Staggered Tire Setup in RWD

[FlyPenFly]

2014 GLK 350, RWD model not AWD.

Car came with the AMG package which included 20" special AMG wheels with 235 45 20 tires all around.

Would it be a big problem to run 245 45 20 in the rear and 235 45 20 in the front? I have a set for the rear from a friend that are nearly new. All tires are Pirelli Scorpions.

Don't want traction control or something to go crazy...

 

[AZjeff]

ABS will hate it.

 

[FlyPenFly]

You think with just a 10mm difference in width same height?

 

[d00df00d]

That second number is aspect ratio, not height. 245/45 will have slightly more height than 235/45.

 

[Olas]

Go to the website www.willtheyfit.com and plug in your tyre sizes - it will calculate for you the difference in rolling diameter. Off the top of my head I think about 10-12mm?

Look in the owners handbook for information on tyre size - many 4wd/AWD cars mandate the same size on every corner but many also allow a %age difference before any issues are encountered. By simple reckoning, if 4wd can tolerate different sizes rwd can too.

 

[Shannow]

If your car can tolerate worn tyres at one end and new tyres at the other, it can tolerate that.

 

[4WD]

There are several tire speed calculators you can Google up - at least get the speed difference as a basis for what variances the ABS and roll over protection can tolerate. Sometimes you can find these kind of threads on sites specific to a vehicle/make.

 

[CapriRacer]

If I recall correctly, the Mercedes ABS is kind of sensitive to tire diameter, and even changing tire size all around can affect its operation - again, if I remember correctly.

Besides, a 255/40R20 would be a much better match on diameter.

 

[JHZR2]

I have a car that came OE with a staggered setup (bmw 135i). Its fine I guess, and I'll get 25k+ of life out of high performance summer tires, so I can't complain much about not rotating. But personally, if I had the option, I'd not do it.

That said, if you need tires anyway, and have a compelling deal in a used set, its possibly worth the chance.

 

[SteveSRT8]

Originally Posted By: Shannow
If your car can tolerate worn tyres at one end and new tyres at the other, it can tolerate that.


This sounds like the debate over MDS in new gen Hemis. The mfgr builds in a bit of tolerance, the only thing here is how much.

 

[slacktide_bitog]

It probably won't hurt anything, but there's no point in doing it, either

 

[Rand]

As capriracer noted a staggered setup is 2 different tire sizes with similar diameter..

and 255/40r20 is alot closer diameter than 245/45r20


To put it simply:
The second number is the sidewall height as a percentage of the section width

Section width is basically the width of the tire.. the tread width is slightly smaller.

Therefore if you keep the same aspect ratio(second number) and make the tire wider.. its also has taller sidewalls.. in this case the rolling diameter increases by aprox 8-10mm

If that is too complicated just throw them into a tire size calculator and see what the allowable spec is for your car usually hidden somewhere in the owners manual.

It might be off too far for the ABS system etc.

 

[FlyPenFly]

Slightly more than a 1% difference in height... nothing in the manual.

 

[4WD]

Thinking a bit more - wouldn't the dashboard message you if it pings the four corners a few times and does not like wheel speed - if so, the risk is just tire mounting costs ...

 

[FlyPenFly]

Well mounting, dismounting, and I'm paying him $180 for tires I might not be able to use and I have no where to put it.

 

[40w8]

I ran my RX8 Mazda with 225/40r18 new front and 225/45r18 half worn in back.

I was maybe 2% higher rolling speed for the front because lower tire.

I drove 300 miles to track without trouble, but when I skidded slightly at 30 mph the traction control went nuts, and not only spun me out, but spun me 360 degrees. No way car would have done that without traction hitting one brake at a time.

I don't think your car will notice slight difference, but watch it.

 

[NGRhodes]

Could be enough to confuse stability control, without knowing for sure, is it worth the risk ?
I would ask MB directly (not a dealer).
You might find you invalidate your insurance for running non-standard tyre sizes too.

 

[CapriRacer]

Originally Posted By: 4WD
Thinking a bit more - wouldn't the dashboard message you if it pings the four corners a few times and does not like wheel speed - if so, the risk is just tire mounting costs ...


If I remember correctly, the incident where I picked up that fussy nature of MB ABS systems, there was no warning lights. Just an occasional shudder throughout the car. (Again, if I remember correctly.)

Also, my experience with vehicle manufacturer's technical hot lines hasn't been very promising. The folks on the other end of the phone lines don't always have access to the information needed. Worth a try, but be careful about what information you get.

 

[4WD]

I tend to buy over size in "fours" and it has not impacted GM's - but on my Explorer I played with the calculators to bump up from 255 to 275 - but changed aspect to compensate.
Indeed mixing sizes is another animal - if it's 1 mph to 2 mph one would still need to know the margin of error. The old "wheel speed means low air" systems would not like it - now they are uber PLC based and as you point out there is little romance for an OEM engineer to put his/her name on this.

 

[40w8]

If you air up tires on cold morning, or just reset TPMS, it will be ready for what it sees, and then, go off only if the tire rolls different from what set.

I don't know of any car that USES GPS to know smaller tires were put on.

I just put 215/40r18 instead of 225/45r18 on my RX8 for 4.6% gear down, and it works great.