Bartman_RENAMED

I just had the OEM 18's with 245/40/18 Falken ST-115 installed last night. Since I know very little about cars, I am paranoid about the effects on ride, handling, etc... At this point, I feel that the car is not as quick and nimble as it was with the stock rims and tires. I also experienced a lot more shimmy or vibration than the EL42.

Could someone please me if these things are normal with an increase in size of wheel and tire?

Skeedatl

Shimmy and vibration is a balance issue. The lower profile with harshen the ride a bit. Also the ST-115 were more designed for quiet ride (as opposed to say the FK451) and maybe at the sacrifice of handling. With quickness, you shouldn't feel the difference, but if the new tires have less grip, the VSA will make the car slower out of the hole.

So, harsher ride is possible, slower is possible as a consequence of the VSA, but the shimmy and vibration certainly aren't normal.

I would go back and have the wheels balanced again. Perhaps you have a faulty front tire (out of round or something).

Bartman_RENAMED

Thanks. I am thinking about having a road force balance. Since I changed the overall diameter of the tire, some of the change in performance may be related to gearing.

Mr Zipps

You are going to feel slower because you put a bigger and heavier wheel on... The vibration is due to wheel balance...

Skeedatl

The rollout length between your new and old tires isn't enough to affect gearing. The extra weight of the wheel as mentioned in the previous post certainly could, but typically in this HP range 100LB is .1s off the 1/4 and there isn't 100LBs difference.

More likely it's a traction issue and VSA is cutting power to keep traction. Does it feel slower say from 30-60, just out of the hole...slower all over?

Bartman_RENAMED

It just feels a little more lethargic overall than it did before, but like I said, I may be paranoid. I watched the guy mount and balance the tires and he didn't seem to be too detail oriented. I will probably have to drive it a little more to get a real good feeling of overall performance.

coop1018

I have not put my 18's on yet- i am waiting out the winter months. I picked them up however and they feel surprisingly light. I feel that even though bigger than the stocks, that they could be lighter given the material used to make them

Bartman_RENAMED

I don't know the specs, but they are supposed to be close to the same weight as the stock rims.

PeterUbers

iTrader: (1)

Bartman,

The reason you're a little sluggish is the following:

1) you DID increase the diameter of the tire a little, and yes, your gearing is slightly worsened
2) the rims are 25lbs (I weighed them yesterday) a piece, stock is around 24-25lbs, perhaps a tad lighter, no less than 24lbs though. With 18's, there is more weight at a longer radius from the axle, therefore due to this, there is an increased amount of power required to turn the wheel, therefore you lose power because more work is going to turning a wheel with more weight pushed further away from the axle.
3) Less nimble b/c now you have more contact surface with the road, despite the fact that stock and a-spec rims both put 235 to the ground, the lower profile of the a-spec rim creates a better "seal" to the road, and a flatter patch of rubber. Hence you're less nimble b/c your tires are encounter more road surface.

The vibration is definitely the balancing -- you need to have them rebalance, then rebalance again. Then have them try moving the rear wheels to the front, and the fronts to the rear and see if that solves the problem.

PeterUbers

iTrader: (1)

Bartman,

How's the difference of stiffness from stock to the 18's? Is it significantly stiffer, or just moderately stiffer? (poor choice of adjectives, i guess)!

Bartman_RENAMED

Stiffness is not much worse at all. I put Falken ST-115 tires on so they are about as quiet as stock tires. I am just having a hard time getting used to the affects of more rubber on the road.

astro

Definitely take it back and have them balance the tires once more if you're experiencing vibrations...
PeterUbers is right on the money as to why the car might feel a little less responsive with the new rims...
but hey, don't worry, just think about how much sexier she is now

PeterUbers

iTrader: (1)

So you don't feel the bumps much worse w/ the 18's?

How do you like the new look of your car w/ the 18's?? Doesn't it look better than the 17's?

PeterUbers

iTrader: (1)

BTW: In a Road&Track test (or maybe it was MT) .. the A-Spec w/ the 18's, 6-spd, and HPTs ran a 14.2 sec 1/4. The 6-spd non-Aspec ran the 1/4 in 14.4 ..

So at least w/ the 6-spd, the 18's improve the launch and seemingly don't detriment the "quickness". Perhaps due to the automatic tranny's taller 1st gear, you're feeling the added weight of the 18's.

I'll let you guys know in a couple weeks what my TL feels like w/ the 18s'... gunna take delivery in a week or so.

Bartman_RENAMED

After a couple of days with the 18's I'm getting use to the subtle differences. I'm going to check tire pressure this weekend and possibly have a road force balance.

I do notice a change in the gearing between 1st and 2nd, but it is slight. The biggest changes are those created by the increased rubber on the road. Steering is much more responsive than with the EL42.

Bottom line...these wheels look awesome on the Redondo Red. I have been getting compliments everywhere I go. I can't wait for the photo gallery to be up again so I can share pix.

PeterUbers

iTrader: (1)

Congrats bartman --- i really liked the red... however, i already told Acura what color I wanted so i couldn't choose another one since they already allocated the car.

PeterUbers

iTrader: (1)

Bartman, i just re-read your first post .. 245/40/18's..

you did NOT increase the diameter (overall) of the wheel&tire. It's the same as stock. So the gearing has not changed. What has changed, however, as mentioned before, is the amount of weight that's pushed out to the perimeter. So your issue of less responsiveness is only due to the increased weight of the wheel.

Can't wait to see your pics.

Bartman_RENAMED

Actually 235/40/18 is the recommended size, so 245/40/18 is slightly larger than the 235/45/17 stock.

PeterUbers

iTrader: (1)

Width x Aspect Ratio = Section Height x 2 = Combined Section Height + Wheel Diameter = Tire Diameter

(straight from tirerack.com)

stock 18's setup:

Diameter = 235 x 0.40 = 94 x 2 = 188 mm + (18"->457.2mm) = 645.2 mm = 25.4 inches

Bartman's setup:

D = 245 x 0.40 = 98 x 2 = 196 mm + 457.2 mm = 653.2 mm = 25.7 inches

Stock 17's setup:

D = 235 x 0.45 = 105.75 x 2 = 211.5 mm + (17"->431.8 mm) = 643.3 = 25.3 inches

So effectively, you're NOT changing the diameter in a way that you'd notice a 1) speedometer difference, 2) seat of the pants difference.

What's doing it is the added weight of the wheel AND the tire. I just got off the phone w/ tirerack (purchased 235/40/18 Kumho ASX's) and they said that going from 235 to 245 adds 1-2 lbs per TIRE ...

25.3 vs. 25.7 vs. 25.4 inches is negligible.
Regards.

PeterUbers

iTrader: (1)

^

Bartman_RENAMED

Let me know how your tires and wheels work out. I will post pix when I can.

PeterUbers

iTrader: (1)

Bartman-- will do, the Kumho's come in monday, the car comes in friday -- i'll email you pix.