Have a tire size question? Read this first! Satisfying your VDC.
Have a tire size question? Read this first! Satisfying your VDC.
Hi all,
I'm from the my350z forums.
I've been a bit more active on this forum since traffic here seems much higher.
I hope this information is relevant to the G crowd.
I see a lot of posts about people asking tires sizes about "Will this tire fit?" or "What sizes are best?"
What people need to understand is that our cars have something called VDC (Vehicle Dynamic Control).
Essentially, VDC keeps your car from sliding.
Our cars (G35 and 350z) both require a staggered tire set up (Front and rear tires are different sizes).
A general rule of thumb is that as long as the stagger between the front and rear tires are within 0.5" to 1.0", VDC will be happy.
Does this mean you can't run the same width's in front or rear?
Not at all! You can still run the same widths as long as you adjust the profile of the tire to satisfy the stagger.
Please refer to a sticky thread on the my350z forums to get you a better understanding of what I am trying to convey. I learned a lot from this thread and other resources online.
In summation, if you still want to run a square set up on your car, it's not a huge deal, you will just have to drive with VDC off. If you would like to keep your VDC, it's a simple as taking a few minutes on a wheel/tire calculator to make sure that your stagger is on point.
For further resources, please refer to any wheel/tire calculator and rimtuck.com.
Thanks for reading y'all.
Shyun
I'm from the my350z forums.
I've been a bit more active on this forum since traffic here seems much higher.
I hope this information is relevant to the G crowd.
I see a lot of posts about people asking tires sizes about "Will this tire fit?" or "What sizes are best?"
What people need to understand is that our cars have something called VDC (Vehicle Dynamic Control).
Essentially, VDC keeps your car from sliding.
Our cars (G35 and 350z) both require a staggered tire set up (Front and rear tires are different sizes).
A general rule of thumb is that as long as the stagger between the front and rear tires are within 0.5" to 1.0", VDC will be happy.
Does this mean you can't run the same width's in front or rear?
Not at all! You can still run the same widths as long as you adjust the profile of the tire to satisfy the stagger.
Please refer to a sticky thread on the my350z forums to get you a better understanding of what I am trying to convey. I learned a lot from this thread and other resources online.
I've been asked many times about altering the tire sizes on 350Zs equipped with TCS and VDC....what you can do, what you can't do, etc. So I figured I'd write this for people to use as a reference on what tire sizes they can get away with without upsetting their cars electronics. At the end of this article, there are some links to the tire size calculators that I used.
This is an actual PM I received from someone who was having problems with their car after putting new tires on his car. (Minor edits made for "printability")
################################################## ########## ################################################## ########## ##########################################
Kelly
I just bought the Axis MAtrix (f) 20x9 and (r) 20x10.5, Tires: Falken grb-fk451 255/35/20zr, 285/30/20zr, and they look and drive great. But sometimes when taking a sweeping turn or making a quick turn the traction control activates more so now then with the stock rims and tires. It seems to stay on longer and come on when there is no real reason. Does anyone else experience this or issues with traction control?
Sincerely,
Confused in treadville
Howdy confused.....put on your thinking cap...this might hurt a little
Yes!, you're having a problem as a result of your tire choice. Here's why.....
The computer (not sure if it's the ECU or the ABS computer) has been programmed to tolerate a variance in rotational speeds between the front and rear tires (it knows each tires rotational speed because of the ABS sensors). It knows that with the car going in a straight line, the fronts and rears should be rotating at a slightly different speed from one another based on their slightly different circumference (the difference on the stock Rays wheels wearing OEM tires sizes is +2.7% (rears are 2.7% bigger than the fronts)). The reports are that the ECU can tolerate about a 3% change from this (in other words, down to roughly 0% f/r delta and up to roughly 6% f/r delta) before it starts to think there is a problem. You have you broken the 3% rule. Here's how....
Let's look at your tires sizes in comparison to the 18 Track OEM wheels that were on my car (I use these because circumferentially, these are about the same as the stock 17's.)
We'll start with the rears first....
The tire on the stock Rays rear wheel is a 245/45-18. That tire has a circumference of 83.8 inches. The 285/30-20 you're using has a circumference of 84.0 inches, which is a difference of just 0.2%. So far so good, right? You've effectively not changed the circumference of the rear tire by going to a bigger diameter but a smaller sidewall. Now let's look at the fronts.
The tire on the stock Rays front wheel is a 225/45-18. That tire has a circumference of 81.6 inches. The 255/35-20 you purchased has a circumference of 84.9 inches, which is a difference from stock of +4.1%. Uh oh!
So, you had almost no change in circumference on the rear end when you went to the 20's, but you had a +3.3" change in circumference on the front
The end result is that there has been enough of a change between the OEM f/r variance and the new f/r variance that your computer believes a slip condition is occuring when it's actually not. Remember that with the OEM tires, the rear's were bigger than the fronts by 2.7% (we'll call this +2.7). With your 20's, the difference is that now the fronts are bigger than the rears by 1.1% (think of this as -1.1%). This is a change of 3.8%, so there's your violation of the 3% rule.
How do you fix this? Easy, drop to a 30 profile on the front tires. A 255/30-20 on the front will drop the difference from the stock tires to the new tires to just .2%, so the computer will effectively not know that there is a dfferent tire there, just like on the back. If you purchased a warranty for your tires, this might be an opportune time for the fronts to pick up some screws in non-repairable places. . Of course, I didn't say that.
Hope this helps!
This is an actual PM I received from someone who was having problems with their car after putting new tires on his car. (Minor edits made for "printability")
################################################## ########## ################################################## ########## ##########################################
Kelly
I just bought the Axis MAtrix (f) 20x9 and (r) 20x10.5, Tires: Falken grb-fk451 255/35/20zr, 285/30/20zr, and they look and drive great. But sometimes when taking a sweeping turn or making a quick turn the traction control activates more so now then with the stock rims and tires. It seems to stay on longer and come on when there is no real reason. Does anyone else experience this or issues with traction control?
Sincerely,
Confused in treadville
Howdy confused.....put on your thinking cap...this might hurt a little
Yes!, you're having a problem as a result of your tire choice. Here's why.....
The computer (not sure if it's the ECU or the ABS computer) has been programmed to tolerate a variance in rotational speeds between the front and rear tires (it knows each tires rotational speed because of the ABS sensors). It knows that with the car going in a straight line, the fronts and rears should be rotating at a slightly different speed from one another based on their slightly different circumference (the difference on the stock Rays wheels wearing OEM tires sizes is +2.7% (rears are 2.7% bigger than the fronts)). The reports are that the ECU can tolerate about a 3% change from this (in other words, down to roughly 0% f/r delta and up to roughly 6% f/r delta) before it starts to think there is a problem. You have you broken the 3% rule. Here's how....
Let's look at your tires sizes in comparison to the 18 Track OEM wheels that were on my car (I use these because circumferentially, these are about the same as the stock 17's.)
We'll start with the rears first....
The tire on the stock Rays rear wheel is a 245/45-18. That tire has a circumference of 83.8 inches. The 285/30-20 you're using has a circumference of 84.0 inches, which is a difference of just 0.2%. So far so good, right? You've effectively not changed the circumference of the rear tire by going to a bigger diameter but a smaller sidewall. Now let's look at the fronts.
The tire on the stock Rays front wheel is a 225/45-18. That tire has a circumference of 81.6 inches. The 255/35-20 you purchased has a circumference of 84.9 inches, which is a difference from stock of +4.1%. Uh oh!
So, you had almost no change in circumference on the rear end when you went to the 20's, but you had a +3.3" change in circumference on the front
The end result is that there has been enough of a change between the OEM f/r variance and the new f/r variance that your computer believes a slip condition is occuring when it's actually not. Remember that with the OEM tires, the rear's were bigger than the fronts by 2.7% (we'll call this +2.7). With your 20's, the difference is that now the fronts are bigger than the rears by 1.1% (think of this as -1.1%). This is a change of 3.8%, so there's your violation of the 3% rule.
How do you fix this? Easy, drop to a 30 profile on the front tires. A 255/30-20 on the front will drop the difference from the stock tires to the new tires to just .2%, so the computer will effectively not know that there is a dfferent tire there, just like on the back. If you purchased a warranty for your tires, this might be an opportune time for the fronts to pick up some screws in non-repairable places. . Of course, I didn't say that.
Hope this helps!
For further resources, please refer to any wheel/tire calculator and rimtuck.com.
Thanks for reading y'all.
Shyun
Joined: Mar 2013
Posts: 1,991
Likes: 390
From: Raleigh, NC
Coupe, Premium package, sport suspension
Just checked my owner's manual for a 2006 G35. This appears to be true for the coupe, but not the case for the sedan. Position is not specified for the sedan; front/rear is spec'd for coupes.
Another key difference is the ability for G's to turn off VDC.
Seems odd that the Z is lacking in that...
Joined: Mar 2009
Posts: 18,299
Likes: 1,488
From: By the sea, Tx
G35 sedan w/ too much money in mods
I've been a bit more active on this forum since traffic here seems much higher.
surprised by this since Driver is also not what it was a few years ago
Our cars (G35 and 350z) both require a staggered tire set up (Front and rear tires are different sizes).
No they don't
A general rule of thumb is that as long as the stagger between the front and rear tires are within 0.5" to 1.0", VDC will be happy.
Again not entirely true
In summation, if you still want to run a square set up on your car, it's not a huge deal, you will just have to drive with VDC off. If you would like to keep your VDC, it's a simple as taking a few minutes on a wheel/tire calculator to make sure that your stagger is on point.
I lol'd.
For further resources, please refer to any wheel/tire calculator and rimtuck.com.
Shyun
surprised by this since Driver is also not what it was a few years ago
Our cars (G35 and 350z) both require a staggered tire set up (Front and rear tires are different sizes).
No they don't
A general rule of thumb is that as long as the stagger between the front and rear tires are within 0.5" to 1.0", VDC will be happy.
Again not entirely true
In summation, if you still want to run a square set up on your car, it's not a huge deal, you will just have to drive with VDC off. If you would like to keep your VDC, it's a simple as taking a few minutes on a wheel/tire calculator to make sure that your stagger is on point.
I lol'd.
For further resources, please refer to any wheel/tire calculator and rimtuck.com.
Shyun
Shuyn thanks for trying to help our fellow brothers and sisters here out. However your OP contains some misinformation that needs to be cleared up.
The simple truth is that to keep the VDC happy, tires F/R need to have a rolling diameter of w/in 3% of each other. Exceed that and the VDC freaks out whether it's turned off or on. Stagger doesn't have anything to do with the system, it doesn't care if your rims are 2" wide or 20" wide.
The G does NOT require a staggered set up on any model or year to function properly either.
Your suggestion to check compatibility with a wheel calculator is spot on, they are very useful when determining if the tire set-up someone's considering will keep the system happy or not.
For example you could run 185-60-18 up front and 245/45/18 in the rear and the VDC wouldn't care because the diameter of each size is 26.7". Or you could run 245/45/18 on all 4 corners for the same reason and be perfectly fine. I haven't used the circumference measurement listed in the my350 post but it pretty much mirrors what I have said here.
Thanks again for trying to help out but please make sure your info is correct before stating it as fact.
Shuyn thanks for trying to help our fellow brothers and sisters here out. However your OP contains some misinformation that needs to be cleared up.
The simple truth is that to keep the VDC happy, tires F/R need to have a rolling diameter of w/in 3% of each other. Exceed that and the VDC freaks out whether it's turned off or on. Stagger doesn't have anything to do with the system, it doesn't care if your rims are 2" wide or 20" wide.
The G does NOT require a staggered set up on any model or year to function properly either.
Your suggestion to check compatibility with a wheel calculator is spot on, they are very useful when determining if the tire set-up someone's considering will keep the system happy or not.
For example you could run 185-60-18 up front and 245/45/18 in the rear and the VDC wouldn't care because the diameter of each size is 26.7". Or you could run 245/45/18 on all 4 corners for the same reason and be perfectly fine. I haven't used the circumference measurement listed in the my350 post but it pretty much mirrors what I have said here.
Thanks again for trying to help out but please make sure your info is correct before stating it as fact.
The simple truth is that to keep the VDC happy, tires F/R need to have a rolling diameter of w/in 3% of each other. Exceed that and the VDC freaks out whether it's turned off or on. Stagger doesn't have anything to do with the system, it doesn't care if your rims are 2" wide or 20" wide.
The G does NOT require a staggered set up on any model or year to function properly either.
Your suggestion to check compatibility with a wheel calculator is spot on, they are very useful when determining if the tire set-up someone's considering will keep the system happy or not.
For example you could run 185-60-18 up front and 245/45/18 in the rear and the VDC wouldn't care because the diameter of each size is 26.7". Or you could run 245/45/18 on all 4 corners for the same reason and be perfectly fine. I haven't used the circumference measurement listed in the my350 post but it pretty much mirrors what I have said here.
Thanks again for trying to help out but please make sure your info is correct before stating it as fact.
I did not know about the G not requiring stagger.
Seems like I found one more thing that is different about the two platforms.
Although this may not be entirely true, there are a few things that may have been misinterpreted in my write up.
By stagger I was referring to diameter.
If you go to tire rack or most other tire stores and look up the specs for the tire, you will find the diameter and therefore determine the stagger.
In a 100 questions faq on my350z, you should find the average diameters for common tire sizes and you'll notice that it mentions that 0.5 - 1.0" are ideal.
Common sizes like 19/35/245, 19/35/275 and 19/35/285, 19/35/285 are just two examples.
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