18" wheels heavier than stock?

[72bluNblu]

Not necessarily.

I've heard from a few people that going to larger rims, 17's, 18's etc, hurts performance because the wheels weigh more. Although it's hard to argue that the additional traction isn't worth it, I really didn't buy it.

But, I also didn't have any proof other than adding up manufacturer's specs. Until now.

So, what I had to compare was your basic 15x7 police wheel. Nothing fancy, pretty similar to a lot of the stock steel rims. On it I had a 225/60/15 Falken Ziex 512. Maybe not the lightest tire out there, but pretty average at about 25lbs. To compare to that, I had a 275/35/18 BFG KDW 2 on an 18x9" Enkei RPF1. One of the lighter rims out there for sure, but not the lightest. Also, a 295/35/18 on an 18x10 Enkei RPF1. The 18x9 weighs in at 17.1 lbs, the 18x10 at 18.45 lbs. The rims are light for sure, but those are MUCH wider tires.

I found the police wheel and tire to weigh 50 lbs. Definitely not all the light. And then things got interesting. The 275/35/18 on 18x9 weighed in at 45.8 lbs. That's 4.2 lbs lighter per wheel, not a small margin, especially talking about rotating mass. The 295? It weighed in at 49.4 lbs. Half a pound lighter than the little 225/60/15 on a 15x7" rim.



Obviously, not the "end all be all". The RPF1's are very light for their size, so there are no doubt 18's out there that would be heavier. And the Falken's may not be the lightest 225/60/15 you can get.  But, considering the difference in tire size, there are more than a few 18" combo's out there that would be lighter than the stock steelies.

Just how much bigger is a 295/35/18 than a 225/60/15? A LOT bigger.

[grimmey71]

I've been curious about this as I've been looking at team 3 wheels which I hear are around 25lbs each(without tires of course)

[brads70]

   Good info to know!  I'm very soon planning on pulling the trigger on these in 18"
http://www.team3wheels.com/lt_iii.html

[cudazappa]

Another thing to consider is the moment is inertia of the wheel/tire.  Where the mass is on that 18" wheel and tire carries more inertia than the 15".  More inertia means harder to stop.  Also the rims you choose to compare are by no means a end all be all comparison.  15x7 civvi wheels are lighter than cop rims and cast 18s will be heavier than forged.

[burdar]

Another thing to consider is the moment is inertia of the wheel/tire.  Where the mass is on that 18" wheel and tire carries more inertia than the 15".  More inertia means harder to stop.

The farther the weight is from the center of the wheel, the more hp it will take to get that wheel moving.  The over all weight isn't the only factor.  I remember watching one of those tuner shows back in the early 2000's.  They were working on some little wagon.  They put the car on a dyno and got a baseline.  Then they installed a big brake kit, larger wheels and built a larger exhaust system.  They put it back on the dyno and it lost 5hp or something like that.  They thought their custom exhaust had lowered the hp so they put the stock system back on.  They put it on the dyno again and they were down something like 12hp from the baseline.  The larger brakes and tires were costing them 12hp.  The exhaust upgrade gave them 7 back.

[HP2]

My 15x10 Aeros with 26x12x15 MT SRs come in at 42# each. Not bad for 12" worth of tire width on a steel wheel.

Inertia is also a factor in real world driving.

There are some very good, lightweight 18" rims out there, but they come with a heavyweight price tag that most won't tolerate, hence the popularity of the Mustang rims. But, must guys that own these cars aren't too worried by reducing wheel weight to the nth degree on the predominately street oriented machine.

[72bluNblu]

My 15x10 Aeros with 26x12x15 MT SRs come in at 42# each. Not bad for 12" worth of tire width on a steel wheel.

Inertia is also a factor in real world driving.

There are some very good, lightweight 18" rims out there, but they come with a heavyweight price tag that most won't tolerate, hence the popularity of the Mustang rims. But, must guys that own these cars aren't too worried by reducing wheel weight to the nth degree on the predominately street oriented machine.

True, you can get lighter wheels in 15". But if I'm not mistaken, those Aero's are not street legal.

And most folks aren't running Aero's with MT SR's. They're running stock, or reproduction stock steelies with BFG T/A's, both of which are ridiculously heavy. Like I said, not the end all be all. The 225/60/15's I compared are the same height as the 275/35/18's, but in a 15" street tire there's only about 3 different tires you can get in a 275, and most folks are running a 275/60/15 BFG T/A. That tire weighs 35 lbs by itself, making the combo over 60 lbs with a stock steel wheel. It's also taller though, so again not exactly apples to apples.

The 18's in question are on my '74 Duster. While its not scientific at all, I can tell you that the car seemed more responsive all the way around with the new wheel combo, including acceleration. Yes, that's only on the "butt dyno". But I'd honestly like to look at the moment of inertia for both sets of wheels. I'm not 100% convinced that its as black and white as it may seem. You'd have to know the weight distribution of the tires to truly get that calculation right. The thing about most of the 15" tires is that they're a harder compound, and they tend to have thicker treads than more modern type tires. Obviously the sidewalls are bigger, and therefore heavier, but I wouldn't go out and say that the moment of inertia on the 15" tires is an obvious clear cut advantage over the 18's if you're talking about the same height tire. I think at best some 15" tires would be better, but not necessarily all. The MT SR's are obviously a lighter tire, they'd have a clear cut advantage. But with a set of BFG T/A's I don't think the benefit would be so clear.

Regardless, the lack of sidewall flex, the improved compounds, and better all around design of the more modern street tires put them ahead in my book, even if you give up a little inertia over some of the 15" options out there.

[SBDave]

Do you have a build thread on the Duster?  Or can you post a picture of it with the new wheels/tires?  Sounds pretty sweet!
Dave

[72bluNblu]

I do have a couple of build threads going,  over on FABO

http://www.forabodiesonly.com/mopar/showthread.php?t=198098

or at protouringmopar

http://www.protouringmopar.com/showthread.php?1279-74-Duster-the-demonizer-build

Pretty much the same thread, slightly different audience so some of the posts are a little different.

Here's one with the new wheels on the car.

[brads70]

My favorite mods you did so far are the fold down rear seat and tucking in the rear bumper. 

[Katfish]

Great info, much larger contact area, and similar weights.

[Super Blue 72]

Nice info.  I always thought the 17+ inch rims were always heavier.

[drewcrane]

Nice info.  I always thought the 17+ inch rims were always heavier.

Some 17,s are  heavier depending on who makes them

[72bluNblu]

Nice info.  I always thought the 17+ inch rims were always heavier.

Some 17,s are  heavier depending on who makes them

A lot of them probably are. It really depends on the rim and manufacturer, in both 17" and 18". Police rims are pretty heavy too.

Like I said, not an "end all be all" kind of comparison. I just wanted to show that if you do your homework, it is possible to actually have 17 or 18" tire and wheel combinations that are, at the very least, similar in weight to a lot of 15" combo's that folks are running. And depending on the particular combo, possibly even lighter.

And I didn't get into the nitty gritty on rotational inertia. Most of the 17/18 combo's would still be slightly worse for that. But realistically, I think the advantages to having a modern tire in a much improved compound is worth some of the disadvantages. Improved sidewall stiffness, better tire compounds, and in this case significantly wider tires are worth some of the trade offs. Not to mention selection and availability.

[7212Mopar]

I thought wheels and tires are more of a concern as part of the unsprung weight consideration that can affect handling, so lighter wheel and tire package is better. If overall wheel/tire diameter and gearing is the same, I doubt that the 18 inch package has any deficiency to the 15 inch package in terms of the engine getting the car moving. The wider package will have better traction for acceleration, braking and cornering.