Quickie rubber question

No but Bronco do......

Lee D

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Just a little hobby site about Landies :-) ________________________________

According to my calculations, it works out at 195R16 or 195/85R16 ( or possibly 190/85R16 which is non-standard)

You'd be fine with a 195R16, if you can stretch to 7.00x16, then a

205R16 will do.

Unfortunatly most imperial tyres do not equate easily into standard metric sizes.

Alex

According to my calculations 165R16 - not 195R16. 195R16 is the same width (not height) as 7.50x16, and it won't fit on a SWB rim. As for something actually available, try 175R16. JD

Really? I don't know where you get your calculations from.

Your calculations appear to have neglected the profile ratio, therefore you would need a 165/100R16 tyre, not 165R16 or 165/85R16

6.5" is the tyre height, convert to mm = 165mm, the height of the tyre.

Standard radial tyres are 82% profile, or should be. The other standard profile is 85%. (ie 195/85R16).

Assuming an 85% profile, the tyre width in mm must be divided by the profile width.

165mm Height / 85% = 194mm

Therefore a 195/85R165 is the closet approximation.

A 195R16 would equate to 6.3" A 205R16 would equate to 6.6" A 205/85R16 woudl equate to 6.8"

Alex

On or around Tue, 13 Jan 2004 13:05:38 +1100, JD enlightened us thusly:

yer all wrong :-)

205R16 is equivalent to 650x16 in theory, although in terms of ride height it's about equivalent to 600x16, since the casing tends to flex more on radials, and will fit on SWB rims - this was the standard fitment on SWB after they gave up fitting crossplies, until recently when they've changed over to 235/85 on everything.

235/70 is same height as 205, but wider, so is a suitable alternative (on wide or LWB rims) for a SWB if you want a wider tyre.

235/85R16 is a tad over a 7.50R16 in diameter terms, though again, in ride height terms it's near enough the same, (again on LWB rims) but is a bit wider, about 9" nominal.

265/70R16 is about the same height as 7.50, but wider still.

31x10.5R15 is also about the same height as 7.50R16 too, but nominal 10.5" width (about equivalent to a 265/70R16)

I mention the last as for some reason they come cheaper than the 16" equivalents. Don't ask me why, there's more rubber in 'em.

Thanks to all of you for the useful discussion. Unbelieveably, it made sense :-)

I haven't neglected the profile ratio, but I did neglect to mention it - I should have! There are two questions to consider - overall tyre diameter and required rim width. The figures I gave are tyres to fit the width of the standard SWB rims. The figures the others have given are to match the overall tyre diameter of the original tyre. Most of these are too wide to fit properly on the 5 inch standard rims. As you imply, cross ply tyres have a height width ratio of 100%, but radials are not made with 100% ratio, standard being 82% if not marked. So there is no direct equivalent between any crossply and radial tyres. You can match either diameter or width, but not both. Just as an aside - need a new tractor tyre at present (18.4x30) and have found that different brands have a difference in overall diameter of two inches! JD

Mmm. It happens with X-ply as well. I've an assortment of 7.50x16 tyres, of which there seem to be about 3 different diameters, and plenty of different widths.

Alex

On or around Tue, 13 Jan 2004 22:34:53 +0000, Alex enlightened us thusly:

in particular, 7.50R16 (i.e. radials) seem to tends to be bigger than the old crossplies.