Any physics majors around?

I'll have to admit...I'm in love with the 18 inch TSW Thruxtons. Beautiful rims.




In fact, they are so beautiful, I can't stop checking on them every night. Of course, however, TSW makes notoriously heavy rims.

The Thruxtons (I am told, after a call to TSW) weigh 27 pounds...which is pretty heavy. I was looking for 18 inch rims around 20 pounds, but sadly, every light weight rim looks notoriously the same (like a baby spider).

My question - I am under the impression that the more the rims weigh has much more an effect on a cars speed than comparable weight from the car itself. Essentially, I believe that a 30 pound weight save on the rims is much more effective than a 30 pound weight save in the car itself, since the rims are actually being accelerated by the engine itself rather than the extra weight which is being pulled by the car.

I have absolutely no data to back this up, but it seems naturally intuitive to me. I mean, why else buy lightweight rims when you could simple take out the spare tire and BAM, your weight (and track time) is right back to where you started? It seems that weight on the epicenter of the focal point is going to be much more dominant than gravitational weight pushing down on that point...

Does anyone know the stock weight of the 17 inch SL rim? Is going to an 18 and using the Thruxtons going to slow me down (at 27 pounds) or does it make more sense to get a lightweight wheel (at around 20 pounds)?

ANY physics majors? Am I babbling?

Thanks,

Joshua

 

my tsw 20 in kayalami are 29 lbs... heavy but compared to stock rims its only 3 lbs more...

 

So the Thruxtons are almost the same as stock...what do you think? I believe I read you said they slowed you down a bit...how does it feel?

Joshua

 

You also have 20's though...I'm sure that is part of the effect as well.

Joshua

 

stock 18 in se rims w/ the stock rsa 's weigh 57 lbs...

my tsw 20's w/ the flaken azenias weigh 60 lbs...

 

ohh... and no i dont know if it has slowed me down... i mean.. it had to of.. buy maybe jut a .01 ... who knmows.. i will see soon ... next wednesday

 

I'm wondering then if a reduction to 18 or so pounds per rim would warrant an outstanding increase in speed. You know any physics? lol

Joshua

 

ahha no not really...

but i wouldnt get those in 18's they will look tooo small.. get 19's

 

well peeps with the light nismos said they spun more too... so it all depends. if u "love" the wheels, not like they're heavier... so get them. you're deciding look over performance. is one really more important to you?

now see my 20s are lighter than stock, so win-win for me

 

The heavier the wheel (tire and rim) the more inertia it has and therefore the slower it will react to and recover from forces like bumps in the road, turning, acceleration and braking. Also a larger rim diameter tends to increase the rotational inertia of the wheel because it concentrates the weight closer to the outside diameter of the wheel. So for two wheels that weigh the same, a 15" and a 20", the 15" will usually have a lower rotational (spinning) inertia but both wheels will have the same inertia with respect to forces like bumps. So the best performing wheel would be the lightest with the smallest diameter rim and tire (all other things being equal).

So as far as your question about 30 pounds on the car versus 30 pounds on the wheels, the heavier wheel will have a more dramatic effect on ride and handling than 30 pounds on the car, also because you are making a greater percentage increase in the weight of the unsuspended components (which aren't 1/10 the weight of the suspended part of the car). As far as acceleration goes the increase in wheel diameter will have an R squared effect on inertia and a proportional effect due to the weight increase (the relationship is mass X radius^2).

 

There it is! Hahahha!

Now, I'm going to be investing a lot of money in getting the car into the 13's (headers, ypipe, emanage, tune, nitrous) in the future. The question is, can I do this on the TSW's, or should I specifically buy a rim that is very, very lightweight...Nismomax you bring up a good point - more wheel spin with lighter wheels...

Anyone with real world data about this? Honestly I'm trying to maintain a balance between performance and looks. I'm getting 18's regardless. I'm on 17's now.

Joshua

 

"more wheel spin with lighter wheels..."
When was the last time you saw a drag car with steel wheels?

F1 cars have 13" wheels. IRL and CART have 15" wheels. Smallest wheel = best performance.

Now that being said, I have 19" SSRs on my car. I get more enjoyment out of good looks than I can out of knocking .1 second off my morning commute (even if I could).

 

Check out this wheel. Not to far off from the good looks the wheel you're looking at but only 19 pounds. It's also has a width of 8 inches with a nice offset of +35mm.

http://www.tirerack.com/wheels/Wheel...All&sort=Brand

 

Phil, I love those Thruxtons too. I saw some on a Solara in person and they looked great. These would be incredible on a smoke max.

 

So 17's are even better for speed than 18's?

Joshua

 

20's huh? Those in your sig?

 

Where did you find this? You think a 20" wheel weighs less than a 20" tire?

 

Is a lighter weight wheel/tire combo better for accellaration than getting a wider tire for better grip/pull?
The stock 17's are only 7" wide, the 18's are 7.5". I got the Thruxton 20's with at 8.5" wide and feel a better grab/pull than my stock 18's or my last pair of Zinik 18's that only weighed 24lbs.

 

I have very light 18's- 19 lbs. each and my tires weigh 26 lbs. each. When I got my wheels, I was so hung up on finding the lightest rim. Now that I did, although they handle incredibly well (8.5" width), they spin so easily in 1st and 2nd gear. Yesterday, in the rain, regardless of how well I feathered the throttle, I'd get wheelspin, and I have 255's w/ only 9K miles on them. With that said, I think you can probably floor it w/ those heavy 20's and will get a better launch w/ less wheelspin.

 

Better grab and pull perhaps - but what about overall accelleration?

It seems that this conversation is starting to become - there are pro's and con's to everything.

If that's the case, and lighter wheels will just get me wheel spin, I might as well get the 27 pound 18 inch Thruxtons and call it a day???

Joshua

 

that's basically what I was trying to say, but overall accel is phenomenal! Get the Thruxton's dude- it's a great wheel and they'll look hot, even in size 18, which I actually prefer anyway.

 

If you want to stick to a close OEM look then get the wheels in my sig

18x8
18.2lbs a piece
About $1,000 give or take a couple hundred

 

Do you experience excessive wheel spin?

PS where did you get them???

Joshua

 

I save my tire "wastage" for the higher end runs...

I think that I've only chirped/spun with these wheels/tires about <5 times. I know that off the line, if I really wanted, I could spin them HARD

www.my350z.com took 3 months to find 2 sets, so that I could have 4 fronts and NmexMAX could have 4 rears

 

Also....this is what I have read and heard of

Rotating mass is equivalent to about 8x the weight of dead mass. I saved roughly 10lbs a corner with my 350Z Track wheels. So that would equal out to 10lbsx8x4=about 320lbs to dead mass.

100lbs=about .1 seconds faster, so I SHOULD be .3ish seconds faster if I could hook up and if this "theory" is true, which I have seen many people go by it, so I would assume that it is.

 

yes the ones in my sig 20x8. surprisingly only 1/2 rubber on the sides and the ride isn't any rougher.

well it's getting cooler, so back to stock soon

 

I get 12-15% better MPG w/ my lightweight wheels.

 

That's a lot
What kind of rims/tyres do you compare...? Just curious.
Thx

 

I'm going to have to go lightweight...I'm going to have to sacrifice the Thruxtons...

Joshua

 

those are nice man

 

Those are sharp man. Dang! Now you guys got me wondering how much my 350z wheels weigh.

 

Gotta love wikipedia. I may have to shave a pound and trade my rear 8.5" in for 8.0's. F0ckit, they still look hella pimp.

Front
Size: 18x8.0
Offset: +30mm
Weight: 24.4
Tire: 225/45/18

Rear
Size: 18x8.5
Offset: +33mm
Weight: 25.8
Tire: 245/45/18

 

Mack,

Those wheels are tight. Don't change a thing (well maybe the fronts).

Consider going 255/40/18's for your next set of tires. That will shave a pound or two plus add some more meat!

Try to get 8.5's for the front. Those 255/40's will slip in pretty on 8.5's. Also, better handling.

Just my opinion!!!

 

You want performance, get lightweight rims.

General rule of thumb is:

19" rims shouldn't weight more than 19 lb
18" rims shouldn't weight more than 18 lb
17" rims shouldn't weight more than 17 lb

However, you should strive to do better. My old 17" rims weighed 14.5lbs. My current 17" rims weigh 16 lbs IIRC.

But seriously, if you want performance, 19" are too big, go with 17's or 18's. Forged is preferable.

Your handling, acceleration, and braking will improve. It's a win win situation.

And the whole wheel spin thing, what a bunch of hogwash. Until you slap a turbo on it, you won't be spinning tires just because you got lightweight rims.

Also, remember that not all tires weigh the same either! Be sure to shop that too. Tires vary by as much as 4 lbs in the same size!

 

I got Motegei trakilites. 14.3lbs per wheel, and 23 lb tires, in the end I have saved about 20lbs per wheel/tire. Car feels really responsive as well.

The wheels are nothing to look at, but hey, they're light.

http://forums.maxima.org/showpost.ph...2&postcount=24

 

Thanks cool! But the lower profile tires worry me a bit. I just pulled off the stock Bridgestone Potenza's that came on these wheels and while they handled like velcro the ride was horrendous, however the fronts were 225/45/18. I put the RSA's back on and still handles great but rides MUCHO better. I would certainly consider the 255/40's but concerned about ride quality a bit as I like to take trips every now and again and be fairly comfy. Wizard thanks for the heads up on tire weight, I had never considered that before but will surely put that on the list of considerations for my next set of meats.

 

Wizard,

Thank you so very much.

Sincerely,

Joshua

 

Werd.

I looked them up on this ebay store:

Only comes in 15 and 17. Does anyone think 17's are too small (I'm sure you all do, why am I even asking???). One piece forged (black) and only 14.3 pounds per tire. Don't even look too bad.

Will the bolt pattern/offset even work? Specifically on this wheel.

Joshua

 

i had black 18's and they looked like 16's....

if u r goign to get 17's make sure they are not black.. if u get 18;s make sure they are not black w/ a chrome lip... always looks smaller

 

Like I said, IDC if they look small, or even how they look, function over form.