V6 new tyres 215's all round

[roofraisers]

Jim,
I read the above post last night & then went to bed. This morning I woke up & thought you have got the low profile figures the wrong way round.

A tyre has a code such as:
"185/60R/15H"
A/B/C

A = Width of tyre (in millimetres)
In this example it shows that the tyre is 185mm wide.

B = Tyre profile as a percentage of width (A).
In this example the ratio is 60% of 185mm. This works out as 111mm.

C = Diameter of inner rim of tyre (or diameter of your wheel rim) (in inches).
In this example it shows that the rim is 15" in diameter.

From this you can also work out your rolling circumference.
e.g. (2 × B) + C = diameter = d
therefore (2 × 111) + (15" × 25.4) = 222 + 381 = 603mm

circumference = π × d = 3.142 × 603 = 1895mm

What I am trying to say is that, If you take a nominal figure "A" & stick with it, the greater value "B" is, the greater the depth of tyre between your wheel rim & the road surface, therefore the greater the rolling circumference distance.

Hope this makes sence,

Nigel.

[Jim the Box]

Jim,
I read the above post last night & then went to bed. This morning I woke up & thought you have got the low profile figures the wrong way round.

A tyre has a code such as:
"185/60R/15H"
A/B/C

A = Width of tyre (in millimetres)
In this example it shows that the tyre is 185mm wide.

B = Tyre profile as a percentage of width (A).
In this example the ratio is 60% of 185mm. This works out as 111mm.

C = Diameter of inner rim of tyre (or diameter of your wheel rim) (in inches).
In this example it shows that the rim is 15" in diameter.

From this you can also work out your rolling circumference.
e.g. (2 × B) + C = diameter = d
therefore (2 × 111) + (15" × 25.4) = 222 + 381 = 603mm

circumference = π × d = 3.142 × 603 = 1895mm

What I am trying to say is that, If you take a nominal figure "A" & stick with it, the greater value "B" is, the greater the depth of tyre between your wheel rim & the road surface, therefore the greater the rolling circumference distance.

Hope this makes sence,

Nigel.

Understand the above Nigel but is there any advantage to fitting 70's, should it save mpg and reduce the gap between my speedometer reading and my actual speed, at the moment it is 6mph out (54mph when reading 60) thanks for explaining it in detail.
Jim

[Surface2air]

http://www.miata.net/garage/tirecalc.html

[Surface2air]

Fitted 215/70/15 all round yesterday, well chuffed... looks good, handles well, garage smells of new rubber, speedo reads the same as it always did. Will let them settle in a bit on a run up to Harrogate today. They ended up sending me the wrong tyres though but made up for it by sending some slightly more expensive ones fitted at the same price.
I ended up with 5 x Continental Vanco Camper.