New tyres are on the to-do list and, unlike my previous car (205/55/16) the tyre sizes are a little less common.

The wheels, which are 18″ TVR Spider Alloys, have (information from Graham Varley’s manual for the Sagaris, but I think it is the same:

  • Dimensions 18″ x 8.5″.
  • The fronts are 5-stud, 4 1/2″ PCD and an offset of 42 mm.
  • The rears are 5-stud, 4 1/2″ PCD and an offset of 33 mm

If the wheel sizes are correct for the Tamora (same as the Sagaris), then the appropriate tyre width for an 8.5″ wheel can be found in reference tables, for example here

Equivalency table
Rim width Minimum tyre width Ideal tyre width Maximum tyre width
5,0 Inches 155 mm 165 or 175 mm 185 mm
5,5 Inches 165 mm 175 or 185 mm 195 mm
6,0 Inches 175 mm 185 or 195 mm 205 mm
6,5 Inches 185 mm 195 or 205 mm 215 mm
7,0 Inches 195 mm 205 or 215 mm 225 mm
7,5 Inches 205 mm 215 or 225 mm 235 mm
8,0 Inches 215 mm 225 or 235 mm 245 mm
8,5 Inches 225 mm 235 or 245 mm 255 mm
9,0 Inches 235 mm 245 or 255 mm 265 mm
9,5 Inches 245 mm 255 or 265 mm 275 mm
10,0 Inches 255 mm 265 or 275 mm 285 mm
10,5 Inches 265 mm 275 or 285 mm 295 mm
11,0 Inches 275 mm 285 or 295 mm 305 mm
11,5 Inches 285 mm 295 or 305 mm 315 mm
12,0 Inches 295 mm 305 or 315 mm 325 mm
12,5 Inches 305 mm 315 or 325 mm 335 mm

It can be seen that, for an 8.5″ wheel, a 225 width is the narrowest that should be used (T350, Tamora), and a 255 width the widest (Sagaris).

The standard tyre size on a Tamora (or T350) is:

  • Front  – 225/35/18
  • Rear   – 235/40/18

This size should have adequate clearance, allow full steering lock, and not cause rubbing. However, the front tyre size (225/35) is a little less common, and the low-profile worries me a little for tyre-protection over potholes.

Tyres that are available in this size include:

For now, those are all the good-quality tyres I can find in those sizes. 235/40 (rear) is a fairly common size, but few manufacturers make the 225/35 (front).

Changing the fronts to 225/40/18 gives a far wider choice of tyres, including trackday tyres (such as Toyo 888s), but will have some effects:

  • Tyre diameter is increased – the tyre sidewall height will increase from 7.875 cm to 9.0 cm, a noticable increase of 1.215 cm
  • This will help protect the wheel from pothole damage
  • This will increase the ride height at the front if the suspension is not changed – that doesn’t worry
  • This may also change the geometry slightly – I don’t know what effect that would have
  • Clearance may become an issue. There is not a lot of space in the wheel arches, and rubbing can occur. See this discussion and this discussion

Increasing the clearances in the arches may not be a simple matter. Before a chance of tyres I will have to investigate the options further, or stick to the tyres available in the default sizes. For a light car, I think the standard tyre sizes are probably adequate. Richard at TrackVRoad believes the 225/40 may be a bit too big and could cause problems with steering lock and catching the light covers.

Other tyre options in slightly different sizes to the default include:

Useful online tyre shops (although I normally get mine from Millers Tyres) are:



I don’t really want to fit trackday tyres at the moment. I will have to do some trackdays and see how I find the car and I consider it to only be an option if I have a second set of wheels. Having read some information about what happens to Toyo 888 tyres in freezing conditions, I couldn’t use them year-round (see below for a copy of the information at the link).

I know some people do use them year-round, but it is a compromise. You can use them in poor weather (cold, standing water) and they will work, but they won’t be as good as a decent set of regular tyres in those conditions. In that setting, the best performing tyres are not trackday tyres. It is similar to my decision to switch to winter tyres on our sensible car. Regular tyres would work, but winter tyres work much better, and I want to be using the best tyre for the conditions.



Recommendations on the Proper Use, Handling, and Storage of Toyo Tires
This advisory applies only to the following products:
All Proxes® R1R™
All Proxes R888™
All Proxes RA1™
This advisory addresses the proper storage of these tires in colder climates. As seen in the picture below, tires stored and operated at sub-freezing temperatures, i.e., at or below 32°F (0°C), will lose rubber compound flexibility and may experience cracking when operated under such conditions.

Toyo tyre with cracks

The rubber compounds used in these tires have unique properties that, when compared to other tires, can cause them to lose some of their flexibility when stored and operated at sub-freezing temperatures. This loss in flexibility can lead to
potential cracking and other damage to the tire.
1. Do not operate the car with these tires, as the tires may suddenly fail.
2. Always store these tires indoors at temperatures above 32°F (0°C).
3. Before mounting or dismounting, store these tires for at least 24 hours in a temperature controlled environment of 68°F (20°C) or warmer.
4. Remove these tires from the vehicle and deflate to half the normal air pressure during prolonged periods of nonuse or storage.
5. Do not move a car that is in storage with these tires, as the tires may crack.


 Tyre tread levels

Following the purchase of a decent tyre tread-depth gauge, I checked all the TVR tyres, results are shown below.

Measurements are displayed in mm as the tread to the outside of the tyre, then the inside. Accuracy is probably to within a few tenths of a millimetre.

TVR Tamora – Toyo T1-S – 5th February 2011

Front driver’s side        – 5.2, 4.7

Front passenger’s side – 5.4, 5.0

Rear driver’s side         – 3.2, 3.0

Rear passenger’s side – 3.4, 3.0