I have read through numerous posts on larger tires on the dmax, but am more confused than ever. According to the GM bulletin, you are not supposed to change tire size on the dmax, yet others say the dealer can program a small change such as a 265http://www.dieselplace.com/forum/smileys/Ermm.gif


I would like to run my Michelin 265's, and have the correct calibration, whether it is from the dealer or an aftermarket programmer.


What gives?

The dealer CAN program for 265s. Some will do it for you, Others won't.


The dealers I have talked to said that they don't have any problem with us going to larger tires. The only thing they said is if any of the parts "Directly" related to the larger tires get worn out while under warranty, we may get the bill to replace the part.


The look of the larger tires makes it worth the risk to me.

sammy, make sure you Michelins are load range E.

Yeah my anti-locks dont work now. I installed the h2's.

"sammy, make sure you Michelins are load range E."


Yes, they are E's. I am taking them off my 6.0 gas.

Yeah my anti-locks dont work now. I installed the h2's.


My anti-locks work fine. My 35's didnt affect any of that .. (atleast not that I have found) I have tried to "lock em up" and the ABS wont let it.

as per bfgoodrich website(I know you are putting on Michelins)


a 245/75R16 All-terrain T/A Load range E has a 3042lb @65psi capacity


a 265/75R16 All-terrain T/A Load Range D has a 3042lb @65psi capacity


the wider the tire the more load it can handle.If you go bigger you don't have to keep the E load rating, granted all tire manufacturers are different.

I have Bridgestone Revos (265/70-17s; D-rated) on H2 rims. My ABS works fine - I found out the hard way. I've put 3,000 miles on 'em with no noticable problems.


I'm not worried about reprogramming to correct the speedo; since with a 3.9% difference I'm off less than 2 mph at 50 mph (or 3.9 mph at 100 mph).

I don't understand why folks run out to correct their speedometer.. Since going to the H2 wheels/tires I'll get an extra 12,800 miles of driving out of my engine warranty and 4600 miles of the bumper to bumper. If I corrected the speedo I wouldn't get any..





It's not called cheating unless you get caught.http://www.dieselplace.com/forum/smileys/HiHi.gif

i put the BFG 265's that were off my 2500HD 6.0 on my Dmax at the dealer before i picked it up, never drove it with 245's has run perfect since the get go..








FWIW yes the D tires are rated for the same load as the E 245's but they do not have any where as stiff a sidewall (E= 10ply) so they do not tow as well with a real big trailer (side to side tire "sway"). If i was pulling a real big trailer (24ft+) all the time i would go for the E's, my current trailer is only 14ft long so i run the D's with no problems

I don't understand why folks run out to correct their speedometer.. Since going to the H2 wheels/tires I'll get an extra 12,800 miles of driving out of my engine warranty and 4600 miles of the bumper to bumper. If I corrected the speedo I wouldn't get any..





It's not called cheating unless you get caught.http://www.dieselplace.com/forum/smileys/HiHi.gif








http://www.dieselplace.com/forum/smileys/Clap.gifhttp://www.dieselplace.com/forum/smileys/Clap.gifhttp://www.dieselplace.com/forum/smileys/Clap.gifhttp://www.dieselplace.com/forum/smileys/Clap.gifhttp://www.dieselplace.com/forum/smileys/Clap.gifhttp://www.dieselplace.com/forum/smileys/Approve.gif

Maybe not a big deal between going from a 245 to 265, but I have to believe that your vehicle is going to run at its optimum level when the speedo is calibrated correctly in today's ECM controlled drivetrains. But obviously people are doing it w/o significant problems!

But obviously people are doing it w/o significant problems!





23,000 + Miles with ZERO problems with 285/75's.


My truck feels like it tow's BETTER with the wider/taller tire. I usually pull a 20 ft enclosed car trailer 8 - 9,000 loaded and never had any problems with the 285's.


With the 245's the anti-locks were kicking in at the slightest sign of a hard stop, now with more meat on the pavement, they hardly kick in at all and NEVER skid so they are working well.


JMHOhttp://www.corvetteforum.cc/zeroimg/smilies/seeya.gifEdited by: HD-Nate

I have another question to add to this, because this is not something that I have read on here yet. My local Chevy dealer has a package going for swapping out the 245's and going to whatever tire size the customer wants, along with adjusting the torsion bars and reprogramming the controller. I am wanting to go to 265's, which my GMC dealer actually recommended that I do. However, when I talked to the Chevy dealership, they said that the new trucks (LLY) cannot be reporgrammed to accomodate a different tire size. I would like to have an accurate speedometer and I like all of the features of the DIC, so I would like for them to be reasonably accurate. Has anyone else been able to change tire size on an LLY and update the controller appropriately? Like I said, I had not heard about this yet so I was wanting to know.

I have another question to add to this, because this is not something that I have read on here yet. My local Chevy dealer has a package going for swapping out the 245's and going to whatever tire size the customer wants, along with adjusting the torsion bars and reprogramming the controller. I am wanting to go to 265's, which my GMC dealer actually recommended that I do. However, when I talked to the Chevy dealership, they said that the new trucks (LLY) cannot be reporgrammed to accomodate a different tire size. I would like to have an accurate speedometer and I like all of the features of the DIC, so I would like for them to be reasonably accurate. Has anyone else been able to change tire size on an LLY and update the controller appropriately? Like I said, I had not heard about this yet so I was wanting to know.





What deal are they offering?

Doesn't the 3500 SRW come with 265's from the factory? Hard to believe calibrations aren't in all computers for that size.

I have another question to add to this, because this is not something that I have read on here yet. My local Chevy dealer has a package going for swapping out the 245's and going to whatever tire size the customer wants, along with adjusting the torsion bars and reprogramming the controller. I am wanting to go to 265's, which my GMC dealer actually recommended that I do. However, when I talked to the Chevy dealership, they said that the new trucks (LLY) cannot be reporgrammed to accomodate a different tire size. I would like to have an accurate speedometer and I like all of the features of the DIC, so I would like for them to be reasonably accurate. Has anyone else been able to change tire size on an LLY and update the controller appropriately? Like I said, I had not heard about this yet so I was wanting to know.





I put 265's on mine and had them tell the computer in my truck, but it did not reset the speedo or odo. I am going to go back tommorow and see what else they can do.

Yes, the 2004 LLY 3500 SRW has the 265's. And the speedo is correct. So someone at your dealer fibbed.

My truck came with 265\70's from the dealer. I believe that if you run a 70 instead of a 75 you won't need to calibrate your speedo...........I gps'd mine and it is pretty much dead on ..........

as per bfgoodrich website(I know you are putting on Michelins)


a 245/75R16 All-terrain T/A Load range E has a 3042lb @65psi capacity


a 265/75R16 All-terrain T/A Load Range D has a 3042lb @65psi capacity


the wider the tire the more load it can handle.If you go bigger you don't have to keep the E load rating, granted all tire manufacturers are different.








That is true only in terms of load. The E range tires have a stiffer sidewall to resist lateral flex which is prominant when heavily loaded. So while the D tire can handle the weight, it is not as good in say crosswinds when heavily loaded.


So if you are planning to haul heavy loads near the limits, I'd stick with E range tires. Otherwise the load range D's are fine.Edited by: SteveCA

Well, everytime that I try to deal with the local Chevy dealership, I remind myself of why I always go elsewhere. Their "deal" for swapping the 245's to 265's was not as good as I would have thought. The package they had was for tires, mounting and balancing, and torsion bar adjustment. The cost for this was $768. By the way, this cost was for putting on Firestone Steeltex tires. The same ones that the local tire shop has for $99. They did call me back and let me know that one of their techs said he can reprogram the controller to correct the speedometer and DIC for the bigger tires, but that GM mandated a $100 fee for this, as the dealer has to call GM and give them the VIN, then GM gives the tech the code for the controller. All in all, this brings the bill to $868. For that price, I'll keep the 245's on for a while until they get good and worn. However, going to a 265/70 does not sound like a bad deal. These would only put the stock speedometer slow by 0.3%. In the meantime, there are some other things that I would like to add to the truck! Edited by: Boilermaker

I took delivery of my 03 CC/Dmax/Alli one year ago. Dealer agreed to swap the mini-meats for 265/75 BFG's. So my truck was delivered with the bigger tires. Right now I'm at 24K miles with zero tire-size-related problems. My speedo is off, at 75 indicated I'm doing 78, but once I made the mental adjustment ("CAUTION: SPEEDS ARE FASTER THAN WHAT YOU SEE ON GAUGE"), I pretty much forgot about it. My ABS works fine and the trans and engine are fine. About my only beef is my mileage, 16.5 city and 19hwy, but I drive 80 on the highway, if I could ever slow down I could probably get closer to the 20-21 that others get.


The most I have towed is 7000 lbs, a spit in the wind for the DMax. If you're going to tow a 14K trailer I'm sure you would notice the difference in the bigger tires.


I have a friend though who ordered a 2500HD/BB/Alli and his dealer absolutely refused to change the tire size - NO WARRANTY - blah, blah, blah. I told him that he might want to look a new dealer. http://www.dieselplace.com/forum/smileys/Big Smile.gif

The dealer also told me they would give me a good deal if I wanted biiger tires through them, but they had to be an oem brand. I told them to price out some 285 Revos and they told me $770! Thanks, what a dealhttp://www.dieselplace.com/forum/smileys/Ermm.gif I went to Discount tire and got Nitto for $600 total.

They did call me back and let me know that one of their techs said he can reprogram the controller to correct the speedometer and DIC for the bigger tires, but that GM mandated a $100 fee for this, as the dealer has to call GM and give them the VIN, then GM gives the tech the code for the controller.


This sounds like a bunch of BS if I have ever heard it!!! For that $100.00 fee, you get to know that GM will void your warrenty any time you have a Driveline type failure, because it will be in their system that you have installed larger than stock tires. I can see if they would like to charge you for recalibrating your ECM, but $100.00 sounds way too high for that service. I say just deal with the 3 MPH your speedo will be off and put that money towards a great fuel filter system!


JMHO


CR

My Service Manager called me back after checking with "GM TechLine". He had given them my VIN and was then told that he could not reprogram my truck for 265's or anything else. TechLine wouldn't give him the code to do it. He was willing but not allowed! We're on good terms and he's a straight-up kind of guy, so I believe him.


Can't understand how some dealers can and some can't. GMC vs. Chevy?

Here is why some dealers can and some cant... You Can Not reprogram the speedometer for anything other than the 245's with the Allison. What is happening is the dealer/tech that does reprogram thinks he is or says he is callibrating the spreedo, but he is only callibrating the ABS thats the only thing you can callibrate to 265. Thats why some say they have had it done and others say the cant do it ..they are recallibrating, but only the ABS.





If you want a correct speedo get an aftermarket programmer. Edited by: tanner

I also seem to recall reading that with the Alli you can only correct the speedo reading - the shift points and ABS are basically fixed within the PCM and you cannot programitically "fix" them due to different tire sizes.

<H1>Info - Inspection of Tire and Wheel Size Prior to Diagnosis for Transmission Shifts, Poor Performance, Speedometer, Cruise Control Concerns #01-03-10-010B - (10/14/2002)</H1>Inspection of Tire and Wheel Size Prior to Diagnosis of Transmission Shifts, Poor Performance, Speedometer, Cruise Control Concerns


2001-2003 Chevrolet Silverado Pickup Models


2001-2003 GMC Sierra Pickup Models


with Duramax™ Diesel Engine and Allison® Transmission


This bulletin is being revised to add the 2003 model year. Please discard Corporate Bulletin Number 01-03-10-010A (Section 03 - Suspension).


Proper diagnosis of engine, transmission, speedometer, and cruise control concerns must begin with an inspection of tire/wheel size.
<UL =BULLET>
<LI>The 2500 series trucks have LT245/75R16E tires as standard equipment.
<LI>The 3500 series trucks have LT215/85R16D tires as standard equipment. </LI>[/list]


A truck that has different tires and wheels will have Engine power/performance concerns, Transmission shift concerns, Speedometer registered speed concerns, and Cruise Control concerns.


Before any diagnosis is performed for these types of concerns, inspect the tires/wheels for the proper tire and wheel combinations.


If a truck is found to have other than the above listed tire sizes, no further diagnosis should be undertaken until the original size tires and wheels are reinstalled on the truck.


The Engine Control Unit (ECM) and Transmission Control Module (TCM) use (RPM) and (VSS) inputs as operational parameters for engine torque, transmission shifting, cruise control operation and speedometer indicated vehicle speed.


Calibrations for different tire/wheel combinations are not available.


Therefore changing of tire and/or wheel size should not be undertaken by dealerships or truck owners.<A name=ss1-1137502><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1137502&amp;psdid=297&amp;evc=sm#ss1-1137502" target="_blank">
<H5>Warranty Information</A></H5>


Reinstalling the proper wheels and tires on the vehicle, prior to performing any type of diagnosis of the truck, would be considered truck owner responsibility and not a warranty repair.



<TABLE width="100%">
<T>
<TR>
<TD align=left width=778>GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
</TD>
<TD align=middle width=42>http://service.gm.com/engif/000/999/999/999999994.gif </TD>
<TD align=middle width=167>WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
</TD></TR></T></TABLE>
© Copyright General Motors Corporation. All Rights Reserved.

Thanks, Tanner,


That clarifies it for me!

That is true only in terms of load. The E range tires have a stiffer sidewall to resist lateral flex which is prominant when heavily loaded. So while the D tire can handle the weight, it is not as good in say crosswinds when heavily loaded.


So if you are planning to haul heavy loads near the limits, I'd stick with E range tires. Otherwise the load range D's are fine.





How about 13,400 pound GVW on D-rated BF Goodrich tires?http://www.dieselplace.com/forum/uploads/Picture_003_modded.jpg

This is an interesting thread for me. I just rolled the first 2000 miles on my 2500 hd with the LBY D/M and Allison. When I was haggling with my dealer over the deal, I said I wouldn't consider buying the truck unless he put some decent tires on it. I didn't specify the size, Just the fact that I wanted some all terrain tread, and not the street tread that was on it. He said he would take care of it for me and I aggreed to buy the truck. When I went to take delivery of my new Chevy, The tech drove it around from the shop in back and to my delight he had installed some BF Goodrich All Terrains 285's on it. I have not given it a second thought untill I read this thread. The only thing about the bigger tires that I have noticed is they scrub the slightest bit when backing up with the wheels turned to the left as far as they will go.The truck looks so much better with the bigger tires than those little 245's.I sure wouldn't think I would have any warranty issues with my dealer after he is the one that installed the tires. The truck has been great so far.

How about 13,400 pound GVW on D-rated BF Goodrich tires?http://www.dieselplace.com/forum/uploads/Picture_003_modded.jpg


A candid of you unloading your truck. How do you reach the pedals!!!!http://www.dieselplace.com/forum/smileys/Big Smile.gifhttp://www.dieselplace.com/forum/smileys/Big Smile.gifhttp://www.dieselplace.com/forum/smileys/Big Smile.gifhttp://www.dieselplace.com/forum/smileys/Big Smile.gif


Zero problems for me with H2's. ABS works.

Looks like you past the weight test on those. Nice to know I have a little extra when I set my 5th wheel down. Later! Frank

A candid of you unloading your truck. How do you reach the pedals!!!!http://www.dieselplace.com/forum/smileys/Big Smile.gifhttp://www.dieselplace.com/forum/smileys/Big Smile.gifhttp://www.dieselplace.com/forum/smileys/Big Smile.gifhttp://www.dieselplace.com/forum/smileys/Big Smile.gif


Zero problems for me with H2's. ABS works.





I was resting, I had unloaded one load, and besides child labor is cheap when you have your own.http://www.dieselplace.com/forum/smileys/Big Smile.gif

here's how to find out about Axle Ratio/Tire Size
http://www.4crawler.com/4x4/4LoCalc.shtml#SpeedoConverter

Food for thought...straight from Allison's website.

"Q. Speedometer / Tires - Can my speedo be re-calibrated after I install larger tires?
A. Speedometer calibrations are only available for tire sizes offered as original equipment. Please consult your GM dealer about correcting speedometer output when tire size is changed.
NOTE: Changing the calibration to correct speedometer readout does not change the TCM calibration, and thus it does not compensate for the adverse impact on transmission operation.

Q. Speedometer / Tires - What effects will big tires have on transmission operation?
A. The TCM calibration is based on factory tire size and rear axle ratio. Changing either of these parameters will have some adverse impact on transmission operation, including features like grade braking and shift stabilization. For instance, we have noted that when P285 tires are installed that the transmission generally does not shift to 5th range when towing heavy loads."

Has anyone running 285s experienced problems w/ the Allison not shifting into 5th under heavy loads?

1. I almost always lock out 5th when towing heavy anyway. But yes, it will go to 5th with the H2s I have.





2. If your ABS stops working, I would put the original tires back on and see if it works. If not, take it to the dealer. My ABS works fine with the H2s.