Gen2 Tyre Size

[gen2]

need some help and advlce concerning tyre spec for gen2,2008 t spirit.

I have different opinions,regarding

195/55/16 standard against

205/55/16

I am told you can't interchange them,but I would like to if anyone here has changed their gen2 from standard ones,and if so has it altered the handling and ride of the car.

many thanks

[cootuk]

http://www.etyres.co.uk/tyre-size-calculator

There's a 1.8% change in diameter, which is within recommendations.

My speedo reads about 3mph high at 70mph now with the 205/55/16, so would have been a bit higher on the old sizes.

Toyota insurance weren't bothered about the change when I rang them, other insurers might be.

If anything the ride is probably improved as you potentially get a wider variety of decent tyres rather than the limited quantity in the "odd" size. i think handling would be more affected by putting a cheap tyre on than changing ratios.

[kithmo]

205/50 R16 might be a more common size, as fitted to Mk3 Mondeos.

[Jellyb]

My Gen 2 runs on 195/55/16, one thing I've noticed is the speedo shows a 10% higher speed compared to my calibrated speedo.

[kithmo]

My Gen 2 runs on 195/55/16, one thing I've noticed is the speedo shows a 10% higher speed compared to my calibrated speedo.

Most UK car speedos are 10% over speed.

[Sagitar]

My Gen 2 runs on 195/55/16, one thing I've noticed is the speedo shows a 10% higher speed compared to my calibrated speedo.

Most UK car speedos are 10% over speed.

We go around this loop from time to time. For various practical reasons, no normal speedo can be absolutely accurate all the time. Tolerances are therefore allowed. Here is the Wikipedia quote about the regulations that apply to the tolerances on speedo readings in the UK. There are similar regulations in other countries.

United Kingdom

The amended Road Vehicles (Construction and Use) Regulations 1986 permits the use of speedometers that meet either the requirements of EC Council Directive 75/443 (as amended by Directive 97/39) or UNECE Regulation 39.^[15]

The Motor Vehicles (Approval) Regulations 2001^[16] permits single vehicles to be approved. As with the UNECE regulation and the EC Directives, the speedometer must never show an indicated speed less than the actual speed. However it differs slightly from them in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

For example, if the vehicle is actually travelling at 50 mph, the speedometer must not show more than 61.25 mph or less than 50 mph.

[johalareewi]

for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

Does this mean 20mph speed limits are technically unenforceable unless you exceed 25mph?

For any speed below 25mph, your speedo only has to be 'not less than the actual speed' and so it can legally stick at 25mph. Ergo, you have no way of knowing for real when you are traveling above 20 and below 25.

[Sagitar]

for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

Does this mean 20mph speed limits are technically unenforceable unless you exceed 25mph?

For any speed below 25mph, your speedo only has to be 'not less than the actual speed' and so it can legally stick at 25mph. Ergo, you have no way of knowing for real when you are traveling above 20 and below 25.

Only in vehicles incapable of exceeding 25 mph. Otherwise the speedo has to be capable of showing all speeds up to the maximum possible speed of the vehicle, so if it was stuck at 25mph it would be illegal.

If you want to explore all the niceties of the regulations covering speedos and speed limits, you really need to refer to the full regulations, not just the extract that I quoted in replying to the original question.

[johalareewi]

Whoops. I meant stops at 25mph going down (but is OK above 25mph).

I remember some old speedos used to have a stop that the needle rested on when the speed got low.