Dinhx8

I just got my winter rims, and they are probalby about 4-5 pounds heavier each- Now, I have searched and read all the threads about various affets of rim weight, unsprung weight, etc and do understand that for the most part. I also found that the stock 18s with the brdigestones are about 48 lbs each. My package came in at 212 pounds for all 4, so thats about 5 pounds heavier per wheel.

My question is this: while I know weight can slow acceleration, braking, etc- (with the combination of the tire), is it 'damaging' in any way to the car? I.e. im not ruining anything by putting more weight on the axles/ suspension am I ...I know Im affecting it, but thats different than inflicting actual harm (like, say riding on an unbalanced wheel). Sorry if this is a dumb question, just curious, and the focus isn't so much "damaged acceleration" but rather is the heavier weight damaging my car as if 'towing" it or so would damage it. (thats an extreme example)

thanks guys and gals

RX8_Buckeye

Did you happen to find the thread I started about upsizing from the OEM wheels and tires? If not, here is a link. It includes some applicable information.
https://www.rx8club.com/showthread.p...t=upsizing+OEM

Basically, assuming everything else stays the same, increasing unsprung mass will increase the loads on the suspension components. In your case, the unsprung mass will be increased about 10%, which is not extremely significant. I wouldn't worry about it at all.

You didn't specify the size of the wheels you are using. If you downsized from the OEM equipment, you are most likely using a higher profile tire. In this case, the tire sidewall is more compliant and will most likely offset the added loads due to the increased unsprung mass.

The worst case scenario is an extremely low profile tire with a very stiff sidewall combined with a heavy wheel. This will significantly increase suspension loads, raising the risk of a durability failure due to an impact-type event, or a fatigue failure well into the life of the vehicle.

Sputnik

Not really.

How did you come to that number?

---jps

Dinhx8

thanks guys-
My new wheels are 18s and I got new tires the exact same size as OEM, so just double double checking - thanks for the thread and thoughts. I think I should be okay due to minimal difference-
As for the 212 Lbs- that was the UPS package weight, including cardboard, lugs and locks, and everything.

Sputnik

I suspected that by the way you mentioned it. And I brought it up because that's not an accurate way to get an idea of the weight, and sometimes it's not even in the ballpark. It's not something you have to do now, but I would get a wheel weighed somewhere down the line to make sure. It doesn't have to be very accurate either.

---jps

dmp

Here's a handy calculator which can help you figure how just how much unsprung weight affects the 'effective weight' of the car:

http://www.d-mphotos.com/movies/WeigthEqv.xls

Dinhx8

thanks guys-
I'll weigh them next time they are off- maybe when I paint my calipers - though, Im assuming UPS wouldn't 'underweight' their package, so if it said 212 lbs, thats the 'worse' it could be (meaning my wheels worse case are 4-5lbs heavier per). If the 212 was rounded up, that hopefully means that there is a remote possiblilty my new rims could even be a bit lighter- given the fact that the lugs are only a few pounds and the cardboard pretty light.

Dinhx8

Okay- so my UPS package was 212 llbs listed with everything. However, I just got an email from the vendor and looks like my wheels are about 9 lbs heavier than stock.
My tires are stock size at 225 45 18....do you all think its a big deal?

dmp

I think a 9lbs per wheel increase is signifcant. that could translate to adding 50?75? pounds to the trunk. More? Check out that spreadsheet.

worth noting, it also matters where on the rim the 9lbs comes from...closer to center-mass is desirable.

Dinhx8

The spreadsheet wasnt 'changing' for some reason when I punched in new numbers- but ill try it again. The vendor actually said the the shipping weight was 29lbs- and they commonly over compensate. So the wheel probably around 26lbs. Basically, what I need to do is weigh em myself. The car drives fine and doesnt feel 10lbs per wheel heavier, though I can sense a bit of weight.

dmp

that spreadsheet was made for a miata - so it may take some fixin' to work right w/ an rx8.

crossbow

https://www.rx8club.com/showthread.p...913#post569913

An increase in wheel weight (especially if it also includes a diameter increase) will increase the amount of wear on attached suspension components, mainly bushings and shocks. Because the wheels are heavier, the braking system also has to work slightly harder to perform its duty (thus additional increased wear).

Of course this all varies as to what extent you push the envelope. Just don't expect a dealer to replace a blown shock if you've done a +2 sizing and thrown on cast 20's. They can and will void the warranty on those wear items (rotors, shocks, suspension bushings) if it can be traced to substaintal increase in diameter/wheelweight. Its definitely happened before.

AF-RX8

Don't you have a scale ? Take 15 minutes and take off a wheel and weigh it, then weigh one of your stock wheels so at least you know the difference in the weight using the same scale.

Do you feel a difference when you drive on the new wheels ?

I went through 6 to 8 sets of wheels on my old car (bmw 330i) and when I put wheels on that were 6lbs or more each, there was a difference in the way the car felt as far as agility and speed

BTW you can never go by the shipping weight, I have found with all the shipping I did, the weight was sometimes right and other times it was off by a few pounds.
Also the cardboard and the wrapping material can weigh a couple of lbs.