Need a real answer about tires

[hogger999]

I'll try to keep this short. I know someone already posted somthing close to this

I went to a tire store today to check on some 265 BFG's. The guy that owns the store told me I could not go any larger than the stock 245's. He said he has had 2 trucks in there and it caused tranny trouble. One was a 3500 dually that wouldn't shift into 4th (he didn't know what trannies they had)

 

So I call my selling Chevy dealer who says (keep in mind we all know guys who have done this) you CANNOT run bigger tires. since 245's were the only tire offered on that model he doesn't even HAVE a program to re-calibrate the speedo.

 

Now I call a friend who owns a garage who I know has 265's on his K2500 HD and he tells me he beleives the first two guys have been smoking crack and refers me to the GMC dealer across town.

 

The GMC service tech who is much more friendly tells me "It CAN be done for a fee of $63. But that GM will only allow me to go up one tire size (fine with me) and that he can only change the speed sensor once. So if I go to 265's I can never run a different size. This is the part where I'm ready to shoot my self in the face. He then tells me that he cant work on my new truck cause its a Chevy and sends me to not only my selling dealer but the same guy I just off the phone with who I kid you not his real name is Opie.  

 

So if you were able to follow this, not only do I have a tire problem but I'm not very optimistic about the relationship with my dealers service department. I've got some doozie stories on them from past experience.

[hogger999]

by the way how did I underline new truck?

[DigUout]

Tell the guy at the tire store to put the 265's on and that you'll take your chances on any "tranny trouble" (what a crock) and don't sweat the dealer because with 265's you won't need to correct your speedo.  If the Tire Nazi won't put the 265's on, tell him you'll just spend your money down the road with someone else.

 They're yanking your hootus hogger.  I'd take your business elsewhere -

[hogger999]

I have no problem shopping around for tires. I just don't want to get into some big drawn out mess with GM should something happen later.

[bassdog]

hogger,

 

I'm running 265's without a problem. This is the tire recommended for the truck and came with this size from the factory. I know it's a different year, but GM has been putting these size tires on these trucks since 88. Some years / models are different, don't know why...

 

Here's a trick for ya, pick out your tires, have them installed, but KEEP the old 245's. Try and pick up a cheap set of rims and install your 245's on those. When your truck needs servicing at the dealer, put the old tires back on    . Dealer can't say squat  ;)

 

As far as speed-o, take a drive behind a friend and have them drive at certain speeds that you want to know. Either keep a mental note, or record the differences if any at all. Keep your $63.

[Zane]

A power programer would let you change the tire size all you want!  

[Shaners]

265's versus 245's will change your speedo about 3-4 mph at highway speeds.  Your speedo will register less mph than what you are traveling...

 

I actually have gone to tire stores that will refuse to put on a tire that is larger than what is listed inside the door jamb.  I know PepBoys around here has that policy...  I don't know if it is for liabillity reasons or why they won't upgrade your tire size, but they won't!!!

[hogger999]

Thanks guys

I found a dealer that is more than happy to work with me which is great since I'm going to be moving within 8 miles of them the closest dealer I have now is 25 miles away.

 

They said with 265's they can change the speedo and the anti lock brakes to compinsate and it wont bother them  warranty wise. They did warn me that it may effect shift points.

 

Thank you Heaton Chevrolet

[CMNTMXR81]

Firstly, the shop owner who told you about the truck with tranny problems, I wouldn't frequent him anymore.  The guy is obviously about as sharp as a rock.  I've never heard of going up two sizes in tires causing a transmission to go south.  Especially a heavier duty unit such as a 4L80E or an Allison.  Something else "did in" the two transmissions in the two trucks in his shop.

 

The Reason your Chevy dealer can't program the PCM for the tire size is exactly for the reason he stated.  They can only recalibrate for sizes available on that particular vehicle.  As such, for Chevy, the LT245/75-16's were the largest optional tire available for an HD.  The GMC dealer may be able to do it because GMC's may have had another optional tire size or he has a friend at the Tech Center in Warren, Mi.  This leads me to my next point, if the service department bends their ear enough, the Tech Center will custom write a revision with that tire size that the dealership can then download through GM's internal system.  While this may not seem like that big of a deal, what it does, is that it causes GM to start asking questions "why?" do you want this custom revision.  This will then get noted with your VIN# and when you go in for warranty service in the future, could come back to haunt you.

 

As to HPP, they do allow you to adjust, but they too only generally offer two or three other popular sizes to chose from.  So you can't just buy an HPPIII, plug it into your data port and custom PROM the PCM with the size you want.

 

Here is the actual difference between the stock 245's and the 265's you want;

 

LT245's

sidewall: 7.23425196803937"

radius: 15.23425196803937"

diameter: 30.468503937007874"

circum: 95.71962813437563"

RPM's/mile: 661.933202572123

 

LT265's

sidewall: 7.8248031496063"

radius: 15.8248031496063"

diameter: 31.6496062992126"

circum: 99.43017063861554"

RPM's/mile: 637.2311300790726

 

As such, your speedo would be 3.876469828143167% too slow.

[hogger999]

So then what did you do when you upgraded you tires

[hogger999]

...And by digging into some previous posts maybe the guy with the tranny trouble had a Diesel and the larger tires just shut it down? (throwing off the shift pattern and causing and error code.)

[CMNTMXR81]

So then what did you do when you upgraded you tires

Nothing.    My speedo is 7.7% too slow with the 285's

 

And those tires didn't kill a transmission.  These are HD transmissions capable of pulling 16,000lbs + of weight.  A tire two to four additional sizes up isn't going to hurt it.

[hogger999]

:yingyang: suddenly I feel a burden has been lifted from my shoulders

[CMNTMXR81]

I'd say the effect of the bigger tires on the transmission is no more different than carrying an extra hundred pounds or so around in your bed.  If that extra hundred pounds is gonna kill your trans, then I think I had better trade my truck in.  

 

Have no fear, your tranny will be fine.