GB/T 7377-2017Series of cycle tyres (English PDF)

1 Scope

This Standard specifies the terms and definitions, classification, specification marks, basic parameters, main dimensions and measurement methods of cycle tyres.

This Standard applies to pneumatic tyres for bicycles, tricycles and trolleys.

This Standard does not apply to tubular racing tyres and non-pneumatic tyres.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 6326, Tyre terms and definitions (GB/T 6326-2014, ISO 4223-1:2002, NEQ)

GB/T 8170, Rules of rounding off for numerical values and expression and judgement of limiting values

GB/T 23657, Series of cycle rims (GB/T 23657-2009, ISO 5775-2:1996, MOD)

HG/T 2906, Static loaded performance testing method for cycle tyres

3 Terms and definitions

For the purposes of this document, the terms and definitions defined in GB/T 6326 apply.

4 Classification

Annex C (normative) Calculation of tyre sizes

C.1 Calculation for sizes of straight side and croctchet type tyres C.1.1 Calculation for sizes of new tyres C.1.1.1 Section width of new tyres (S)

For tyres with a nominal section width SN of less than 28, the section width of the new tyre is calculated according to formula (C.1):

Where, S - New tyre section width, in millimeters (mm);

SN - Nominal section width of the tyre, in millimeters (mm).

SN is 28 (inclusive) to 57 (inclusive) tyres. The section width of the new tyre is calculated according to formula (C.2):

SN is 62 (including 62) or above tyres. The section width of the new tyre is calculated according to formula (C.3):

C.1.1.2 Section height of new tyre (H)

The section height of the new tyre is calculated according to formula (C.4):

Where, H - Height of new tyre section, in millimeters (mm);

H - Height of new tyre section, in millimeters (mm).

C.1.2.3 General rules of calculation The calculation of the maximum tyre size is used by vehicle manufacturers to design tyre clearances.

C.2 Calculation for size of off-road croctchet type tyres C.2.1 Calculation of new tyre size C.2.1.1 Section width of new tyre (S)

The section width of the new tyre is calculated according to formula (C.8):

Where, S - The cross-sectional width of the new tyre, in millimeters (mm);

SN - The nominal section width of the tyre, in millimeters (mm).

NOTE: See Figure C.1 for illustration.

C.2.1.2 Section height of new tyres (H)

The section height of the new tyre is calculated according to formula (C.9):

Where, H - The cross-section height of the new tyre, in millimeters (mm);

I - Increased height, in millimeters (mm). When SN< 28, I =4 mm; when SN>=28, I =5.5 mm; for off-road (D-type) tyres (when SN>=35), I =6.5 mm.

NOTE: See Figure C.1 for illustration.

SN - Tyre section width code.

The calculation results are rounded into integers according to GB/T 8170.

C.3.2 Section height of new tyre (H)

The section width of the new tyre is calculated according to formula (C.14):

Where, H - Height of new tyre section, in millimeters (mm).

The calculation results are rounded into integers according to GB/T 8170.

C.3.3 Outer diameter of new tyre (D0)

The outer diameter of the new tyre is calculated according to formula (C.15):

Where, D0 - Outer diameter of new tyre, in millimeters (mm);

D2 - Nominal outer diameter of the rim, in millimeters (mm), see GB/T 23657.

C.3.4 Maximum tyre size used C.3.4.1 Maximum total tyre width used (Wmax)

The maximum total width used of the tyre is calculated according to formula (C.16):

Where, Wmax - including anti-scuff lines, logos, decorative patterns, manufacturing deviations and usage expansion.

C.3.4.2 Maximum outer diameter used of tyre (D0,max)

The maximum outer diameter used of the tyre is calculated according to formula (C.17):

Annex D (informative) Calculation of tyre load

The tyre load is calculated as shown in formula (D.1):

Where, W - The theoretical load capacity of the tyre, in kilograms (kg).

A - Speed coefficient. On good road conditions:

When the trolley speed is 10 km/h, the soft side trolley tyre is 1.45;

When the bicycle speed is 20 km/h, the bicycle tyre is 1.20; the tyre for heavy-duty bicycle is 1.30;

When the speed of the dual-purpose vehicle is below 30 km/h, the tyre size of the dual-purpose vehicle is 1.10;

When the racing speed is below 40 km/h, the racing tyre shall be 1.10.

0.0158 - The conversion factor when air pressure (P) uses kilopascal (kPa).

K - Tyre type coefficient. For passenger tyres, it is taken as 0.425; for truck tyres, it is taken as 0.465.

P - Inflated internal pressure of tyre, in kilopascals (kPa).

Dr - The fitting diameter of the rim, in centimeters (cm).

S0 - The inflated section width of the tyre on the ideal rim, in centimeters (cm):

Where, S - The width of the inflated section of the tyre on the rim, in centimeters (cm);

C0 - Rim width used, in centimeters (cm).