6Speeder

When you are talking about rotating weight, the distance from the point of rotation is also important. 18" rims have their weight further out than the 17's which causes part of the loss. Good post.

JEEP/C5

This is a good tread; I love it when everyone brings up valid points for pros and cons of different aftermarket products. But for many of us, even if we loose a few HP it would not really matter unless you race. I think put what you want on your car and either add 10 - 20 more hp to compensate or don’t worry about it.

Also I am all for adding a “little” more weight due to wider tires and wheels combos for increased cornering traction and straight line traction - which is a real problem for many of us. If you loose 15 hp but have greater traction you may find your ET drop or your faster on that oval! Now you may be winning or more consistent with more weight add!

Love to see more comparisons with same size tire diameters and then test on track to see ¼ mile runs.

ZZOOM06

Great post Alan! It's about time someone took the time to do something like this. I've known since day 1 that my heavy chrome MS wheels were hurting me, and now thanks to you I know just how much!
Good job and thanks for all your effort! If you haven't done so already, you need to post this over on ZO6Vette too.

Jimbo

pianoprodigy

Thanks, Jim. Done.

HawkIVette

geez, guys. Piano took the time to do this test and although, it's not a great amount of HP loss, it is some and that's all he is saying. I found it interesting and appreciate that he took the time to do the test, wrote it up and posted it for all of us to see.
Am I going to run right out and buy new wheels and tires- no, but it something to consider when I do buy new wheels/ tires for my car to drag race. Hey, every little bit helps when you're shaving hundredths of seconds in the quarter. I right now run 12.3 in the quarter and am looking to get into the 11's. Will new tires and wheels do it, probably not. But it's worth considering.

Thanks Piano for your post. And others, shut the F' up if you don't have anything constructive to say. Maybe you should re-read the Forum rules.

2ndVette

great thread. Those that deny that all things being equal, that a lesser weight is not beneficial are not worth listening to anyway.

shurite44

I bracket drag race, so I keep detailed wx and time data. After looking at wx info I can usually predict my ET within a few hundreds of a second. The reason I bring this up is usually when I talk about this someone tells me in is my imagination. Believe me a bracket racer knows when a mod affects his time.

After I switched from my OEM thin spokes to 18x10.5 rear and 18x9.5 front chrome reproductions I lost on average 1-2 tenths in the qtr mile ET.

No other changes were made and traction was really never an issue for me.

I know the wheels were much heavier but I did not weigh the new tires to compare against the runflats. I would guess they were probably about the same weight since I went with 285's and 315's. I say this because although the runflats are heavy I did go with a considerably bigger tire.

I wish I would have stayed with OEM wheels, I won't make the mistake again.

Anyway that is my story and I am sticking to it.

LV Vette

By the way, today I got new BFG drag radials in 295/35-18 size. I had them mounted on my old (lighter) 18" wagon wheels. Glad I saved them. Just driving on the street and playing around, you can feel the difference besides the traction.

Clayton from Las Vegas

shurite44

I love the chrome reproduction wheels, they look great. Best thing is to have a nice set of OEM wheels for the track and use the reproductions on the street.

There is another alternative, besides of course paying 3-5K for wheels. You can have OEM wheels chromed. A forum vendor offers trade in service for a fairly reasonable price. Chroming an OEM wheel only adds about 2lbs per wheel.

You can also have OEM wheels widened, even the magnesium's can be widened. So for a fairly reasonable price you can have a light weight, strong, chrome racing wheel in any width you want.

Edit: I thought I should add so I don't mislead anyone, magnesium wheels as far as I know can not be chromed.

TomT

This was a good thread 'till the petty remarks started.
Like they say, "If you live in a glass house, don't spit into the wind."

Ikester

Dam you! Now i want to throw some stock wheels back on so i can dyno 425hp+ to the wheels! id feel better.

My CCWs are heavy as schiznit! (19s)

J-Rod

Good info. I've seen similar results with RWHP losses. Rotating mass is exactly that rotating mass. it takes energy to spin big heavy wheels. In fact there was a "ricer" mag that took a civic with big wheels and tires, and swapped them out for the 14" stockers and picked up tons of time at the drag strip.

ericdwong

Great test. It just shows how heavy wheels = performance robbers. I've always been an advocate of light weight wheels. Some people claim it doesn't make a difference, but it makes a HUGE difference, even just a few pounds. Heck, I went from my Goodyear M&S (snow) Runflat tires on wagon wheels to my OEM Y2k rims with Kuhmo Ecsta MX nonrunflats and it made a HUGE difference in the way it rides, handles, brakes and accelerates. I hate that bogged down feeling when driving with heavy rims.

Rob 99

Pianoprodigy, Interersting thread thanks for taking the time to do it and post such a detailed report, i was under the assumption that all aftermarket wheels were just as light or lighter than the stocks so i learned somthing here.
I would have like to seen a more straight up comparo using the same tires on the two diff wheels, ( i realize tough to do)that would have taken the tire size debate out of it and simplified the test results, but in any case i think most of us get the idea.

Warp Factor

pianoprodigy, don't even bother responding to these guys. Don't waste your time. You went to a lot of work and got interesting results . Some people don't like the results or will find fault with the methodology, but no experiment is perfect, and they have yet to post results of their own experiments that were better thought out and executed.
I appreciated your post, and it was great food for thought.
Thanks.

___________________________
2000 FRC, ECS Paxton

Jesse

Please read:

http://forums.corvetteforum.com/showthread.php?t=1118172&forum_id=109

Answer the question asked by the thread creator with personal experience or fact, and keep the attitudes and sarcasm out of the thread...

RoHo

Hey Piano, let me say thanks much for the info and by the way, thats was one of the best looking RX7 I'v seen.

Y2KVert

Not to Your test would have shown more correct results had you used the same wheel and tire diameter. I agree that weight does play a contributing factor as to your hp loss but the wheel diameter I feel also plays a role in your equation. A taller wheel will yield a reduction in gear ratio and a smaller wheel will yield an increase likewise.

pianoprodigy

Yes, I realize this. I asked my buddy who has Nitto Drag Radials in the same size on 18" Z06 wheels if we could use his, but he didn't seem crazy about the idea, so I had to work with what I had.

I do know that when people get a shorter gear ratio (3.73, 3.90, 4.10, etc) that their RWHP numbers on the dyno generally go down (dunno if you were implying that or not).

Y2KVert

Yes shorter gears will drop your rwhp. I was referring to wheel diameter affecting finla gear ration. Think of it this was if you have a wheel that is 18" and it makes 20 turns for every 4 turns thatn a 20" wheel is going to take more revolutions to arrive at the same ration because it is taller.