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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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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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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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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
 

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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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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.

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
 

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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.
 

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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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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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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.
 

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Suggest you use the website below and check the tire sizes.
Thanks for the reference tool! I will certainly be using it when researching wheel and tire options for a spare set of wheels for the track.

In addition to keeping the final tire diameters the same, I was surprised to see some AWD vehicles with matching tires all around, actually use different tire pressures from front to rear? I have a 2014 E350 wagon and the pressures are quite different from front to rear, with the rear being higher pressure. You'd assume you'd want the same pressure all around to keep the resulting diameters the same. Maybe accounting for more weight in the rear of the vehicle? I don't question it though, I run what the manual says!
 

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Both our GLA and TTS cite a higher pressure in the front to help counter engine weight and thereby oversteer. Transverse AWD vehicles typically need to push the engine forward to accommodate the transmission/transfer case, making them a bit nose heavy.
Note also fully loaded and nominal pressure ranges.

Thanks for the reference tool! I will certainly be using it when researching wheel and tire options for a spare set of wheels for the track.

In addition to keeping the final tire diameters the same, I was surprised to see some AWD vehicles with matching tires all around, actually use different tire pressures from front to rear? I have a 2014 E350 wagon and the pressures are quite different from front to rear, with the rear being higher pressure. You'd assume you'd want the same pressure all around to keep the resulting diameters the same. Maybe accounting for more weight in the rear of the vehicle? I don't question it though, I run what the manual says!
 

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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.
I'm not sure if you are considering both different sizes and perhaps mixing tires from different manufacturers, but a mix from different manufacturers is definitely a "No No."

I made the mistake of mixing Michelins on the front and Contis on the rear of my CLS63S and it was scary. I should have know better -- I quickly changed the rears to Michelins. The Michelins were quick to turn in and there was instant oversteer.
 

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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.
I'm not sure if you are considering both different sizes and perhaps mixing tires from different manufacturers, but a mix from different manufacturers is definitely a "No No."

I made the mistake of mixing Michelins on the front and Contis on the rear of my CLS63S and it was scary. I should have know better -- I quickly changed the rears to Michelins. The Michelins were quick to turn in and there was instant oversteer.
An excellent point!!!
 

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I meant to say understeer, but can't seem to edit. Likely still too few posts. I have 4k+ posts on the Audi forum and 8K+ posts on the Mazda forum, does that count? ;)

Both our GLA and TTS cite a higher pressure in the front to help counter engine weight and thereby oversteer. Transverse AWD vehicles typically need to push the engine forward to accommodate the transmission/transfer case, making them a bit nose heavy.
Note also fully loaded and nominal pressure ranges.
 
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