OEM Safe
Within ±3%
Inside factory tolerance — ABS, ESP and cruise control stay calibrated.
Fitment comparison
245/35 R20versus305/30 R20
Δ Ø +11.5 mmSpeedo +1.69%OEM-safe
305/30 R20 stands taller than 245/35 R20 — bigger rolling diameter, slightly more clearance, calmer cruise revs.
Stepping from 245/35 R20 to 305/30 R20 keeps the 20-inch wheel but widens the section by 60 mm. This tire combination moves rolling diameter a touch off the original spec. Expect a slight but noticeable shift in indicated speed compared to the original tires. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeReasonable performance-leaning swap as long as fender and suspension clearance check out.
Quick fitment verdict
245/35 R20 → 305/30 R20 at a glance
Fender Clearance
Likely rubs
Significantly wider/taller — rubbing risk on liners or fender lip is real.
Speedometer Impact
+1.69%
At a true 100 km/h the dash reads 101.7 km/h — negligible.
Daily Driving
Livable
Daily use is fine; expect a slightly different ride and cruise rev count.
Side-by-side telemetry
Dimensional read-out
Current
245/35 R20
- Diameter
- 679.5 mm
- Sidewall
- 85.8 mm
- Wheel
- 20″
- Width
- 245 mm
Δ delta
Ø +11.5 mm
SW +5.8 mm
RH +5.8 mm
NewNew
305/30 R20
- Diameter
- 691.0 mm
- Sidewall
- 91.5 mm
- Wheel
- 20″
- Width
- 305 mm
Real-world effects
How this swap actually feels
- Steering response48/100 · Softer turn-in
- Ride comfort72/100 · More cushion
- Fuel economy4/100 · Slightly higher drag
- Highway cruising67/100 · Lower cruise revs
- Pothole resistance68/100 · More 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 ~5.8 mm — more clearance, slightly more wheel-gap.
Suspension travel · arch clearance
Wheel gap
Wheel gap visually increases
How the arch-to-tire gap reads from across the parking lot — the visual stance change everyone notices first.
245/35 R20
305/30 R20
Wheel-gap Δ+5.8 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 101.7 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 245/35 R20 → 305/30 R20 swap — steering, comfort, stance and dash behavior in plain enthusiast language.
Steering feel
+5.8 mm sidewallSofter, more relaxed turn-in
Taller sidewall flexes a touch more before loading the contact patch — calmer, comfort-tuned.
Ride firmness
35% → 30%Softer over potholes and joints
Bumps and expansion joints are absorbed better — a comfort win for daily driving.
Fender relationship
+60 mm widthWheel sits closer to the fender
Wider tire pushes the contact patch outboard — flusher stance, but verify fender lip clearance at full lock.
Speedometer behavior
+1.69%OEM-safe speedometer reading
Inside the factory ±3% tolerance — ABS, ESP and cruise control behave as designed.
Daily drivability
Ø +11.5 mmLivable upgrade with minor trade-offs
Daily use is fine; expect a slightly different cruise rev count and a touch more road feel.
Direct answer
Is 305/30 R20 OEM-safe?
Yes. Overall diameter changes by +1.69% versus 245/35 R20. OEM-safe. Speedometer, ABS, ESP and gearing remain inside the factory tolerance.
Direct answer
Will 305/30 R20 rub?
Possibly. Width changes by +60 mm and diameter by +11.5 mm. Possible rub at full lock or full suspension compression — verify fender lip and inner strut clearance before committing.
Direct answer
Does the speedometer change?
Yes — by +1.69%. Swapping 245/35 R20 for 305/30 R20 changes overall diameter, so at an indicated 100 km/h your true speed becomes 101.7 km/h. That's within the ±3% OEM tolerance — no recalibration needed.
Direct answer
Does lower sidewall affect comfort?
Yes — softer ride. Sidewall changes by +5.8 mm (35% → 30%). Ride softens and absorbs bumps better, with slightly less precise turn-in.
Current Tire
245/35R20
New Tire
305/30R20
Fitment · Scaled comparison
● Excellent fit
245/35 R20
Diameter
+11.5 mm
+1.69%
Sidewall
+5.8 mm
Speedometer
101.7 km/h
at true 100
Clearance
Excellent fit
305/30 R20
Ground line · Scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+11.5 mm
1.69%
Speedometer at 100
101.7 km/h
+1.69% error
Ground clearance
+5.8 mm
ride height delta
Sidewall change
+5.8 mm
revs/km: 460.7
Permalink for this comparison:
/compare/245-35-r20-vs-305-30-r20Detailed comparison
| Metric | 245/35 R20 | 305/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 679.5 mm | 691.0 mm | +11.5 mm (+1.69%) |
| Sidewall height | 85.8 mm | 91.5 mm | +5.8 mm |
| Circumference | 2.135 m | 2.171 m | +36.1 mm |
| Revs / km | 468.4 | 460.7 | -7.8 |
| Ground clearance | reference | +5.8 mm | +5.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.7 km/h | +1.69 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
245/35 R20- Profile
- 35%
- Circumference
- 2.135 m
New
305/30 R20- Profile
- 30%
- Circumference
- 2.171 m
Side-by-side fitment
GeometryCurrent
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
New
305/30 R20- Section width
- 305 mm
- Aspect ratio
- 30%
- Sidewall
- 91.5 mm
- Wheel diameter
- 20″(508 mm)
- Overall diameter
- 691.0 mm(27.20″)
- Circumference
- 2.171 m
- Revs / km
- 460.7
Real-world consequences
Pros / consWider tire (+60 mm)
Section width- More dry grip and cornering bite
- Sharper steering response on initial turn-in
- Bigger contact patch under braking
- More road noise on coarse asphalt
- Worse aquaplaning resistance in standing water
- Higher rolling resistance, small MPG hit
- Possible fender or strut contact at full lock
Lower profile (-5% 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
Taller overall (+11.5 mm)
Rolling diameter- Higher ground clearance and approach angle
- Longer effective gearing — calmer highway revs
- Bigger contact patch lengthwise
- Speedometer reads low by ~1.7%
- Reduced fender, strut and bumpstop clearance
- Slower 0-60, more downshifts under load
How it changes driving feel
Seat-of-the-pantsSteering response
Sharper turn-in
Ride comfort
Harsher impacts
Road noise
Louder on coarse asphalt
Wet / aquaplaning
Reduced standing-water margin
Fuel economy
Small MPG penalty likely
Curb / pothole protection
Higher wheel-damage risk
Fitment risk check
Verify before installFender rubbing
Width jump >20 mm — verify fender lip and inner liner clearance at full lock.
Suspension clearance
Wider tire may contact strut or control arm on full compression.
Cluster preview
Within toleranceSpeedometer impact
At a true 100 km/h, your dashboard will read 101.7 km/h after switching to 305/30 R20 — a +1.69% 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 +5.8 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
245/35 R20
Back to
305/30 R20
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