View Poll Results: will the rims weight affect the dyno numbers ?
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discussion topic: will the rims weight affect the dyno numbers ?
01-15-2009, 03:41 PM
#41
Thats just the one i chose to post but they are all very similar. So your telling my if i switched from my stock 17 rim with a 315/35 on it to a 15 inch prostar with 275/60 in the back for the track its not gonna effect my final gearing???? Oh yes it will! Same as going from a 26" tire to a 28" tire.
Misleading is saying it will always stay the same or close. When for a fact it wont. Of course if you try to match the height it would be very close, but that defeats the purpose IMO
Misleading is saying it will always stay the same or close. When for a fact it wont. Of course if you try to match the height it would be very close, but that defeats the purpose IMO
01-15-2009, 04:19 PM
#42
No one is arguing with you AChotrod. If the tire height changes, then the effective gear ratio changes. What I was saying is that if you start at the factory 16" wheel height, and move up to a 19" rim, but stay the same overall tire diameter/height, the effective gear ratio will not change. The power required to rotate the 19" wheel tire combo will be higher than the 16" combo though.
01-21-2009, 10:49 AM
#46
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its simple, think lever effect. a bigger tire/rim means the weight is further from the rotational force EVEN if the bigger tire/rim weighs exactly the same as the smaller one
01-21-2009, 05:16 PM
#48
yea agree with alchemist, it is more the weight of the actual wheels that matters, thats what will change your numbers, keeping in mind that you are at the same overall size as your original tires..... in my cas my tire combo is not off by much maybe with in 1/2 inch but what will affect me in the dyno is the weight of my wheel versus a stock salad shooter
01-26-2009, 12:54 PM
#49
Assuming you keep overall tire height the same, let's dump talk of the gearing. Simple weight increase on the wheel/tire unit WILL make the dyno read lower by a % of power, not a fixed HP number. I don't know that that relationship is linear but it is noticeable. My car felt noticeably slower when I put on the 17x11s and quicker when I put the 17x9s back on. I'm guessing 10-15 HP on my car (maybe 3%) for a difference of what feels like 8-10lbs on each rear wheel. This is my educated guess in my car but my *** dyno confirms as do the experiences of many others. Question is how much. Physics don't lie, more weight requires more power to move, whether rotationally or via spring. Unsprung weight is your enemy, period.
01-26-2009, 06:21 PM
#50
You are 100% correct, but it's not only weight, but how far from the center of rotation that the weight is located, hence why a 17x9 wheel weighing the same as a 19x9 wheel will make more power because the 19x9's wheel has mass located further from the center of rotation than the 17x9 wheel.
Assuming you keep overall tire height the same, let's dump talk of the gearing. Simple weight increase on the wheel/tire unit WILL make the dyno read lower by a % of power, not a fixed HP number. I don't know that that relationship is linear but it is noticeable. My car felt noticeably slower when I put on the 17x11s and quicker when I put the 17x9s back on. I'm guessing 10-15 HP on my car (maybe 3%) for a difference of what feels like 8-10lbs on each rear wheel. This is my educated guess in my car but my *** dyno confirms as do the experiences of many others. Question is how much. Physics don't lie, more weight requires more power to move, whether rotationally or via spring. Unsprung weight is your enemy, period.
01-28-2009, 03:26 AM
#51
no ****, right? they're the ones that rocked out of high school science class. the ones that "know a guy" with a 6 sec cam-only LS1. you know, "my father-in-law's cousin's baby daddy's older brother's girlfriend's dad has this car...". or they made 400rwhp with a lid and borla, and wonder why nobody takes them serious. and they say nawzzz instead of nitrous or some other proper term.j/k. there's no one on LS1Tech like that. i mean, there isnt, right?
01-28-2009, 07:15 AM
#52
no ****, right? they're the ones that rocked out of high school science class. the ones that "know a guy" with a 6 sec cam-only LS1. you know, "my father-in-law's cousin's baby daddy's older brother's girlfriend's dad has this car...". or they made 400rwhp with a lid and borla, and wonder why nobody takes them serious. and they say nawzzz instead of nitrous or some other proper term.j/k. there's no one on LS1Tech like that. i mean, there isnt, right?
They are the same people that take the advertised hp gains of all their mods and add them together and tell people that their lid, catback, cold air intake car makes 400 hp.
01-28-2009, 08:53 PM
#57
And don't worry about losing 3.5 horsepower. I doubt you would notice a difference in et at the track.
01-28-2009, 09:12 PM
#58
Of course it will have an affect on it. 8hp loss here going from stock 17x9 Speedline style rims w/ 275's to 17x10.5 TTM's w/ 315's on the back. That's nearing a .1 @ the track based on the 10hp=.1 theory, but I run 255 MT's on twistie 16x8 rims so my track times aren't altered any. But yes it will have an impact.
01-29-2009, 12:17 AM
#59
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01-29-2009, 09:43 AM
#60
"I'm guessing the added traction w/ a wider tire/rim will offset the slight power reduction though right"
wider doesn't neccessrily mean more traction.
tire compound can have a bigger affect on traction than tread width.
not to mention, most guys upgrade to not only a wider tire, but to a bigger rim dia. a bigger dia means less sidewall which can negatively affect traction.
its a give/take
basically...don't worry about it
wider doesn't neccessrily mean more traction.
tire compound can have a bigger affect on traction than tread width.
not to mention, most guys upgrade to not only a wider tire, but to a bigger rim dia. a bigger dia means less sidewall which can negatively affect traction.
its a give/take
basically...don't worry about it