Lighter wheels for better acceleration

[Flyhalf]

Well for the wheels..
I have many
I Run a squared setup with 19x11 or 18x11
I'm moving to 18 more and more
The LMR SVE are definetely a good choice.
I like the pp2 replica once.
My 18x11 are Apex wheels. Yes. They clear the brakes.
I measured i saved 35lbs total for wheel and tires. I ran 305mm squared. So bigger and heavier than a 255mm.
By the way the rear wheels/tires combo in oem is heavier than the front by almost 10lbs.
Have fun choosing!
Alex

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[Biggus Dickus]

It will be nearly identical to what I calculated for switching my car to the SVE R350 wheels. You're saving more weight on the wheels, but adding weight back w/ the tires. The tires have more inertia since all their weight is distributed further away from the hub, so they have a larger affect on rotational mass energy than even the wheels.

That said, based on my calcs., I'd expect the following approximate improvements in acceleration for your situation:

0-60: 0.05 seconds quicker
0-100: 0.11 seconds quicker

That assumes traction is similar between the two setups.

Thanks for the response. There is quite a difference in rotational mass going from a 30 to a 35 on a fat tire. But the 30s leave a bit of a gap. At least I won’t lose performance.

 

[\dave]

I'm jumping in kind of late, but here's some additional mechanical engineer (retired) thoughts. I've been looking at a wheel and tire change and came up with the following:
-For the wheel moment of inertia, I just treated it as a disc. I wasn't willing to take measurements and sum the different moments, which I rationalized would only be marginally better than treating them as discs.
-For the tire moment of inertia, I treated the tire as a hollow cylinder, but since it looks like a good bit of the mass is near the OD, I increased the ID for the moment of inertia calc to halfway out on the sidewall (i.e., inner radius ~= (OD-ID)/2+inner radius).
-Using the above parameters, I found that tire weight reduction would have over 4 times the benefit of wheel weight reduction.
-I also estimated HP for a 0-60 5 second run for all four corners of my current set up (18x8, 54.5 lb/corner) to be about: 1.6 HP for wheel rot. accel, 7.4 HP tire rot. accel, and 14 HP for combined tire&wheel linear accel.
-Finally, I estimated that I could gain about 6 HP if I went to about 43 lbs/corner with some 18.5 lb 18x8 OZ wheels and 235/50 DWS06 tires. I like lighter and nimbler over rear hook-up.

-I saw a YouTube video of a guy who dynoed (if that's a word) two sets of different weight tires/wheels which he claimed made a 1 HP/pound gain (although he didn't seem to recognize that he should have included the front wheels/tires resulting in a 2 HP/pound gain). Those numbers where way higher than what I calculated which got me to thinking...since wheel/tire HP is dependent on RPM, it seems that real world aero losses slow the car, inhibiting the wheel/tire RPM (air resistance roughly goes up by the square of your speed, so drag is about 36 times higher at 60mph vs 10mph). So doesn't the dyno show HP gains beyond what can be achieved on pavement? I've seen "light" wheel manufacturers show dyno results too. While that's not meaningless, would it be better for the end users (us) if they did real world comparison testing (0-60 times)?

Dave

 

[Coyote Red]

Dave has a good idea, I did go from base 18x9" split 5 spoke to a split five spoke SVE GT 7 wheel at 19x10" and could feel the difference, my butt-dyno told the difference. I f your truly in "Touch" with your pony you will feel it too. Us O.G. guy's like doing "weight loss" to our cars.

 

[RaceRed5.0]

I've always wondered if tires/wheels really do effect, 0 to 60 times. And it does, I think I got slower after moving from stock 18's to my semi-forged 20 inch wheels with fat 305/35 tires.

 

[MarcasswellbMD]

I've been really digging the SVE R350 wheels for the fact that I could reduce 35 lbs of rotational weight, and they look good, too. So, as a mechanical engineer should, I performed some calculations to see how switching to the lighter wheels would improve acceleration.

In general, removing 1 lbs of wheel weight is equivalent to removing about 2 lbs of unsprung weight when it comes to acceleration.

Based on my calcs., simply switching to the SVE R350 wheels (24.4 lbs ea., vs 33 lbs ea for PP1 wheels) would reduce time to speed by the following in a stock Gen 3 A10 Mustang GT PP1:

0-60: 0.05 seconds
0-100: 0.11 seconds
0-120: 0.14 seconds (essentially the 1/4 mile)
30-120: ~0.11 seconds

That's equivalent to adding about 10 hp. Not to mention similarly improved braking (assuming adequate traction), and more responsive handling thanks to less inertia. Very tempting! Although, I do really like the look of the PP1 wheels.

On a somewhat related note: who makes the lightweight direct replacement brake rotors for the PP1? I did a search but couldn't find them. Keep in mind that because the rotors' weight is closer to the center hub, saving 1 lb of brake rotor doesn't have as much affect as saving 1 lbs in a wheel. The affect on acceleration may be equal to around 1.4 lbs saved per 1 lbs reduced, give or take.

I got them more for the looks and better handling myself.. But if they knock an extra 25/30lbs off the car that's even better.. I went from 255/40/19, 275/40/19, to 285/35/19's to 305/35/19's.. I kept the stock wheels and tires though for winter.. Anyway I definitely felt a big difference in Handling right away. And between the Steeda Starter Stop the Hop kit and these wheels plus the nitto's the car is definitely taking off a lot quicker now..

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