I'd like to know what the handling difference would be with a 255/40/18 front and 275/40/18 as opposed to 245/35/18 front and 275/35/18 rear on 18" Rota P45R. Also, would running lower profile mean less tread life compared to higher profile?



Thanks!

 

I doubt will will notice the handling between the sizes you mention since the difference is quite small.

Tire wear will be the same.

--Spike

 

275/35/18

The speedometer will read 104.31 MPH at 100.0 MPH.

 

the car will understeer more with the 245's in the front.

 

^^ That’s correct. Wider front tires on the Z provide less understeer. 10mm=3.9 inches, so the difference is small; but it’s probably slightly noticeable (or not, depending upon the tire).

As David mentions, a 35 aspect ratio to width on the OP’s second choice is less than the stock sidewall height, so there could be a problem with VDC or TCS (if the car is equipped with these features).

--Spike

 

i have 275/40/18 on the back, and its a huge difference. ride is sooo much smoother, and it def improves handling.

 

Faster acceleration, better steering response, and better braking with the 35 series tires. The 40's will have a smoother ride, more accurate speedometer reading, and will fill the fenders better.

 

fixed

 

^^ Thanks. I keep doing that (misplaced decimal point).

--Spike

 

Is it uncommon for 18" to be using a 35 profile? All I've seen are 40 and 45's on 18. Is it bad to use 35 profile on 18"?

 

ive ran 35s before and still do sometimes no difference in my opinion

 

I recommend a 255/40/18 front and 275/40/18 rear if those sizes are available in the tires you are looking at. 245/40/18 and 275/40/18 is still a great combo but the front tire will be slightly stretched on a 9.5 wide rim. I would not run a 35 series in the widths you listed as you will sacrifice ride quality and the speedometer will be off by about 3 mph.

The only time I recommend going to a 35 series on the 18x9.5 P45R's is if you want to run a wide tire. We run 265/35/18 front and 295/35/18 rear on our shop Z and it works well, you have to roll your rear fenders to fit this tire size though.

-Dan

 

^^ Very good post with excellent advice.

--Spike

 

Did you notice less responsive handling when you went to the 265/35/18 Front and 295/35/18 Rear combination when compared to stock?

I just got my tire setup: 18in rims 9.5/10.5 with 265/35/18 Front and 285/35/18 Rear and if feels mushier than stock. They are stickier, but steering response and feedback is worse.

 

^^ What is your tire (brand and model)?

--Spike

 

No we did not notice less response in the handling. What kind of tires did you get? It almost sounds like you were used to a stiffer sidewall and went with a tire that isn't performance oriented or has a softer sidewall. Also what tire pressure were you running on the stock wheels compared to your new setup?

-Dan

 

Stock setup:

Front Stock 225/45/18 Bridgestone RE50 35psi
Rear Stock 245/45/18 Bridgestone RE50 35psi

My current setup is:

Front TE37 9.5 +22 265/35/18 BFG KDW 35psi
Rear TE37 10.5 +22 285/35/18 Toyo T1R 35psi

These are high performance tires, but just not brand matched. I know I should get matching tires, but the KDWs and T1Rs are Brand New and came with the rims. If mismatched tires are the cause of my understeer or mushy steering, then I guess I'll have to find a set of T1Rs for the front.

Am I suppose to run the KDWs and T1Rs at a higher psi because of the smaller sidewall?

 

^^ You have the tire pressure right… it should be the recommended PSI for stock tires.

The problem might be a difference is sidewall rigidity between your front and rear tires. The Toyo’s have a softer sidewall than the BFG’s.

You said the tires are new, so that might be the problem. New high-performance tires are quite slippery for the first 100 miles or so (you really notice this), and then become much better.

I would run this setup a while longer to determine if it’s just the “greasy” layer on new high-performance tires causing the problem (and, I bet that is the problem). I think you will notice a significant improvement after a few days.

If it’s the sidewall flex, you probably will also be able to accommodate to this different handling. In fact it will begin to feel normal within a short time.

--Spike

 

What's the negative thing about having stretched tires?

 

One downside of stretched tires: If you get anywhere close to a concrete curb, this piece of cement will try very hard to deeply gouge your expensive Volks. It happens a lot much to the dismay of people owning expensive wheels.

--Spike