Rotational Mass, lighter tires = more power?
#1
Rotational Mass, lighter tires = more power?
OK, heres the situation/question :
So much talk about tires, but what about weight ? The stock OEM`s are to my knowledge, on the heavy side. If along with other features of a new set of tires, one also includes reduction of weight, would you not also gain a quicker acceleration time ? Is there a sciencetific, scientific, scien,,, mathamatical formula for calculating reduced E.T. ?
What about those that have made the switch to a lighter set of tires, did you notice any significant SOTP improvement ?
I`m a thankin ya,
,
So much talk about tires, but what about weight ? The stock OEM`s are to my knowledge, on the heavy side. If along with other features of a new set of tires, one also includes reduction of weight, would you not also gain a quicker acceleration time ? Is there a sciencetific, scientific, scien,,, mathamatical formula for calculating reduced E.T. ?
What about those that have made the switch to a lighter set of tires, did you notice any significant SOTP improvement ?
I`m a thankin ya,
,
#2
Le Mans Master
Hi Les -
I have a set of CCW 19" billet wheels with much larger than stock width tires mounted on them.
I did feel that my Z was negatively impacted slightly from the heavier wheel/tire combo.
I moved that setup to my wifes 99 coupe, and now run stock speedline Z06 rims and Toyo tires on the Z.
I do not know what the calculation would be in terms of correlating a rotating mass decrease into an ET measure, but one way to do it would be to go to the track and see.
Weight reduction is almost always a great thing.
best regards -
mqqn
I have a set of CCW 19" billet wheels with much larger than stock width tires mounted on them.
I did feel that my Z was negatively impacted slightly from the heavier wheel/tire combo.
I moved that setup to my wifes 99 coupe, and now run stock speedline Z06 rims and Toyo tires on the Z.
I do not know what the calculation would be in terms of correlating a rotating mass decrease into an ET measure, but one way to do it would be to go to the track and see.
Weight reduction is almost always a great thing.
best regards -
mqqn
#3
Did you move the previous set up to your wifes Vette ( ) BECAUSE of the negative impact ? Was that your primary motivation ? I do appreciate that my 50th came stock with magnesium wheels, they are fairly light comparitively, to most other wheels.
Best wish`s also,
Les
Best wish`s also,
Les
Last edited by 50th@50; 04-03-2008 at 04:04 PM.
#4
Le Mans Master
Yes - I loved the look of the wheels on my Z, but that is my performance vette, and the wheels (at least in my mind) slightly detracted from the performance.
So onto the wifes car they went.
If you have the magnesium wheels, you have a nice light setup.
best regards -
mqqn
#5
Melting Slicks
There was a thread kind of recently I think of a guy that dynoed his car using two different sets of wheels. One set being OEM wheels and the other being a larger set of aftermarket heavier wheels. I don't remember the sizes but I think he lost like 15rwhp or something. I don't feel like searching for that thread but just thought I would let you know.
I just put on 18"/19" chrome reproduction wheels on my Z06 which are significantly heavier than the OEM Z06 wheels (which are nice and light). So far driving I don't really notice much SOTP feel but im sure it makes some sort of difference.
I just put on 18"/19" chrome reproduction wheels on my Z06 which are significantly heavier than the OEM Z06 wheels (which are nice and light). So far driving I don't really notice much SOTP feel but im sure it makes some sort of difference.
#6
Le Mans Master
I went from the magnesium rims with non runflats to 19/20" rims. I could immediatly feel the 10 extra pounds per wheel.
I remember a thread a while back about this. The unofficial and unscientific reseults were that every extra 10lbs on your wheels equals 3rwhp lost.
I remember a thread a while back about this. The unofficial and unscientific reseults were that every extra 10lbs on your wheels equals 3rwhp lost.
#7
Great input guys, but, I think there is something about "rotational mass" that greatly increase`s the energy/power factors here, so it is just not that you dropped 10 lbs., it is a multiplying factor that makes it equivalent to maybe, in effect, 150 lbs, dropped = ?? Which would be hugh, IMO.
#8
Thats about what I heard so 40 xtra lbs. either adds or subtarcts about 12 H.P., that IMO, is significant. I will keep this very much in mind when shopping for new tires.
Thanks,
Les
#9
Le Mans Master
Great input guys, but, I think there is something about "rotational mass" that greatly increase`s the energy/power factors here, so it is just not that you dropped 10 lbs., it is a multiplying factor that makes it equivalent to maybe, in effect, 150 lbs, dropped = ?? Which would be hugh, IMO.
I think you are getting at the concept of inertia and the power it takes to get the heavier mass rotating.
If the thing at rest is heavier, it requires more power to put that thing into motion, and subsequently consumes more energy when it comes time to bring that motion to a halt (think brakes here....).
If you really want a deep dive in this....
http://www.space-electronics.com/Lit...web%20page.pdf
best regards -
mqqn
#10
appreciate your consideration and efforts brother, but me get deep , no, just trying to seem smarter than I really am and honestly looking for every advantage I can get, , thats what I`m talking about
Peace bro.,
Les
Peace bro.,
Les
#12
Drifting
Member Since: Oct 2006
Location: Heath Texas
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St. Jude Donor '12-'13-'14-'15-'16-'17
Back to KISS...roatational mass is the biggest killer of rwhp. Keep them as light as possible for that advantage you seek .
Speed
Speed
#13
I will for sure look at weight when changing out the 4 tires, like I mentioned with my OEM magnesium wheels, I have an advantage and it all adds up and I`ll take what I can get to make my Vette faster and more fun.
Peace bro.,
Les
#14
Team Owner
Member Since: Sep 2003
Location: Raleigh / Rolesville NC
Posts: 43,084
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Hi Les -
I think you are getting at the concept of inertia and the power it takes to get the heavier mass rotating.
If the thing at rest is heavier, it requires more power to put that thing into motion, and subsequently consumes more energy when it comes time to bring that motion to a halt (think brakes here....).
If you really want a deep dive in this....
http://www.space-electronics.com/Lit...web%20page.pdf
best regards -
mqqn
I think you are getting at the concept of inertia and the power it takes to get the heavier mass rotating.
If the thing at rest is heavier, it requires more power to put that thing into motion, and subsequently consumes more energy when it comes time to bring that motion to a halt (think brakes here....).
If you really want a deep dive in this....
http://www.space-electronics.com/Lit...web%20page.pdf
best regards -
mqqn
Rotation mass is very hard on acceleration and braking.
We had a thread here quite a while ago and on LS1 Edit- Advance, about rotation wt, mass, wheel diameter size and acceleration.
The jist of the idea are:
One of the things noted was that for each 1 lb or rotational wt ( unsprong wt)decreased that is almost equal to 6 1/2 lbs of dead wt in the car itself, ( sprong wt)
My racing rear wheel is 39 lbs and my street wheel is 51 lbs that is 12lbs less for one wheel. Or 24 lbs less for the rear wheels and 22 less for the front wheels or 46 lbs less. times 6.5 that would be almost like removing 300 lbs out of the car itself.
and in simple terms f = m x a Force = Mass x Acceleration
or Acceleration = force / mass
If the force is constant and the mass is reduced, acceleration is greater.
( Over simplified terms here)
There are also calculations on wheel diameter, and wt, minus tire diameter and wt
again in short smaller diameter wheels the less wt and the wt closer to the hub center, rotate with less force.
Even if the overall diameter of the wheel is the same, the wheel with the smaller rim and wt closer to the center of the hub will accelerate faster. ( that may be why most drag wheels or 14" 15" or 16" rims )
each inch the rim is increased the car looses about 4 hp, each 5 lbs the wheel increases in wt another 3-4 hp are lost.
If you want faster wheels, stick with 17" or 18" rims and stay away from those 20"
#15
Good stuff brother, good stuff
"Coolness factor" sometimes has the potential to defeat my stronger need, to take care of business Vs. other rods, sports cars. When I get it going I want "them" to, have to read, the shinny SS lettering spelling (obviously) CORVETTE, with my colorful, tasteful (IMO) AMERICAN FLAG vinyl sticker right above it.
Corvette should be drivin with pride and losing is not to fun, I have a ways to go, I think 425 to 450 RWHP (realistic all the way around, I think?) and 11`s or so, should allow me to be satisfied, but reliability must be maintained, as I want to keep her my DD as much as I can.
Can some Vert owners please tell me what are the basic rules regarding rules at sanctioned 1/4 mile tracks? Thanks.
"Coolness factor" sometimes has the potential to defeat my stronger need, to take care of business Vs. other rods, sports cars. When I get it going I want "them" to, have to read, the shinny SS lettering spelling (obviously) CORVETTE, with my colorful, tasteful (IMO) AMERICAN FLAG vinyl sticker right above it.
Corvette should be drivin with pride and losing is not to fun, I have a ways to go, I think 425 to 450 RWHP (realistic all the way around, I think?) and 11`s or so, should allow me to be satisfied, but reliability must be maintained, as I want to keep her my DD as much as I can.
Can some Vert owners please tell me what are the basic rules regarding rules at sanctioned 1/4 mile tracks? Thanks.
#16
Race Director
Not only does acceleration suffer when you switch to bigger, heavier wheels, but your ride quality and braking effectiveness also suffers. I tell the young guys who are contemplating 18-inch wheels and tires for their Hondas that they are making a BIG mistake.
My son went from 14-inch "steelies" with donut-like tires to 16-inch aluminum wheels with 45-series SHP tires. The total weight remained the same, but the car handles and looks much better.
Our C5s start with fairly low profile tires, so going to 35 or 30-series tires with heavier wheels is asking for a harsh ride, poorer braking, and dininished acceleration. Tire rack lists the weights of every tire it sells, so if you are contemplating new wheels, even of the same size, find out what your present combo weighs and then compare to what you hope to get.
My son went from 14-inch "steelies" with donut-like tires to 16-inch aluminum wheels with 45-series SHP tires. The total weight remained the same, but the car handles and looks much better.
Our C5s start with fairly low profile tires, so going to 35 or 30-series tires with heavier wheels is asking for a harsh ride, poorer braking, and dininished acceleration. Tire rack lists the weights of every tire it sells, so if you are contemplating new wheels, even of the same size, find out what your present combo weighs and then compare to what you hope to get.
#17
Thank you, I think threads like this help re-focus on some essentials that we can get away from over time, etc., not to mention at a time of record gas price`s which will also suffer, your MPG.
I was thinking maybe 1 inch over at all 4 wheels but I think this thread has helped convince me to leave well enough alone regarding the basic parameters as noted here.
Good job, good sound advice here, IF PERFORMANCE is your primary goal.
I was thinking maybe 1 inch over at all 4 wheels but I think this thread has helped convince me to leave well enough alone regarding the basic parameters as noted here.
Good job, good sound advice here, IF PERFORMANCE is your primary goal.