1977 Triumph TR7 — Base Model
The 1977 Triumph TR7 Base Model came from the factory equipped with 185/70R13 tires. If your vehicle has since been fitted with aftermarket or upsized wheels, your actual tire size may no longer match this factory spec — always confirm against your door placard before buying.
185/70R13
| Section width | 185 mm |
|---|---|
| Aspect ratio (sidewall height) | 70% (129.5 mm) |
| Rim diameter | 13" |
| Overall tire diameter | ~23.2" |
| Revolutions per mile | ~869 |
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What this size means for your Triumph TR7
On the 1977 Triumph TR7 Base Model, the factory 185/70R13 measures about 23.2″ in overall diameter with a 129.5 mm (5.1″) sidewall, and completes roughly 869 revolutions per mile. Its 70-series aspect ratio gives a tall sidewall of the kind used on trucks, SUVs, and older passenger cars, built for cushioning and load. In tire terms it is a small-diameter fitment typical of older or economy vehicles.
Because the 1977 Triumph TR7 predates many current tire lines, confirm this size is still stocked before ordering — some vintage fitments are now served mainly by specialty and classic-car tire suppliers.
Triumph TR7 tire sizes by year
- 1981 Triumph TR7 185/70R13
- 1980 Triumph TR7 185/70R13
- 1979 Triumph TR7 185/70R13
- 1978 Triumph TR7 185/70R13
- 1976 Triumph TR7 185/70R13
How to read a tire size
A tire size like 225/45R17 breaks down into three parts:
the first number is the section width in millimeters
(the tire's width from sidewall to sidewall), the second is the
aspect ratio — the sidewall's height as a percentage of
that width — and the number after the "R" is the rim
diameter in inches. A letter prefix (P or LT) indicates
Passenger or Light Truck construction; its absence usually means
Euro-metric sizing.
Some trucks and off-road tires instead use "flotation" sizing, like
37X12.50R17 — here the numbers are the tire's overall
diameter and width in inches directly, with the rim diameter last.
Always verify against the tire information placard on your driver's-side door jamb or your owner's manual before purchasing — tire size can vary by factory option package even within the same trim.