Drive Train Question
Thread Starter
Member
Joined: Jul 2022
Posts: 159
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GLS 450 (2022), EQE SUV 350 (2025). GLS 450 (2007)
Drive Train Question
Hi folks. I've got a 2022 GLS 450 with 4-Matic AWD and it's got the staggered tire setup - with different-sized tires on the front and back. I used an online tire calculator to calculate the circumference of the two sizes, and to my surprise they were about 1" different (each was close to 97").
I always thought that cars with all/four wheel drive required all four tires to be of the same circumference. How is it that the MB mechanical drivetrain setup allows this not to be the case? Yeah, I'm a retired engineer and just can't help thinking about such minutiae.
Thanks to anyone who can help!
I always thought that cars with all/four wheel drive required all four tires to be of the same circumference. How is it that the MB mechanical drivetrain setup allows this not to be the case? Yeah, I'm a retired engineer and just can't help thinking about such minutiae.
Thanks to anyone who can help!
Out Of Control!!
Joined: Sep 2018
Posts: 14,710
Likes: 4,600
From: unbegrenzt
2017 GLE350 4MATIC
Hi folks. I've got a 2022 GLS 450 with 4-Matic AWD and it's got the staggered tire setup - with different-sized tires on the front and back. I used an online tire calculator to calculate the circumference of the two sizes, and to my surprise they were about 1" different (each was close to 97").
I always thought that cars with all/four wheel drive required all four tires to be of the same circumference. How is it that the MB mechanical drivetrain setup allows this not to be the case? Yeah, I'm a retired engineer and just can't help thinking about such minutiae.
Thanks to anyone who can help!
I always thought that cars with all/four wheel drive required all four tires to be of the same circumference. How is it that the MB mechanical drivetrain setup allows this not to be the case? Yeah, I'm a retired engineer and just can't help thinking about such minutiae.
Thanks to anyone who can help!
Longer answer: front and rear axle ratios are not exactly the same (haven’t checked 167 ratios). This combined with slightly different tire diameters creates torque bias front to rear under steady state driving conditions. The center differential is constantly differentiating under this scenario to account for rotational speed differences between front and rear propshafts.
Super Member
Joined: Sep 2020
Posts: 676
Likes: 259
From: Los Angeles
Panamera, '63 Impala
They don't have to be the same circumference. But the difference in circumference must not differentiate too much from the factory sizes. A general rule of thumb is to not exceed more than 3% difference from the factory measurements.
MBWorld Fanatic!
Joined: Jan 2023
Posts: 3,137
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GLE 580
What is the reason for this limit? Just curious.
