I was just going to purchase a set of tires from tire rack (245/40/18) and the guy said they won't work because they'll cause problems with the anti slip, abs and vdc systems. I was thinking of originally going with 245/45/18 but I was recommended by almost everyone (tire retailers) to go with the smaller 245/40/18's. I know there's a lot of people running both but I can't get confirmation from infiniti or from tire retailers about this. Is there anyone out there that has experienced any issues with any one of these two tires sizes relating to abs or vdc problems. I had just order my wheels previous to speaking to this guy. I just want to by my tires in peace.

 

I assume you're getting FOUR for all corners? If that's the case ... they'll work just fine. It'll only start to get tricky when the fronts and rears do not have the same rolling diameter or at least within +/- 1.5% of each other. The only side effect of 235/40 is an approx. 3.5% optimistic speedo and odo reading. You do gain the same percentage in rear-wheel torque, however

 

i'm running 245/45/18s (yokahama evs100s) and have not experienced any vdc problems that i know off.........in fact, i purposely brook the rears loose with vdc "on" just to see if the vdc kicked in or not............it kicked in(light lit up, reduced power) however, with this tire size, it's approx 1.3% bigger then oem diameter, so therefore, the vdc kicks in a tiny bit later.....and on seperate sidenote, i'm rolling on the milage "slower" too........abs, haven't had the need to jam on the brakes, so i dont know.............hope that make sense....

 

Yes I'm looking to run them on all fours. I don't see it being a problem with (245/40/18).That's still under 3%. The tires I want to buy are 25.7" in diameter which is about 2.3 percent of stock. Tire rack keeps telling me that its 3 percent and that its to close. Stock is 26.3. I would sure like to order these tires. Anyone have these on there sudan. Maybe after they wear it becomes a problem?

 

Tirerack saleman unfortunately do not always know the reason behind what they are told to tell you. I give him credit for pointing it out however.

In this case, the essence of how VDC, traction control, ABS and Brake biasing works is largely dependant on front-to-rear speed differential. In the case of the SEDAN ... it is 1:1. By switching to idential tires at all four corners ... you will not have altered the most important parameter (F-R ratio).

If it comforts you ... I use tires that are 6% smaller on the track (road course) and they were fine.

 

Thanks KLg35 and THX723
Your information is helpful. There our so many more choices in the 40 series. And the main tire I want to buy is on national back order in the 45 series (pirelli zero nero m+s). Your information is comforting. I wanted to feel free to be able to purchase either 40 or 45 series with out headaches. Thank you.

 

I have seen a report from a 350Z owner who was running equal front and rear tires, the opposite of making the sedan have differing tire heights running into problems with ABS performance being hindered.

"I RAN THE 275'S ON THE FRONT--DIDN'T LIKE THE WAY ABS WORKED WITH SAME DIA TIRE-FRONT AND REAR."

When pressed for more info on the above comment.

"WITH THE 275'S UP front, it would go into ABS quicker, and not stop."

This same person also did the developement work for Penske DA shocks on his Z.

On the subject of 245/40-18's coming from someone that pushes the cars handling daily, no that size will not change the VDC's ability to do it's job. Even as they wear. Until I wore out my rear tires, that's the tire setup I was running.

 

That's an interesting report.

I do know Zs and the Coupes do not have the same 1:1 ratio like the Sedan. Do you happen to know the full details of his tire specs (front and rear) at the time?

JRitt ... another person who sees the same tracks I do is running 275 front and rear at the track w. his Z and I'm not sure he's complained of any braking issues.

So, if I read it right, ABS engaged sooner? and his car took longer to stop? Sorry ... his phrasing is a bit cryptic to me.

Thanks,

 

On a further note;
Last summer I ran 225/40f & 245/40r on my sedan.

These were Yok ES100, which yield 1.53 % diff front to rear.
(got a deal I couldn't turn down)

The rear was the smaller DIA, which meant on a 1:1 system,
I was running with 1.5% rear slip all the time.

What I noticed was the VDC kicked in sooner than it should
& it kicked in harder. Didn't notice any ABS difference though.
(sometimes it turns out, the deals you can't turn down,
are the deals you should turn down)

So for this year ......
I'm going to go with 245/40 on all 4

 

A dealer told me that the only problems (vdc) that they ran into with a sudan was with a staggered set up. He couldn't remember the set up though.

 

That is an extrememly vague statement they made. Being 'staggered' does not reveal any details on what the Front-to-Rear rolling ratio is. As long as you abide to the 1:1 ratio or stay close to it (1.5% being the limit) ... you'd be fine.

 

Well I've had the staggered set-up for a couple weeks, running 245/40/18 and 265/35/18 on Kumho Ecsta ASX with a difference of approximately 1.6% and have had no issues with ABS or VDC at all. This includes some wonderful light snow driving. Maybe its because I drive like a grandma....

 

How you drive deffinitly has an impact.

Daily driving, I noticed no difference.

I really noticed it when driving "mucho gusto"
The VDC seemed more intrusive than before.

 

are you sure about this? while i realize that the coupes come stock with a staggered setup, we have to realize that the difference in speeds for the two wheels is 2.7% - is the ratio for the coupes really set at 1:1.027?

 

That is exactly what I was inferring ... that is the Front-to-Rear 'speed' ratio of the Coupe/Z is 1:1.027. Nothing more. That is the target ratio one should aim for should they choose to retain their repsective stock VDC response.