Welcome to the North American Subaru Impreza Owners Club Wednesday July 30, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
Click here to visit TireRack
Brakes & Suspension Forum sponsored by The Tire Rack

Losing traction? Need new tires?
Click here to visit the NASIOC Upgrade Garage...
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Brakes, Steering & Suspension

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 02-08-2002, 09:12 AM   #1
GooseMan
Scooby Specialist
 
Member#: 2462
Join Date: Sep 2000
Chapter/Region: SCIC
Location: Los Angeles/Montreal
Vehicle:
2012 Volvo S60 T5
2005 Triumph Sprint ST

Question H-R-W-XYZ....ratings..what do they REALLY mean?

I'm planning on getting a set of Kuhmo 712's this spring, and I can get a good deal on them. The W rated ones are about 40-50 bucks cheaper OVERALL (for all 4) than Z rated.

I know that the ratings are heat ratings for maximum speed (for instance, W is only for 100mph, whereas Z is for 149+ mph (I'm just making those numbers up)).

I rearely go over 100mph, so I dont really NEED Z rated tires....or do I???

Do Z rated tires actually have better GRIP than W rated? I guess they would be more heat resistant, but is the compound actually grippier? What benefit would I have with Z rated? Should I pay the extra cash?
GooseMan is offline   Reply With Quote
Old 02-08-2002, 10:13 AM   #2
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Default

With the 712s, there's some difference between the two. One is a good tire, one gets complaints. Now, of course, I forget which. I believe the W-rated tires are the "good" ones. Something is different about them...search?
Julian is offline   Reply With Quote
Old 02-08-2002, 10:18 AM   #3
peepshow
Scooby Specialist
 
Member#: 1777
Join Date: Jun 2000
Chapter/Region: South East
Location: Charlotte, NC USofA
Vehicle:
2005 LGT
#92 FZippy

Default

Here is a cut and paste from the Tire Rack website. I think it will answer your questions:

Speed Rating

P195/60R15 87S - The tire speed rating (S) is the maximum speed for which the tire is rated. For example, the “S” rating identifies speeds up to 112 mph (180 km/h).

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.

In Europe, where selected 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 capabilities 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 “odd” 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 (to reflect its required load) against a large diameter metal drum and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire’s required speed has been met.

Speed Rating - Miles/Hour - Kilometers/Hour - Typical Use
N=87 MPH, 140km/h, Spare Tires
P=93 MPH, 150km/h
Q=99 MPH, 160km/h, Winter, LT Tires
R=106 MPH, 170km/h, LT Tires
S=112 MPH, 180km/h
T=118 MPH, 190km/h
U=124 MPH, 200km/h
H=130 MPH, 210km/h, Sport Sedans
V=149 MPH, 240km/h, Sports Cars
Z=149 MPH, 240km/h and over, Sports Cars
W=168 MPH, 270km/h, Exotic Sport Cars
Y=186 MPH, 300km/h, Exotic Sport Cars


*Today, the Z-speed rating is the only speed rating that is still branded “within” the tire size, as in P225/50ZR16. All other speed ratings are shown in the tire’s service description.

When Z-speed rated tires were first introduced, they were thought to reflect the highest speed rating that would ever be required. Since that time the automotive industry has found it necessary to add W- and Y-speed ratings (indicated in the tire’s service description) to identify the tires that meet the needs of new vehicles that have extremely high, top speed capabilities.
Miles/Hour Kilometers/Hour
P225/50ZR16 149+ 240+
P225/50ZR16 91W 168 270
P225/50ZR16 91Y 186 300


While all Z-speed rated tires are capable of speeds of 149 mph and above, prior to the W- and Y-speed ratings were identified in the service, how far above 149 mph was not identified
peepshow is offline   Reply With Quote
Old 02-08-2002, 10:37 AM   #4
SubaruStu
Scooby Specialist
 
Member#: 8972
Join Date: Aug 2001
Chapter/Region: E. Canada
Location: Ottawa
Vehicle:
2003 WRX Wagon
Silver

Default

You've got it right in that it is resistance to heat buildup from
friction, and the resistance to flying apart from centripetal
acceleration. Traction is traction, based on the UTCQ (?). and
shouldn't matter from one speed rating to the next, but the
higher up the the chain you get, the better the construction of
the tire to resist the effects of speed.

In general (my opinion) nobody needs a Z-rated tire for the
street. You can get a decent tire with anything over a Q-rated
tire. The ratings are also based on continuous use, not just
blasting up to xxx km/h and back down. If you are really into the
"performance" then you can get a H or V-rated tire for less than
expensive Z-rated.

My 2Cents.

Stu
SubaruStu is offline   Reply With Quote
Old 02-08-2002, 10:47 AM   #5
Xio
Scooby Specialist
 
Member#: 3805
Join Date: Jan 2001
Chapter/Region: International
Location: Paris, FR / Houston, TX
Vehicle:
2011 STi Sedan SWP
2011 Outback ABP

Default

Just a note: According to Tirerack the Kumho 712 is available in stock 205/55-16 size in V and W ratings.
The W rated version is a bit softer compound (lower treadwear rating) and has slightly stiffer sidewalls than the V rated. Sometimes I wonder if people that complain about Kumho's sidewalls have the V rated, because I have W rated on my 2.5RS and have little or no problems with rollover when auto-xing as long as I bump the pressure up to 40+ lbs.
Xio is offline   Reply With Quote
Old 02-08-2002, 11:30 AM   #6
Dolphin Overton
Scooby Specialist
 
Member#: 1925
Join Date: Jul 2000
Chapter/Region: RMIC
Location: denver
Vehicle:
01 Allroad 6spd
13 Daytona 675R 99 Sprint

Default

They sell a Z rated Kumho also which I have and beleive totally sux donkey balls. A z-rated tire gives not only improve traction at higher speeds but also better response and road feel.
Dolphin Overton is offline   Reply With Quote
Old 02-08-2002, 11:37 AM   #7
rkkwan
Scooby Specialist
 
Member#: 5596
Join Date: Apr 2001
Chapter/Region: TXIC
Location: Houston, TX
Vehicle:
2010 Honda Fit Sport
Black

Default

Great explanation by dsmawd.

Also remember, if a tire only has a "Z" rating without clarification whether it's a "W" or a "Y", it means it has to be designed a few years back at least. Since most tire manufacturers update their tires with better design and material often, I'd NOT get such a "Z" rated tire. Such rating really means nothing other than -

"It's better than a 'V'-rated one from a few years back".

-Ray
rkkwan is offline   Reply With Quote
Old 02-08-2002, 12:36 PM   #8
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Default

Xio has the real answer. W-rated for the 712s.
Julian is offline   Reply With Quote
Old 02-08-2002, 12:49 PM   #9
jmott
Scooby Guru
 
Member#: 6713
Join Date: May 2001
Chapter/Region: TXIC
Location: Houston TX USA
Vehicle:
2007 Prius
brown

Default

all the ratings really mean is how fast the tire can go safely.

that said, Z rated tires TEND to have stiffer side walls and more performance oriented tread etc.
jmott is offline   Reply With Quote
Old 02-08-2002, 02:25 PM   #10
slater
Scooby Specialist
 
Member#: 5848
Join Date: Apr 2001
Location: burlington, vermont
Vehicle:
1992 vw corrado vr6
silver w/ schrick/quaife

Default

just my $0.02 . . . i had a set of the W-rated 712s, and hated them. soft, soft, SOFT! almost unstable-feeling. i was never happier than the day they came off my car.

maybe i have higher standards? possibly.
slater is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Model Codes and What They Really Mean stimpy Subaru Conversions 126 07-15-2014 03:05 AM
what do they really want out of me?? Meat Supply Off-Topic 21 10-21-2008 12:47 AM
Bush's team / Do they really believe what they are saying unkadave Political Playground 15 07-17-2005 09:54 PM
Boost Guage Readout - What do they exactly mean? apollo Newbies & FAQs 7 01-14-2005 08:38 AM
Valve spring and what do they mean to you. WRXwannbe Normally Aspirated with bolt-on Forced Induction Powertrain 13 10-19-2001 05:32 AM


All times are GMT -4. The time now is 03:35 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.