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H Rated Tires and Speed Limiter Questions


Texas Jim

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Howdy all,

'06 DTS Performance Sedan speed limiter is set at 123 mph. On my other '06 it is at 130 mph. Can anyone explain why they are different? Both cars have 245x50x18 "H" rated tires. It is kinda puzzling to me.

Should I take it to the dealer and try to get them to reset it or could that cause problems with the dealer saying I am abusing the car. Only did it once just to see where it shut off. Usually don't go over 85 or so.

One other question.

The mileage is not real good either. You have to drive with a very light foot to get even close to 20mpg on the highway. The other one was not too much better but I could get 21 to 21.5 from it if I was careful. Thats on the highway at 75 to 85 mph.

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At the threads below you have over and over cited differences between this car and your previous car. Reviewing the threads below, I can see why you feel this way... It's as if they are two different cars.. Personally I have no explanation for this... but it sure is weird.. I hope you can figure this one out... Are you sure that they had the same engines? The Y vs. 9 engine would account for differences...

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http://caddyinfo.ipbhost.com/index.php?sho...c=12336&hl=

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Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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At the threads below you have over and over cited differences between this car and your previous car. Reviewing the threads below, I can see why you feel this way... It's as if they are two different cars.. Personally I have no explanation for this... but it sure is weird.. I hope you can figure this one out... Are you sure that they had the same engines? The Y vs. 9 engine would account for differences...

http://caddyinfo.ipbhost.com/index.php?sho...c=12176&hl=

http://caddyinfo.ipbhost.com/index.php?sho...c=12336&hl=

http://caddyinfo.ipbhost.com/index.php?sho...c=12733&hl= ://http://caddyinfo.ipbhost.com/index....quot;] [/color]

Thanks for the quick reply. I will drop the subject. I didn't realize I had posted so much complaining about it.

You are absolutely right in that they feel like 2 different cars. Both have the 9 engine and the dealer printed the build sheets for me for both cars. All the suspension, engine and wheel / tire options are exactly the same RPO's. It is puzzling about the big difference in the tactile feel of the 2 cars that on paper are identical.

I will not post any more threads about it. Unless I get some answers from GM that may help someone else if they ever have a similar problem.

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You just paid a lot of money for that car, you can moan all you want! Especially if you want the speed limiter to what its supposed to be.

There's nothing in the warranty that says you can't drive that thing as hard as you want AS LONG as you follow the "heavy use" or "severe conditions" maintenance schedule and have receipts/proof that you have done the required service.

A good tool I use to keep track of all my service is http://www.mygmlink.com

What is sounds like is your simply experience the far ends of the production variation, remember their pumping a lot of units out everday (the Deville and now DTS line is the top selling fullsize luxury car), their not limited production sedans.

The Green's Machines

1998 Deville - high mileage, keeps on going, custom cat-back exhaust

2003 Seville - stock low mileage goodness!

2004 Grand Prix GTP CompG - Smaller supercharger pulley, Ported Exhaust Manifolds, Dyno tune, etc

1998 Firebird Formula - 408 LQ9 Stroker motor swap and all sorts of go fast stuff

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At the threads below you have over and over cited differences between this car and your previous car. Reviewing the threads below, I can see why you feel this way... It's as if they are two different cars.. Personally I have no explanation for this... but it sure is weird.. I hope you can figure this one out... Are you sure that they had the same engines? The Y vs. 9 engine would account for differences...

http://caddyinfo.ipbhost.com/index.php?sho...c=12176&hl=

http://caddyinfo.ipbhost.com/index.php?sho...c=12336&hl=

http://caddyinfo.ipbhost.com/index.php?sho...c=12733&hl= ://http://caddyinfo.ipbhost.com/index....quot;] [/color]://http://caddyinfo.ipbhost.com/index....quot;] [/color]://http://caddyinfo.ipbhost.com/index....quot;] [/color]://http://caddyinfo.ipbhost.com/index....quot;] [/color]://http://caddyinfo.ipbhost.com/index....quot;] [/color]://http://caddyinfo.ipbhost.com/index....quot;] [/color]://http://caddyinfo.ipbhost.com/index....quot;] [/color]

Thanks for the quick reply. I will drop the subject. I didn't realize I had posted so much complaining about it.

You are absolutely right in that they feel like 2 different cars. Both have the 9 engine and the dealer printed the build sheets for me for both cars. All the suspension, engine and wheel / tire options are exactly the same RPO's. It is puzzling about the big difference in the tactile feel of the 2 cars that on paper are identical.

I will not post any more threads about it. Unless I get some answers from GM that may help someone else if they ever have a similar problem.

OH NO!! I don't think my post about implied that you were complaining or moaning about it at all, I am sorry if you got that impression....Maybe when I said over and over it appeared too hard, I am sorry I didn't mean to imply that you were complaining, I meant to imply that 'something is bugging you" :lol:! But, I totally understand your concern, it would bother me also..... But I myself am at a loss to figure out why. I am considering contacting someone very knowledgable about the Northstar platform to see why this might be happening.... Mike

Keep posting about it I am interested in WHY these differences are happening!

I was just pointing out that you have been finding differences since you bought your car.... and its very odd.... and I also wanted to consolidate the perceived differences you are finding....

I am VERY interested in this, keep posting and lets find out why, I think we are all interested!

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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You just paid a lot of money for that car, you can moan all you want! Especially if you want the speed limiter to what its supposed to be.

There's nothing in the warranty that says you can't drive that thing as hard as you want AS LONG as you follow the "heavy use" or "severe conditions" maintenance schedule and have receipts/proof that you have done the required service.

A good tool I use to keep track of all my service is http://www.mygmlink.com

What is sounds like is your simply experience the far ends of the production variation, remember their pumping a lot of units out everday (the Deville and now DTS line is the top selling fullsize luxury car), their not limited production sedans.

Thanks for the ideas. I also use mygmlink. I like it. Never really thought about the variation in production runs. That could be the answer and there is nothing at all that I can do about it. Just the luck of the draw that the first one happened to have everything biased towards tight, firm, controlled ride and this one more towards smooth and soft.

Years ago I worked for a while as a Linclon/Mercury salesman. When we got in a trailer of new cars, they were unloaded at the main dealership and then we drove them to a storage lot a couple of blocks away. Narrow streets prevented the 18 wheeler from unloading at the storage lot.

Taking 10 cars as an example ... 8 would be just about exactly identical in ride, drive and performance. One would be noticeably better one way or the other and one would be a dog. Probably the same variations I am experiencing.

Mine is not a dog by any stretch of the imagination, that is not what I meant. Everything on the car always works flawlessy It is just a different ride and handling from the first one but I am quickly getting used to it. :)

The power and performance is wonderful. I love the way it runs. It is a fantastic highway car. Will cruise at any speed you want to run and it NEVER seems to be in a strain. It just wants to RUN. :) Add the quite smooth comfortable ride and I reckon I should quit griping and just enjoy the Cadillac experience. After all, thats what I bought it for. :)

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Could the speedometer in the new DTS be reading low? If the speedometer is off, then perhaps 123 mph is indicated when the car is going 130 mph? I imagine the speed limiter is established for a set rpm in 4th, not for an indicated speed. Top speed tests are very hard to go by though, as a headwind or tail wind or other environmental things can effect the test.

Bruce

2023 Cadillac CT4-V Blackwing

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Could the speedometer in the new DTS be reading low? If the speedometer is off, then perhaps 123 mph is indicated when the car is going 130 mph? I imagine the speed limiter is established for a set rpm in 4th, not for an indicated speed. Top speed tests are very hard to go by though, as a headwind or tail wind or other environmental things can effect the test.

Don't think it is the speedometer reading affecting it. It comes up on the DIC as "This Vehicle Is Speed Limited to 123 mph" and if you look at the speedomater at that time, it is indicating 123 and the digital readout in the DIC is at 123 also. Ditto with the first one and the 130 mph message.

Not totally certain, but I think that the last time I saw the message, it was still in 3rd gear, just before shifting to 4th. Will have to check to see if there is any difference if it is in 3rd or 4th. I wouldn't think so, as it looks to me that that should be hard coded in the PCM but I could be wrong.

A couple that I rented last year before I bought mine, would say "This Vehicle Is Speed Limited to 112mph."

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Maybe this is a PCM flash of some sort since this is the same vehicle, I would bring this into the dealer and see that is going on, maybe there is a PCM update

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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OH NO!! I don't think my post about implied that you were complaining or moaning about it at all, I am sorry if you got that impression....Maybe when I said over and over it appeared too hard, I am sorry I didn't mean to imply that you were complaining, I meant to imply that 'something is bugging you" :lol: ! But, I totally understand your concern, it would bother me also..... But I myself am at a loss to figure out why. I am considering contacting someone very knowledgable about the Northstar platform to see why this might be happening.... Mike

Keep posting about it I am interested in WHY these differences are happening!

I was just pointing out that you have been finding differences since you bought your car.... and its very odd.... and I also wanted to consolidate the perceived differences you are finding....

I am VERY interested in this, keep posting and lets find out why, I think we are all interested!

I didn't take it that way at all. No need to apoligize. I just realized that I was kinda beating a dead horse, so to speak.

Yes it does kinda bug me that there is that much difference in the 2 supposedly identical cars. :) If it was a cheap Kia or a Hyundai I could understand it a little better, but this is almost $60,000.00 each of Cadillac automobile, and it is a little irritating to me that there is that much variation and I can find no good explanation for it. EGreen may have hit the nail on the head about the production variations and it all came together to create this kinda unique situiation.

If I find out anything more I will let you know.

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The message has to have an explanation. I have searched and will continue to search till I find out why. Maybe someone understands the difference between the two cars.

Look inside the door and see what the speed rating is on the tires, is there ANY way to see what the speed rating was on your prior car? Or to have the dealer call up the VIN and give you details, maybe this one is a H rated and the other one a W rating tire?

See this thread to the end:

http://caddyinfo.ipbhost.com/index.php?showtopic=12943

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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The message has to have an explanation. I have searched and will continue to search till I find out why. Maybe someone understands the difference between the two cars.

Look inside the door and see what the speed rating is on the tires, is there ANY way to see what the speed rating was on your prior car? Or to have the dealer call up the VIN and give you details, maybe this one is a H rated and the other one a W rating tire?

See this thread to the end:

http://caddyinfo.ipbhost.com/index.php?showtopic=12943

I have the build sheets that the dealer printed for me for BOTH cars.

VIN on current car 1G6KD57986U******

VIN on previous car 1G6KD57906U******

I am totally certain both had the same tires. Same make, model and size. Bridgestone Turenza EL400, 245x50x18 "H" rated. The other one would run faster than this one. It would run 130 mph. This one is the one that will only go 123 mph, which in itself, is not that big a deal. Only did it a couple of times to check it. Obviously can't drive that way very often. :) Now if we had StefanK's autobahn .........

To clarify a bit ........ the message I am talking about is in the display in the dash just under the speedometer. I THINK it is called the Driver Information Center, Where it normally displays your MGP, tire pressure, battery voltage and things like that. When you hit 123, it chimes real loud several times and then displays "This Vehicle Speed Limited to 123 MPH"

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I know the message your talking about, and it most likely doesn't leave third, I know that mine when at the 112 barrier isn't really that close to the top of third.

If indeed they have the same options and production codes I'm not sure what to tell ya. Maybe it borrowed parts from the discontinued Pontiac Bonneville :P

It could also be the perceived "smoother" ride is actually they way it was designed. Not sure how hard you took corners in your previous vehicle but put this one threw some turns and see how well it handles, if it does indeed have the magnetic ride it will firm up for sure, especially when you move the shifter over in the shift gate to "manumatic" mode or clutchless manual. Thats when it should come to life as a performance land yacht vehicle :)

When you do decide to throw it around a bit make sure your up to operating temp (ambient temperature is one of the biggest influences on Fuel Economy, humidity can effect it too). Make sure the tires are inflated to your liking, then have at it! Take a trip to see Bruce and test it out with his AP-22 :)

The Green's Machines

1998 Deville - high mileage, keeps on going, custom cat-back exhaust

2003 Seville - stock low mileage goodness!

2004 Grand Prix GTP CompG - Smaller supercharger pulley, Ported Exhaust Manifolds, Dyno tune, etc

1998 Firebird Formula - 408 LQ9 Stroker motor swap and all sorts of go fast stuff

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125mph seems an odd number to me; I would expect 130mph. I agree that if the DIC is saying hey, speed limiter here then it is not a speedo accuracy problem.

Bruce

2023 Cadillac CT4-V Blackwing

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125mph seems an odd number to me; I would expect 130mph. I agree that if the DIC is saying hey, speed limiter here then it is not a speedo accuracy problem.

Howdy Bruce,

It is even an odder number than that. It is 123 mph not 125 mph. I have never seen or heard of one do that number before. 123 mph. My understanding, which admittadly, could be wrong, is it should be at 130.

I will go to the dealer next week and ASK them what it is supposed to be and see if they can explain it. :)

As I said earlier, will not normally be driving anywhere near that speed, but it kinda irritates me about the odd number..

As EGreen said, would be interesting to have it hooked up to an AP22. Will check online and see what one cost. Might be an interesting tool to have. I am on the west side of Ft. Worth ..... right off I-20 west. Lot of wide open road there. :):):) Would love to check 0 to 30 and 0 to 60 times on it. It FEELS quick, but that is all subjective. On smooth asphalt it will be almost spinning the tires all the way thru 1st and will chirp them when it shifts to 2nd. You have to really stay on top of the steering as it will go first one way then the other from torque steer. There are a couple of econo box racers that are wondering what happened to them from the old man in the big ole Cadillac. :):) That was fun.

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I know the message your talking about, and it most likely doesn't leave third, I know that mine when at the 112 barrier isn't really that close to the top of third.

If indeed they have the same options and production codes I'm not sure what to tell ya. Maybe it borrowed parts from the discontinued Pontiac Bonneville :P

It could also be the perceived "smoother" ride is actually they way it was designed. Not sure how hard you took corners in your previous vehicle but put this one threw some turns and see how well it handles, if it does indeed have the magnetic ride it will firm up for sure, especially when you move the shifter over in the shift gate to "manumatic" mode or clutchless manual. Thats when it should come to life as a performance land yacht vehicle :)

When you do decide to throw it around a bit make sure your up to operating temp (ambient temperature is one of the biggest influences on Fuel Economy, humidity can effect it too). Make sure the tires are inflated to your liking, then have at it! Take a trip to see Bruce and test it out with his AP-22 :)

Howdy,

Thanks for all your ideas and suggestions.

I am not aware of a manumatic mode on the DTS. The CTS has it, but the DTS does not. Or if it does I haven't found it yet. :)

As for cornering, went to my work partners house the other day, He lives way out in the country on a little 2 lane road with a BUNCH of very tight curves and a few 90 degree corners. Threw it around pretty good. It holds the road very well and will spin the inside tire coming off the curves and corners hard. It is very competant and drives very well, but not like the other one. This one has just a little more body roll and more dive on hard braking and just don't seem to be "ON RAILS" like the other one.

Also got into a little cornering and handling tussle with a new Cobalt SS on what we call a traffic circle. That is where several streets come together and the center road that connects them is round and about 100 yards in diameter. I will be the first to admit that it's very possible that he did not know how to drive it real well. But before I passed him his outside tires were smoking just a little bit so I think he was getting on it pretty hard. Darling wife was with me that time. :( It was a real quite ride the rest of the way home.

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Oh, we should try to get together one weekend then. You will want a fairly remote area that is as flat as possible for testing.

Bruce

2023 Cadillac CT4-V Blackwing

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Oh, we should try to get together one weekend then. You will want a fairly remote area that is as flat as possible for testing.

Bruce,

ANY time that is convenient for YOU. I will MAKE the time to meet and I will drive to your side of town. Is there a decent area anywhere within a reasonable distance from you in Plano?

You name the time and place. I will be there. :)

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Side note: the Impala is limited to 123 mph also. http://www.code3vehicles.com/id15.htm

Apparently this is a popular top speed based on google searches; it equates to 198 km/hr, but not sure why that is significant.

Bruce

2023 Cadillac CT4-V Blackwing

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125mph seems an odd number to me; I would expect 130mph. I agree that if the DIC is saying hey, speed limiter here then it is not a speedo accuracy problem.

It is even an odder number than that. It is 123 mph not 125 mph. I have never seen or heard of one do that number before. 123 mph. My understanding, which admittadly, could be wrong, is it should be at 130.

Yes it's seemingly odd, but when I had my '95 Eldorado I noted many OBDI owners spoke of a 112mph limiter while others spoke of a 115mph limiter. Maybe this is "old hat."

On smooth asphalt it will be almost spinning the tires all the way thru 1st and will chirp them when it shifts to 2nd. You have to really stay on top of the steering as it will go first one way then the other from torque steer. There are a couple of econo box racers that are wondering what happened to them from the old man in the big ole Cadillac. :):) That was fun.

Yeah, my '95 did that also. It was a real head turner (especially mine!). :) I miss that. The '95 was a whore in some respects; the current one is a tad (but not much) slower and has more genteel transmission behavior. Less torque steer as well.

Don't give up your quest. Many of us, I think, would like to know the answer.

Personally, I'm not a big fan of the "production tolerances" idea. You describe behavior differentials that seem beyond that.

Regards,

Warren

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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Yes it's seemingly odd, but when I had my '95 Eldorado I noted many OBDI owners spoke of a 112mph limiter while others spoke of a 115mph limiter. Maybe this is "old hat."

Personally, I'm not a big fan of the "production tolerances" idea. You describe behavior differentials that seem beyond that.

Regards,

Warren

Warren,

My 2003 Taurus DOHC is limited to 112. My 2006 Chevy van is 100 more or less. It does not have a digital speedometer.

I agree about the differences being outside of the "production tolerances" idea. I am going to go take a couple of other Performance Sedans for some good long drives. Not just around the block. See what they drive like. I am beginning to think that the first one was some kind of abberation and this one is "normal." This conclusion reached based on other peoples input not empirical evidence. WIll know more next week after driving some other cars.

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I'm left to wonder if Cadillac ever sourced it suspension components, especially springs, from more than one supplier.

I'm inclined to doubt it, but I wonder: is it possible?

Any chance your two very different vehicles had suspension components derived from different suppliers?

Regards,

Warren

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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I'm left to wonder if Cadillac ever sourced it suspension components, especially springs, from more than one supplier.

I'm inclined to doubt it, but I wonder: is it possible?

Any chance your two very different vehicles had suspension components derived from different suppliers?

Regards,

Warren

Never thought of THAT. It is possible I reckon, but I have no clue how you would ever find out or what you could do about it if true. Still, something to think about. :) Thanks.

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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. Could have done more but the remote 2 lane road got real narrow. Funny, the faster I went the narrower the road became, couldn't look down at the speedo beyond that, so no point in pushing further. It was in Utah, where the Road Runner cartoons were filmed .... honest!

:ph34r:

- sorry for repeating myself, I have written of this episode in the past .... :rolleyes:

post-168-1173675224.jpg

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