.