What do with tyres in different conditions

[pugwash]

7 sisters last march saw something that i have been thinking about for a while.

Steep slope with a shale covering. Not a lot of grip. 2 vehicles of similar specs (big petrol engines, lockers etc etc). 2 different tyres- simex 35s and 34" swamper boggers.

the car with 35" just drove up (with lockers and a bit of the right foot), the swampers had to be winched up.

what i am trying to work out in this scenario is- would the swampers have done better if the pressure had been let down?

in a more general way i am also trying to work out the best mud tyre spec. Simexes are bloody good at digging- have a narrow footprint (relatively) and huge sude lugs- they also self clear very well. However some of the american stuff is designed to be very very wide (15" in some cases) and run at very very low pressures. So in a totally general way if you came across a patch of mud are you better off trying to cut through it to find the bottom with simexes, or try to float on top of it with huge american tyres?

i know this is all a generalisation but i have been wondering about tyre pressurs and their affects in different size tyres for ages.

[dollythelw]

Im nothing short of shocked as to what boggers at 0-5psi will scale

[fisha]

i think it depends on the ground underneath.

A lot of the sites that you guys down south seem to post pictures of are fiarly hard ground with a layer of slime / mud on top. In those conditions the thinner tyres seem to cut through and down into harder layer where as the wider tyres may float on top and stay in the slime layer.

Of the off roading i've done, a fair bit of it cna be on marsh / moorland where there is no solid layer to cut down through to. In such cases, the wider flotation tyres are better for sitting on top of the ground . . . where possible. Thinner tyres, no matter how luggy would just sink down up to the axles.

Basically, there is no specific rule of which is better all the time. Its more of which is suited to the current conditions.

[dollythelw]

I guess to get the best of both worlds buy a tyre the airs down well and get beadlocks

[Bull Bar Cowboy]

Jim,

A lot depends on driver ability, and the ability of the driver to interact with the vehicle ………. maybe then comes the performance of the actual tyre itself. Sometimes just watching is more than intersting.

I am not a great lover of Simex …….. good tyre and all, but way too expensive for what it is. Before all the ‘yes but’ and ‘moaning’ bar stewards come out of the cupboards …… yes, I have driven motors , with Simex (both ET and JT) …..

Horses for courses ……… I don’t think you will ever find a tyre that does all you want in all conditions ………. What we look for is the best compromise tyre. Example ........ you aint gonna go far on Simex ET in the desert

I was well impressed with the Grizzlys under most conditions ……. Good in mud ‘n’ slim, average in bog (again an aggressive ‘digging’ tyre… just what you need in a bog ), poor on rock, good at loose surface, well road mannered (but very f’kin noisy)….. however, for what they are, they cannot be considered cheap.

BFG's are nothing more than average ......... as with a load of other 'mud terrain' tyres

Now I have changed to Super Swamper TSL LTB (34’s)………. Its too early to give a real answer on these ………. 8 ply Cross ply means stiff walls …….. I’m running 15psi road pressures ………. So far the rock performance exceeded that of the grizzly, and (very important to me) the wet grass side slope performance is first class. Now I need some rain to test the rest of the attributes.

I think this is an impossible question to resolve.

Ian

[dollythelw]

havent they broken in yet Ian? chuff 'em right down off road and make them squeel for a bit if you get a chance

[GBMUD]

As Ian suggests, too much is down to the driver and, IMHO, the rest of the vehicle. Rogue Vogue drives stuff with open diffs that plenty of people with diff-locks and similar tyres would be winching through. I have personally driven stuff (hills) in my Defender on BFG MTs without the rear locker that has stumped another 90 with Simex and lockers and a much more trick suspension system. Just my (Orange ) springs and shocks were suited to the terrain and his was not.

What I am saying is that tyres are not the be all and end all. There is plenty to think about before that.

Chris

[pugwash]

What I am saying is that tyres are not the be all and end all. There is plenty to think about before that.

Thanks for all your replies guys.

I totally agree that driver ability and technique are more important, but all things be equal tyres can play a big part!

it was more the technical side of things i was interested in- has anyone done any calculations into the flotation difference between a vehicle on 35x10x15 at 28psi and 40x15x15 at 2psi.

i am often left with the thought that an awful lot of our info is from "experience" and "conjceture". I always fancy actually running scientific tests- if only i could invent them.

ok so change of topic- what test can you come up with to compare tyres? Autocar do a tyre test everyear and psyeudo scientifically measure all sorts of things! can we do the same thing in the mud comunity?

[BogMonster]

i think it depends on the ground underneath.

A lot of the sites that you guys down south seem to post pictures of are fiarly hard ground with a layer of slime / mud on top. In those conditions the thinner tyres seem to cut through and down into harder layer where as the wider tyres may float on top and stay in the slime layer.

Of the off roading i've done, a fair bit of it cna be on marsh / moorland where there is no solid layer to cut down through to. In such cases, the wider flotation tyres are better for sitting on top of the ground . . . where possible. Thinner tyres, no matter how luggy would just sink down up to the axles.

Basically, there is no specific rule of which is better all the time. Its more of which is suited to the current conditions.

Yep - same here. Not for the first time I refer anybody who says that tyres can always dig down to the hard, to the Hitachi thread - dig away!

33x12.50R15 are the preferred size round here for Defenders.

I also agree with Chris re. the driver. I have been away with (or recovered) some clueless drivers in vehicles broadly similar to mine (open diffs and ordinary MT's) and driven straight up or through things that they have had to have several goes at and/or got hopelessly stuck in. Reading the ground is more important than anything else, especially when it's soft!

[JST]

i think the wagon on simex made it because Tim had it boucing around 9000rpm all the way up and the other vehicle had to be winched becasue it was a jeep.

[pugwash]

i think the wagon on simex made it because Tim had it boucing around 9000rpm all the way up and the other vehicle had to be winched becasue it was a jeep.

well i did say there was a bit of right foot.

but i reckon even if that third jeep (the one that only had a tug once) floored he still he wouldn't have made it- the swampers just didn't seem to be developing the grip.

[TJ101]

i think the wagon on simex made it because Tim had it boucing around 9000rpm all the way up and the other vehicle had to be winched becasue it was a jeep.

yer-yer ok,, now how did i know my name would crop up,,

think i will go with Chris's post,, driver skill

I think you are asking the $64,000 question Jim,, of which, i doubt if there is a perfect answer !!

Ian likes his grizzlys, but i could not get on with them, but i do like BFG Muds, as a all round tyre, been stuck with a V8 on Simex at 7S, but not problem , at the same place before with a 200TDi on BFG's, just drove it wrong !!

[Ex Member]

IME, lower pressures ALWAYS means better traction. People that do not air down do not know what they are doing.

[pugwash]

IME, lower pressures ALWAYS means better traction. People that do not air down do not know what they are doing.

that's a hell of a statement.

there must be loads of us on here who haven't got a clue.

Hope the rest of you are reading this and taking note.

Anyway before this thread descends into myd slinging.

Am i right in thinking that it isn't actually the pressure in a tyre that matters, but how much air is holding up each kilo of weight? ie a 2 tyres, A and B, with B twice the size of A, would mean that A would need twice the pressure of B to hold the same weight at the same relative height?

[white90]

every time I've aired down I've lost a bead

don't want beadlockers so I leave the pressure up and winch if I have to.

[SteveG]

that's a hell of a statement.

there must be loads of us on here who haven't got a clue.

Hope the rest of you are reading this and taking note.

Anyway before this thread descends into myd slinging.

Am i right in thinking that it isn't actually the pressure in a tyre that matters, but how much air is holding up each kilo of weight? ie a 2 tyres, A and B, with B twice the size of A, would mean that A would need twice the pressure of B to hold the same weight at the same relative height?

This is another subject again, on how and when to air down and to what level.

So totally ignoring rocks, bogs, sand and other s**t and just concentrating on mud there is no easy answer!

On mud do you run a narrow tyre that bites down? Dependes on consistency of mud and tyre shape! If a mud fills up and doesn't self clean - we all know that it soon acts like a slick and there's no digging there. A tyre like simex takes really sticky clay mud to clog up and so is better in most conditions. A BFG clogs up more easily and if you air down it cleans better and therefore bites better in most conditions.

Same as most off-road tyres - air them down and they clean out more easily (excuse the bad grammar! )! This in my opinion is the major benefit of airing down rather than wider footprint.

Funny how driving TC and ABS equipped LR's also shows you that with a narrow tyre and road pressures you can go far with judicous (but correct!) use of the right foot. TC and AT's/road biased M/S tyres can work well in slippery mud witn the right throttle control.

Anyway that was just to add to the easy question of what tyres to go for!

Cheers

Steve

[LR90]

Am i right in thinking that it isn't actually the pressure in a tyre that matters, but how much air is holding up each kilo of weight? ie a 2 tyres, A and B, with B twice the size of A, would mean that A would need twice the pressure of B to hold the same weight at the same relative height?

Don't think of height.

Just think of the contact patch and the air pressure that needs to be exerted on it to support the weight on that wheel.

So, bigger contact patch needs less pressure to support the weight, or the other way round, if you lower your pressures the contact patch will increase to compensate.

[Ex Member]

that's a hell of a statement.

there must be loads of us on here who haven't got a clue.

Hope the rest of you are reading this and taking note.

Anyway before this thread descends into myd slinging.

Am i right in thinking that it isn't actually the pressure in a tyre that matters, but how much air is holding up each kilo of weight? ie a 2 tyres, A and B, with B twice the size of A, would mean that A would need twice the pressure of B to hold the same weight at the same relative height?

Sorry but it is true. If you are making it through obstacles at road pressures, you are not doing anything difficult. The main reason for getting larger tyres is to allow you to run at lower pressures. I see it all the time. Watch people not be able to make it up a hill, them just idle past them with open diffs just because you are running at the right pressure. A proper tyre off road should be bagged out and be conforming to the terrain.

For carp like mud it does not matter much, but I don't consider mud to be anything real as far as "difficult" off roading.

[reads90]

Well i have found here in Queensland that the Simex ET's are useless for the dust and rocks. So having to look at other options. They say here that down the coast in mexico (where there is mud) the simex are good but up here they just dig and dig. So the weapon of choice is a swamper or mickey

[GBMUD]

Well i have found here in Queensland that the Simex ET's are useless for the dust and rocks.

Depends. Rogue Vogue was driving up some rocky riverbeds/small waterfalls at 7Sisters with Simex copies, let down well they were deforming round the rocks and the lugs catching on the corners of the rocks and lifting the vehicle up semingly enormous steps. I am sure that there are better tyres for the job but the Simex copies were performing just fine.

Chris

[reads90]

Depends. Rogue Vogue was driving up some rocky riverbeds/small waterfalls at 7Sisters with Simex copies, let down well they were deforming round the rocks and the lugs catching on the corners of the rocks and lifting the vehicle up semingly enormous steps. I am sure that there are better tyres for the job but the Simex copies were performing just fine.

Chris

small water falls , made me laugh . where i was on the weekend it has not rained for 3 years , so no water falls there. It is just dust and more dust, and as some of you know from Slindon in the summer simex dig and dig in that sort of terrian.

[jules]

All good for challenge but racing is a little difrant

I have to run the freelanders at around 34psi were as normall racing landies run between 25-28psi

The rocks rip the side wall clean out and also (wait for it, wait for it) when cornering very hard the beeds come off if you running low pressure.....

some of the racers have moved over to running bead lockers

if you deflat the tyres on too much ie. below 20psi you lose handling and it saps masive amounts of power even if it dose help through the sticky stuff.

I scotland 04 I lost the air in both left hand tyres and came off the end of the stage with the front tyre missing and the rear smoking still took the tomcat behind 8 miles to catch me...

racing in sand you don't have too much choice and you need to drop the pressure out.

I have only ever bothered to drop pressure when competing and I lent my tyre deflators to some other chaps at the event and seen them then sufering with broken shafts due to under estimating the increase in grip..

For laning and playing there is no point in dropping the pressure..

[dollythelw]

you should start a training camp Jules - would save working all those hours? I'd sign up

[jules]

Har, Har

You know what I meen

50% tyre

50% driver

I did instructing for a few years in the weekends for Land Rovers and a little for Mitubushi but the money just isn't there... and the racing took over..

[dollythelw]

the day I stop learning is the day I die, Im always up for training, I raced bikes for 20 years at clubman, national and european level and still took training all the way through, motorcross camps, speedway training, motard, Keith Code etc etc - cross discipline helps produce a better result (IMO), so Im well up for any ideas that help me improve