H speed rating on original tires on '97 ETC?

[dochawk]

I just looked at the door of my other eldorado, and actually looked things up.

It shows "H" rating for front and rear tires, and has a second decal noting "high speed" inflation pressure (35 rather than 30).

Does this mean that it's computer limits it to 130 rather than 112 or 118?

More curiosity than any inclination to drive that fast . . .

hawk

[savemy67]

Hello Richard,

When I bought my 1995 Chevy Impala SS in 1995, it came with Z rated tires.  Then, the Z rating was for tires rated to run at speeds in excess of 149 mph.  Try as I might, I was never able to get the car to travel at a speed in excess of 149 mph.  I only got to 147.

Today, the Z rating has been supplanted.  H is rated for a maximum speed of 130 mph.  The ratings below H, - S, T, and U - have a 6 mph difference between each letter rating.  It may be that your '97 could go to 130 mph, but the determining factor is what is programmed in your car, not the speed rating of the tires.  This information may or may not be in the owners manual, but you may be able to find it on this, or other forums.

Christopher Winter

[Carl Fielding]

Doc , governed F.C.O. on my 2002 STS is abrupt 129 mph by test. I would guess your '97 is the same. My 1995 FwB is 107 , also abrupt by test. That E550 brand X of mine you drove in 'Vegas wold have been gentle at 134 if you had pushed it more.  Dinner time , bye !  - CC

[dochawk]

Yes, but 134 on a Vegas freeway generally doesn't end well . . .



My understanding, which I'm trying to confirm, is that Caddies of this vintage were computer limited to the rating of the tires that the car shipped with.

[Greg Powers]

From a strictly tire guy perspective, the vehicle is set at the factory at what ever predetermined top speed it will register. The speed rating on the tire has as much to do with the ride and handling as it does the speed. As stated, legally you can only drive at 70 to 80 mph top speed so a higher speed rating for speed alone seems useless. A tire however is designed for more than speed alone. Performance rated tires (HR, VR, ZR, WR) are constructed with stiffer sidewalls and often special bead packages to enhance control and road handling, often the tread design is a directional pattern.  Often cars with these tires have  enhanced handling suspensions and other ride systems. Thus for years the Seville SLS vs STS, the Eldorado vs ETC or the Deville DHS vs DTS. The touring tire (SR, TR) will often be a softer ride but you do sacrifice some handling. And if you are a older Cadillac driver, whitewalls are only manufactured in SR and TR ratings and becoming much harder to locate these days. - Greg