OEM Safe
Within ±3%
Inside factory tolerance — ABS, ESP and cruise control stay calibrated.
Fitment comparison
245/45 R18versus245/35 R20
Δ Ø +1.8 mmSpeedo +0.27%OEM-safe
245/35 R20 stands taller than 245/45 R18 — bigger rolling diameter, slightly more clearance, calmer cruise revs.
Going from 245/45 R18 to 245/35 R20 steps up to a 20-inch rim while trimming sidewall to stay near OEM rolling diameter. This sizing approach preserves rolling diameter within a hair of the original. There's no meaningful speedometer deviation — the dashboard speed stays honest. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick fitment verdict
245/45 R18 → 245/35 R20 at a glance
Fender Clearance
Clears fender
Width and diameter stay close to stock — arch clearance unchanged.
Speedometer Impact
+0.27%
At a true 100 km/h the dash reads 100.3 km/h — negligible.
Daily Driving
Drop-in swap
Geometry stays in OEM envelope — no surprises in traffic or on the highway.
Side-by-side telemetry
Dimensional read-out
Current
245/45 R18
- Diameter
- 677.7 mm
- Sidewall
- 110.3 mm
- Wheel
- 18″
- Width
- 245 mm
Δ delta
Ø +1.8 mm
SW -24.5 mm
RH +0.9 mm
NewNew
245/35 R20
- Diameter
- 679.5 mm
- Sidewall
- 85.8 mm
- Wheel
- 20″
- Width
- 245 mm
Real-world effects
How this swap actually feels
- Steering response100/100 · Sharper turn-in
- Ride comfort20/100 · Firmer ride
- Fuel economy69/100 · Unchanged
- Highway cruising61/100 · Lower cruise revs
- Pothole resistance11/100 · Less wheel protection
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Ride height
Lifted stance
Chassis sits higher — slightly more clearance, wheel-gap visually grows.
New tire lifts the chassis by ~0.9 mm — more clearance, slightly more wheel-gap.
Suspension travel · arch clearance
Wheel gap
Wheel gap stays virtually unchanged
How the arch-to-tire gap reads from across the parking lot — the visual stance change everyone notices first.
245/45 R18
245/35 R20
Wheel-gap Δ+0.9 mm
Static · unloaded chassis
Fender relationship
Tucked · Flush · Poke
The visual relationship between the tire's outer edge and the fender lip — the lens enthusiasts use to judge a fitment.
Tucked
Inside fender
Flush
Lip-aligned
Poke
Outside fender
Width & offset dependent
Speedometer reality
Dash reads 100.3 km/h
Taller rubber: at a true 100 km/h your dashboard reads optimistically high.
ABS · ESP · cruise control
Setup telemetry
How this setup changes the car
Driver-perspective read-out of the 245/45 R18 → 245/35 R20 swap — steering, comfort, stance and dash behavior in plain enthusiast language.
Steering feel
-24.5 mm sidewallSharper steering response
Shorter sidewall transmits inputs faster — quicker turn-in, more confident on-center feel.
Ride firmness
45% → 35%Slightly firmer over rough pavement
Expect more chatter on broken tarmac and a sharper pothole strike — keep an eye on wheel damage risk.
Fender relationship
+0 mm widthFender gap reads near-identical
Width delta is too small to change stance — same visual signature as OEM.
Speedometer behavior
+0.27%OEM-safe speedometer reading
Inside the factory ±3% tolerance — ABS, ESP and cruise control behave as designed.
Daily drivability
Ø +1.8 mmDrop-in swap, daily-safe
Geometry stays in the OEM envelope — no surprises in traffic, parking or on the highway.
Direct answer
Is 245/35 R20 OEM-safe?
Yes. Overall diameter changes by +0.27% versus 245/45 R18. OEM-safe. Speedometer, ABS, ESP and gearing remain inside the factory tolerance.
Direct answer
Will 245/35 R20 rub?
Unlikely. Width changes by +0 mm and diameter by +1.8 mm. Very unlikely to rub with OEM wheel offset.
Direct answer
Does the speedometer change?
Yes — by +0.27%. Swapping 245/45 R18 for 245/35 R20 changes overall diameter, so at an indicated 100 km/h your true speed becomes 100.3 km/h. That's within the ±3% OEM tolerance — no recalibration needed.
Direct answer
Does lower sidewall affect comfort?
Yes — firmer ride. Sidewall changes by -24.5 mm (45% → 35%). Ride becomes firmer and steering sharper, but potholes and expansion joints hit harder and wheel damage risk rises.
Current Tire
245/45R18
New Tire
245/35R20
Fitment · Scaled comparison
● Excellent fit
245/45 R18
Diameter
+1.8 mm
+0.27%
Sidewall
-24.5 mm
Speedometer
100.3 km/h
at true 100
Clearance
Excellent fit
245/35 R20
Ground line · Scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+1.8 mm
0.27%
Speedometer at 100
100.3 km/h
+0.27% error
Ground clearance
+0.9 mm
ride height delta
Sidewall change
-24.5 mm
revs/km: 468.4
Permalink for this comparison:
/compare/245-45-r18-vs-245-35-r20Detailed comparison
| Metric | 245/45 R18 | 245/35 R20 | Difference |
|---|---|---|---|
| Overall diameter | 677.7 mm | 679.5 mm | +1.8 mm (+0.27%) |
| Sidewall height | 110.3 mm | 85.8 mm | -24.5 mm |
| Circumference | 2.129 m | 2.135 m | +5.7 mm |
| Revs / km | 469.7 | 468.4 | -1.2 |
| Ground clearance | reference | +0.9 mm | +0.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 100.3 km/h | +0.27 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Dimensional comparison
Side-by-sideScaled engineering side-profile of both tires. Width, sidewall and overall diameter are dimensioned so you can see the change at a glance — without parsing the numbers.
Current
245/45 R18- Profile
- 45%
- Circumference
- 2.129 m
New
245/35 R20- Profile
- 35%
- Circumference
- 2.135 m
Side-by-side fitment
GeometryCurrent
245/45 R18- Section width
- 245 mm
- Aspect ratio
- 45%
- Sidewall
- 110.3 mm
- Wheel diameter
- 18″(457 mm)
- Overall diameter
- 677.7 mm(26.68″)
- Circumference
- 2.129 m
- Revs / km
- 469.7
New
245/35 R20- Section width
- 245 mm
- Aspect ratio
- 35%
- Sidewall
- 85.8 mm
- Wheel diameter
- 20″(508 mm)
- Overall diameter
- 679.5 mm(26.75″)
- Circumference
- 2.135 m
- Revs / km
- 468.4
Real-world consequences
Pros / consLower profile (-10% aspect)
Sidewall- Sharper turn-in and less sidewall roll
- More planted on smooth tarmac
- Bigger brake / caliper visual real estate
- Harsher ride over expansion joints and potholes
- Higher wheel-damage risk on impacts
- Less curb protection for the rim lip
- More sensitive to correct tire pressure
+2″ rim upsize
Wheel diameter- OEM+ look, fills the arch better
- Sharper response with matching low-profile rubber
- Bigger brake clearance for upgrades
- Heavier wheel, more unsprung mass
- Harsher ride, more wheel-damage risk
- Tire and wheel cost both go up
How it changes driving feel
Seat-of-the-pantsSteering response
Sharper turn-in
Ride comfort
Harsher impacts
Road noise
Similar cabin noise
Wet / aquaplaning
Comparable wet behavior
Fuel economy
Negligible change
Curb / pothole protection
Higher wheel-damage risk
Cluster preview
Within toleranceSpeedometer impact
At a true 100 km/h, your dashboard will read 100.3 km/h after switching to 245/35 R20 — a +0.27% offset. Use the speedometer error calculator for any indicated speed, and the speedometer error guide for the full background.
Ground clearance change
The new tire's half-diameter changes ride height by +0.9 mm. Small differences are absorbed by suspension travel, but anything beyond ±10 mm can affect headlight aim, fender clearance and bump-stop margin. See the plus-sizing guide before committing.
Back to
245/45 R18
Back to
245/35 R20
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