Triumph Pistons & Rings

Hepolite numbers in orange = Standard Stock Item. Hepolite ring set numbers are prefixed ‘R’.
Split skirt is the non-thrust face, i.e. faces forward. The lower the Hepolite number the earlier the bike.

Order of entries is:- Alphabetical by engine size then by compression ratio (c.r.) All dimensions in inches unless stated otherwise.
If there is ‘Y’ in the ‘Fit Orig’ column, these rings fit the OE pistons but there may be more than one set to choose from! ‘N’ means that these rings do not fit.

 Machine

Piston

Gudgeon

Rings

Model

Year

Bore

c.r.

Hepolite Number

O.E.

Comp Hght

Lgth

dia

lgth

Hepolite Number

Welworthy Number

Comp rings

Oil ring

Fit Orig?

Qty

Hgt

Depth

Qty

Hgt

Depth

T15 and T20 Tiger Cub

T15

54-57

57

7

11952

Yes

1.22

2.22

9/16

5570

2

1/16

.092

1

3/32

.092

Y

T15

54-57

57

9

11982

1.44

2.44

9/16

5570

2

1/16

.092

1

3/32

.092

Y

T20

54-69

63

5810*

2

1/16

.091

1

3/32

.091

Y

T20

54-69

63

7

12581

Yes

1.12

2.06

9/16

5812*

2

1/16

.102

1

3/32

.102

N

T20

54-69

63

9

12600

Yes

1.43

2.36

9/16

5812*

2

1/16

.102

1

3/32

.102

N

T20

54-69

63

10.5

13469

1.63

2.56

9/16

10872

2

1/16

.102

1

3/32

.102

N

* Some books list R5810 as correct for 12581/12600 pistons – R5812/R10872 are inter

350cc pre-unit

3T

46-59

55

6.3

10500

1.28

2.47

9/16

3840

2

1/16

.088

1

3/32

.088

Y

T85

46-59

55

7

10499

1.47

2.66

9/16

3840

2

1/16

.088

1

3/32

.088

Y

350cc unit

T21, 3TA

57-69

58.25

7.5

13952

1.42

2.48

9/16

10280

2

1/16

.092

1

1/8

.089

Y

T21, 3TA

57-69

58.25

9

14180

1.52

2.58

9/16

10280

2

1/16

.092

1

1/8

.089

Y

T21, 3TA, T90, T35

57-69

58.25

9

16986

1.52

2.58

9/16

10280

2

1/16

.092

1

1/8

.089

Y

500cc pre-unit

T100, 5T, TR5

38-58

63

7

10334

1.38

2.69

.689

3850

2

1/16

.091

1

1/8

.089

Y

T100, 5T, TR5

38-58

63

6.8

11563

1.44

2.75

.689

3850

2

1/16

.091

1

1/8

.089

Y

T100, 5T, TR5, GP

38-58

63

8

12420

1.5

2.81

2

1/16

1

1/8

T100, 5T, TR5, GP slipper

38-58

63

8.5

8421

1.66

2.66

.689

3850

2

1/16

.091

1

1/8

.089

Y

T100, 5T, TR5, GP

38-58

63

9

13423

70-3615

1.59

2.91

2

1/16

1

1/8

T100, 5T, TR5, GP

38-58

63

12

10652

1.94

3.25

2

1/16

1

1/8

500cc unit

5TA, T100

59-74

69

15034

70-6907

1.39

2.49

.689

13570

2

1/16

.1

1

1/8

.1

Y

T100, T100A

59-74

69

9

15123

1.58

2.7

.689

13570

2

1/16

.1

1

1/8

.1

Y

T100

59-74

69

9

18786

70-6884

1.8

2.92

.689

13570

2

1/16

.1

1

1/8

.1

Y

T100

59-74

69

9.4

18782

1.99

3.12

.689

2

1/16

1

1/8

T100R, T100T

59-74

69

9.75

18786

70-6884

1.8

2.92

.689

13570

2

1/16

.1

1

1/8

.1

y

T100R, T100T

59-74

69

10.2

18782

1.99

3.12

.689

2

1/16

1

1/8

c.r. of 18786 and 18782 varies with model they are fitted to

650cc pre-unit & unit

6T, CI head

50-72

71

7

11564

70-2891

1.3

2.61

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

6T, alloy head

50-72

71

7.5

15897

1.42

2.73

.689

2.34

11050

2

1/16

.1

1

1/8

.1

Y

6T, CI head

50-72

71

7.5

15695

70-3610

1.34

2.65

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

T110, TR6

50-72

71

8

13529

1.45

2.76

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

T110

50-72

71

8.5

12713

1.45

2.76

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

T110, TR6

50-72

71

8.5

13528

1.45

2.76

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

T110, TR6, T120

50-72

71

8.5

15219

1.48

2.8

.689

2.34

11050

2

1/16

.1

1

1/8

.1

Y

6T, CI head

50-72

71

8.5

11134

1.53

2.84

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

T110, TR6

50-72

71

9

13980

1.51

2.82

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

T110, TR6

50-72

71

9

14087

1.64

2.95

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

6T, CI head

50-72

71

9

13414

1.59

2.91

.689

2.34

3870

2

1/16

.1

1

1/8

.1

Y

T110, TR6, T120, T120R, TR6 etc

50-72

71

9

17844

70-9488

1.65

2.95

.689

2.34

11050

2

1/16

.1

1

1/8

.1

Y

T110, TR6

50-72

71

10.5

15639

1.89

3.2

.689

2.34

11050

2

1/16

.1

1

1/8

.1

Y

T110, TR6, T120, T120R, TR6 etc

50-72

71

10.5

18514

1.85

3.16

.689

2.34

2

1/16

1

1/8

11050/3870 are inter

750cc twin

TR7R, T140

73-88

76

7.4

71-7086

1.65

2.54

.750

2

1/16

.114

1

1/8

1/8

TR7R, T140

73-88

76

7.9

20432

71-3676

1.58

2.64

.750

26490

2

1/16

1

1/8

TR7R, T140

73-88

76

8.5

19255

1.68

2.74

.750

26490

2

1/16

.121

1

1/8

.139

Y

TR7R, T140

73-88

76

10.5

19378

1.98

3.04

.750

2

1/16

1

1/8

Trident, see Rocket Three; Tigress see Bantam and TR25W, T25 see BSA B25

T10, Tina

50.4

15957