Can I mix "W" rated and "Z" rated tires

MarkY · MarkY's Garage

I'm looking to get some new tires for my 88 Carerra. The OEM tire sizes are 205/55/16 and 225/50/16 on stock Fuchs.

I was looking at putting some Goodyear Eagle F1 GS-D3 and noticed that the 205/55/16 come in a "WR" tire and the 225/50/16 come in a "ZR" tire. This is from Tirerack.com.

Should putting different rated tires on the front and rear be avoided? My second choice is Michelin Pilot Sports.

These will be used as a weekend driver, sometimes spirited driving. They won't be used for a track tire.

Any other opinions welcome.

Thanks

Andras · 04-29-2004, 04:56 AM

Mark,

The tire letter designations are for "safe speed" ratings. Therefore, if you go over 150 MPH at a steady speed, your "W" tires will delaminate before your "Z" tires will.

If they are both radials, you should have no trouble at highway speeds. Just don't put this combination on the track for the 24 Hours of Daytona.

kqw · 04-29-2004, 06:05 AM

Correct me if I 'm wrong but......."W" rated tires are actually rated higher than "Z".....

I had the same question when I purchased Bridgestone S03's.

Talk to the guy's at Tire Rack....

KTL · 06:24 AM

Actually, W & Y tires are Z-rated tires.

Some tires can be labelled something like 225/50ZR16 91W

Speed ratings:

Z = above 149 mph
W= up to or in excess of 168 mph
Y = up to or in excess of 186 mph

http://www.tirerack.com/tires/tiretech/general/speed.jsp

In my opinion, yes you can mix the W, Y or Z tires. You have no choice with some brands of tire. Look at the Kumho MX tires in 205/55-16 and 225/50-16:

Kumho MX sizes and pricing

I have these on my car and I love 'em.

masraum · 04-29-2004, 06:28 AM

I agree with Kevin, if they are both the same make/model of tire, just two different ratings, i think that is OK. If you use two different models of tire then, to me, that would be the problem more than the speed rating would.

kqw · 04-29-2004, 06:30 AM

Thanks to KTL.......

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 225/50ZR1691W, 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

chrisp · 04-29-2004, 06:40 AM

They should be fine. There is a difference in the construction between the two.

Basically what the speed rating is is the point at which the vibration wave that is created as the tire rolls along the pavement becomes destructive to the carcass. Destruction is usally caused by heat but there are also other factors.

So, the construction of the tire can, in effect, "tune" the point at which this wave starts to happen. Generally the carcass is stiffened to "support" a higher speed rating. So a Z rated tire is most likely has a bit softer construction than a W tire.

Am I a tire engineer? No. But I did stay at a Holiday Inn Express last night!

kqw · 04-29-2004, 06:53 AM

Didn't Kumho have a tire recall recently????????

KTL · 04-29-2004, 06:59 AM

Recall is for the Ecsta V710 racing tires

http://www.tirerack.com/tires/kumho/kumho_710.html