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H Rated Tires and Speed Limiter Questions


Texas Jim

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It is interesting that the DIC gives you that very specific mph number (123) instead of 130. I also figured it was just part of production variations, but that's obviously a difference in the software, for it to be looking for 123 mph vs. 130 mph.

It does seem that it's some sort of PCM software "adjustment" that occured between the production of your two models.

Jason(2001 STS, White Diamond)

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but when I had my '95 Eldorado I noted many OBDI owners spoke of a 112mph limiter while others spoke of a 115mph limiter

hmmm, I have seen 125 in my '95 etc. No DIC message, no limiter intervention.

Base Eldo's are limited to 112 mph. 93-95 ETC's have no limiter as they are Z rated.

My base 95 Eldo has no limiter since I installed a chip. (Fastchip)

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Regarding Texas Jim, H rated tires are 130 mph. Since the same year & model car hit the limiter at 130 mph, this one should be the same. I think a PCM reflash is in order. As a side note, my Eldo came with S rated (112) tires. Before I replaced the chip it hit the limiter at exactly 112 mph.

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but when I had my '95 Eldorado I noted many OBDI owners spoke of a 112mph limiter while others spoke of a 115mph limiter

hmmm, I have seen 125 in my '95 etc. No DIC message, no limiter intervention.

Base Eldo's are limited to 112 mph. 93-95 ETC's have no limiter as they are Z rated.

My base 95 Eldo has no limiter since I installed a chip. (Fastchip)

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Regarding Texas Jim, H rated tires are 130 mph. Since the same year & model car hit the limiter at 130 mph, this one should be the same. I think a PCM reflash is in order. As a side note, my Eldo came with S rated (112) tires. Before I replaced the chip it hit the limiter at exactly 112 mph.

The other car would hit it at EXACTLY 130 and give the SPEED LIMITED message on the dic. My Taurus hits it at exactly 112. A couple of Cadillacs I rented last year hit it at exactly 112. This one hits at 123. Very odd. I will talk to the dealer about a reflash.

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Regarding Texas Jim, H rated tires are 130 mph. Since the same year & model car hit the limiter at 130 mph, this one should be the same. I think a PCM reflash is in order. As a side note, my Eldo came with S rated (112) tires. Before I replaced the chip it hit the limiter at exactly 112 mph.

Went by the Cadillac dealership today and talked to the Service Manager about reflashing the PCM. He said he could do that but he didn't think it would make any difference. He is wondering if the car is actually going faster than the speedometer says. The speed limiter works directly off of the transmission not the speedometer.

He is going to hook up some type of computer that interfaces with the car computer and leave it on for the weekend. There will be a button I push when the speed limiter kicks in and the computer records all the vital statistics from all the car computers. Then he can analyze everything it records and we will proceed from there. :):)

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After you said that the message on the DIC actually says that the speed is limited to 123mph, I suspect it is operating as designed. Why they changed this from 130mph or when they changed it (apparently mid-year 2006) are not obvious. But to me it changed it from an error to a design setting. I think you or the dealer need to call the Cadillac help line and ask them what it is supposed to be set to. My impression from seeing that some other cars are limited to 123mph is that this is GM's version of 130mph for whatever reason this year.

My CTS may have the same limit; the 2004 I know went to 130mph but I have not tried with the 2005. Perhaps the 2006 models have a different limit.

Bruce

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Maybe a switch to the 124MPH U-Rated tires? :P

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After you said that the message on the DIC actually says that the speed is limited to 123mph, I suspect it is operating as designed. Why they changed this from 130mph or when they changed it (apparently mid-year 2006) are not obvious. But to me it changed it from an error to a design setting. I think you or the dealer need to call the Cadillac help line and ask them what it is supposed to be set to. My impression from seeing that some other cars are limited to 123mph is that this is GM's version of 130mph for whatever reason this year.

My CTS may have the same limit; the 2004 I know went to 130mph but I have not tried with the 2005. Perhaps the 2006 models have a different limit.

I suspect you are right. The 1st DTS was built October of '05. This one was built June of '06. Anything could have changed in that time frame.

I may try the computer thing with the service manager and if no answers from that, be satisfied with what I have and just forget about the whole thing. It isn't worth the hassle and aggravation. :)

After all, I "DO" have a very nice Cadillac. It looks good, drives good, runs good Etc ... Etc. That should be enough. :)

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