Re: 4ksq Tires and Suspension Questions

[Todd Phenneger <phen9461@uidaho.edu>]

>It has to do with the tires grip/compound.  The 205/55 are usually V
>rated and not only have stiffer sidewalls they are also softer
>compound (Treadwear 140 compared to 160 for 195's). The 195's are
>usually H rated and therefore softer sidewall.

That tire size has nothing to do with the speed rating.  Yes, higher
speed ratings do have stiffer sidewalls, better construction, and
usually stickyer compounds, and it is easyier to find higher speed
ratings like Z and W in the lower profile tires, but you can have a 195
tire in q/s/h/v/ or Z ratings.  Doesn't really matter.  Just like you
can have a (s) rated 225 tire.  Many manufacturers even make the same
tire in different speed ratings.  Well, same tire outside at least but I
guess they MUST change the inside.

>If you choose a 195/60 tire with exactly the same compound and speed
>rating as 205/55 the difference in handling will be marginal unless
>internal design of the belts is also different.

This is true.

>Most common mistake people make is they assume that a wider tire
>makes larger contact with the pavement.  That is not the case.  Even
>if you get 255's they will still have the same contact area as 195's.
>Simple physics dictates the rules.  The reason you want the wider tire

Uh, show me the physics.  a 245 will to put more rubber on the road.  I
am not following you on this one,
where are you getting your "Phisics info"  A larger tire has more air in
it to compress yes, but the width greatly out weighs the difference in
front to back contact area.

>is that as the tire rolls under load the block of tread will be in
>contact with the surface for shorter period of time (to get the same
>area the larger width of contact reduces the length of contact along
>the tire) on a wider tire there fore reducing it's chance to overheat
>under braking and acceleration.

This is a minimal factor in in heat.  And if you take two cold tires,
one narrow and one wide, but both Z rated, and of the overall same
height, the wider, lower profile one will offer more surface area and
grip. THis doesn't mean the car will handle better if the suspension
cant handle that much tire and wheel but it will have more grip in the
tire dept.

>There are a lot of things to consider with tires and wider does not
>automatically mean better.  It usually does though.

Very true, here we agree

>You have to compare:
>- - Speed rating (Z,V,H,S,T with Z the highest)

And dont forgert those new ratings for F-50s, McLarens, XJ 220's, and
Porsche GT-1's.  I think there is a W and maybe a Y.   Not sure what the
differences are in speed.  V is up to 150 mph I think, Z was over 150
years ago but now I think is like 150 - 168?????  What are W and these
others.  168 - 200 and then a 200+ tire.  Does anyone know?
--
Todd Phenneger
84' 4kq, Borla 2.5" muffler, K&N filter in drilled box
15" wheels with 205/50-ZR 15 Bridgestone RE-71s
Boge TG struts, coil-overs to come, as is the turbo.

"In the confrontation between the stream and the rock,
the stream always wins...
not through strength, but through persistance."