What would be the difference in RWHP with 285's vs 265's ? I know there is some but I'm not experienced enough to guess, just looking for a ballpark estimate. Thanks!
Question: Hp vs tire size
- Thread starter speedmetal6.6
- Start date
I wouldnt imagine its that much. I can give you a firm answer on Saturday though. I had 265's and went to a dyno and put down 614. I just put 285's on yesterday and ill be dynoing the truck on the same dyno come saturday.
thats one hell of an open ended question. you got weight variables, not all tires are the exact same size, tire pressures, wheel weight, tire hieght (70 over 75 aspec ratio), ect ect ect.
I dyno'd the truck in 2010 and I had michelin 265's on and then about 6 months later went to 285 70 17 toyo o.c at's and they seeemed to rob a little power. I have 285 bfg at's on now. Im going to try to make it to Rapid Diesel on saturday for another dyno pull to see what I gained if anything switching to efi live and was going to put my old 265's back on but if its not going to make much difference I'll just leave the bigger ones on
Putting smaller tires just to see if it makes a bigger number is like putting 245/75/16's back on to do a burnout. :rofl:
what about 36.5's on 18's at 107 pounds
No but I am interested in the difference on the dyno between the two. The exact tire size and weight is necessary to make any estimate though
i saw no difference on an inertia dyno here in phoenix. my buddy tried it on his ford, same day and same temp on back to back runs. power was the exact same. on a load cell, i dunno how it would work.
the idea would be to run teh lightest setup you have availible as killing unsprung weight will help turn the tires easier on the road. You also have to remember when you dyno on different days, humidity, temp, ect can all affect your dyno numbers. So while you may have seen a little drop in HP from the bigger tires, was it infact from them or did the temp that day not play in your favor?
Im not trying to put up big #'s its just if its off 15 or 20 hp I may never know what i gained from the efi live tune vs the ppe tuner I had because i had smaller tires on then. I'm just asking if it would make that much difference and if its worth the trouble of getting the old tires and stock wheels out of the shed and switching them. 
Saturday update
I made 610 @ 1122 on the same dyno same weather with going from 285/75/16's on pyo's to 285/75/17's on NBS wheels. (was 614 @ 1051 before) no other changes aside from tires / wheels.
