maremrak Posted March 28, 2006 Report Share Posted March 28, 2006 My Caddy does not have a speed limiter. It is 1995 STS with Z-Rated tires written on a passenger door. This summer I want to see if I can reach 150 MPH, but I only have Bridgestone H rated tires on. Do I need to upgrade to Z rated tires, or I will be OK? Thanks! 1960 Sedan De Ville (sold) 1970 Coupe De Ville (sold) 1987 Mazda RX-7 (sold) Link to comment Share on other sites More sharing options...
danbuc Posted March 28, 2006 Report Share Posted March 28, 2006 With the right tire pressure, and in good condition they can be used above 130mph, but not 20mph above 130mph. I'd say maybe 135mph is the max, but I wouldn't sustain that speed for very long. It will put too much stress the tires. A blowout at 130+mph would most likely be fatal. My advice is to buy yourself a good set of Z-rated tires first. Have them road force balance and get a four wheel alaignment. After that, find a long, straight, deserted stretch of highway and have at it. Keep in mind that it takes a really long time to stop from 150+mph. Be safe, and good luck. It's alot of fun driving that fast, but it can turn bad..quick. Link to comment Share on other sites More sharing options...
Bill K Posted March 28, 2006 Report Share Posted March 28, 2006 Reading about ratings they use the term "maximum sustained speed". Does this mean if your speed is just higher for a couple of min. its OK? I would think so but I cant find any info to support that thought. As mentioned, I would be darned sure that the rest of the suspension is in very good to excellant condition before going to 150. Although there is no shame in saying "my car could go 150 but I dont have the right tires to do it". Link to comment Share on other sites More sharing options...
caddypete Posted March 28, 2006 Report Share Posted March 28, 2006 You cannot sustain a high rate of speed because of heat buildup and centrifical forces. But back in the sixties and seventies before radial tires and their steel belts, we had bias tires which today would be lucky to rate as a 80 mph tire but every car built back then would easiely top 120 except for the few 4 bangers, your everyday dad's Olds was pumping out 300 hp.Also retreads where common back then and they are even lower rated,and with 75mph freeway speed limits back then. You are never safe at high speeds in a car, but H rated tires is not your biggest worry they will not come apart. Link to comment Share on other sites More sharing options...
mikeal1892 Posted March 28, 2006 Report Share Posted March 28, 2006 The Z rated tires will cost some big money ? Michael Link to comment Share on other sites More sharing options...
JasonA Posted March 28, 2006 Report Share Posted March 28, 2006 This is precisely why tire stores generally don't install tires with a LOWER speed rating than originally equipped, and precisely why nobody has found a single Cadillac dealer yet who will raise their speed limiter for them. There are too many variables. I would not drive 150 mph on H-rated tires. "Could" you do it without incident? Maybe. But my life is more important to me than knowingly driving faster than the tires are rated for, just to find out what I already knew (the top speed). There are rather affordable Z-rated tires you could put on the car. But yeah, they'll cost at least $500 for the set probably. I'd only do that if you needed new tires anyway. Otherwise, it's not worth it (IMHO). Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
CaddyChris Posted March 28, 2006 Report Share Posted March 28, 2006 I think my STS would not do very well at 150mph and I don't know if I would have the stones to do it. The suspension needs some serious work and I don't have Zs on it so I wouldn't even attempt it. Than you get down to the ticket and license revoking. This is just me, by all means do what you like but 150mph is very fast for these cars. The windnoise mine exhibits at 90+ is enough indication to me... Christopher Petro 94 sts 67 coupe de Ville Link to comment Share on other sites More sharing options...
chazglenn3 Posted March 28, 2006 Report Share Posted March 28, 2006 I don't think the cost of Z-rated tires is much higher than the H-rated tires. The problem is that the rubber is softer and the Z-rated tires wear out MUCH faster than the H-rated. I had a 1988 Thunderbird Turbo Coupe that had the Goodyear Gatorback tires on it from the factory...they lasted a whole 20K miles! Charles Charles Link to comment Share on other sites More sharing options...
OynxSTS Posted March 28, 2006 Report Share Posted March 28, 2006 Contrary to some of the above posts... any tire can blow out at any speed... are Z rated tires stronger? better built? carry more liability insurance? or is this all marketing? I don't know... I can say that I have pushed "unrated" tires which are good for only 85 MPH well over 130 Miles per hour and sustained that speed for several minutes and I'm still alive to type this. If you plan to regularly drive your car over 130.. buy the W or Z rated tires... if this is a "do this once to see if the car can really do it" then save your money by the lower rated tires... PS on my car H rated tires were almost 50% less expensive! Z/W rated tires are not cheap! Easin' down the highway in a new Cadillac, I had a fine fox in front, I had three more in the back ZZTOP, I'm Bad I'm Nationwide Greg Link to comment Share on other sites More sharing options...
maremrak Posted March 28, 2006 Author Report Share Posted March 28, 2006 After all, I think it's not worth the money and the risk. I would need to spend 600 bucks at least for a new set of tires, and at that speed anything can go wrong. My fastest was 125 MPH, I may push it next time to 130-135 for a few seconds, and that's close enough. Thanks all for your replies. 1960 Sedan De Ville (sold) 1970 Coupe De Ville (sold) 1987 Mazda RX-7 (sold) Link to comment Share on other sites More sharing options...
Montana95eldo Posted March 29, 2006 Report Share Posted March 29, 2006 well i put h rated tires on my 95 eldo and it still only goes 112...... imagine that!!!!! Link to comment Share on other sites More sharing options...
maremrak Posted March 29, 2006 Author Report Share Posted March 29, 2006 I know. The same is true for a Superman costume. Wearing one it doesn't make you fly. 1960 Sedan De Ville (sold) 1970 Coupe De Ville (sold) 1987 Mazda RX-7 (sold) Link to comment Share on other sites More sharing options...
gc_caddy Posted March 29, 2006 Report Share Posted March 29, 2006 I bought a set of Bridgestone FUZION Zri tires about 6 months ago. These are "W" rated tires (168 mph), so they are higher rated than "Z". They are not all-season tires, but performance summer tires. But they worked great in the rain, and OK for snow (1-2 inches). They were VERY resonably priced at about $109 Canadian each. The tread pattern is unidirectional and very nice looking. The sidewall is firm too, so there is very little wearing of the tire shoulders. The ride is smooth and quiet. I am very happy with them. Tire wear is very good. Glenn. I don't think the cost of Z-rated tires is much higher than the H-rated tires. The problem is that the rubber is softer and the Z-rated tires wear out MUCH faster than the H-rated. I had a 1988 Thunderbird Turbo Coupe that had the Goodyear Gatorback tires on it from the factory...they lasted a whole 20K miles! Charles Link to comment Share on other sites More sharing options...
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