Can some one tell me the difference between a tire thats W-speed rated and Z- seed rated.

I'm looking at these two tires. http://www.discounttire.com/dtc/findTireDetail.do?rc=TFMINT&yr=2005&sp=true&sw=false&cs=205&pc=28749&rd=17&vid=008416&ar=45

http://www.discounttire.com/dtc/findTireDetail.do?rc=TFMINT&yr=2005&sp=true&sw=false&cs=205&pc=41441&rd=17&vid=008416&ar=45

W speed rating is less than Z. but you honestly dont' need better than H rated.. H = 130mph..

W speed rating is less than Z. but you honestly dont' need better than H rated.. H = 130mph..

Here's a good discussion of tire codes:

http://www.diynet.com/diy/ab_tires/article/0,2021,DIY_13697_2271480,00.html

FWIW: www.diynet.com has some great how-to articles.

from the link ^^^^^^

speed rating letters...
F = 50 mph
G = 56 mph
J = 62 mph
K = 68 mph
L = 75 mph
M = 81 mph
N = 87 mph
P = 93 mph
Q = 100 mph
R = 106 mph
S = 112 mph
T = 118 mph
U = 124 mph
H = 130 mph
V = 149 mph
Z = 149+ mph

scions really only need about a P to R rated tire

FYI, a few years back the tire industry decided that the "Z" (149+ mph) speed rating needed to be further defined so they added the speed ratings of V @ 150 mph, W @ 169 mph, & Y @ 188 mph, so all new high speed tires being introduced today will have a speed rating of either V, W, or Y, however, since the "Z" rating is still thought of as the "High Speed" rating, the tire manufacturer are allowed to use the "Z" symbol in the size description of the tire. In this case, both speed ratings will appear on the tire as follows: 215/35ZR18 84W.

http://www.tirerack.com/a.jsp?a=DJ1&url=/tires/index.jsp