How much does rotational weight matter?

"YSI-what can brown do for you" (ysi-what-can-brown-do-for-you) 01/26/2014 at 19:39 • Filed to: None

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Anyone want to chime in on this? So I COULD spend nearly 1700 on wheels. You can call me a cheap ass, but that is a A LOT of money. While 16lbs is really light, I could get a quality wheel(Enkei NT03) for 1200 but they are 2lbs heavier. So will the 2lbs make a huge difference in terms of performance?

I mean they are still 3lbs lighter than stock. They are cheaper, plus they look fantastic! Oh and they come in black. I know 500 dollars doesn't seem like a lot. . . but it totally is. Also jam out to this right here.

https://soundcloud.com/daataa/mitch-m…

Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney > YSI-what can brown do for you 01/26/2014 at 19:46

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Rotational mass matters a lot . But, 2 lbs per corner isn't awful, but may be noticeable.

ohmysti > YSI-what can brown do for you 01/26/2014 at 19:46

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weight of original wheels?

YSI-what can brown do for you > Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney 01/26/2014 at 19:49

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How noticable? I will still be losing weight over stock. Although that depends on what tires I get.

YSI-what can brown do for you > ohmysti 01/26/2014 at 19:49

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21lbs.

desertdog5051 > YSI-what can brown do for you 01/26/2014 at 19:50

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Aside from Autocross, are you racing in a big series? If not, I would not sweat it.

YSI-what can brown do for you > desertdog5051 01/26/2014 at 19:52

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I might do a track day once a year, but those are expensive. I think Chicago SCCA does some track days, but I don't know how much those cost.

ohmysti > YSI-what can brown do for you 01/26/2014 at 19:53

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500 bucks is a big jump for 2lbs, money better spent elsewhere imo. go with the nt03s... better yet buy a used set and save more money!

YSI-what can brown do for you > ohmysti 01/26/2014 at 19:56

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I will be looking on the forums for a set. Hopefully black was a popular color!

deekster_caddy > YSI-what can brown do for you 01/26/2014 at 19:56

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While people are answering this question, I'm also curious how it affects how much abuse the wheels can take. The lighter, the weaker? So at some point does a lightweight wheel become unsafe for track use?

YSI-what can brown do for you > deekster_caddy 01/26/2014 at 19:57

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I think it comes down to the design of the wheel and how they were made. A forged wheel will be stronger than a cast wheel of equal weight.

Crocket Bernet > YSI-what can brown do for you 01/26/2014 at 19:58

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Get the cheaper wheels and diet. Two birds one stone.

desertdog5051 > YSI-what can brown do for you 01/26/2014 at 19:59

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If you were in an IMSA class or similar and doing this on a serious basis, I could see the money spent as good. You are going to spend 99% of your time daily driving.

Why spend a ton of money on something that will not provide a return on your investment?

deekster_caddy > YSI-what can brown do for you 01/26/2014 at 20:00

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I can tell you that the tires on my Volt are amazingly lightweight, and everything on that car is overthought, so it must be worth something! I didn't think the rims were especially lighter than the average 17" wheel (probably cost related) but the tires are surprisingly light.

They are Goodyear Assurance Fuel Max tires. I will be replacing with a set of Michelin Pilot SuperSports somebody gave me that happen to be very close in size. I'm not too worried about the 1/2 mile of range I might lose.

deekster_caddy > YSI-what can brown do for you 01/26/2014 at 20:02

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Understood. I'm thinking along the lines of 'how light before you have to worry about this in the turns'

YSI-what can brown do for you > desertdog5051 01/26/2014 at 20:03

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Fair enough. Plus it isn't like I am not losing weight, I am just not losing as much.

ohmysti > YSI-what can brown do for you 01/26/2014 at 20:03

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good luck heres my set for inspiration

YSI-what can brown do for you > deekster_caddy 01/26/2014 at 20:06

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What happened here?!?! XXRs are pretty heavy and they tend to break as well. So it can also be caused by the casting process. The XXR 527 is similar(and heavier) then Weds tc105n, yet the 527 break fairly often(when driven hard). Both are cast though .. .

Evan, Pope Of Jalopnik by Self-Appointment > deekster_caddy 01/26/2014 at 20:06

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Quality wheels shouldn't do this, unless you are using them for ridiculous things. This usually happens to cheap replica wheels.

YSI-what can brown do for you > ohmysti 01/26/2014 at 20:07

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Nice color combo! My friend did the same thing on his car. White and bronze go very well.

Evan, Pope Of Jalopnik by Self-Appointment > Crocket Bernet 01/26/2014 at 20:08

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Technically 8 pounds in rotational mass in the wheels counts for a whole lot more than that in the cockpit.

ohmysti > YSI-what can brown do for you 01/26/2014 at 20:08

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thanks! i got them for a steal :D

Evan, Pope Of Jalopnik by Self-Appointment > YSI-what can brown do for you 01/26/2014 at 20:09

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Here, read this: http://grassrootsmotorsports.com/forum/grm/37-p…

And then see what you value more. If you're primarily DD'ing it, the two pounds aren't huge...but you might notice a difference.

deekster_caddy > YSI-what can brown do for you 01/26/2014 at 20:10

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I don't know about this one - I was just GIS for broken hubs. But this is what I was thinking of. I thought I saw pics of a Mustang that came back from a track day with wheels like this once. I expect that it's not a very common thing, just curious if it's something you need to worry about with ultra light wheels.

YSI-what can brown do for you > Evan, Pope Of Jalopnik by Self-Appointment 01/26/2014 at 20:11

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Alright, that isn't too big of a deal then. Although, after searching for a bit I noticed that the NT03 isn't offered in 17" in a 5x100 bolt pattern :/

Soloburrito > YSI-what can brown do for you 01/26/2014 at 20:12

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First off, apologies if this doesn't apply to your situation but I figured I'd share my opinion on upgrades.

In my case, I'm a newb so I decided all that money I wanted to spend on upgrades would be much better spent on track days and consumables.

Until I feel my talent can maximize my car's potential, I'm not doing more than brakes/tires.

YSI-what can brown do for you > deekster_caddy 01/26/2014 at 20:12

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If it is a quality wheel, then you shouldn't. Like Volks, their wheels are 16 or 17lbs for 18x9.5, but they are very strong.

Evan, Pope Of Jalopnik by Self-Appointment > YSI-what can brown do for you 01/26/2014 at 20:12

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It isn't? Hmmm that is weird. I gotta say I have a thing for NT-03s, especially after seeing them in person.

Textured Soy Protein > deekster_caddy 01/26/2014 at 20:13

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As long as you're getting wheels from a good brand at a place like Tire Rack, and people use for racing without issues, light weight wheels aren't likely to have problems.

As others have mentioned, it's mostly with replica wheels that are usually knocking off some premium JDM wheel with cheap lightweight cast construction.

YSI-what can brown do for you > Soloburrito 01/26/2014 at 20:14

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Brakes/tires/wheels are all coming at once. The problem is, is that the stock tires suck nuts. The car has a ton of potential, but the wheels like to slip, ton of fun. . . but not fast for sure. Plus, the car looks 1000x better!

iDriveCode3 > Evan, Pope Of Jalopnik by Self-Appointment 01/26/2014 at 20:18

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The two lbs aren't huge, whereas depending on the car, $500 can go a long way. I do like the looks of the Enkei's; what's the other model look like, I wonder.

YSI-what can brown do for you > Evan, Pope Of Jalopnik by Self-Appointment 01/26/2014 at 20:18

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Me too, but now I have to start all over. I don't want to get 18s, they will make the car slower.

Soloburrito > YSI-what can brown do for you 01/26/2014 at 20:18

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That's a good point. Also I realize I dodged your question entirely. Probably because I don't know.

Your stock wheels seem decently light at least. My mustang wheels are a thick coat of brake dust away from 30#.

YSI-what can brown do for you > Soloburrito 01/26/2014 at 20:19

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Well my stock wheels are 17x7. I think Mustang wheels are 19s, right?

And its all good, we are talking about wheels here.

Evan, Pope Of Jalopnik by Self-Appointment > YSI-what can brown do for you 01/26/2014 at 20:22

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Yeah that's probably a good idea

Jeff-God-of-Biscuits > YSI-what can brown do for you 01/26/2014 at 20:27

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When I was doing a lot of motorcycle riding, I got a set of Dymags for my FZR1000, and I was astounded at how much lighter they were. Then I installed them and was flabbergasted at how dramatic the change in handling was. I had always heard the expression that a when a particular motorcycle feels really controllable, it feels as though it steers on the rear wheel. With the new wheels, it was just that. It turned my big heavy literbike into a 600. Now due to bearing issues, I didn't install the front at the same time, and I didn't notice the same level of improvement when I replaced the front wheel. But I was sold on how much difference a set of wheels could make.

YSI-what can brown do for you > Jeff-God-of-Biscuits 01/26/2014 at 20:29

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Alright, so do you think that spending 500 bucks more on a set of wheel is worth it?

Crocket Bernet > Evan, Pope Of Jalopnik by Self-Appointment 01/26/2014 at 20:30

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Im aware, twas a joke.

Squid > deekster_caddy 01/26/2014 at 20:34

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Wheels are a consumable and should be treated as such especially with track use. While a higher quality wheel from a company that actually track tests and races their wheels it is less of an issue with them breaking, and when they do it generally is a spoke that breaks from repeated curb hits. Catastrophic failure like what you pictured looks like it was more of a problem with a cheap wheel being used out of its safety zone, but I'd be afraid to drive with those on my car at any point in time.

What really matters is what the maximum stress the wheel is rated to handle. Cars on track with sticky tires can put over 1,000 lbs of force into the wheel so there are massive amounts of stress that a wheel needs to withstand. It is more you needing to take that into account and how much your car weighs and if you are going to be running Hoosiers or the like. The lightness is not the weak point of the wheel, but more of the design of the wheel its self and how it handles the forces.

deekster_caddy > Squid 01/26/2014 at 20:40

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Thanks. I completely understand what you are saying. I'm just not sure if they actually have 'load ratings' as such. If you track race, do you get wheels magna-fluxed periodically or just get new ones each season? I suppose at that level you would call the wheel manufacturer and ask them what they recommend. Looks are no longer important when it comes to performance like that.

Squid > YSI-what can brown do for you 01/26/2014 at 20:40

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Save the 500, as long as you get your wheel and tire package below or at the same stock weight it shouldn't be an issue. The lower the rotational mass the quicker you can stop, go and turn but that really only comes into play for serious racing. You DDing won't notice too much of a difference as long as you keep the weight in the same ball park.

Oh and thanks for reminding me of Mitch Murder. . .

Jeff-God-of-Biscuits > YSI-what can brown do for you 01/26/2014 at 20:42

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Well, what do the stock wheels weigh vs the weight of the new choices? I am pretty sure that either wheel will be a decent weight savings, but as with most things there that diminishing returns curve that really starts to go vertical quickly. If the cheaper wheel is 8 pounds lighter, and the other is 10 pounds, than it might not be much difference. However, if the cheap is only 1/2 pound under stock, then I might just go with cosmetics. Or a big brake kit!

edit. I should read more carefully.... Personally, I would go with the cheaper wheel. Or start hitting the forums for people that have used the lighter one to see if you could try it out and see if you see a difference.

YSI-what can brown do for you > Squid 01/26/2014 at 20:44

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Alright, fair enough. Not planning on tracking the car very often, maybe once or twice a year. Although, it will help while autocrossing but I think tires are the best mod you can make for autox.

And, doesn't lower rotational mass help while DDing as well as it provides slightly better acceleration and fuel economy?

Squid > deekster_caddy 01/26/2014 at 20:45

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You just use the wheels until they stop being round or start showing fatigue. AFAIK. If you run a race team I'm sure there is a budget for new wheels at least every other season. It just seems wasteful to stop using a perfectly good wheel after one season. I'm sure the wheel manufacturer has a say in that as well, but there are some of the spec miata guys running on the gen I and gen II 6ULs from 949Racing with no issues.

YSI-what can brown do for you > Jeff-God-of-Biscuits 01/26/2014 at 20:46

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The stock ones are 21lbs, the NT03s are 18 and the Weds tc105n are 15.8lbs. So far people have said, it won't make too much of a difference.

I would go with a BBK but those are $$$ for the fronts they are 3k!!!

Squid > YSI-what can brown do for you 01/26/2014 at 20:50

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Yeah but we're talking like tenths which really are not a huge impact for DD duty. You'll notice your suspension being more responsive in controling the car since it will have less unsprung mass to deal with but you can put that extra 500 into a nice set of tires and come out ahead.

Main thing is that you want to avoid adding weight on the wheels more than anything. But the 2 pounds in your case really wouldn't be a large impact as long as the alternate package met the stock weight.

YSI-what can brown do for you > Squid 01/26/2014 at 20:53

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The alternative package is actually lighter, BUT the NT03s don't actually exist in 17x9, which is really annoying. So I am going to have to start over. I am not getting RPF1s, though. Don't ask me why, but I just can't!!!

Squid > YSI-what can brown do for you 01/26/2014 at 20:55

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No worries. That is a bummer that they don't exist. good luck finding wheels that work.

YSI-what can brown do for you > Squid 01/26/2014 at 21:02

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I was thinking Rotas. . . but some people say they suck, others say they are awesome.

Squid > YSI-what can brown do for you 01/26/2014 at 21:03

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Don't waste your time with the imitation wheels. It really is luck of the draw with them. some are strong and some are weak and you don't know what you got until one breaks on you.

The WB > YSI-what can brown do for you 01/26/2014 at 21:47

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If you're just putting lighter wheels on OEM parts, you'll notice zero difference for the majority of factory cars.

YSI-what can brown do for you > The WB 01/26/2014 at 21:50

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I am planning on doing upgrades. It is going to be much slower. Springs and dampers(or Coilovers) and LCA are going to be in the cars future. Plus it isn't just lighter, it is wider as well. Getting some stickier tires for autox and maybe a track day or two.

The WB > YSI-what can brown do for you 01/26/2014 at 21:56

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If you're doing all that, you might notice a difference with some tuning.

However, there are a lot of things you can spend 1700 dollars on that will make a much larger difference in lap times (and even fuel mileage) like exhaust.

I'm not trying to convince you not to get them, but if it were me, I would feel like that was the type of upgrade to make once the "cheaper" (more speed per dollar) upgrades were made.

Also, a single pot hole will turn a bad day into a reaaaaaaally bad day.

revrseat70 > YSI-what can brown do for you 01/26/2014 at 22:29

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I've heard each pound of rotational mass amounts to about 4 pounds of unsprung weight as far as straight line gains go. So go with what you want to spend money on because you probably have 5-8lbs of unnecessary weight just in your glove box and trunk. Take that $500 and make a good payment on the car. As stated before, if you're going to keep it for a while, paying it off is the most important investment you can make.

Evan, Pope Of Jalopnik by Self-Appointment > Crocket Bernet 01/27/2014 at 01:05

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Oh well in that case carry on. I've actually heard people say that and mean it so I wasn't sure. In fact, I once had someone swear to me that wheel weight didn't matter at all. I had to walk away before my right arm involuntary slapped him across the head.

YSI-what can brown do for you > revrseat70 01/27/2014 at 11:24

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I could also get my fatass moving, should have the same effect :D

YSI-what can brown do for you > The WB 01/27/2014 at 11:43

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Haha, I already spent 1500 on the exhaust. I think that is WAY more than enough. I was thinking I would spend something similar or less than that one wheels.

I could get some Rotas, which I was(and currently am) thinking about. They aren't too heavy(17.8lbs) and they look great! Plus they are around 900 bucks :D

revrseat70 > YSI-what can brown do for you 01/27/2014 at 12:12

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Exactly. That's just straight line effect though. Zero-G forward motion. It will affect other aspects of the driving experience. Its the same reason a Lotus won't go faster than a heavier car with more horsepower. At a certain point, less weight doesn't equal faster. But at low speed/ high-G situations, weight means A LOT. So you would feel some effect. But not nearly as much as the difference between stock wheels and anything lighter.

YSI-what can brown do for you > revrseat70 01/27/2014 at 12:16

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Well lower weight does help slightly with braking, acceleration and the response you have. Other than that though, the performance gains will come from stickier/wider tires, which is going to be my favorite mod probably. That and the exhaust.

revrseat70 > YSI-what can brown do for you 01/27/2014 at 12:23

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Yup. Exactly. Tires are the best investment you can make besides getting a sporty car from the start.

The WB > YSI-what can brown do for you 01/30/2014 at 16:49

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That's not terrible for wheels in larger sizes. And there is something to be said for looking nice. :D