New tyres for Defender???

Guys,

While we are talking about tyres

I'm thinking about new tyres for my defender puma, which has 235 x 85r x 16 Continental AT'S, from when I bought it new.

I went on a trip into the Simpson a couple of months ago, and found them a bit narrow in the sand. I also had some trouble with side wall damage, as the walls seem to bulge a fair bit wider than the tread with this particular tyre. They are Great on the highway, so I dont want to get silly with a huge tyre. I would just want to compromise a little and get something wider.

I dont mind if the tyre is slightly larger in diameter either. I understand the downsides of speedo readings and fuel economy.

What are others using in the world of AT's, if they have decided to size up.

I like Michelin and Continentals,I've been seriously considering replacing the new wranglers on my puma with Michelins. Pat

Wider will be worse in sand not better, due to incrased rolling resistance.
It is the length of the contact patch that increses when pressures are lowered that matters.

If you put 255/85r16s on you'll find that your speedo reads exaclty right (same as GPS), and they look good too and teh width difference is marginal,with a SLIGHT increase in clearnce under diff....

Vlad,
Thanks for that info regarding width and performance.

You are saying a 255/85r16s is the go.

What about a 265/75r16s. Apparantly this gives you the same rolling length as a standard 235/85r16s. Is this size too wide??

No that should be fine as well.

If you do the maths, a 265 x 75 x16 tyre is about 30mm smaller in diameter than a 255 x 85 x 16 and 2mm smaller in diameter than a 235 x 85 x 16.

So the 255 x 85 x 16, being the larger diameter would be better in sand.

The 255 x 85 x 16 is 840mm in diameter.

I have put Coopers ST Maxx on my 2010 Defender (same size as original), as I wanted a tyre that performed better in clay / mud, without going to a full mud tyre.

Got sick of getting bogged in the house paddock with the General Grabbers.

We have two speed traps in town and my Tdi is wearing 255x85x16 and the TDCi wears 235x85x16 and both read within a K or two of being spot on so the puma will read wrong with the bigger tyres. Pat

Dear Xtreme and others,

Hey I'm not great at maths, so I hope you can help me out here, cause I would like to do my own calcs on the tyre diameter as you have done.

To calc the dia (which is the height off the ground) of the tyre, you need to know either the radias, or the circumference (rolling length) of the tyre. That bit is easy.

We know the dia of the wheel is 16", but we don’t know the wall height of the tyre, or do we?

On the wall of the tyre we get profile info like 85 or 75. I am assuming that these figures are a percentage of road going width. Is that right? Sorry this is probably common knowledge to most people, but I’m not sure.

eg. a 255 x 85 x 16 tyre would have – 255mm of rubber on the road, and a side wall height of 216.75mm. Is this correct?

Therefore the rolling length is (406.4mm wheel + (216.75 x 2 tyre wall heights)) =839.9 dia x (22/7) = 2638.96mm

Currently the puma reads 104-105 kph to gps reading of 100kph