2011 Silverado 1500 5.3 33" tires speedometer is off st

[BamaBoy]

I have 285/65/R18 nitto trail grapplers and when I enter the size by sidewall or height my speedometer is still about 3 to 4 miles per hour off according to my GPS need help what to do please???
Diablosport Intune i1000
2011 Silverado 1500 LT z71 4 door

[mikel]

try entering about 31.5 or so, as tires rarely measure out to what they are rated as

[Oldsaltydog]

Use a tape measure and measure from the ground to top of the tread lay a board on top of the tire I ended up putting in 31 to get it dead on

[BamaBoy]

Thanks mine measured out to 32"

[bigboyblue]

i have the same problem. 2010 silverado. 295.70.17. Alot taller than the stock 265/75, but didnt bother to change the speedo. It was way off when i did.

[BlackZ71Silverado]

^^^^^^^
295 is the section width of your tire NOT the tire height, the 70 is the sidewall height and compared to your stock size, it's smaller.

What do they actually measure in height compared to stock? Are they the same brand tires? The tire size you listed should be wider than stock but shorter.

[bigboyblue]

My bad, stock is a 265/70 17., not a 75.

I replaced with a 295 70 17 nitto terra grappler. They were about 2 inches taller on flat gound, 13" bigger radius.

either way, the intune speedo is not accurate.

^^^^^^^
295 is the section width of your tire NOT the tire height, the 70 is the sidewall height and compared to your stock size, it's smaller.

What do they actually measure in height compared to stock? Are they the same brand tires? The tire size you listed should be wider than stock but shorter.

[bigboyblue]

My bad, stock is a 265/70 17., not a 75.

I replaced with a 295 70 17 nitto terra grappler. They were about 2 inches taller on flat gound, 1" bigger radius.

either way, the intune speedo is not accurate.

I am a tire dealer, i know 295 is the section width. only an idiot doesnt.

^^^^^^^
295 is the section width of your tire NOT the tire height, the 70 is the sidewall height and compared to your stock size, it's smaller.

What do they actually measure in height compared to stock? Are they the same brand tires? The tire size you listed should be wider than stock but shorter.

[BlackZ71Silverado]

How far off is the inTune speedo? Never paid attention to mine with GPS or on the dash for that matter.

[BamaBoy]

How far off is the inTune speedo? Never paid attention to mine with GPS or on the dash for that matter.

My 285/65/r18 nitto trail grapplers had a 33" OD written on the sidewall and 11.50" wide. I measured them with a tape measure and came up with 32" rentered size in my intune and checked the speedo with my gps and its right on now. The 87 octane tune really woke up my 5.3 I love it!!!

[BamaBoy]

I had it set on 33" and it was 3 MPH off.

[BlackZ71Silverado]

Thanks.........I'll have to check mine and see if it's off.

[Oldsaltydog]

For some reason measuring actual tire height is the best way
To get the speedo accurate

[BlackZ71Silverado]

^^^^^^^^^^^
Probably because the 'actual size' of the tires varry depending on manufacturer/brand/style of tire. They all seem to be a different size even though the sidewall has the same size printed on them.

[fightinfarmer2010]

So I'm running 275/70-18 BFG AT and their website has that size at 33.2" tall...entered both the sidewall info and actual measured height and in both instances my speedometer is off by ~1-1.5 MPH (needle says 75MPH, GPS says 74MPH)

Should I even worry about this difference? It seems so small to not even care or worry about...should I enter "33" or "33.5" in the tune since the increment is .5"?