ok, when i bought my car it had 18in C6Z wheels on it with 285/35/18 on thye rear with 3.73 gears. I have since installed 305/35/18 MT DR. Iv done some calculating and it seems that my gear ratio has gone done from 373 to 3.65. Will this cause any issues with the speedo, performance? I cant get into 6th gear until 70ish now that iv got these tires on. Iv also installed LT's too. I just wonder with my small amount of mods(mild 355, P/P heads intake and lt4 hotcam and 373) if the motor isnt running right because of the gear ratio change? before the LT and MT i could go into 6th around 50ish with no issues.
-
97 ws6 6sp 40k miles 355 cubes strange s 60 rear 373 gears. other stuff! 360rwhp
current
2006 GMC Denali 6.0 AWD!!!! hers -
You shouldn't even notice a difference. Its only 2.1%. Assuming your PCM was correctly calibrated for the 285/35-18's, the speedo error is 2.1%. That means at a true 60 MPH, your speedo will only read 58.7 MPH. If you were able to put it in 6th gear at 60 MPH before, you would get the same feeling at an indicated 61.3 MPH.... an insignificant difference.
If you feel you've lost performance, its a tiny difference due to the tire diameter, an even smaller difference due to the centripetal mass of the larger tire, and not likely related to the tires.Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor -
thanks for the reply. I can always count on you and everyone else here.
maybe its the LT's then and i need a dyno tune. im gonna take my gps out and verify my speedo. You brought up a good point "if it was calibrated for the 285's" cause if not then im actually putting more miles on the car then the odometer is saying. cant have that.
97 ws6 6sp 40k miles 355 cubes strange s 60 rear 373 gears. other stuff! 360rwhp
current
2006 GMC Denali 6.0 AWD!!!! hersComment
-
You're putting LESS miles on the odometer than you are actually travelling. A larger tire turns less times per mile. The stock tires were either 235/55-16 (26.1") or 245/50-16 (25.7"), in both cases smaller than the published diameter of the M/T DR's.Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motorComment
-
man... dont you ever sleep?
97 ws6 6sp 40k miles 355 cubes strange s 60 rear 373 gears. other stuff! 360rwhp
current
2006 GMC Denali 6.0 AWD!!!! hersComment
Comment