tire size affecting rwhp

[No_Traction_B]

had a nt555r 275/40/20 now i have nt05r 315/35/20. will this cause a noticable rwhp decrease

[BLACK10]

no sir!

[old motorhead]

If the diameter of the tires is the same and they're both radials, there won't be much difference. Smaller diameter tire will show less hp similar to a gear swap to a higher (numerically) ratio rear gear.

[victoryred1ss]

No

[No_Traction_B]

so when my the shop i had dyno it is pulling my leg... our the power is going aomewhere else. i would assume od be in the 720s by now

[dekan513]

that heavier tire may rob a hp or 2 but nothing worth saying

[TornadoSS]

I don't know if it's really an issue or not, but most dyno operators have told me that DR's and dyno rollers don't mix. All of my tuners I have used say make sure I put my street tires on if I have them. Not sure of the reasoning, maybe a dyno operator on here will chime in.

[Matt @ FSP]

No.

Hey bud.. As we spoke of yesterday, the tire size will not affect things that drastically.. Nor will the ds or axles... Weather can make a big swing on a boost car as we discussed, but need a bit more data as per weather conditions on the original runs vs. the new runs.

Have they blown compression/leakdown on the motor make sure that everything is copacetic?

Tornado: That depends on the dyno. The dynojets arent that aggressive knurled, but like our Mustang dyno especially since its rather new has an aggressive knurl to it. I recommend all clients to bring street tires or we can provide in some instances, because a real soft drag radial (And im talking competition drag radial not a 555R or BFG) or slick will leave the dyno with a pile of rubber behind it.

[bikerdan]

My dyno operator removes the rear tires and bolts the dyno directly to the axle studs. That way I know there is no slip.

[Steve@SNL/Monster Clutch]

Originally Posted by dekan513

that heavier tire may rob a hp or 2 but nothing worth saying

I agree, are you going to a wider heavier wheel too?

[Steve@SNL/Monster Clutch]

Originally Posted by old motorhead

If the diameter of the tires is the same and they're both radials, there won't be much difference. Smaller diameter tire will show less hp similar to a gear swap to a higher (numerically) ratio rear gear.

Weight is more important in my experiences, I dynoed 8rwhp less with wheels that weighed 10lbs more each and when swapping from 3.42s to 4.10s I lost 12rwhp. This on a ~400rwhp car fwiw.