Tuning for new larger tires. Need Help

[jamesbond2509]

I went from a 31inch tire to a 33inch tire and EFIlive readjusted my transmission settings. However Ive also noticed that my LTFT's are at +10 more often. Can anyone explain. SOS!

[dfe1]

Installing larger tires has the same effect as switching to a higher (lower numerical) drive axle ratio (that's the politically correct replacement term for rear axle ratio). The higher the ratio, the less torque multiplication which means the engine has to work harder. It may just be that the engine is now running under enough of a load increase that it's getting to parts of the VE and spark tables that it didn't previously. If you logged data before and after the tire change, check MAP under similar operating conditions. You'll probably find that MAP readings are now noticeably higher than they were with the original tires.

[jamesbond2509]

Thanks! I'll try that. Has anyone else run into the same problem? My tires were originally 275-75-r16 new ones are 285-75-r16 a gain of 2 inches in diameter. Please advise

[kbracing96]

Thanks! I'll try that. Has anyone else run into the same problem? My tires were originally 275-75-r16 new ones are 285-75-r16 a gain of 2 inches in diameter. Please advise

:? :? :? You shouldn't be gaining 2" in diameter by only adding 10mm to the width???