Narrow or wide

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biggles
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Narrow or wide

Post by biggles » 01 Aug 2018 16:52

Soooo... storm trooper needs new shoes. The Cooper SST 305/70R16s are over 10 years old and been on two patrols. They are starting to loose lugs and I get laughed out of tyre places when i suggest balancing them. They also sound like freight trains. I have kept them on the troll to run them out but time has come...

I have set my heart on the Cooper SST Pro... thoughts? These tyres and rims are used for trail driving and i swap to the scorpions for long trips. I have another set of rims with Scorpions on for when I do long road trips.
So need an agressive tyre that will be used on the toughest trails, dunes but a fair amount of tar. Eg. I will have these on for the Dunes trip in Sept towing the caravan.

The real question is:

305/70R16s or 285/75R16? Is it just the looks of the wide tyres? I kinda like the way the 285s sit... :helpsign:
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Re: Narrow or wide

Post by Peter Connan » 01 Aug 2018 17:36

I bought my car with 31x10.5's (265).
I then replaced them with 33x12.5's (315)
I replaced those with 32x11.5's (285)
I replaced those with 255x85R16's

On this last set, I have been through Botswana (lots of mud and fairly soft sand), but have not done any serious rock crawling yet.

But for sand and mud, I can confidently say: the narrower the better.

The science behind it: the contact area is effectively dependent on the tire pressure and the weight pressing down on that tire. The ground pressure will thus be the same, irrespective of tire size. Thus, the narrower the tire, the longer the footprint. And narrower footprint has less friction, less chance of sidewall damage and is more directionally stable.

But, the same is not necessarily true when braking on tar or gravel roads...
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Re: Narrow or wide

Post by nisjeep » 01 Aug 2018 18:54

There's only 2 ways of driving in sand. Floating (big contact patch so wide and deflated) or spinning faster than the sand can get out of the way.
Both of them require big ass tires. So now I will sit on my hands while a mod tells me why a marie biscuit is better.

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Re: Narrow or wide

Post by Kagiso II » 01 Aug 2018 19:05

nisjeep -- Peter Conan is 100% correct .. If I could get it at the time, my tyres would be 235/85 x 16 All Terrains and I would need LESS energy to drive on any of mud or sand [Botswana powder / Namib sand / Linyanti mud .. ]
After a LOT of years of driving on all types of roads, I have learned my lesson the expensive way [Ground clearance ?? eisjjj, that is another matter all together
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Re: Narrow or wide

Post by Tinus lotz » 01 Aug 2018 19:32

On your car go for 285 75 16 and and st pro is a good choice....with the 305 the sidewall is not straight on patrol rims the 285 75 16 looks just ......best....

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Re: Narrow or wide

Post by gupster » 01 Aug 2018 21:15

I think Peter has hit the nail on the head with the explanation that a thinner tire has a longer footprint and so works better in sand. I had always wondered why 4x4s up Africa favour a thinner tire and was surprised at the reason but it makes sense. I must admit though that it looks wrong and the fat tires have more appeal.
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Re: Narrow or wide

Post by nisjeep » 01 Aug 2018 22:43

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Re: Narrow or wide

Post by Peter Connan » 02 Aug 2018 05:11

nisjeep wrote:
01 Aug 2018 22:43
.
This looks like quad bike information? The rules are different for them, because there is not enough weight to crush the sidewalls.
Anyway, if 10psi is high pressure, then 6psi is NOT low pressure.

On sand, you want to drop down to 0.4-0.6 bar, from 2.3-2.8 bar which is our "high pressure".

One thing I should have added: no one will ever convince me that the biggest tire you can fit and have enough torque/low enough gearing for is NOt the best tire off-road. But that is biggest diameter, not widest.

And the higher the profile (higher the sidewall) the better too. The higher the sidewall, the longer you can stretch that contact patch.
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Re: Narrow or wide

Post by Michael » 02 Aug 2018 05:55

Ja this is one of those topics that can run for weeks. Everyone has their opinion and liking and thats why skinnies and fatties will both always be for sale.

Im not going to hide the fact that I prefer fat tyres and they have served me well to date. Did the whole Botswana in March and even towed a vehicle for two days through very thick sand and hectic mud with ease.

Like Peter mentioned about the higher sidewall is one reason I went for 15" and moved away from 16".
If I buy tyres again it will be 35" x 15" as I will then have a quite a bit of rubber on the ground when deflated
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Re: Narrow or wide

Post by biggles » 02 Aug 2018 11:55

Thanks guys, for kickstarting my mind on the whole debate. I think all the factors have been mentioned.

Would imagine skinny tyres are quieter?

I would also like to add that increased friction is a good thing... friction is the same as traction...

I am leaning to wide. The patrol is heavy and I tow a caravan in sand so weight distribution on a big footprint is good.

I think the marie biscuits work well on lighter vehicles like Defenders...

When can I get a good price on tryes?
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