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Unread 07-07-2008, 04:29 AM   #1
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Okay so better handling got it, but can someone explain more into what size tires and ratings, what size rim, and what width can do? Is there a size or width that is usless and just wasting money?

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Unread 07-07-2008, 10:10 AM   #2
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Okay let me give some more info: I am thinking about getting a Eclipse or Supra and im try to figure out what I need to look into from buying tires and rims. I want to turn this project car into a track car trying to stay more toward street then drag.

I was wondering if anyone knows of a chart than show the different increrment (not sure how its spelt) on what size rim and width tires add to performance.

Last edited by mike149; 07-07-2008 at 10:13 AM. Reason: typo

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Unread 07-07-2008, 11:05 AM   #3
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Well i dont really think there is a chart for performance gains per tire size. There are too many factors to consider than just tire siz. Sure it helps to have larger tires, but a good suspension tuned right can have a better gain than just buying a wider tire.

In general, wider is better. But You must consider the added drag a bigger tire adds. So going with a 335 on an eclipse for instance would be absolutely pointless. It would do more bad than good. But if you drag race a 1000whp supra, then you need all the rubber you can get in the rear.

If your looking for a street/track based car, 255-285mm tires would do very well, and rim size doenst play a whole lot. 18" is about the best size imo, but i think it comes down to what looks best on your car.

I own a supra and i think 18"s fit best. Staggered wheels look great on it too, so i plan to run 285-295x35x18 in the rear and 255-265x30x18 in the front. On an eclipse i think going with the same sized wheel would look best, and perform best if you get a GSX.

Any ways i think ive said enough, hope this helped.

PS: Go for the supra!
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Unread 07-07-2008, 11:51 AM   #4
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Say your tires say 89 Y on the side (this is from a sport tire, my BFGoodrich g-Force T/A KDW 2), this is known as the service description.

A service description identifies the tire's load index and speed rating. It can be found on the sidewall of the tire after the size listing.

The load index is the tire size's assigned numerical value used to compare relative load carrying capabilities. The speed rating is a letter denoting a fixed maximum speed capability.

A service description identifies the tire's load index and speed rating. Service Descriptions are required on all speed rated (except for Z-speed rated) tires manufactured since 1991.

The first two digits (89) represent the tire's load index and are followed by a single letter (Y) identifying the tire's speed rating.

Load Index

The load index (89) is the tire size's assigned numerical value used to compare relative load carrying capabilities. In the case of our example the 89 identifies the tires ability to carry approximately 1,279 pounds.

The higher the tire's load index number, the greater its load carrying capacity.

89 = 1,279 pounds
88 = 1,235 pounds
87 = 1,201 pounds
86 = 1,168 pounds
85 = 1,135 pounds

A tire with a higher load index than that of the Original Equipment tire indicates an increase in load capacity. A tire with a load index equal to that of the Original Equipment tire indicates an equivalent load capacity. A tire with a lower load index than the Original Equipment tire indicates the tire does not equal the load capacity of the original.

Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 110.

Speed Rating

In Germany some highways do not have speed limits and high speed driving is permitted. Speed ratings were established to match the speed capability of tires with the top speed capability of the vehicles to which they are applied. Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at "unusual" mile per hour increments). Despite the tire manufacturer's ability to manufacturer tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits.

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 ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.

It is important to note that speed ratings only apply to tires that have not been damaged, altered, under-inflated or overloaded. Additionally, most tire manufacturers maintain that a tire that has been cut or punctured no longer retains the tire manufacturer's original speed rating, even after being repaired because the tire manufacturer can't control the quality of the repair.

Over the years, tire speed rating symbols have been marked on tires in any of three ways shown in the following examples:

225/50SR16
225/50SR16 89S
or 225/50R16 89S

Each of these was an acceptable method of identifying speed ratings.

Early tires had their speed rating symbol shown "within" the tire size, such as 225/50SR16. Tires using this type of branding were not to have been produced after 1991.

Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

M 81 mph 130 km/h
N 87 mph 140km/h Temporary Spare Tires
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars


When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.

W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars


While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.

225/50ZR16 in excess of 149 mph, 240 km/h
205/45ZR17 88W 168 mph, 270 km/h
285/35ZR19 99Y 186 mph, 300 km/h


Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:

285/35ZR19 99Y 186 mph, 300 km/h
285/35ZR19 (99Y) in excess of 186 mph, 300 km/h


As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.

Hope this answers your questions.

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Unread 07-08-2008, 09:25 AM   #5
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This is a good website that may give you a bit of an insight into wheels and tyres etc
Hope it helps,
Steve.


http://www.chris-longhurst.com/carbi...yre_bible.html
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Unread 07-12-2008, 08:38 PM   #6
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Basically, a higher load rating will protect you from pot holes. All tires have a rim width range, wider means stiffer. Best tires are Star Specs or RT 615s . Best winter tires are Continental Extreme Contact.
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Originally Posted by mike149 View Post
Okay so better handling got it, but can someone explain more into what size tires and ratings, what size rim, and what width can do? Is there a size or width that is usless and just wasting money?

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