Changing tyre size

[pjwhitfield]

Can someone clear something up for me?

I have a 2005 C70 with 225/50/16 tyres, these are (for want of a better phrase) rocky horse sh!t to easily pick up (and are usually twice the price of others).

Previously when attempting to pick one up I was told I could swap to a different, more common size and when I've checked the car specs (https://www.wheel-size.com/size/volvo/c70/2005/) both the 225/50/16 and 205/55/16's use exactly the same rim "7j16 ET43".

So now that I need tyres desperately I feel the need to make the move however before I ordered them I decided to give National Tyres a ring and just check to be certain.

I was virtually laughed at "no mate, you cant change tyre sizes, they wouldn't work mate"

Can someone help me out here and give me a definitive answer on this?

[S60D5-185]

Originally Posted by pjwhitfield

I was virtually laughed at "no mate, you cant change tyre sizes, they wouldn't work mate"

Have a look at this.

Difference is negligible in terms of gearing speedo accuracy bearing in mind that it looks like both sizes were available on those rims from the factory according to your link.

https://www.1010tires.com/Tools/Tire...5R16/225-50R16


Before doing anything else I would check with your insurance company though.

I have just changed the tyres on my XC90 from a V speed rating ( 149 mph ) to an H rating (130 mph ) due to the fact that I have fitted Yokohama Geolander All Terrain tyres and these are only available in H rating.

My car has top speed of 118mph so H rating is easily within spec but it came with V rated from the factory.

I contacted my insurance company before purchasing the tyres and was told that it was not an issue .

[Welton]

For insurance purposes you can only use tyre sizes tested and approved by the Volvo Factory, the sizes are usually listed inside the fuel filler cap along with the tyre pressures.

Any tyre size different to what is stated is classed as a 'modification' by your insurance co.

My insurers were very twitchy about it when I asked so I asked Volvo UK....they said the same "only the sizes approved by Volvo".

Outside of this you'd have to use a specialist insurer I guess.

[Dippydog]

Both speed and weight rating are as important[more so?] actual tyre size-as long as you're not going stupid trying to fit too wide a tyre to too narrow a rim or too narrow a tyre to too wide a rim.

[green van man]

I went from 205 /70/16 to 235/85/16 on my landrover, as it was a standard landrover size insurance company were happy with it and not classed as a modification.

The 205/70/16 is the discovery 1 standard size, the 235/85/16 is the standard defender size. The difference is that I now no longer sit on the diff pans when following defenders in the ruts off road.
The fact I had to cut the rear arch to accommodate the bigger tyres was covered by landrover doing it on the Camel Trophy Discovery 1s back in the day, so again it was an option from landrover and insurance happy.

It also made the speedo read faster, there is now no margins for error as it reads dead on road speed as calibrated against my sat nav.
This has the same effect as a defender owner swapping the transfer gear to discovery ratios to give the car longer legs on the motorways. Any one who has sat in a defender at 70 will know they howl, the taller gearing makes them more civilised and is a common mod.

If volvo offered the bigger tyres then it shold be no problem.

Paul.

[AndyV7o]

Ditto all the above, some sound, sensible, factual advice for a change!

[pjwhitfield]

Thanks folks, thought I was going mad for a while following the answer I got from a "professional tyre fitter".

Both tyres are listed as being sizes used by Volvo on my car, currently the Speedo doesn't appear to be correct for instance I always seem to register about 34-35 on the dial when passing one of those digital speed signs showing 30. Hopefully changing tyre size will correct that.

[Dippydog]

Wouldn't worry too much about speedo error as they all over read to some extent. My cars read 3 to 4mph faster when compared to sat nav reading.

[AndrewBrown]

Originally Posted by pjwhitfield

Thanks folks, thought I was going mad for a while following the answer I got from a "professional tyre fitter".

Both tyres are listed as being sizes used by Volvo on my car, currently the Speedo doesn't appear to be correct for instance I always seem to register about 34-35 on the dial when passing one of those digital speed signs showing 30. Hopefully changing tyre size will correct that.

I would not take advice from a "professional tyre fitter". about sizes speed ratings etc etc

I do my own research because in all my years in the motor trade I have found most tyre fitters only know how to take tyres off and put them on again,but most don't even do that properly,

you know....not used the heavy spot or the valve alignment spot as put on the tyres by the manufacturers, most of them don't even know these marks exist let alone what they are for

not even going to mention wheel damage or body damage from incorrect jacking up

In short if you find a good tyre fitter who does his job properly I would keep going to him as they seem to be a rare thing now

[ITSv40]

Agree with the above ^^^^^^^

I have been using the same local independent for the last 20 years or so and have exceptional service on every visit. I learnt my lesson years ago thinking the national chains would offer the best prices and service - how wrong was I.