# Thread: Will these Wheels harm my haldex?

1. I am looking at buying nice used set of staggered wheels.

Front: 18x8 et 36
Rear: 18x9 et 36
Rubber: 215/40/18

Just wondered if the circumference will be with in the %4 spec? I can't seem to find consistent info anywhere.

Anyone running similar set ups?

thanks!

2. Originally Posted by JimJames
I am looking at buying nice used set of staggered wheels.

Front: 18x8 et 36
Rear: 18x9 et 36
Rubber: 215/40/15

Just wondered if the circumference will be with in the %4 spec? I can't seem to find consistent info anywhere.

Anyone running similar set ups?

thanks!

How are you going to fit a 15" tire on an 18" rim?

Her is a great tire/wheel calculator.

Just punch in the OEM dim's of your car in the #1 tire size, then
punch in what you would like to use in the #2 tire size.
Then click on the compare tires button.

http://www.1010tires.com/tiresizecalculator.asp

3. it's a typo sorry, should be 18. I don't see any way to account for wheel width on that calculator there. I am pretty ignorant when it comes to wheels and tire though. is there some other way to go about compensating for the wheel width when I am comparing?

4. Originally Posted by JimJames
it's a typo sorry, should be 18. I don't see any way to account for wheel width on that calculator there. I am pretty ignorant when it comes to wheels and tire though. is there some other way to go about compensating for the wheel width when I am comparing?
The wheel width is not needed to do the calculating. You are calculating the circumference of the tire so that it is as close to OEM. This way, your speed is correctly reported and also the haldex system will work properly.
if using staggered set up, you may need 2 different proflies to get as close to matched circumference of both front and back.

5. Originally Posted by brendan_TT
The wheel width is not needed to do the calculating. You are calculating the circumference of the tire so that it is as close to OEM. This way, your speed is correctly reported and also the haldex system will work properly.
if using staggered set up, you may need 2 different proflies to get as close to matched circumference of both front and back.
Well put. ;-)

6. Yes, Maybe I am completely ignorant here or you don't understand. I am looking at buying a staggered set with the above tires already mounted. I don't need to know which tires I need. I need to know if the difference between an 8" and 9" rim with the above tire specs will harm the haldex. If I was buying new tires to be mounted then I could see that being useful. But the fact both wheels are running the same tires and have different widths the calculator can't tell me what i need to know.

7. Originally Posted by TTC2k5
Well put. ;-)
I learned from the best!

Originally Posted by JimJames
Yes, Maybe I am completely ignorant here or you don't understand. I am looking at buying a staggered set with the above tires already mounted. I don't need to know which tires I need. I need to know if the difference between an 8" and 9" rim with the above tire specs will harm the haldex. If I was buying new tires to be mounted then I could see that being useful. But the fact both wheels are running the same tires and have different widths the calculator can't tell me what i need to know.

When you talk about "staggered" I do not believe the rim width comes into play like you may think. Staggered refers to having a smaller width tire on the front, VS a wider tire on the back. It is the tire width and profile that dictates the final circumference of the set up.

If your stock rims and tires are 225/45/17 that equates to 78.44 circumference.
With the set up that you want to buy, 215/40/18 your circumference will be 77.81
At that margin, you will be less then 1% from OEM... But, your tire width will be 10 MM less, and most want to go wider.

Hope this helps.

8. Originally Posted by JimJames
Yes, Maybe I am completely ignorant... .
Mayby this, ^^.

0. ignore width of wheels...IT IS IRRELEVANT. Circumferance is relevant, width is not.
1. use the calculator at the link above.
2. input standard TT size tire: 225/45-17
3. input the tire size the you said was on the wheels you are about to buy: 215/40-18
4. click button to calculate
5. read data provide by calculator.
6. decide if you want to buy the staggerd wheels or not.

cheers.

9. Running that set up will be 100% ok. I ran the exact same thing on 2 different sets of wheels

10. Originally Posted by TTC2k5
Mayby this, ^^.

0. ignore width of wheels...IT IS IRRELEVANT. Circumferance is relevant, width is not.
1. use the calculator at the link above.
2. input standard TT size tire: 225/45-17
3. input the tire size the you said was on the wheels you are about to buy: 215/40-18
4. click button to calculate
5. read data provide by calculator.
6. decide if you want to buy the staggerd wheels or not.

cheers.
So what is a good range? What is "too" much?

11. Originally Posted by JimJames
Yes, Maybe I am completely ignorant here or you don't understand. I am looking at buying a staggered set with the above tires already mounted. I don't need to know which tires I need. I need to know if the difference between an 8" and 9" rim with the above tire specs will harm the haldex. If I was buying new tires to be mounted then I could see that being useful. But the fact both wheels are running the same tires and have different widths the calculator can't tell me what i need to know.
I know what you are getting at. You want to know if the added stretch on the back rims will put the backs out of spec with the fronts. I'm going to say you should fall well within the 3% range and you should be fine.

Personally, I'm running a true staggered set up without any issues.

12. Originally Posted by Mantvis
So what is a good range? What is "too" much?
If it very difficult to find something difinitive in any search. But, in the searches I've conducted "too much," in most haldex literature, is most often quoted as 4% difference in "rolling radius" (not diameter, not circumferance) from one tire to another.

cheeers

13. Thanks everyone for the help. All good info. now I am less ignorant.

14. actually has absolutely nothing to do with different width wheels
u can run an 8" wide and an 11" wide and as long as the two tire sizes are within the 4% margin diffference u wont have a problem
just make sure the two tire sizes have the same or within 4% circumfrence diffrence

15. It's 3%, not 4%. (speaking from personal experience). Even at 3% I had issues. Personally I would keep it under 1% which is easy to do.

I run an 8" up front and a 9.5" rear and I have no issues now that I'm at 0.1% difference.

I used this calculator to find out the sizes I had to run.

http://www.miata.net/garage/tirecalc.html

16. Thanks Neb

When you had issues, did you have to replace your Haldex pump or just through codes?

17. I didn't throw any codes or have to replace anything. I would get this terrible shuddering that felt like one of my wheels was falling off. There's a thread or two I made that has a bit more info if you do a search for my name.

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