Buy 305/40 R21 Tyres

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305/40R21 V (113)
  • C
    Fuel Efficiency
    Fuel Efficiency / Rolling Resistance: C

    How much fuel the tyre uses as it rolls. Graded A to E, where A is the most efficient and E the least.

  • D
    Wet Grip
    Wet Grip / Braking Performance: D

    How well the tyre stops in the wet. Graded A to E, where A is the shortest stopping distance. Each grade is worth roughly 3 metres, about a car length.

  • B73 dB
    External Noise
    Noise Emission / Exterior Noise: B (73 dB)

    How loud the tyre is from outside the car, measured in decibels. Graded A to C, where A is the quietest.

  • Tick Icon 4x4
    4x4 tyre:

    Designed for SUVs and 4x4s, rather than cars, vans or commercial vehicles.

  • Tick Icon Reinforced (XL)
    Extra Load or Reinforced tyres:

    A stronger sidewall lets this tyre carry more weight than a standard tyre of the same size. Marked XL on the sidewall.

  • Tick Icon Winter
    Winter tyres:

    Designed for temperatures below 7°C. Summer tyre rubber hardens in the cold and loses grip, while a winter compound stays soft and holds the road in cold, wet and snowy conditions.

Fit from:17-11-2026
Fully Fitted Price
£353.99
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305/40 R21 Tyres: The Key Facts

  • 1winter tyre
  • DEU wet grip
  • 73EU road noise (dB)

Load and speed ratings on sale

RatingMax load per tyreTop speedTyres
113V1,150 kg149 mph1

Cars that use 305/40 R21

Porsche Cayenne

305/40 R21 Size Guide

Tyres.co.uk stocks 305/40 R21 for the Porsche Cayenne. 305mm is the width. 40 is the sidewall aspect ratio, so the sidewall is 40% of 305mm, or 122mm. R21 is for a radial tyre that fits a 21-inch rim, which gives an overall diameter of 777mm. That low profile keeps the steering sharp while leaving some sidewall to take the edge off rough roads.

Part of the sizeValueWhat it means
Section width 305 The width of the tyre across the tread, measured in millimetres.
Profile (aspect ratio) 40 Sidewall height as a percentage of the width - here, 40% of 305 mm (about 122 mm).
Construction R Radial construction, which is what nearly all road tyres use.
Rim diameter 21 The wheel diameter the tyre fits, measured in inches.
Your tyre dimensions
MeasurementValue
Sidewall height 122.0 mm (4.80 in)
Overall diameter 777 mm (30.6 in)
Circumference 2,442 mm (96.2 in)
Revolutions 659 per mile · 409 per km
Similar sizes
SizeOverall diameter
265/70 R16777 mm · 0.0%
265/65 R17776 mm · -0.1%
275/35 R23777 mm · -0.1%
285/65 R16777 mm · -0.1%
275/40 R22779 mm · +0.2%
315/35 R22779 mm · +0.2%