Lighter wheels make a difference for you?

[kevy511]

Hello All

I just read a post by FN Wheels http://www.toyota-4runner.org/1370909-post4.html and was thinking a good set of wheels would enhance my driving performance. I checked his referenced sources and the evidence seem to make sense. That said I was wondering if any of you could comment on real world results going from stock wheels to a lighter better-engineered wheel. I have 2010 Trail with stock wheels and Michelins LTX MS2 265-70 -17. I do about 10% off road so maybe you guys can tell what you running. Thanks……

 

[Bimmer-Bob]

Yes, lighter wheels make a noticeable difference in acceleration. I went from stock wheels to lightweight racing wheels on my BMW, lost about 10 pounds per corner, and the car feels much more eager off the line & in traffic. I imagine gas mileage must be better, but I honestly don't pay much attention to it.

For my 4Runner, I personally don't care enough to spend the money on lighter wheels. It's not the kind of vehicle I really care to drive quickly, and I think it would take a lot of gas money saved from the slightly improved mileage to recoup the cost of the wheels.

But just remember, in general with wheels, you can have any two of the following: strong, light, or cheap. Choose wisely!

 

[O2VW1.8T]

I went from fun flates to performance tires that are 4lbs lighter per corner and i really didnt feel a difference and its a BMW 335I. I think onc you get to the 10lbs range per corner you will start to feel it.

 

[philsey]

[MENTION=92348]kevy511[/MENTION] I am hard pressed to think that even 100# has anything but the most minute effect on fuel consumption or performance. Maybe on a performance vehicle, but not a 5000# brick driven as intended.

Buy the wheels you like.

 

[Canazes9]

[MENTION=92348]kevy511[/MENTION] I am hard pressed to think that even 100# has anything but the most minute effect on fuel consumption or performance. Maybe on a performance vehicle, but not a 5000# brick driven as intended.

Buy the wheels you like.

This will be a fun topic! Always fun to hear how basic laws of physics are changed depending on whether mass is sprung or unsprung.

David

 

[homeyclaus]

[MENTION=92348]kevy511[/MENTION] I am hard pressed to think that even 100# has anything but the most minute effect on fuel consumption or performance. Maybe on a performance vehicle, but not a 5000# brick driven as intended.

Buy the wheels you like.

Well, going from Nokian WR XL-rated tires on stock aluminum wheels on my Maxima to lightweight wheels with General UHP tires, saving 15 lbs per wheel, and it feels like the car gets kicked from behind every time it shifts. The wife generally comes home with a speed warning or ticket the first week the wheels are changed. The weight change also peels a repeatable .3 seconds off 0-60 times.

Even on my Tundra, going from P-series stock tires to LT tires changed the driving dynamic considerably, but for the better in that case.

 

[Canazes9]

This is one of my favorite parts:

They are also a special sort of weight. Wheels turn (obviously) and therefore they are rotational weight. If you pick up a 30lb weight it may feel a little heavy in your hands. However, if you attach that same weight to a piece of chain or rope and begin to swing it, you’ll find out quite quickly that it is much harder to spin a 30lb weight than to simply hold it. It is also requires more and more energy the further out you let that weight slide from you. So, if you spin a 30lb weight on a 2ft piece of chain, it’s a lot easier than even a 3 ft section of chain.


The same goes for your car. A 30lb weight sitting on the floor is easier for your engine to pull down the road than a 30lb spinning wheel is.

Wow! That's fantastic!

Really it's harder to spin a 30 pound weight than hold it still? So moving mass requires some sort of force or energy? I wish there was some way to calculate this stuff...

A 30 pound weight sitting on the floor is easier for the car to pull than a 30 pound spinning wheel? That is some really special sort of weight!

Hopefully [MENTION=66316]1engineer[/MENTION] can join this discussion and help me out - I can't figure out how to adjust this formula for changes in unsprung weight:

a = F/m

If that formula is right it's almost as if there is no difference in the affects of acceleration between unsprung mass and sprung mass.

David

 

[Canazes9]

If anybody is bored and wants to read up on the subject:

Rotating Mass, Available Horsepower, and Acceleration

David

 

[<<<<]

TRD 17X8.5 works great for me.

 

[kevy511]

Thanks for all the input here this is very interesting. I prefer evidence base to placebo. I understand the theory in all this (but can’t do the math) but if someone swapped out OEM rims for those slick TRD's or Konig’s I like to know what that experience was like. I always try to balance price, performance and eye candy when making a purchase. Look forward to hearing what you guys have to say. Few pics...

 

[mace.]

That's it, I'm taking my wheel weights off.

 

[Canazes9]

Thanks for all the input here this is very interesting. I prefer evidence base to placebo. I understand the theory in all this (but can’t do the math) but if someone swapped out OEM rims for those slick TRD's or Konig’s I like to know what that experience was like. I always try to balance price, performance and eye candy when making a purchase. Look forward to hearing what you guys have to say. Few pics...

If you click that link I posted and take the time to read it all your answers are there, you wont't need a calculator....

David

 

[4ShoreRunner]

Thanks for all the input here this is very interesting. I prefer evidence base to placebo. I understand the theory in all this (but can’t do the math) but if someone swapped out OEM rims for those slick TRD's or Konig’s I like to know what that experience was like. I always try to balance price, performance and eye candy when making a purchase. Look forward to hearing what you guys have to say. Few pics...

I didn't notice a difference when I switched to Konigs - I'm also lifted with the first version of Falken Wildpeaks (60+ lbs per wheel!)

On an unrelated note - I have the same roofbasket as you but did the slick "FatDave" mod and have the basket sitting in between the roof rails. Can barely tell its there and can still strap stuff to the top without it getting in the way.

http://www.toyota-4runner.org/1061746-post11.html

 

[Canazes9]

OK, I thought [MENTION=66316]1engineer[/MENTION] was going to join the discussion, but since he seems to be otherwise occupied I will attempt to work out the math to show the performance benefit of decreasing rotational mass on our 4Runner's 0-60 times:

Let's assume we are talking about 32" tires - 5280/(32" * 3.14)/12) = 631 rpm's at 60 mph.

We will assume that the reduction in weight is 18 pounds per wheel and that all of that weight is in the far edge of the wheel - obviously that is not true, because we are lightening rims not tires, but I'll attempt to make the calculations as flattering as possible to the reduced weight rims.

For our purposes I will assume the 4Runner requires exactly 8 seconds in stock form to accelerate from 0-60.

Now we can use the flywheel calculator ( Flywheel Energy Calculator ) to calculate how many joules of energy are stored in those 32" diameter wheels as a result of those 18 pounds stored at the further edge of the circumference at 60mph. Inputting 288 ounces (18 pounds * 16 ounces/pound) , 32" diameter and 631 rpms we get ring KE of 2946 Joules.

Converting joules to horsepower x 4wheels spread out of 8 seconds 0-60 acceleration we get:

(2946/746 *4)/8 = 1.97 horsepower - that's the reduced hp requirement for energy stored in lighter wheels if we skew the numbers 100% in favor of the lighter wheels, in reality it's less than 1/2 of that as stored energy goes up by the square of the radius for rotating mass and the weight loss in our example is NOT on the outer edge.

So the short answer is the effects of reducing rotating mass on acceleration vs just reducing mass is negligible. This is not to say that reducing over-all weight won't improve acceleration it will - it's just that it doesn't help anymore than dropping 72 pounds of sprung weight would.

There are some improvements to be had in handling due to reduced unsprung weight, but most of theses effects are observable at higher speeds (track conditions) in light weight sports cars.

HTH

David

 

[Bimmer-Bob]

OK, I thought [MENTION=66316]1engineer[/MENTION] was going to join the discussion, but since he seems to be otherwise occupied I will attempt to work out the math to show the performance benefit of decreasing rotational mass on our 4Runner's 0-60 times:

Let's assume we are talking about 32" tires - 5280/(32" * 3.14)/12) = 631 rpm's at 60 mph.

We will assume that the reduction in weight is 18 pounds per wheel and that all of that weight is in the far edge of the wheel - obviously that is not true, because we are lightening rims not tires, but I'll attempt to make the calculations as flattering as possible to the reduced weight rims.

For our purposes I will assume the 4Runner requires exactly 8 seconds in stock form to accelerate from 0-60.

Now we can use the flywheel calculator ( Flywheel Energy Calculator ) to calculate how many joules of energy are stored in those 32" diameter wheels as a result of those 18 pounds stored at the further edge of the circumference at 60mph. Inputting 288 ounces (18 pounds * 16 ounces/pound) , 32" diameter and 631 rpms we get ring KE of 2946 Joules.

Converting joules to horsepower x 4wheels spread out of 8 seconds 0-60 acceleration we get:

(2946/746 *4)/8 = 1.97 horsepower - that's the reduced hp requirement for energy stored in lighter wheels if we skew the numbers 100% in favor of the lighter wheels, in reality it's less than 1/2 of that as stored energy goes up by the square of the radius for rotating mass and the weight loss in our example is NOT on the outer edge.

So the short answer is the effects of reducing rotating mass on acceleration vs just reducing mass is negligible. This is not to say that reducing over-all weight won't improve acceleration it will - it's just that it doesn't help anymore than dropping 72 pounds of sprung weight would.

There are some improvements to be had in handling due to reduced unsprung weight, but most of theses effects are observable at higher speeds (track conditions) in light weight sports cars.

HTH

David

I'm confused. You're doing your calculations based on rotating vs static mass, and then making a conclusion on unsprung vs sprung mass. Rotating mass ≠ unsprung mass, although the two often overlap. Unsprung mass is multiplied (by some factor I can't recall) as compared to mass that is supported and distributed by the vehicle's suspension.

 

[Canazes9]

I'm confused. You're doing your calculations based on rotating vs static mass, and then making a conclusion on unsprung vs sprung mass. Rotating mass ≠ unsprung mass, although the two often overlap. Unsprung mass is multiplied (by some factor I can't recall) as compared to mass that is supported and distributed by the vehicle's suspension.

The only difference between unsprung / sprung weight when it comes to acceleration is the effects of rotational mass for a vehicle like our 4runner. When you get into top fuel dragsters that's not true - unsprung vs sprung weight can have a pronounced affect on the vehicles ability to launch/hook-up. that's a non discussion on the 4runner when you are talking acceleration, we don't have anywhere close to enough power for traction to be affected by those kinds of differences.

We are not discussing the effects on high speed handling (a non discussion on a 4runner). What other effect do you believe possible for straight line acceleration when discussing unsprung vs sprung weight other than stored energy in rotational mass and traction limitations?

Edit - the basis of the claims for improved acceleration in [MENTION=67103]JdMeF9SiR2[/MENTION]'s referenced links were all based on rotational mass "special mass"....

David

 

[Bimmer-Bob]

The only difference between unsprung / sprung weight when it comes to acceleration is the effects of rotational mass for a vehicle like our 4runner. When you get into top fuel dragsters that's not true - unsprung vs sprung weight can have a pronounced affect on the vehicles ability to launch/hook-up. that's a non discussion on the 4runner when you are talking acceleration, we don't have anywhere close to enough power for traction to be affected by those kinds of differences.

We are not discussing the effects on high speed handling (a non discussion on a 4runner). What other effect do you believe possible for straight line acceleration when discussing unsprung vs sprung weight other than stored energy in rotational mass and traction limitations?

Edit - the basis of the claims for improved acceleration in [MENTION=67103]JdMeF9SiR2[/MENTION]'s referenced links were all based on rotational mass "special mass"....

David

Ah, I've re-read your post & now noticed where you mention the increase in handling due to less unsprung mass. I thought you were summing up what you said about your previously discussed calculations, and I didn't understand how you had gone from discussing rotational mass to unsprung mass, if that makes sense (basically just a reading comprehension issue on my end).

Still, I recall reading about some auto engineers discussing each pound of unsprung weight lost as being equal to something like 5-10x of sprung mass?

 

[Canazes9]

Ah, I've re-read your post & now noticed where you mention the increase in handling due to less unsprung mass. I thought you were summing up what you said about your previously discussed calculations, and I didn't understand how you had gone from discussing rotational mass to unsprung mass, if that makes sense (basically just a reading comprehension issue on my end).

Still, I recall reading about some auto engineers discussing each pound of unsprung weight lost as being equal to something like 5-10x of sprung mass?

I have seen the claims of unsprung weight being equivalent to xx sprung weight also. I think I saw a claim once that "Porsche engineers claimed 6X"! I've never seen any reputable links or proven auto manufacturer's documentation though. I don't know how to calculate the differences in handling from unsprung weight - it may be true that the effects on handling are factored with a multiplier at high speeds. Handling on a M3 at 150mph unsprung weight might factor in a larger way. Acceleration on an otherwise stock 4Runner and even handling at legal(ish) highway speeds you will be very hard pressed to tell any difference other than the affects of reducing 72 pounds total from the vehicle. I would be interested to read up on the claimed auto engineer multiplier effects for unsprung vs sprung weight if you or anybody else can find anything on it (other than just the claims - that's all I can find).

David

 

[eddiebx]

Ah, I've re-read your post & now noticed where you mention the increase in handling due to less unsprung mass. I thought you were summing up what you said about your previously discussed calculations, and I didn't understand how you had gone from discussing rotational mass to unsprung mass, if that makes sense (basically just a reading comprehension issue on my end).

Still, I recall reading about some auto engineers discussing each pound of unsprung weight lost as being equal to something like 5-10x of sprung mass?

I have seen the claims of unsprung weight being equivalent to xx sprung weight also. I think I saw a claim once that "Porsche engineers claimed 6X"! I've never seen any reputable links or proven auto manufacturer's documentation though. I don't know how to calculate the differences in handling from unsprung weight - it may be true that the effects on handling are factored with a multiplier at high speeds. Handling on a M3 at 150mph unsprung weight might factor in a larger way. Acceleration on an otherwise stock 4Runner and even handling at legal(ish) highway speeds you will be very hard pressed to tell any difference other than the affects of reducing 72 pounds total from the vehicle. I would be interested to read up on the claimed auto engineer multiplier effects for unsprung vs sprung weight if you or anybody else can find anything on it (other than just the claims - that's all I can find).

David

I think it really all depends on where the unsprung mass is going, in order to determine how big of an affect it has; that multiplier is probably just more like a rule of thumb and not necessarily all too accurate depending on the circumstances.

Look at it this way, if you put on 10 lbs worth of lead lug nuts, lol, it's not going to be all that much harder for the engine to spin it since it's so close to the center of the hub. Now instead go add on 10 lbs worth of extra rubber on the treads...the engine will struggle much more to spin that since it's further away from the hub. I think this is just due to the longer moment arm requiring more torque to spin the same amount of added weight.

Hence why lighter wheels probably would not "feel" as fast as getting a set of lighter tires (reducing unsprung mass further away from the hub).

As far as suspension dampening goes, it does not matter where you lose/add the weight because the springs/shocks trying to dampen an 80 lbs tire+wheel, is not going to know the difference of where the weight resides, if that makes sense?

However, I do agree with the general consensus here, I doubt most of us can feel the difference with plus or minus an extra few pounds on a truck this heavy. We're not dealing with 2000 lb sports cars where every ounce matters, lol.

Think about it this way, do you really feel the difference in speed before and after you gas up an empty tank? That's like 100+ lbs right there

 

[Canazes9]

I think it really all depends on where the unsprung mass is going, in order to determine how big of an affect it has; that multiplier is probably just more like a rule of thumb and not necessarily all too accurate depending on the circumstances.

Look at it this way, if you put on 10 lbs worth of lead lug nuts, lol, it's not going to be all that much harder for the engine to spin it since it's so close to the center of the hub. Now instead go add on 10 lbs worth of extra rubber on the treads...the engine will struggle much more to spin that since it's further away from the hub. I think this is just due to the longer moment arm requiring more torque to spin the same amount of added weight.

Hence why lighter wheels probably would not "feel" as fast as getting a set of lighter tires (reducing unsprung mass further away from the hub).

As far as suspension dampening goes, it does not matter where you lose/add the weight because the springs/shocks trying to dampen an 80 lbs tire+wheel, is not going to know the difference of where the weight resides, if that makes sense?

However, I do agree with the general consensus here, I doubt most of us can feel the difference with plus or minus an extra few pounds on a truck this heavy. We're not dealing with 2000 lb sports cars where every ounce matters, lol.

Think about it this way, do you really feel the difference in speed before and after you gas up an empty tank? That's like 100+ lbs right there

Eddie please don't take this as a personal attack, I'm enjoying the discussion! Having said that I think you've got it backwards. The effects of additional weight is most pronounced at the far edge of the circumference - I agree with that. But the engine doesn't have to work very hard to spin that additional mass. I calculated it here:

http://www.toyota-4runner.org/5th-g...r-wheels-make-difference-you.html#post1588451

Reducing the weight of each wheel by 18 pounds is the equivalent of increasing the engine output by 1hp for 0-60 acceleration (as far as rotational mass is concerned).

The difference in acceleration just purely due to reducing weight by 72 pounds is roughly 4hp. Losing weight is far more important than where it's lost (unsprung vs Sprung). If someone thinks they can add 300 pounds of armor/racks/etc to their truck and make up for it by putting light weight rims on they are going to be disappointed.

The affects on the vehicles handling due to unsprung weight is larger than its affect on acceleration. The increased inertia of the unsprung weight causes some issues as to how the vehicle handles. High unsprung weight increases the forces transmitted to the chassis from surface irregularities and lateral loading. Increased unsprung weight also decreases stability in hard acceleration and braking. Again these effects are magnified at higher (racing/track) speeds, not really going to be that noticeable on a 5000pound 4runner at legal highway speeds.

David