dim74

Hey guys I am thinking on putting my 2014 glk250 on 18" rims however I haven't seen anyone doing it.

Could I get so help not sure what Rims I need , I am a newbie.
I assume 18",5X112mm, not sure for offset.

Thank you in advance

andreigbs

You might want to try https://www.miata.net/garage/tirecalc.html or a tire/wheel site like discounttire.com or tirerack.com which can calculate different sizes.

I assume going to 18" is considered -1 for your vehicle, if it came equipped with 19" wheels/tires or -2 if equipped with 20" wheels/tires.

There are some folks who have even gone to 17" rims, especially for winter use, so 18" shouldn't be a problem.

Good luck.

CarbonKevinYWG

You can't just change the rim diameter, keep the tire width and aspect ratio, and expect the final tire diameter to be the same size. Look into the various stock tire sizes for the GLK, 17" was available in Europe, IIRC.

dim74

Hey first of all thanks so much for the reply,

I have seen 17" on the road as well. I have 235/45r20 right now, and have brand new 235/45-18 winters in my garage, I am just scared to make a mistake haha.
I read that the offset required is 40mm-50mm. is that something you might be able to confirm?
that is mostly what I am worried about.

Thank you!

dim74

Hi there,

thanks for the reply. so going from 235/45-20 to 235/45-18 would not be okay as per your knowledge?

thank you!

CarbonKevinYWG

235/45R20 has a diameter of approximately 28.3"
235/45R18 has a diameter of approximately 26.3"

That's a 7.6% difference in circumference, and not acceptable IMO. I would stay within 1%-1.5% if possible.

dim74

that's awesome, helping a lot as I don't know much when it comes to wheels.

big thanks!

andreigbs

Agreed with CarbonKevin. I would not run that setup on the GLK. Is it possibly from another MB vehicle? If going from 19" to 18" I would make sure the tire and rim combo is 235/55.

Width is 235, height is 55. In general, if you reduce the overall rim diameter you will need to increase the tire height to compensate and keep overall diameter near original. For example, the overall diameter for a 235/55 tire is 28.2" which is nearly identical to your OEM size 20" diameter tire (28.3")

You want to keep the final diameter and circumference the same as stock, otherwise you will be messing with vehicle speed sensors, possible transmission/gearing issues and definitely speedometer/odometer issues.

In a phrase: I advise against running that potential setup.

dim74

AWESOME , THANK YOU, I READ THAT 235/60-17 WAS A GOOD CHOICE I MIGHT TRY THAT.
sorry caps

andreigbs

235/60R17 would be an OK choice. Overall diameter is 28.1" However, you need to be sure the front brake calipers clear the inner side of the wheels. Offset is important, so double-check that it's close to 35mm. The larger the offset, the more inside the wheel well they fit, and may not clear the brakes. Think muffin top.

dim74

thanks,i read that the offset should be 40-50 mm is that correct ?

andreigbs

I would try to stay as close to 35mm as possible, though Discount Tire lists 17" wheels that fit the GLK as having offset numbers from 32 to 45mm. I don't see higher, but there may be.

I can't vouch for which is the best, only what I think. Closest to OEM is best...

dim74

thank you so much for all the help, much appreciated!

andreigbs

I stand corrected: 35mm offset doesn't look to be stock. It looks like for the 235/60R17 setup, you would want an offset of 47.5, according to https://www.wheel-size.com/size/merc...lk-class/2014/