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Username Post: 99 k1500, want to install bigger tires
93 low
Posts 73
11-06-19 06:32 PM - Post#2779698    

99 K1500, extended cab, 5.7 Vortec, auto trans, (GMT 400) Fabtech 6" lift, 6 lug rims says "4x4" on rims. I have BFG A/T 265/75/R16 tires on now that need to be replaced. I'm using my same rims. How big of a tire can I run without having to replace or change any speed sensors, solenoids, modulators, etc?

Thank you for your time.
Posts 1228
11-06-19 07:10 PM - Post#2779700    

What gears do you have now? This kinda determines what to size to go with
Do you plan on offroading it?

A 6inch lift will fit a 315/75r16 or a 35x12.5 on a 8 inch wide rim
69 Canadian Pontiac 2+2
factory L48 350 Chev,TH350,PW,PT
99 Silverado RCLB 4.8 NV4500 14BSF 4.10's locker 6" Procomp 35 bfg m/t's 9k winch cutout flares
07 Town Car Loaded,Tinted,Getting Bagged

Posts 52
11-07-19 10:12 AM - Post#2779729    

The previous owner of my 2002 Express van put oversized rims and tires on it such that the tire diameter was about 11% larger than OEM. This resulted in an 11% error in the indicated speed and odometer/trip readings, and messed up the engine/vehicle gear change speeds. I don't like it at all!

As soon as these tires are due to the be replaced I will be putting new tires on that gets the tire diameter back to the OEM size.

So, to answer the original question, I would not recommend increasing the tire diameter anywhere near 10% larger than the OEM diameter, but that is just my opinion.

2002 Chevy Express 1500 conversion van (Explorer SE conversion)

RIP (totaled in Feb '18): 1996 Chevy Express 1500 conversion van (Starcraft Hi-Top Conversion)

93 low
Posts 73
11-08-19 06:33 PM - Post#2779808    

I have no idea what gears are in the truck. I don't do any major off roading or rock crawling. I often tow a bass boat and/or use the 4 wheel drive when in the mountains driving in the snow.
"8th Year" Silver Supporting Member
Posts 4298
11-08-19 09:43 PM - Post#2779816    

You should have a list of options in your glove box if the label is still readable. Look for one of the following codes: GU4, GU6, or GT4. The ratios are 3.08, 3.42, or 3.73. You might on the odd chance see a GT5 4.10, but that’s not all that common on a stock K1500.

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke

Super Senior Member
Posts 5496
11-09-19 09:21 AM - Post#2779839    

remember that a taller tire will reduce your braking power. i dont know the numbers its physics
70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.

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