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I have two sets of wheels. One factory set, 15x6 with 205-65-15s on them. One aftermarket set 16x7 with 205-50-16s. I just switched back to the 15s to save the expensive tires till I have time to use them again and noticed how huge of a difference the change in wheels made. the wheel packages are the same weight but the 16s carry the weight more towards the outside of the wheel so it has a bit more leverage on the axels and brakes. BUT running the 15s I was burning the edges off the rear tires in the corners. The 16s fixed this problem but they are a little too heavy for my taste. What I want to know is if anyone knows how much lighter 16s would have to be to make up for the differance in leverage form the 15s. any other suggestions are welcome as well

 
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hmm wait until zzyzx gets in here...

 
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a halfway decent estimate would be to use I=m(r^2)
for two wheels to be equal, m(16^2)=m(15^2), so the 16s should weigh about 87% of what the 15s weigh for them so feel about the same. but that IS just an estimate, wait for one of the more educated ppl on here to give you a more solid answer.

 
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^^ thats pretty close.... Physics are fun!!

Thecheat, Your running in to a tire problem. The tires you are running dont have a stiff enough side wall. or your running them at too a too low tire pressure. SO, what PSI are you running the tires you have now, what type of tires are they (make/model), and..... how much camber are you running on your car... (Tire roll over can be reduced by running more negitive camber)

 
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oh how do i miss this guy ^^^

 
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hey, i think i asked you guys about this question.....

what psi should i fill into my new 215/45/R17 tires??

anywa, my new rims actually lighter 4 pounds compared to the black steelie, hehe...

 
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PSi on 17s... some where between 32 and 34, depending on the tire.

as far as your 17s being 4 lbs lighter... thats great for unsprung weight (Better handling) but they still have a greater Moment of inertia, and thus hinder acceleration and Braking.

if Hypnotiks formula is a good estimate then a 17 would have to weigh about
15.5LBS to equal the stock 15" steels (assuming the 15s weigh 20LBS) or (for the 03+ ex wheels) they would have to weigh about 12.84LBS.
Now if you compair them to my Rotas at 11.8LBS then the 17s would have to weigh about 9.1LBS.....

Just cause I'm board...
Stock 15s (Steel) 20LBS
16" = 17.57
17" = 15.5
18" = 13.8
19" = 12.46

Now Vs The 03 + alloys 16.5LBS
16" = 14.5
17" = 12.8
18" = 11.45
19" = 10.28

Whats the weight of the stock 14"s???

 
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zzyzx, you amaze me everytime i read your posts. bravo!

 
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Awesome information!

 
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on my 15s I have yokohama yk420 tires running at 34lbs 0 toe and factory camber (like 1 degree negative front and 1.5 in the rear) On my 16s I have yokohama es100 tires running 35 lbs. I like that little physics deal there, very cool. I'm thinking I'm going to wear out the yk420s on the 15 inch wheels then replace them with someting better and do some time comparisons. my initial skidpad (onramp) results show that I am only 4 mph faster with the 16 inch es100s so I bet that sticky ruber on the lighter, better handling 15s would get me the same laterl grip with better braking and quicker acceleration. the only thing I still worry about is the edge of the tire rolling under and getting chewed off, which is what the current set of 15s are doing.

 
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Its strange that the rear tires are geting shoulder wear, thats VERY uncommon on a FWD car. that tells me that either the tire pressure is Way too low in the back, or there is some positive camber back there... or that you have excessive weight in the back of the car.

I'd reverse your camber settings, try -1.5 in the front and -.5 to -1 on the rear. You'll need a camber kit.

also, the ES100 are a stickyer tire, and would explain the +4 mph on the on ramp.

are you running 35 psi on all 4 tires?

 
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yeah I was a little supprised that a wider wheel and lower profile with a sticky tire only helped 4mph but it seems like thats just the way it works. Tire presure is the same all the way around. My guess on the rear tire wear is that the tires are a little too much for the wheels. A good fried of mine is having the same problem on his peugot. they are 205 60 15s on a 15x6 stock wheel (alloy). I think some 15x6.5 could clean that up but I already bought now set of wheels and really dont feel like doing it again. Next time I'm sticking with 15's and just going wider. I think i am going back to 195s for this set of wheels, they seemed to turn in a lot easier and I liked the shorter gearing. No excessive weight but I've got a RSX rear sway bar and that dramaticly accelerated the tire edge wear so I think its putting a bit more force into the outside rear tire then these tires can handle. freaks my allignment guy out to no end. I was going to try that allignment but I couldnt get my guy to do it. I found a new place but I havent had time to go have it done yet. What wheels size are you on? 15x6 or is it wider?

 
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It works like this. If you take a five pound weight and put it on the end of a 12in stick then hold it out from your body so the stick is level, you will feel that weight as a certain value lets say it feels like ten pounds. now make that same stick twice as long and do the same thing. you will feel more weight even though the weight hasnt changed. When we are discussing the weights of wheels there are two things to consider. The weight that the suspension has to move in order to work, unsprung weight. And the weight that the brakes and engine have to stop and move, rotational weight. The reason that the weight will seem greater at the end of the 24in stick is leverage. This is the same reason that a bigger wheel will have to be lighter to have the same affect as a smaller wheel on the brakes and engine. So while the unsprung weight is the same, the rotational inertia is greater if the total wheel and tire package is the same weight. The farther you get from the hub, the greater the effect. This isnt as big of a deal if you drive on highspeed tracks but it is a huge deal in the canyons where firm braking and quick acceleration are important. I thought that going to a wider wheel with a shorter sidewall would help the performance of the car even without a sticky tire to back it up but from the look of things, the only gains I got were from the tires.

does this make sense?

 
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Are all the factory Honda alloys lighter than the steelies? I noticed an ad @ my local dealership for chrome Accord rims ( I know they won't fit, but I was always under the impression that large chrome rims are heavier)

 
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I think the 02-03 alloys are the same weight as the steelies but the rest of the alloy 15s should be lighter

 
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thecheat has a good analigy of this, esentially the Lighter 17 has a Higher Inertia because a larger porportion of its weight is farther from the center of rotation.