BrianK

I really had my heart set on a set of Volk GT-C's for my FD until I found out that they are 22-24 lbs in 18" form. Once I read that, I pretty much nixed them from the decision making process, but now I'm thinking they might be ok for a street wheel and I'll just switch back to the stockers for any track time.

So my question is - if I were to do that (which I'm still not completely sure about), is there a noticeable performance hit while driving around town, or do you really only feel it on the track?

sszablya

it'll be noticeable. 22-24 lbs is not unusually heavy for an 18" wheel. you're looking at 6-8 lbs more per wheel than stock. Some forged wheels can be as low as 19 lbs in 18" trim.

SleepR1

BrianK,

I bet you will, unless you've 500 rear-wheel-hp under the hood

Seriously, 18-inch wheels and tires will add about 15 lbs more per corner (265/35-18s are not light tires), compared with stock. You figure ~39 lbs for the stock wheel/tire setup and between 52 and 54 lbs for your 18-inch setup.

From my own personal experience with 16-inch setups...my 8 x 16, 38-mm offset SSR IA2s with half-worn 225/50-16 Pirelli P-Zeros were 35 lbs each corner. My 9 x 17, 45-mm offset SSR IA2s with new 255/40-17 Yokohama AVS I's were 45 lbs each corner. The AVS I's are half worn now, so I'd imagine we're closer to 40-lbs with my current road setup.

Could my butt-dyno tell the difference. The anwer is yes when I went back-to-back comparison between the old 16-inch setup, and the, "then-new" 17-inch setup. I've had my current setup since Feb, so now everything feels as it should

mp5

iTrader: (3)

Dont forget tires have at least as mutch effect on weight as your new rims will.
I just bought 18,s and went with Toyos t1s for that reason. good luck!

maxcooper

It has also been my experience that you can feel a relatively small difference in wheel/tire weight. Another of my local track friends noted that his car felt a lot faster when he switched back to stock wheels for track work (he had bigger 17" wheels for the street).

Heavier is always worse; here are some specifics:
- Ride is more harsh because you change the sprung/unsprung weight ratio
- Lose grip because it is harder for the suspension to keep the tire on the ground
- Lose acceleration because it takes a lot of power to accelerate the wheels (rotationally) and tires in low gears

But, 22-24 lbs is not that heavy for 18s. A better argument against the 18s is that you end up with tiny sidewalls, which significantly increases the chance of wheel damage and makes the ride harsh. I persoanlly think 17s are better for the car. I only got 18s for the track because I could get wider tires that way. I would gladly trade them in for 17" wheels if someone would make some 285/35-17 tires.

-Max

SleepR1

Let's all beg Hoosier Racing Tire to make a 285/35-17 R3S03

BrianK

Thanks for the input.. I'll think I'll start searching for 17's.

Wade

iTrader: (1)

Go with the wheels you like...

Despite the highly accurate "butt dyno" the effect on acceleration is almost nonexistent.

The effect of four wheels which weigh 10 lbs more than stock EACH is roughly 2% hp change in lower gears. Or about like adding 68 lbs of dead weight inside the vehicle. In 3, 4, 5th gear where wind drag is a bigger factor and rotational inertia is not, the effect is even less. If you care this much about weight then you have probably already removed your stereo and AC, right?

You may feel the difference in handling or when going over BUMPS though.

Wade

maxcooper

I would be surprised if it was only 2% in first gear, but that is also the gear that it typically doesn't help to have more power in. The rolling resistance from the wider tires may also be a contributing factor in the butt dyno tests.

-Max

SleepR1

you bet my butt-dyno's accurate...probably more accurate than that stupid G-tech Pro

Tim Benton

iTrader: (1)

Heavier wheels made more of a difference in braking than acceleration on my car. I could feel the fact that I had added almost 30 pounds in total to the unsprung rotational weight when I got the 17x8 and 17x9 konig villans. The rubber was actually the heaviest part of the new wheel tire combo since the 17x9 was only 3 pounds heavier than the stock rim, but add in the tire weight and it was 12 a side in the rears with 265/35 rubber. I couldn't tell the difference in acceleration, but when it came to moderate to hard braking, the extra rotational weight was noticable.

Tim

SleepR1

Hey, Tim--I think that big brake kit is now justified

Tim Benton

iTrader: (1)

It made enough of a difference that it was the main factor in my decision to buy the 99 spec rims from Japan. The 17x8 rim up front was within a .25lb of the stock 16x8 rim, and the 17x8.5 was less than a pound (around .75) more than the 16x8 (using a digital scale at work). Add the rubber, and granted I had 265/35 rear, and I went with the stock japanese set up of 255/40 with the 17x8.5 and I saved 28 pounds over the Konig villans and only added 2 pounds over the 16x8 245/45 setup I had stock with more total contact patch. Excellent trade off IMO, going with the 99 rims and rubber.
99 front brakes coming soon, for sure.
Tim

DaleClark

iTrader: (55)

Also, a lot of the acceleration difference isn't from going to a heavier wheel, but going to a *larger* wheel. As you increase the total diameter of the wheel, it's like changing your gear ratio.

The majority of the people on this forum who aren't hardcore track addicts or the like will probably never notice the difference in handling with a heavier wheel package than stock. You will notice the difference in gearing when going to a larger diameter wheel package - many times that can be felt.

Really, just find a wheel/tire package that looks good and fits your budget, and go from there. Try and get as much rubber as you can for your budget too.

Dale

rynberg

That is only true if you are not reducing the height of the tire sidewall. There are exceptions but most people understand the "plus" concept.

225/50 16 => 245/40 17 you have increased wheel diameter without increasing the wheel PLUS tire diameter

SleepR1

rynberg,

You'd think people understand the plus concept, but there are many FD owners with 275/40-17, 285/40-17s, 295/35-18s in back, yielding 25.7, 25.9, and 26.1 inches in overall diameter, respectively. The stock overall diameter of a 225/50-16 is ~24.9 inches, so the rear-end gearing starts to get taller as we go with taller tires in back, not to mention the increasing unsprung weight of such heavy wheels and tires!

Wade

iTrader: (1)

Max,

I'll see if I can get the computations to support this. As you and others have suggested, the other factors might be causing the percieved acceleration loss, like larger contact patch and larger diameter.

Wade

maxcooper

You can do like I did for the flywheel -- calc the start and end RPMs (of the wheels -- not the engine) for revving through each gear, get some time estimates from CarTest, make an educated guess at the rotational inertia, and then calc the average power required to accelerate the wheels through each gear. It should get us in the ballpark.

-Max

Wade

iTrader: (1)

http://www.audiworld.com/tech/wheel13.shtml

Wade