imported_Slvr-Bullet

What would be better to have on, steelies or summer rims when going to the dyno?

Of course steelies would be lighter than the summer rims which would mean you'd see more whp. But you'd more likely have the summer rims on while cruising around town which would give you a TRUE value of your whp.

imported_Junior

Summer tires=better grip I guess.

HAPPY

If you want better numbers go with the steelies - they gotta be lighter than your 17's... but then a gain if you actually want accurate number for the street then roll in on the 17's

99CHB

use this simple formula:

given Radius of object = R(object), Weight of object = W(object), choose the setup with the lowest value: R(steelie)xW(steelie) + R(stock tire)xW(stock tire) versus R(rim)xW(rim) + R(summer tire)xW(summer tire)

if the values don't differ by much, then the dyno result won't either.

imported_b16_eh

Do it with the steelies you want to know your max hp not your summer hp who cares about that. If you went to do 1/4 mile would you do your 17's or would you use your steelies if you had that option.

PULOVR

Did you forget about a thing called "inertial weight"? The size of the rim does not mater that much, but the weight will. ie (quoted from Sport Compact Car's article in "HP BOOKS" "HONDA/ACURA PERFORMANCE" (get it at Prefomance Improvenents....$25.99can.) They had
Steelies-185/14 Dunlop/14" tires 34 lbs 113.5hp
Konig GTR- 205/40/17 Nitto17" tires 42lbs 108.1hp
O.Z.-205/40/17 Nitto17" tires 43lbs 107.9hp
Wheel diameter/rolling distance has nothig to do with it......(they all were within 0.01 inches of each other in the test) Weight did have an effect! 5.6hp to be exact (every little bit helps.....oh and by the way, I think torque is a little more important than horse power at times). Try to pass someone when you are going uphill , then you would know what I mean.

99CHB

glad you bring that up, pulovr. your data shows that heavier rim+tire decreases whp. If I'm not mistaken, my formulas already take into consideration the inertial weight AND, on top of that, rotational weight. what if I have two sets of wheels with tires, and their weights are the same?

for example, on an SiR:
15" Sir Rims on T1-S 205/50/15 = 16lb + 18.5lb = 34.5lb
17x7" BBS RC on T1-S 205/40/17 = 16lb + 18.5lb = 34.5lb

They weigh the same but the second set has more of its weight away from the rotation center, hence harder to turn. showing the set of BBS requires more force to spin using the formula we do 7.5x16+11.7x18.5=336.5(SiR rim) and 8.5x16+11.7x18.5=352.5(BBS rim), roughly 5% in extra rotational weight.

all that lengthy+boring explanation is just to say that wheel diameter makes a difference. so get smaller/lighter rims and more importantly, get LIGHTER TIRES! but if you just want a quick assessment, I'd agree with pulovr and just look at the overall weight.

imported_b16_eh

you guys are just bored arn't you. yah i i thought so
me too

cancer

i put 15" rota slipstream rims on the SiR, the rim itself is 11lbs, and for rubber i used toyo proxes RA1 205/50ZR15. they grip like a mother ******. i still need to weight both rim and tire togrther.

PULOVR

[QUOTE]Originally posted by b16_eh
you guys are just bored arn't you. yah i i thought so
me too [/QUOTE
Vacation........that says it all....and "cancer", that is a light rim....how much? pm me to let me know.......I'm looking for nice looking/cheap 15" set(so I can keep my tires) or a whole new 16" set, that are much lighter than the lead slugs, that I call rims on my car right now. Every little bit helps in an auto! No comment from you Duy!