C4 tire diameter
Thread Starter
5th Gear
Joined: Apr 2005
Posts: 5
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From: Southwick MA.
C4 tire diameter
Looking to put C5 wheels on my 96'. If I stagger 17" front, 18" rear and run different diameter tires will I have problems with ABS or traction control? If so, whats the limit on front/rear diameter difference? Thank you for your input.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
You shouldn't have abs or tc problems. You are limited by clearances. You will effectively raise gear ratio. (lower numerically). Mounted tire diameter will differ between individual tires. You will impact handling (probably negatively). You limit rotation options with different sizes. IMO for a street car there are more negatives than positives.
Thread Starter
5th Gear
Joined: Apr 2005
Posts: 5
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From: Southwick MA.
Thanks for the quick reply. I am not looking to go crazy with the difference in dia.'S maybe 1". I just don't care for the real low profile tires on rear like 35 that you would nneed to get close to a 45 in the front. I will lower the rear abit if needed to cut down on the rake.
Le Mans Master
Joined: May 2005
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From: Central Maryland
My '94 has been running 18" C5 thinspokes in the rear, and 17" in the front, for as long as I've owned it (since 2004). I've had no problems with TC or ABS. The only downsides (both very minor) in my case have been:
1. Speedometer is slightly off. Reads two or three MPH low at highway speeds. I'm aware of it, and calibrate it out mentally.
2. On rare occasions, when the rear suspension goes into full compression, the inner edge of the rear tire treads kiss the inner fenderwells of the car. It has caused no problems.
Watch the diameter, and keep it as close to stock as possible, and you'll minimize both of these issues.
Most C4s used different tire sizes (of the same rim diameter), so rotating them front-to-rear isn't really an option anyway.
Live well,
SJW
1. Speedometer is slightly off. Reads two or three MPH low at highway speeds. I'm aware of it, and calibrate it out mentally.
2. On rare occasions, when the rear suspension goes into full compression, the inner edge of the rear tire treads kiss the inner fenderwells of the car. It has caused no problems.
Watch the diameter, and keep it as close to stock as possible, and you'll minimize both of these issues.
Most C4s used different tire sizes (of the same rim diameter), so rotating them front-to-rear isn't really an option anyway.
Live well,
SJW
Thread Starter
5th Gear
Joined: Apr 2005
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From: Southwick MA.
Melting Slicks
Joined: Oct 2010
Posts: 3,034
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From: Tollesboro Kentucky
tire sizes
If you go to www.miata.net they have an online tire size calculator.Very handy guide to compare tire sizes so you can see the height differences.Also tells you how much your speedometer will be off,fast or slow.this should be all the info you need for a correct choice.i put C5 wheels on my C4 and the 285/35 18 was almost a perfect match for the 285/40 17 tires my car came with from the factory.Hope this helps!
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Race Director
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If you go to www.miata.net they have an online tire size calculator.Very handy guide to compare tire sizes so you can see the height differences.Also tells you how much your speedometer will be off,fast or slow.this should be all the info you need for a correct choice.
i put C5 wheels on my C4 and the 285/35 18 was almost a perfect match for the 285/40 17 tires my car came with from the factory.Hope this helps!
i put C5 wheels on my C4 and the 285/35 18 was almost a perfect match for the 285/40 17 tires my car came with from the factory.Hope this helps!
On average (varies slightly between tire brands), there is only 0.12" difference in the overall diameter between these two tires.
You won't even notice a difference in the speedometer keeping the size that close.
Pro
Joined: May 2006
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If I´m not mistaking the difference in diameter between front and rear shouldn´t be more than 5 %. Could be different for different cars.
The ABS system keeps track of the wheel speed on all four.
Depending on how the system is programmed, if the system is programmed with different sizes on front and rear, you can´t change either to similar size front and rear.
I´m sure there is someone that can verify this or explain better.
But, as stated before, there are some calculators on the net so you can find out what tire to use when you go bigger in wheel size.
The ABS system keeps track of the wheel speed on all four.
Depending on how the system is programmed, if the system is programmed with different sizes on front and rear, you can´t change either to similar size front and rear.
I´m sure there is someone that can verify this or explain better.
But, as stated before, there are some calculators on the net so you can find out what tire to use when you go bigger in wheel size.
Race Director
Joined: Oct 2005
Posts: 11,776
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From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
If I´m not mistaking the difference in diameter between front and rear shouldn´t be more than 5 %. Could be different for different cars.
The ABS system keeps track of the wheel speed on all four.
Depending on how the system is programmed, if the system is programmed with different sizes on front and rear, you can´t change either to similar size front and rear.
I´m sure there is someone that can verify this or explain better.
But, as stated before, there are some calculators on the net so you can find out what tire to use when you go bigger in wheel size.
The ABS system keeps track of the wheel speed on all four.
Depending on how the system is programmed, if the system is programmed with different sizes on front and rear, you can´t change either to similar size front and rear.
I´m sure there is someone that can verify this or explain better.
But, as stated before, there are some calculators on the net so you can find out what tire to use when you go bigger in wheel size.
But if he uses the listed size above (285/35-18) and keeps his stock 255/45-17 front tire he will be fine.
The ABS sensor won't know the difference between the stock 285/40-17 rear, and the new 285/35-18 rear.
They are only 0.12" different in overall diameter, with the 18" being .12" shorter.
Le Mans Master
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Stock C4 diameter is 25.5 inches.
IIRC if you deviate from that diameter make sure the rears are taller (bigger in diameter) than the fronts.
I've used .2 - .5 in difference front to rear with little issues with the ASR. Spedometer will be off a little as well.
IIRC if you deviate from that diameter make sure the rears are taller (bigger in diameter) than the fronts.
I've used .2 - .5 in difference front to rear with little issues with the ASR. Spedometer will be off a little as well.
Thread Starter
5th Gear
Joined: Apr 2005
Posts: 5
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From: Southwick MA.
Thanks everyone for the input and info. Again, my biggest concern is different overall diameter differences front to rear. If I know the stagger limit if any, I can choose from many wheel size/tire size combinations within that limit of overall diameter difference. If as one response said I need to stay within 5%, that means with a 26.0" dia on the front, I would need to go no more than 27.3" on the rear. Does this sound right?
Last edited by Rick96red; Jun 17, 2011 at 10:15 PM. Reason: added info
Le Mans Master
Joined: May 2005
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From: Central Maryland
245/45 ZR 17 front
275/40 ZR 18 rear
I'm sorry, but I don't know the rim widths or backspacing, and that's not easy to measure with them on the car with tires mounted.
Live well,
SJW
