Can I fit bigger tires on my Mercedes-Benz CLS55?

Yes, within the ETRTO ±3% overall-diameter tolerance shown above. Plus-1 is the standard upgrade; anything beyond ±3% is excluded because it pushes speedometer and TPMS out of factory range.

Do bigger tires change my speedometer?

Not within ±3% overall diameter — that is inside the SAE J1349 speedometer envelope. Safe-verdict sizes produce sub-1 mph error at 60 mph.

Mercedes-Benz CLS55 tire upsize & plus-size guide

Q: What is the OEM tire size for the Mercedes-Benz CLS55?

255/40R18. Confirm on the door-jamb placard.

Every safe upsize, plus-size, wider, and winter-narrower option for the Mercedes-Benz CLS55; covering its factory tire size, each inside the ETRTO ±3% overall-diameter tolerance, with speedometer impact and catalog availability per size.

By Mark Bishop · Last verified 2026-05-17 · Mercedes-Benz CLS55 fitment specs

This guide takes the factory tire size of the Mercedes-Benz CLS55 and shows every geometrically valid alternative; the plus-sizes that fill the wheel arch, the wider sizes that add grip, and the narrower winter sizes that bite through snow. All math is derived from the ±3% ETRTO safe-fit rule, not scraped listings.

255/40R18; factory fitment (2006)

Overall diameter 661.2 mm (26.03 in). Alternatives below are grouped by upgrade intent; every one is inside the ±3% safe-fit envelope for this size.

Plus-1 (next rim size up)

Plus-1 keeps overall diameter constant while bumping rim diameter by one inch and dropping aspect ratio by ten points. The standard daily-driver upgrade; sharper steering response, mild ride penalty, modest tire-cost premium.

Size	OD (mm)	%Δ	True @ 60 mph	Verdict	In catalog
`255/35R19`	661	-0.02%	59.99 mph	Safe	Yes
`225/40R19`	663	0.21%	60.13 mph	Safe	-
`265/35R19`	668	1.04%	60.63 mph	Within tolerance	Yes
`245/35R19`	654	-1.07%	59.36 mph	Within tolerance	Yes
`285/30R19`	654	-1.15%	59.31 mph	Within tolerance	-
`235/40R19`	671	1.42%	60.85 mph	Within tolerance	Yes
`275/30R19`	648	-2.06%	58.77 mph	Within tolerance	-
`275/35R19`	675	2.10%	61.26 mph	Within tolerance	Yes
`235/35R19`	647	-2.13%	58.72 mph	Within tolerance	Yes
`245/40R19`	679	2.63%	61.58 mph	Within tolerance	Yes
`265/30R19`	642	-2.96%	58.22 mph	Within tolerance	-

Plus-2 (two rim sizes up)

Plus-2 lifts rim diameter by two inches with a twenty-point aspect drop. Noticeable ride penalty, higher pothole risk, and a meaningful tire-cost premium. Suitable for performance trims and aesthetic upgrades.

Size	OD (mm)	%Δ	True @ 60 mph	Verdict	In catalog
`255/30R20`	661	-0.03%	59.98 mph	Safe	Yes
`225/35R20`	666	0.65%	60.39 mph	Safe	-
`265/30R20`	667	0.88%	60.53 mph	Safe	Yes
`245/30R20`	655	-0.94%	59.44 mph	Safe	-
`285/25R20`	651	-1.62%	59.03 mph	Within tolerance	-
`235/35R20`	673	1.71%	61.03 mph	Within tolerance	Yes
`275/30R20`	673	1.78%	61.07 mph	Within tolerance	-
`235/30R20`	649	-1.85%	58.89 mph	Within tolerance	-
`275/25R20`	646	-2.37%	58.58 mph	Within tolerance	-
`285/30R20`	679	2.69%	61.62 mph	Within tolerance	Yes
`225/30R20`	643	-2.75%	58.35 mph	Within tolerance	-
`245/35R20`	680	2.77%	61.66 mph	Within tolerance	-

Same rim, wider footprint

Same rim diameter as your OEM, just a wider footprint. Increases grip and footprint contact at the cost of fuel economy and steering effort. Confirm fender clearance at full lock before purchase.

Size	OD (mm)	%Δ	True @ 60 mph	Verdict	In catalog
`285/35R18`	657	-0.68%	59.59 mph	Safe	-
`265/40R18`	669	1.21%	60.73 mph	Within tolerance	-
`275/35R18`	650	-1.74%	58.96 mph	Within tolerance	Yes
`275/40R18`	677	2.42%	61.45 mph	Within tolerance	-
`265/35R18`	643	-2.80%	58.32 mph	Within tolerance	-

Winter / narrower contact

Narrower than OEM, aspect ratio raised to preserve overall diameter. Higher contact pressure improves snow and slush bite; the Nokian-style rule of one width step down for winter on the same overall diameter.

Size	OD (mm)	%Δ	True @ 60 mph	Verdict	In catalog
`225/45R18`	660	-0.23%	59.86 mph	Safe	Yes
`225/50R17`	657	-0.67%	59.60 mph	Safe	Yes
`235/50R17`	667	0.85%	60.51 mph	Safe	-
`235/45R18`	669	1.13%	60.68 mph	Within tolerance	Yes
`245/40R18`	653	-1.21%	59.27 mph	Within tolerance	Yes
`245/45R17`	652	-1.35%	59.19 mph	Within tolerance	-
`245/50R17`	677	2.36%	61.42 mph	Within tolerance	-
`235/40R18`	645	-2.42%	58.55 mph	Within tolerance	Yes
`245/45R18`	678	2.50%	61.50 mph	Within tolerance	Yes
`235/45R17`	643	-2.71%	58.38 mph	Within tolerance	-
`225/55R17`	679	2.74%	61.64 mph	Within tolerance	Yes

Other geometric alternatives

Geometrically valid alternatives that don't fit a named category. Often combinations of rim and aspect change that happen to land in tolerance.

Size	OD (mm)	%Δ	True @ 60 mph	Verdict	In catalog
`255/45R17`	661	0.02%	60.01 mph	Safe	-
`255/50R16`	661	0.03%	60.02 mph	Safe	-
`285/40R17`	660	-0.21%	59.87 mph	Safe	-
`285/45R16`	663	0.26%	60.15 mph	Safe	-
`235/55R16`	665	0.56%	60.34 mph	Safe	-
`225/55R16`	654	-1.10%	59.34 mph	Within tolerance	-
`275/45R16`	654	-1.10%	59.34 mph	Within tolerance	-
`265/45R17`	670	1.38%	60.83 mph	Within tolerance	-
`275/40R17`	652	-1.42%	59.15 mph	Within tolerance	-
`245/50R16`	651	-1.48%	59.11 mph	Within tolerance	-
`265/50R16`	671	1.54%	60.93 mph	Within tolerance	-
`245/55R16`	676	2.22%	61.33 mph	Within tolerance	-
`225/60R16`	676	2.30%	61.38 mph	Within tolerance	-
`265/45R16`	645	-2.47%	58.52 mph	Within tolerance	-
`265/40R17`	644	-2.63%	58.42 mph	Within tolerance	-
`275/45R17`	679	2.74%	61.64 mph	Within tolerance	-
`235/50R16`	641	-2.99%	58.20 mph	Within tolerance	-

Which upsize path fits your priorities?

Every option on this page is inside the ETRTO ±3% overall-diameter tolerance, so any of them is mechanically safe on the factory rim geometry. The difference is what each trades. Use this to pick the category, then read the verdict table above for the exact sizes.

Category	Ride comfort	Handling	Fuel economy	Road noise	Tire cost
Plus-1	Slightly firmer	Sharper	≈ neutral	≈ neutral	Modest premium
Plus-2	Firmer	Sharpest	Slightly worse	Slightly higher	Higher premium
Wider (same rim)	≈ neutral	More grip	Slightly worse	Slightly higher	Modest premium
Winter narrower	Softer	Softer dry	≈ neutral	Lower	≈ neutral
Narrower (same rim)	Softer	Less grip	Better	Lower	Often cheaper
OEM-equivalent	≈ OEM	≈ OEM	≈ OEM	≈ OEM	≈ OEM

"≈" means no meaningful change versus the factory size. Comfort and noise assume the same tire model and load rating; switching brand or category (touring → performance) usually moves these more than the size change does.

Winter setup for the Mercedes-Benz CLS55

For winter, the European engineering rule is to step down one width while raising aspect ratio to hold the same overall diameter; the "Winter / narrower contact" rows in the table above. A narrower footprint concentrates the vehicle's weight over less rubber, raising contact pressure so the tread bites through snow and slush instead of floating on it. Keep the overall diameter within ±3% of 255/40R18 so ABS, TPMS, and (on AWD trims) the center coupling stay inside their factory calibration. Fit four matching winter tires, never two.

Mercedes-Benz CLS55 fitment specs; OE sizes, load/speed ratings, and recommended tires by year
Best tires for the Mercedes-Benz CLS55; data-backed rankings
Every vehicle running 255/40R18 and its full alternative-size table

FAQ

Can I put bigger tires on my Mercedes-Benz CLS55?

Yes; within limits. Any size in the tables above is inside the ETRTO ±3% overall-diameter tolerance, which keeps speedometer, TPMS, and ABS calibration intact. The Plus-1 category is the standard bigger-wheel upgrade; Plus-2 is the aesthetic/performance maximum. Sizes beyond ±3% are excluded because they push those systems out of factory range and can rub at full steering lock.

What is the OEM tire size for the Mercedes-Benz CLS55?

The Mercedes-Benz CLS55 we cover shipped with 255/40R18 as its factory size. Always confirm against your door-jamb placard, as trims and options can change it.

Will bigger tires hurt my Mercedes-Benz CLS55's fuel economy or ride?

Plus-1 is close to neutral on both. Plus-2 and wider sizes add rotating mass and footprint, which costs a little fuel economy and ride comfort for sharper steering and grip. The decision matrix above shows the trade-off per category. Staying within ±3% overall diameter means the transmission and speedometer are unaffected.

Do I need new wheels to change tire size on my Mercedes-Benz CLS55?

Not for same-rim changes (wider, narrower, winter-narrower keep your factory rim diameter). Plus-1 and Plus-2 raise rim diameter and require wheels in the new diameter with a compatible bolt pattern and offset; check the wheel bolt-pattern page linked below before buying.

Sources & methodology

Last verified 2026-05-17 against the standards below.

ETRTO 2024 Standards Manual §2.3 (section width, aspect ratio, overall diameter formula). European Tyre and Rim Technical Organisation, Brussels.
SAE J1349 (speedometer accuracy reference envelope).
NHTSA FMVSS 138 Tire Pressure Monitoring Systems; rev/mile calibration requirements.
Tire Industry Association Technical Bulletin TB-2019-04 (plus-sizing guidance).
Nokian Tyres "Why winter tyres should be narrower" technical bulletin, 2019.