Tire sizing question - Mercedes GLA Forum
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post #1 of 15 Old 05-05-2019, 09:55 PM Thread Starter
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Tire sizing question

Hey fellas, I have a few questions for your AWD GLA250,

1. Is there major harm from using staggered tire size set up, specifically 225/50RF18 and 235/50RF18?

2. Any issues of using 225/50RF18 for all four? instead of original 235/50RF18's?

Thank you!
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post #2 of 15 Old 05-06-2019, 01:14 AM
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Fronts and rears should have the same circumference circumference. Varying from OEM while maintaining equalsize all around will affect your speedometer and may affect handling and performance (safety) if taken to an extreme.
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post #3 of 15 Old 05-06-2019, 07:58 AM
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For any AWD cars, it is important to maintain all four wheels at exactly the same size. Otherwise, it will harm your AWD system.
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post #4 of 15 Old 05-06-2019, 08:50 AM
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Quote:
Originally Posted by Wayne View Post
Fronts and rears should have the same circumference. Varying from OEM while maintaining equal size all around will affect your speedometer and may affect handling and performance (safety) if taken to an extreme.
Not sure on a GLA but with my SLK I do know that you must have less than 3% difference in the circumference of the tires. More than 3% will cause problems with cruise control and ESP, as the computer will pick up the difference and think something is wrong like a tire spinning or sliding and will try to do something to prevent an accident.

Suggest you use the website below and check the tire sizes.

Custom rims, wheel tire packages

2019 GLA250 Black/Black replaced 2016 GLA250 Black/Black
Second car 2007 SLK350 Black/Black
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post #5 of 15 Old 05-06-2019, 10:40 PM
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Calculations from tire sizes don't appear to hold between manufacturers. I used math and tables to evaluate an equivalent Michelin MP4S size to the original tires and the height wasn't close.
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post #6 of 15 Old 05-07-2019, 07:43 AM
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Exactly. There's a lot going on between various systems, not the least of which speedo. AWD in particular can be aversely effected by a staggered setup (Audi RS3 comes to mind with OEM wider front tires to offset weight-oversteer but a rare exception).
I've run a very small delta from OEM circumference, re-employing some hand me down winter rims, but never staggered.

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Originally Posted by gbarringer View Post
Not sure on a GLA but with my SLK I do know that you must have less than 3% difference in the circumference of the tires. More than 3% will cause problems with cruise control and ESP, as the computer will pick up the difference and think something is wrong like a tire spinning or sliding and will try to do something to prevent an accident.

Suggest you use the website below and check the tire sizes.

Custom rims, wheel tire packages

2018 GLA 250 AWD in MA and FWD in FL
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post #7 of 15 Old 05-07-2019, 08:46 AM
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OP question was if staggered tire size tires ok Many vehicles use staggered tires. They are okay as long as you keep the circumference the same or within a set range for the make and model vehicle. The example he had only had a 1.5% difference.

2019 GLA250 Black/Black replaced 2016 GLA250 Black/Black
Second car 2007 SLK350 Black/Black
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post #8 of 15 Old 05-07-2019, 09:03 AM
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Originally Posted by gbarringer View Post
OP question was if staggered tire size tires ok Many vehicles use staggered tires.

Are those many vehicles also AWD? OP specifically mentioned that he has AWD 250. In the past, I was told not to even mix old/worn out tires with new tires in an AWD vehicle because most AWD systems use the rotational speed difference as a hint to transfer power from axle to axle.
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post #9 of 15 Old 05-09-2019, 12:06 AM
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Originally Posted by Foxbat121 View Post
Are those many vehicles also AWD? OP specifically mentioned that he has AWD 250. In the past, I was told not to even mix old/worn out tires with new tires in an AWD vehicle because most AWD systems use the rotational speed difference as a hint to transfer power from axle to axle.

yes, correct. Subaru as another example: 1) all tires same size, and 2) different size/width/weight front/rear can mess with the monitoring of AWD systems and grip sent to tires and 3) tire replacement generally needs to be all 4 same time to maintain that consistency.

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post #10 of 15 Old 05-09-2019, 02:47 PM
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Performance cars with AWD do come with staggered wheels. The MB CLS53 has 245/40/19 on front and 275/35/19 on rears is just on example. The Circumference is only 0.7% difference. The MB AMG GLC63 AWD has 265/45/20 on fronts and 295/40/20 on rears with a Circumference difference of 0.3%. Yes, you can have staggered wheels as long as the circumference is the same or very near the same. As the tire gets wider the sidewall height ratio goes down which keeps the circumference the same so the wheels turn at the same speed.

2019 GLA250 Black/Black replaced 2016 GLA250 Black/Black
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