sclx

I have been reading about everyone's wheel and tire purchases, and I have decided to go with 19". However, I see the most popular tire sizes are these:

Front 235/35-19 - 25.48" tall, 2% speedo error, 76mph instead of 75
Rear 275/30-19 - 25.50" tall, -2% speedo error, 73mph instead of 75

The stock tires are these:
Front: 225/40/18, 18x8, 25.09" tall
Rear: 255/40/18, 18x8.5, 26.03" tall

The stock tires are 1 inch taller on the rear as designed. Why is everyone putting on tires that are about half an inch too short on the rear? Is there a fitment issue? Why wouldn't the best setup be the following?

Front 235/35-19 - 25.48" tall, 2% speedo error, 76mph instead of 75
Rear 275/35-19 - 26.58" tall, 2% speedo error, 77mph instead of 75

If these would fit, it would also fill the wheel well much better. Am I missing something?

Thanks.

t0e

iTrader: (1)

Ok here what I came up with For the Back. Here the link if you want to figure out the rest.
http://www.1010tires.com

---Stock OEM Diameter:---
======---Stock OEM REAR Diameter:---==================

REAR TIRE info: Rear: 255/40/18, 18x8.5, 26.03" tall

STOCK Back Tire Diameter= 26.03" tall
Sidewall Height: 4.01 in 101.85 mm
======---Stock OEM REAR Diameter:---==================

============AfterMarket Setup REAR ===============

[Rear] AfterMarket Setup --> 265/35/19''

Diameter = 26.30" tall
Diameter Difference: 1.03%
Speedometer Difference: 1.036% too slow
Sidewall Height: 3.65 in 92.71 mm
============AfterMarket Setup REAR ===============
-------------------------------------------------------------------------------------------------------------------------------
======---Stock OEM Front Diameter:---==================
Front Tire Info: Front: 225/40/18, 18x8, 25.09" tall
StockFront Tire Diameter= 25.09" tall
Overall Diameter: 25.08 in
Sidewall Height: 3.54 in 89.916 mm
======---Stock OEM Front Diameter:---==================

============AfterMarket Setup FRONT===============

[Front] AfterMarket Setup --> 225/35/19''

Diameter: 25.20 in 640.08 mm
Diameter Difference: 0.48%
Speedometer Difference: 0.484% too slow
Sidewall Height: 3.10 in 78.74 mm
============AfterMarket Setup FRONT ===============

Dam Tired after this one.

4TehNguyen

iTrader: (1)

also there might not be matching front rear tire sets in 275/35 or 275/40

yellowssm

I am running 245/35/19 front and 275/30/19 rear right now but I am thinking of running 275/35/19 rear next time. Anyone have any input on this good or bad idea?

sclx

Why was this thread moved? It is very specific to the IS350 only. I never check the wheel forum, only the 2nd gen IS area because I'm interested in EXACT tire fitment for that car only.

Anyway, so the closest for the rear may actually be 265/35-19. I don't see anyone doing that on the rear of the new IS. Anyone? Is there a reason? Why is everone putting on tires that are way too short on the rear?

t0e

iTrader: (1)

Some Tire manufacture dont make that specific size. Thusly, having to opt for a bigger size.

sclx

There are several matching sets in the sizes I was thinking of going with:

235/35-19 Front
275/35-19 Rear

My original question is why do most people on the new IS go with a smaller diameter in the rear than stock? Does anyone have good or bad news about trying these two sizes front and rear?

t0e

iTrader: (1)

I think you need to differentiate between RWD and AWD....

AWD vehicles have a smaller diameter than RWD setups.

sclx

RWD, otherwise the stock sizes would not have been staggered.

Leechiro

good Q sclx. btw, are you going 19x8.5 and 19x9.5? and what offsets?