New Tyres

[D R Oldfield]

I need 2 new tyres for my 2.8 what speed rating should I get , at the moment I have 255/35zr18 94y is that the correct speed rating or can I go for a lower rating ?
Thanks

 

[t-tony]

I beleive im right in saying that the speed rating on a tyre ie 94Y states that that tyre is capable of maintaining a speed of 94 mph continually for 10 minutes.
When did you last do 94 mph continually for 10 minutes?
I will get some pictures tomorrow.

Tony.

 

[D R Oldfield]

Does going for a lower speed rating affect your insurance

 

[t-tony]

Does going for a lower speed rating affect your insurance

Can't answer that. Best to keep your car on the tyres specified in the owner's handbook I would say. But if you then fit different sized wheels and tyres what then?

I did find this,

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 manufacturers' ability to manufacture tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits. The maximum operating speed of a vehicle must be limited to the lowest speed rated tire on the vehicle.

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.

225/50SR16 112 mph, 180 km/h
225/50HR16 130, 210 km/h
225/50VR16 in excess of 130 mph, 210 km/h

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:

L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h Temporary Spare Tires
N 87 mph 140km/h
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 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

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 tire's capability, allowing drivers to match the speed of their tires with the top speed of their vehicle


Tony.

 

[D R Oldfield]

Wow 186 mph does seem excessive what rating have other people used

 

[t-tony]

The point is that tyres, regarding speed ratings are over rated. To be on the safe side, it makes sense.

Tony.

 

[Stevo7682]

The Y rating is because of the the size ( it is a sport low profile size ) you wouldn't get a 155/ 13 in a y as cars fitted with that size don't go that fast the speed and load index of the tyres increase with the size as they can be fitted to larger and faster vehicles
The 94 refers to the load index of the tyre

and as Tony has posted the y is the speed rating for the tyre

all cars that still have the standard tyre set up will be overshod to have a safe margin in the tyres abilities.
For example a lot of modern bmw are capable of approaching or hitting it's 155mph limiter a V rated tyre is rated to 149 mph but that is under the cars max speed so minimum tyre speed would be a W to allow the margin of safety ( doesn't matter you don't drive at that speed it's construction and use regulations all car manufacturers follow ) the load index of the tyre will be relavent to the vehicle size and max load capacity.
Stephen.

 

[D R Oldfield]

So what is the top speed of a 2.8 z3 I have just had a look in the hand book and it doesn't specify 18" wheels on a z3 the max is 17 and the max speed rating is w the wheels are genuine Bmw any thoughts ?

 

[Stevo7682]

Just had a quick look on oponeo there and in your rear size pretty much everything is either 94 w or 94 y both of which will be fine just buy the brand you are after in either speed rating