Stock Tire/Wheel Information
| Spitfire Stock Tire/Wheel Info | Mk1 | MkII | Mk3 | Mk 4 | 1500 |
|---|---|---|---|---|---|
| stock wheels | 13 x 3.5″ D steel | 13 x 3.5″ D steel | 13 x 3.5″ D up to FM 75000 13 x 4.5″J after | 13 x 4.5″ J steel | 13 x 4.5″J: up to 1979* 13 x 5″ J: 1979-80 |
| offset | ? | ? | ? | +0.5″ | +0.5″ |
| tires | 5.20S x 13″ Dunlop C41 | 5.20S x 13″ Dunlop C41 | 5.20S x 13″ Dunlop C41 | 5.20S x 13″ Dunlop C41145SR-13 radial | 155SR x 13 Dunlop SP68 or Goodyear G800 |
| optional factory wheel | 13 x 4.5″ J wire wheels | 13 x 4.5″ J wire wheels | 13 x 4.5″ J wire wheels | 13 x 4.5″ J wire wheels | n/a |
| optional factory tires | 5.20 – 13″ | 1.45SR x 13 radial Dunlop SP41 | 5.20S – 13″ 1.45SR x 13 radial Dunlop SP41/SP68 | 1.55SR x 13 radial Dunlop SP68 or Goodyear G800 | n/a |
| tire pressure front | 18 lb/sqin | 18 lb/sqin 21 lb/sqin (optional tires) | 18 lbf/in (cross ply) 21 lb/sqin (radial) | 21 lb/sqin | 21 lb/sqin |
| tire pressure rear | 24 lb/sqin | 24 lb/sqin 26 lb/sqin (optional tires) | 24 lb/sqin (cross ply) 26 lbf/in (radial) | 26 lb/sqin | 26 lb/sqin |
| lug circle diameter | 3.75″ | 3.75″ | 3.75″ | 3.75″ | 3.75″ |
| offset | probably +0.5″ | probably +0.5″ | probably +0.5″ | +0.5″ | +0.5″ |
| lug nut | 3/8″ UNF | 3/8″ UNF | 3/8″ UNF | 3/8″ UNF | 3/8″ UNF |
| lug nut torque | 38-48 ft# (5.2-6.6 kgf/m) | 38-48 ft# (5.2-6.6 kgf/m) | 38-48 ft# (5.2-6.6 kgf/m) | 38-48 ft# (5.2-6.6 kgf/m) | 38-48 ft# (5.2-6.6 kgf/m) |
| wheel weight | let me know | let me know | let me know | let me know | 18lbs. each |
*In 1976 only, US Spitfires shared wheels with the Austin Marina. The wheels were 13 x 4.5″ and had “square holes”
| GT6 Stock Tire/Wheel Info | Mk1 | MkII & GT6+ | Mk3 |
|---|---|---|---|
| stock wheels | 13 x 4.5″ J steel | 13 x 4.5″ J steel | 13 x 4.5″ J steel |
| offset | +0.5″ | +0.5″ | +0.5″ |
| tires | 155SR x 13 Dunlop SP68 or Goodyear G800 | 1.55SR x 13 radial Dunlop SP41/SP68 (Mk2), Goodyear G800 (+) | 5.20S x 13″ Dunlop SP68 |
| optional factory wheel | 13 x 4.5″ J wire wheels | 13 x 4.5″ J wire wheels | 13 x 4.5″ J wire wheels |
| optional factory tires | 155SR x 13 Dunlop SP68 or Goodyear G800 | 1.55SR x 13 radial Dunlop SP41/SP68 | Dunlop SP68 |
| tire pressure front | 20 lb/sqin | 24 lb/sqin | 24 lb/sqin |
| tire pressure rear | 24 lb/sqin | 28 lb/sqin** | 28 lb/sqin |
** According to a Jan. 1969 Triumph Service Bulletin the tire pressures for the GT-6+ using 155SR-13 G 800 Goodyear tires were revised as follows: Front-24 psi and Rear-30 psi
Today currently available size close in diameter to the original “5.20S 13” (ie, keeping transmission ratios and speedo accurate) is 155 SR 13 (or 155-13, or 155-80-13 as the 80 means the height/width ratio of the tyre, 80 is the “normal” ratio, not mentionned means 80)
175/70/13 would have the same overall wheel diameter (same transmission ratio)
Note:
Do you have a vibration that feels like a tire out of balance but doesn’t go away no matter how many times your balance them? It might be your drive shaft is out of balance. Drive shafts came from the factory balanced with little weights that are often knocked off. Call you local “hot rod” or 4×4 shop for suggestions to who can balance it again.