Tyers for a Bristol 407

[GREG]

Taken from a UK tyre web site showing a Taxi tyre is LEGAL up to 99MPH --

TYRE SPEED SYMBOLS & CATEGORIES
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Most car and van tyres used in the UK have both a load and speed rating after the tyre size, e.g. 195/65R15 is usually followed by 91V. This means the tyres can carry their rated load upto a maximum non-stop speed of 240 kph. When replacing tyres it is important to ensure the new tyres, even if a different size, have the same or a higher speed rating. However, in the UK, with a national speed limit of 70 mph, it is quite safe and not illegal to fit a tyre with a lower speed rating, provided you do not exceed this reduced rating. The table below shows the maximum speeds applicable to each speed letter.
Max Speed
(sustained)
Kilometres/hr Speed Rating Max Speed
(sustained)
Miles/hr
N P Q R S T U H V W Y Z
300 Kph 190 Mph
290 Kph
280 Kph
270 Kph 170 Mph
260 Kph
250 Kph
240 Kph 150 Mph
230 Kph
220 Kph
210 Kph 130 Mph
200 Kph 125 Mph
190 Kph 119 Mph
180 Kph 113 Mph
170 Kph 106 Mph
160 Kph 100 Mph
150 Kph 94 Mph
140 Kph 88 Mph
130 Kph 81 Mph
120 Kph 75 Mph
Max Speed
(sustained)
Kilometres/hr N P Q R S T U H V W Y Z Max Speed
(sustained)
Miles/hr
Speed Rating

Marking Charactistics
Speed Symbol "N" For vehicles with a speed capability not exceeding 140 Km/h (88 Mph)
Speed Symbol "P" For vehicles with a speed capability not exceeding 150 Km/h (94 Mph)
Speed Symbol "Q" For vehicles with a speed capability not exceeding 160 Km/h (100 Mph)
Speed Symbol "R" For vehicles with a speed capability not exceeding 170 Km/h (106 Mph)
Speed Symbol "S" For vehicles with a speed capability not exceeding 180 Km/h (113 Mph)
Speed Symbol "T" For vehicles with a speed capability not exceeding 190 Km/h (119 Mph)
Speed Symbol "U" For vehicles with a speed capability not exceeding 200 Km/h (125 Mph)
Speed Symbol "H" For vehicles with a speed capability not exceeding 210 Km/h (130 Mph)
Speed Symbol "V" For vehicles with a speed capability not exceeding 240 Km/h (e.g. 225/55 R 15 91V)
Speed Symbol "W" For vehicles having speed capability not exceeding 270 Km/h (e.g. 225/60 R 15 96W)
Speed Symbol "Y" For vehicles having speed capability not exceeding 300 Km/h (e.g. 275/40 R 18 94Y)
Speed Category "VR" For vehicles having speed capability over 210 Km/h (e.g. 195/50 VR 15)
Speed Category "ZR" For vehicles with a speed capability over 240 Km/h (e.g. 205/40 ZR 17)
ZR+ Speed Symbol "W" Tyres marked with both designations for vehicles with speed capability over 240 Km/h but not exceeding 270 Km/h
ZR+ Speed Symbol "Y" Tyres marked with both designations for vehicles with speed capability over 240 Km/h but not exceeding 300 Km/h

Other Technical links:
Tyre Load Tables || Tyre Size Calculator || Vehicle Wheel Fitment

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[pasini s]

Hello Greg,


the 'taxi' tires fitted on my 409 when I bought it were marked 'C' (as for
'Cargo', I suppose, i.e. vans etc; later I found on the Austone web site
that they are widely used on cabs) and the speed rating for these tires is
very low. Even if they are good tires and probably safe up to 99 mph, a 409
has a declared top speed of 132 mph and weighs nearly 2 tons, so the MoT
would never pass it with 99mph tires; even more important, in case of an
accident the insurance company would not pay any damage.

BTW, what tire pressures are you using on your V8 Bristols?

Cheers

Stefano

[GREG]

Hi Stefano,

I thought that the statement lifted from a U.K. tyre company would finally dispel the myth that Taxi tyres are illegal in the U.K. !! I should have known better.

The Bristol will still pass an MOT with Taxi tyres -- lots of them do. Just to be safe you can inform your insurance company what tyres you have fitted. Does anyone think cross ply tyres are safer than Taxi tyres ?

Taxi tyres are essentially a van tyre (and we all know how fast white vans go ) with a stiffer wall and can easily handle the weight of a Bristol. How much do you think a London cab weighs ? especially with 7 people and luggage.

As Stefano says, his car was purchased with Taxi tyres on and had probably passed the MOT with them on.

I run the tyres on my Taxi at 30 psi, the same as my Bristols.

It's up to you......

[penman]

Hi Greg
They might be legal in the UK but surely Stefano has to comply with Italian legislation.

[GREG]

quote Hi Greg
They might be legal in the UK but unfortunately Stefano has to comply with Italian legislation.
Today 08:29 AM

First prize for stating the bleeding obvious!

I know Stefano uses Vreds now ( the best in my opinion )

I was answering the original question.

[pasini s]

Hello Greg,
out of curiosity, I rang my insurance broker and asked about the matter.
They would not accept a low speed rated tire on a car insured by them. I
fully agree that cross-ply tires are not safer than those 'taxi' tires but
the law requirements in Italy are extremely strict about tires and in case
of an accident there would be trouble if I had fitted taxi tires with a low
speed rating.

During the long and exceedingly tiresome process of registering the 409 in
Italy, the MoT inspector confirmed that they require tires of a speed rating
exceeding the declared top speed of the car (this applies to vans too,
incidentally, so those fast Mercdes-Benz 'Sprinters' use special tires) and
thus the Austone tires were not approved, even if I pointed out that they
were good enought to pass the British MoT. I passed the inspection with the
Avons.

I am using 38-39 psi now on my 409....maybe too hard, but this summer is
very hot and I have been always told that when temperatures go near 40°C it
is better to keep the tires a bit overinflated. Or is wrong? Surely the ride
is a bit hard....

Cheers

Stefano

[GREG]

I was only commenting on the UK

39 does sound high and I thought hot air expanded.

Let me know if you find out any more on if it's correct to over inflate in high temperatures. I would of thought that it's the other way round if anything.

The "C" is not for cargo. It's a load rating.

[Kevin H]

Originally Posted by pasini s

I am using 38-39 psi now on my 409....maybe too hard, but this summer is very hot and I have been always told that when temperatures go near 40°C it is better to keep the tires a bit overinflated. Or is wrong? Surely the ride is a bit hard....

Hi Stefano,

This doesn't make sense to me for normal everyday use. My understanding is that tyre pressure increases with heat. If your tyre pressure is 39 when cold, add in the heat of a summer's day and some friction from driving and your pressures may end up at 45 psi.

That's probably not a safety issue but it would definitely make for a hard ride.

The only time I have ever run with tyre pressures at around 40 psi is on a track or a road rally. Makes a big difference to handling.

Personally I think you should experiment with the tyre pressures of your V8 Bristol in the 28-32 psi range, see what feels right/best.

Cheers,
Kevin