Tyres that REALLY work

[ShaunW]

1 hour ago, Gully said:

Just bear in mind that they will have a smaller rolling radius, so your speedo will read high. Not sure if the mintylamb website calculator is up and running again, but Google the site as there is a calculator on there that will tell you the difference that tyre size will make (it's not huge).

Gully

2piR before and after will give you a ratio to see what the speedo effect might be. Just remember that 70 or 75 is a percentage of the width not an actual tyre wall height. 

[Blitz]

any Problem with 75s fouling the arches ? Or is the difference negligible. Ie if I go 165/75 13 

 

[Clive]

I haven't heard of 75 profile tyres. Do they exist? 

But a small difference in gearing is noticeable.changing a diff from 3.89 to 3.63 is under 8% different,but makes an enormous difference to the way a car drives. So tyre size can have an effect maybe half that? 

Which wheels are you using? If std I would keep to a decent quality 155 80 tyre. (many people will be surprised at that from me!) John Bonnet built a remarkable spitfire, and used 155 tyres and they gave amazing grip levels. It isn't all about tread width. Especially on a swing axle car.

[Anglefire]

7 minutes ago, clive said:

 

I haven't heard of 75 profile tyres. Do they exist? 

 

Apparently yes - but not in 13” rims only 14”?

 

[Guest]

12 minutes ago, clive said:

If std I would keep to a decent quality 155 80 tyre. (many people will be surprised at that from me!) John Bonnet built a remarkable spitfire, and used 155 tyres and they gave amazing grip levels. It isn't all about tread width.

 

2 minutes ago, Anglefire said:

Apparently yes - but not in 13” rims only 14”

I run 155/80/13 on my Alpine and it grips brilliantly with Michelin tyres - size is not everything !!

Agree Mark, I checked a couple of well known tyre websites for 75's and only found them in 14" 

Regards.

Richard.

[Pete Lewis]

A thought,  unless you change the weight or pressure a great fat tyre will still keep the same footprint of a narrow one

Load x area = pressure  

Pete

[Blitz]

I’m struggling to get my head around the height percentage. Has to be 13 rim obviously then ether 155 or 165 for width as 175 is overdoing it. 

What works best with 155?

or with 165 ?

to keep things stock ish without effecting gearing and Speedo’s etc  

thanks

Grant 

 

 

[Pete Lewis]

80 is the std  ratio for a ordinary tyre so an olde 155 13 is now a 155 80 13

The rim width is the controlling factor  many fit /you can fit a 175 80 13 to 5 or 5.5 rim but its too wide for a  4.5" rim

Of you  may only  have a   3.5 or 4" rim then no more than 155 80  orig was 145 13

Dropping to lower  profile is not recomended as the tyres play a big part of the suspension and the bump and rebound you get

We have a local  spitty IV with 185 and they foul the wings /look a bit on steroids

As yours is a nice spitty 4 dont wreck it with any oversize tryes  

[Mad4classics]

2 hours ago, Pete Lewis said:

80 is the std  ratio for a ordinary tyre so an olde 155 13 is now a 155 80 13

The rim width is the controlling factor  many fit /you can fit a 175 80 13 to 5 or 5.5 rim but its too wide for a  4.5" rim

Of you  may only  have a   3.5 or 4" rim then no more than 155 80  orig was 145 13

Dropping to lower  profile is not recomended as the tyres play a big part of the suspension and the bump and rebound you get

We have a local  spitty IV with 185 and they foul the wings /look a bit on steroids

As yours is a nice spitty 4 dont wreck it with any oversize tryes  

Going tooo oversize is not a good idea. Modern tyres are matched to modern suspension setups.

You must look at the manufacturers recommendations for rim size and consider the rolling radius when selecting an alternative tyre size.

For instance, the difference in rolling radius between 155/80 x 13 and 175/70 x 13 is less than 3%.

Taking Falken SN832 as an example the 155/80 x 13 approved rim width range is 4.0 to 5.0 and the 175/70 x 13 is 4.5 to 6.0 according to the 2018 Falken Pattern Digest page 25.

David

[ShaunW]

I just knocked this up, it might help.
Pls let me know if it's wrong or if you want any tyre/wheel sizes adding.

I put 185/60/13 in because this thread made me check my tyres, and that's what I have for some reason.  No issues with clearance and they don't look particulary small, not so I'd noticed anyway. They just...just stay inside the arch, enough to be legal. (5mm ?)

At 40 my speedo theoretically reads 41.9 so that should help with managing not to get flashed by speed cameras.
 

[Clive]

185 60 14 are a popular(ish) size, I run them on my cars (amongst other sizes, got an autosolo so will fit 185/60 13 so want lower gearing (probably!)

I reckon for comparison sizes you should have started with the 155 80 13, as that is std across the range (more or less).

And I think you have got the size % difference wrong. For example compare 185/60 13 to 155/80 13:

1816/1735=1.047 which is 4.7% difference. (the first one for 185/65 14 is correct, but something has gone wrong after that)

There are some calculators on the web, I have used this one for many years

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

[ShaunW]

Thanks Clive, yeah I nearly didn't bother with the %bigger column, it's just the difference between the current line and the previous one, it doesn't refer back to the 155/80 13 as it probably should. 

[Clive]

Ah, I see, you have put them in size order......makes sense now. But I would say the % difference to the reference size is the most useful bit of info?

[ShaunW]

This site is quite good too...Visual tyre size comparison

[Mad4classics]

Did you mean to have so many 14 inch tyre in the table? You've lost 175/70x 13 along with several others in your latest table.

David

[Blitz]

New tyres on sat. Falcons 155/80 13 

[ShaunW]

14 hours ago, Mad4classics said:

Did you mean to have so many 14 inch tyre in the table? You've lost 175/70x 13 along with several others in your latest table.

David

The problem I've had is finding out what tyres are actually available. I thought it was a bit short of 13s but couldn't find a site that listed them all rather than just the ones company ABC were selling. 

[Mad4classics]

9 hours ago, ShaunW said:

The problem I've had is finding out what tyres are actually available. I thought it was a bit short of 13s but couldn't find a site that listed them all rather than just the ones company ABC were selling. 

Not easy, tyre manufacturers sell tyres to meet local regulations - in Europe ETRTO, one of a number of regualtory bodies for tyres worldwide. If you want to buy the latest standard it's  €150; as with all standards - expensive.

https://www.etrto.org/Publications/Order

However, found this on the British Tyre Manufacturers Association website.

https://btmauk.com/advice-about-tyres/

David

ETRTO-2016-Approved-Rims (1).pdf

[Anglefire]

This document is of interest for those wanting larger tyres. https://btmauk.com/wp-content/uploads/2014/12/ETRTO-2016-Approved-Rims.pdf 

[Guest]

Mark,

That is identical to the last link David placed on his reply just above yours - mind you, anything that good and important is always worth mentioning a few times !!

Regards.

Richard.

[Anglefire]

Oh bugger. I didn’t look at that link - only went through the first one ?

[Blitz]

Tyres fitted this morning. Surprised to find they have inner tubes. Didn’t realise that the wheels have no beeding on the inner side ??

[Blitz]

Oh forgot to mention my rear tyres were dated 1997 

[Clive]

They don't use inner tubes, never have from the factory. Did the fitter use inner tubes? If so that is incorrect and he doesn't know the job (though would say he does)

 

[NonMember]

A lot of tyre fitters trained this century will be accustomed only to the double-seat style wheels that modern cars have, which are supposed to be more resistant to shedding tyres. They often, mistakenly, think that a single-seat wheel like our cars have is therefore not suitable for tubeless tyres.
Mind you, I've also come across a young tyre fitter who declared, with absolute conviction, that it is no longer legal to use inner tubes at all. I asked him what he'd suggest for a car with wire wheels, where the rim itself is not guaranteed to be sealed. Before he could come up with an answer, his father (who had owned the garage for years) came out and told him to stop being ridiculous and just fit my inner tubes. (I don't have wires, I have 45-year-old porous alloys)