Wheel Weights (weight of wheels, not balancing) [Merged 2-8]

[Mike 99GSX]

I have been spending the last week trying to find out why my car wasn't as fast at the track last week as I thought it would be. I know I have some tuning and better driving to do but I thought my traps would be higher. My mods are in my profile but basicly its a 2g, 16g, FMIC, VPC/GCC and all the other stuff. I've only had 2 passes so far with my second being a 13.5 at 100 MPH with a 1.9 60'. I'm working on fixing a few tuning things but was wondering this: When I was doing more roadracing, I had to by 18" wheels because the Baer 4 piston brakes that I have do not fit in the stock 17" wheels. I didn't really do my homework on the wheels. I ended up buying a set of Moda R6 18x8 wheels which look great but weigh in at 50 pounds each with tires! I weighed my stock wheels and tires and they weighed 41 pounds each. Also each rotor/caliper weighs about 5 pounds more than stock. So overall, I increased my cars rotational weight by about 55 pounds. Is this significant? I'm looking for someones opinion on how much is too much. Am I losing alot on my ETs or is it insignificant? Any thoughts?

 

[Nailz]

Whether you're adding weight or taking it out, every bit makes a difference in the long run. 55lbs isn't too bad but its the 18s that will hurt your ETs more then the weight.

 

[Mike 99GSX]

If I don't spin and get a good 60' time, then how would the 18s hurt my overall ET?

 

[larryd]

Rotational mass does actually steal power from the car. The heavier your wheels/tires are the slower your car will be. Ofcourse once you start making good power it becomes less and less of a factor.

 

[Mike 99GSX]

I understand why rotational mass slows a car down but what I don't understand is how wheel diameter slows a car down if thats what he was saying. Maybe he just meant that an 18" wheel is generally heavier than a 16" wheel? I thought he was saying it takes more initial momentum to turn an 18" wheel or something?

 

[Nailz]

The bigger the wheel gets the taller the gearing will get as well. Thats why most race cars you see use 16"s or smaller wheels. Like Larry said, once you start making alot of power then the wheel size doesn't matter as much but it can still slow you down.

 

[gfultz]

Unsprung weight slows you down. Rotational mass will slow you down even if you launch cleanly, in theory to launch clean with those wheels is a lot different than launching cleanly with 16" TE37's. Also, do you still have those brakes on your car??? Those can really kill you in a 1/4mile time. I can't remember the exact equivalent that I read in one of the tuner mags, but, unsprung weight reduction plays a far more significant factor in lowering your 1/4 mile than sprung weight. I think the example was on a civic si where they swapped out the stock wheels for TE37's and it was the equivalent of removing the power sterring, radio, rear seats, and air conditioning.

 

[mike9146]

Larger wheels place the rotating mass further out from the axis of rotation. This of course, assumes that the extra diameter of the wheel will be heavier than the amount of tire that it replaces. Overall diameter being equal, of course. The further an object of equal mass is from the center of rotation, the more energy it takes to accelerate it at the same rate. Look up "polar moment of inertia."

 

[Mike 99GSX]

Good info guys. Yes I do still have the Baer brakes. It sounds like I'll have to make a decision on ditching them if I get more into the dragracing instead of roadracing. For now I think I can find a 17" wheel that will still fit with the calipers and be significantly lighter than the Modas. I love the TE37s but there so damn expensive!

 

[DirtyBirdRacing]

What would be best for drag racing:

-18 inch wheel with 225/40-18 tires (25.5 inch outside diameter, wheel weighs 24 pounds)

-17 inch stock 2g wheels with 215/50-17 tires (25.1 inch outside diameter, wheel weighs 25 pounds)

Is was think that since the tires mass would be less on the 18 inch wheel and since the 18 inch wheel weighs less, that in terms of rotational mass it would "free" up some horsepower and thus help in dragracing.

Bill

 

[slprlaser]

Just for reference when I had my first 92 AWD Laser 2 years ago, I took a scale with me when i had some new tires put on the stock rims. The stock mesh Laser wheels weigh 19.5 lbs a piece. I thought that this was light for a stock rim. I am just thinking of painting the mesh part black and leaving the lip polished....

 

[rubbersidedown]

if i'm not mistaken it is generally better to use "beefier" tires or tires with higher side walls (i don't how else to put it for some reason) as opposed to low profile tires, when drag racing. This has something to do with allowing more flex in the tires and taking some strain off of the drivetrain. i think there are some other reasons for it as well but my brain is failing me for some reason.... oh and would the break calipers really heart that much? Do they really increase rotational mass even though they don't rotate themselves? I'm sorry if i'm sounding stupid but i've been feeling really sick lately and sleeping a lot, so my comprehension may be a little shitty overall cause i'm just not all here at the moment.

 

[Mike 99GSX]

The main reason the brake calipers suck in this case is because their physical size requires me to use at minimum a 17" wheel and I couldn't find any reasonably priced 17's that would fit so I had to get 18's.

 

[igs]

Originally posted by Nailz
Thats why most race cars you see use 16"s or smaller wheels.

Most race cars use 18" wheels. 18"x13" to be exact.

What's our stock wheel size? 17"x6.5". Good for jokes but not much else.

 

[slprlaser]

Last time I checked Shepard uses 225/50 16's as well as ALL fast DSM's, there are no DSMs running 18x13 what are you talking about? Thats 800+ RWD territory...

 

[NDgsx]

Originally posted by Nailz
The bigger the wheel gets the taller the gearing will get as well.

100% wrong. Wheel diameter doesn't change anything but your tire size. A 225/40r18 tire will be the same height as a 225/50r16, absolutely no effect on gearing.
DSMs make a thing called torque, they're not hondas. Having larger rotors is NOT going to make even a .10 of a second change in your time. Get lighter wheels and if you are really worried about rotational weight get a set of Pirellis, they are the lightest tires out there.

Oh and unsprung weight has nothing to do with rotational weight, just think about it for a minute and you'll realize that.

 

[NDgsx]

Originally posted by igs


Most race cars use 18" wheels. 18"x13" to be exact.

What's our stock wheel size? 17"x6.5". Good for jokes but not much else.

They're all talking about drag cars. Roadracing cars use a wheel that big to be able to fit appropriate rotors and reduce sidewall flex.
You want sidewall flex for dragracing, wrinklewalls are the easiest example.

 

[Nailz]

Originally posted by NDgsx


Get lighter wheels and if you are really worried about rotational weight

Nick, look at my sig and you'll see I already have that taken care of

 

[Mike 99GSX]

That was my whole point. Drag racing and road racing are two different things. I doubt John Shepherd has 13.5 rotors and 4 piston calipers on his drag car as it would be a waste of weight and money in his case. That why I said I'll have to make a decision on what is more important or just live with a compromise between the 2.

 

[MNGSX]

I looked over various wheels for all attributes puting performance aspects first and looks second. I left cost third.

I also looked over tires in much the same manner.

I have made my decision with the wheels. However, Along the way I started looking at tire weight.

It is something much funkier than wheel weight.

I think some people may have ended up spending alot extra on a super Ultra-Ultra- light wheel and negated it with tire selection...

I'm not saying you can compensate for two layers of spinning chrome with a tire that is'nt porky... Just that the difference between a tire and wheel assembly containing say a cast rota vs a forged TE-37 may well suprise you depending on the tire each person put on it.

I have come across a closeout lightweight forged 17x8 wheel that.... well makes me.

:laugh: and untill I get my order in or else

Lets just say around 15lb in the 17x8 size.

A stock 2g swirly wheel is around what 27-28lbs? I don't have a nekid 97-99 around to plop down on the bathroom scale.

I then looked up tire spec sheets.

They vary greatly as far as weight is concerned.

For a baseline I looked at the weight of my current shoes.

215/55/16 Kuhmo 712 23lb.

Now when you go plus one in an 712 and go wider to say

245/40/17 they weigh 26.3lb

About 3lb heavier

Use a 255/40/17 and it's a whopping 28.2 lb

About 5lb heavier.

Adding to confusion for those who only want 225 wide tires. Lets say in a kuhmo mx.

A 225/16 is actually 3lb heavier than a 225/17 in this model of tire.


When you look from one brand or model of a tire to another it can go the other way.

Lets say a Kuhmo 712 like my 215/55/16 vs a Kuhmo Ecsta MX in 245/40/17

23lb vs 23.3lb

Not bad for a plus one rim increase and a pretty good leap in section width?

Get this a 235/45/17 is only 20#.....

A 255/40/17 is 24.6

yet go up in profile..

255/45/17 and it is down to 20# again!

The last three were all the same model of a given brand with only sizes being the difference.

Now change brands and a bridgestone So3 pole position in 245/40/17 is 28#. So 5# heavier than a kuhmo MX.

I told you its funky. Rotational mass is the big deal... What part makes up the rotational mass which has the biggest effect? The part which is nearest the circumference of the circle... Which means of course it is the tire.

Kinda like why it does'nt take an oz of lead to balance a naked wheel on a tire balance machine. Yet it might when you put the tire on.

Weight out around the tread and belt has alot more leverage to throw its self around than aluminum spokes an inch longer or a rim with a 1" bigger od.

Tire heft is'nt the only issue in selction... I just think it is an overlooked factor in comparison by most people.

Lets just say I'm cutting weight, adding bling and all the while not spending too much cha-ching.

 

[aleccolin]

Anyone know of any good resources for establishing the weight of factory DSM wheels, and also the weight of various sizes and brands of tires?

 

[Defiant]

About halfway down this page:

http://members.shaw.ca/costall/1000Q/answers-specifications.htm

I don't know where you'd track down tire weights.

 

[lngbrdr]

Okay my stock wheels came with my car and are a tad bit bent so at higher highway speed I have a little vibration so I am getting new wheels. Unfortunetly I am stuck at the stock size (just got new tires like 2 weeks ago). So ohh well no bling bling wheels for me so I figure I might just get some lightweight racing wheels instead. So how much does a stock GST wheel weigh, just the wheel not including the tire? I'm just trying to find out how much weight I would actually save and if it is worth it to get racing wheels.

Okay just found it on another site they weigh 22lbs. Not too sure exactly how much racing wheels weigh but 17's weigh around 15 or less, using a little math then 16's should weigh around 13 or less. So I am wondering would the 9 or more pounds of savings per wheel be a good thing to look into buying?? So my question is does the weight savings with racing wheels justify purchasing them over some nice looking chromed out bling bling heavy ass wheel?

 

[midnght]

So my question is does the weight savings with racing wheels justify purchasing them over some nice looking chromed out bling bling heavy ass wheel?

Yes, it does for performance. Also you can find some nice NON-chrome performance wheels. Rotating mass freed will yield better more significant gains than most. 9lbs or more is a great loss wieght.


What types of wheels are you concidering?

 

[lngbrdr]

Yes, it does for performance. Also you can find some nice NON-chrome performance wheels. Rotating mass freed will yield better more significant gains than most. 9lbs or more is a great loss wieght.


What types of wheels are you concidering?

Personally I don't have a brand that I am stuck on and therefore am looking at anything. I am thinking on a black car black rims are getting played out and whites look dumb as hell, so I am thinking silver or possibly gunmetal. What brands do you all suggest? note I dont have a fortune to spend so I am thinking somewhere around $100 a wheel, is that reasonable?