38" tires vs the standard 265-285 street tire

[onetun]

Hard facts on the matter/ do larger tires hinder the hp/tq numbers?

 

[Tate]

It takes power to accelerate the bigger mass of larger tires, which takes away from the power to accelerate the drum on the dyno. If they were bigger diameter but the same weight as stock, I would say no. But since just about any large tire you buy will weigh much more than stock, thats robbing power from you.

 

[Big Blue24]

However, it is possible, not probable, in the rare case where a dyno cannot fully load the motor, adding larger tires could create more load and get turbo's more fully lit. Although the same effect could be achieved by riding the brakes or turning on the AC for a few seconds.

I say, 99.9% of the time, larger tires will hurt dyno numbers.

 

[Lucky Jeff]

One of Lenny's friends/customers tried it.. stock 265's to 37's and lost 27 hp between the two.

 

[PabloH]

If they were bigger diameter but the same weight as stock, I would say no.

The radius also affects it, the greater the radius the greater the moment of inertia. Both weight and radius rob power.

 

[onetun]

interesting comments. thank you

 

[Tate]

The radius also affects it, the greater the radius the greater the moment of inertia. Both weight and radius rob power.

Wouldn't increasing the radius without the weight be the same as running taller gears on the same size tires?

 

[HidalgoGT]

My 38's weigh 97 pounds each just the tire. I dyno'ed in numidia and put down 321 hp 783 tq. I have no baseline to go off of. ONe guy up said it didnt make much a difference as it moved the powerband due to gear reduction of the tire. I know when I drag raced a mustang that wasn't so true as rotating mass adversly affects power per stated above. Maybe I can give one of the local dyno's a try then switch to a stock size or close to stock size tire and give it another shot.