Do BIG tyres really make all the difference??

[Chicken Drumstick]

I've been watching this on YouTube:

2013 Ultimate Adventure Week

http://www.youtube.com/playlist?list=PLGvTvFzdMg_MMpFAtJqtF0nXkcSHBloT-

Kinda looks like a cool thing to do, with some interesting vehicles, although as usual in the US, no LR products at all

However in Part 1:

http://www.youtube.com/watch?v=StTJghDn88Q&list=PLGvTvFzdMg_MMpFAtJqtF0nXkcSHBloT-&index=3

The presenter clearly states he checks all the vehicles before they start, with one requirement being a minimum of 35" tyres!!!

Which leads me to my question. Are giant tyres really the be all and end all?

Personally I love the monster truck look and was running some 33" Simex's on a Disco 10 years ago, which was quite a rare think in the UK at that time. And I fully appreciate larger tyres increase under the axle clearance as well as improve approach, departure and breakover angles.

But is there a size where it really matters less? Watching these US vids it sure looks like fun stuff, but I'd happily tackle many/most maybe even all the obstacles in a well prepped 90 or CCVT vehicle on some 235/85's....

So do 35-38" tyres really let you conquer terrain that the same vehicle on 31-32" tyres wouldn't?

[Team Idris]

Generally speaking they do, but we honestly believe that Barry's Gforce truck should have a try 33" tyres. In it's case portals give it excellent clearance already! On solid clay with a wet surface you don't want to skit about the surface with low ground pressure. And big tyres usually come with big width, and that's not helping in trees. Big tyres also soak up impacts that might bend a rim on a smaller size. It's another give/take thing

For me 33" inch fit in the garage, fit on the trailer and don't overstretch the axels. Big tyres would mean bigger axels adding more weight and needing a bigger-tyres footprint to hold the truck up in mud

We've also had our ass kicked by Zukes with 31" tyres, as they slip between the terrain easier.

[n.r.g97]

I use 235/85/16's for trialling and occasionally punch hunts, they measure about 32" and I have Nissan patrol axles so should have less diff clearance, but I very rarely have problems with grounding out, if I do then its driver error.

I have gone a size or 2 up (255/85/16) for KoV, so im hoping that big tyres aren't the be all and end all but I think that as I have a much shorter w/b than most of the KoV vehicles it should stand half a chance.

I think its more about having the right tread pattern, but then that's also dependant on the weight of the vehicle.

[mickeyw]

I'd say it largely depends what size tyres made the ruts before you got there. If they were bigger than yours, you will have to work harder to get around.

[Soren Frimodt]

In the terrain we wheel in, here in Denmark. A bigger tyre is definitely better 90% of the time. Much of the ground and climbs are loose with lots of sand, or at least a mixture of sand and dirt, giving much the same substance as pure sand when dry. When wet though it is the most soft sh*t you'll ever see! It takes all your speed and power if you hammer into it. We do, too have a lot of clay-ish areas, but most of the time we wheel there, it's dry and solid as a rock So on a very rare occasion my 7.50 Agro tyres shines when the clay is slippery as soap, yet firm. But for by far the most part I can out-wheel the agro tyres hundreds of times on my 35" Krawlers. So in my opinion bigger is better.

[RedLineMike]

37" tyres make a big differance having started with 35" simex,

[dirtydiesel]

Large diameter tyres make a huge difference,

They allow you to roll over obsticles easier, crossing ruts on 38's is a non event compared to 32's

[FridgeFreezer]

Definitely.

Tyres are the single biggest change you can make - going from road tread to AT to MT etc. makes the most difference (for a given surface), size gets you the next biggest improvement as you don't bottom out in ruts and roll easier over obstacles.

If you think about how people get stuck when off-road, #1 is bottoming out (clearance), #2 is loss of traction / insufficient grip in my experience.

[discomark10]

Depends on what terrain, most of the time larger diameter (taller) and wider will be an advantage as it will give you a larger footprint (more friction/grip)

Sometimes, like in sticky mud a tall thin tyre will work better.

[discomikey]

http://www.youtube.com/watch?v=B6yDscUo210&feature=c4-overview&list=UUgNSRjY0I9FCzsi9ku3ccbw

not if you havent got a clue how to use them, and upgrade neccisary things along with them

that goes for twin lockers and a 6bt too...

[Bingy]

Im glad this topic came up

This is a quote from a bloke on the v8 forum

As a landy man - with a 90 5.0 RV* on gas - I have also been on the big comedy tyres - 37 to 35 to 33 and now plain old 265/75 16s - can say with all honesty that big tyres KILL the car. The rotating mass is just such a dampner - and the inertia is crippling. Not to mention that your rear diff will literally last 5 minutes (as mine did) - big tyres put big strain on the drive train. The R380 is at its limits with what we are talking about - the LT230 will be fine, but its the diffs that are vulnerable with big tyres. Changing to smaller tyres is the best thing i ever did - my off road performance is identical and if anything I am more manuverable - unless you are doing challenge events IMHO big tyres are a waste of time, bowler, british army, camel trophy - all modest diameter tyres. My suggestion for your engine would be to source an early 5.0 crank (2 bolt) + rods and I think you can use the 3.9 pistons with that (or maybee 4.2??) - All the best - Dave (my landy was the cover car for LRM Feb 13 if you want a look)

Any comments

[Daan]

Im glad this topic came up

This is a quote from a bloke on the v8 forum

Any comments

I am afraid he is right; big tyres work, but if you can't make the car reliable, or get the correct ratio, they are liability.

[Bingy]

I am afraid he is right; big tyres work, but if you can't make the car reliable, or get the correct ratio, they are liability.

So if he were to change the ratios of the diffs and transferbox, together with

diff pegging and a better gearbox

he could have kept the 35 tyres on''?

[The Saint]

Im glad this topic came up

This is a quote from a bloke on the v8 forum

Any comments

That was on my thread Not my post though I think his comments were ignored.

[FridgeFreezer]

Sounds like he neglected to change his gearing. Big tyres bring issues, as any mod will. They rub stuff, they don't fit inside bodywork, they put extra load on the drivetrain and screw the gearing up.

It's also quite hard to see past a bonnet-mounted spare 37", and you won't want to pump one up with a single-barrel foot pump if you get a flat.

However, those things are not the fault of the tyres.

Thanks to the portals, my gearing comes out about where a standard 110 is - so performance is plenty lively, low range is proper low, the drivetrain has an easier time of it, and the Volvos are built for 7.5 tonnes on 37" tyres from the factory so stuff doesn't break.

He cites bowler (racing), army (racing) and camel (driving it like you stole it, with a truckload of spares following) and in all those the requirements are different. Racers throw money at other stuff that would be pointless for mud-plugging or everyday driving.

True, strictly speaking for a lot of stuff big tyres are unnecessary (but so are 99% of all mods) - but they do make a lot of stuff easier.

[elbekko]

The aim of the Camel Trophy was also to do it with stockish vehicles, fitting 37s under a Disco won't highlight the performance of a stock Disco. I'm sure much of their journey would've been a lot easier with bigger tyres.

I'd definitely say bigger = better, but only if you've reached the limit of what you can do with smaller tyres.

And to the person who said small, thin tyres are better in the mud: only if the mud isn't deep enough to sink down into it.

[The Saint]

I think he was trying to imply that he is an authority on all things Land rover because he has had a cover car I resisted telling him that I had one in 2006.

[CwazyWabbit]

I think he was trying to imply that he is an authority on all things Land rover because he has had a cover car I resisted telling him that I had one in 2006.

Over the years there have been a lot of Land Rover mags, a lot of issues and hence a lot of covers............

That's not a dig at you Saint Undeniably some of the cars have taken a lot of work....... it's just it must be an awful big club by now

[The Saint]

No offence taken, I don't think that having a cover car is an entry into the font of all knowledge elite land rover owner club. Hence why I didn't feel the need to mention it

[discomark10]

And to the person who said small, thin tyres are better in the mud: only if the mud isn't deep enough to sink down into it.

sloppy mud has almost no grip as its mainly water.. when you have grip in the slopy stuf its down to your tyres reaching something which it can gain a bit of traction on.

whether you sink is not down to the depth necessarily, but down to the type of mud under the watery slop.. if its more solid mud then thin tryes are better, but if its silty/soft mud the wider will be an advantage

[discomark10]

But it's all down to the terrain! 1 tyre is not perfect for all situations

[FridgeFreezer]

The Narrow Vs Wide is a separate argument, and again it's all down to terrain. Sometimes narrow tyres that cut through are the best answer - but only if there's something to cut through to.

[discomikey]

i dont really think that this thin v.s. fat will ever be solved, however at harper we convinced our lecturer to let us play experiment with tractive effort comparing fat to thin.

it wasnt the most scientific at all, we completed this experiment on one ground surface, (dry soil) with different size tyres, but on different trucks,

so the range of variables is large including tyre tread, wheelbase, vehicle weight, gearing, suspension configurations (and therefore antisquat properties) and we only have these results for one surface, not all.

at the end of the day it was pretty much even though and the results were worked out as a percentage of each vehicle weight, meaning they are somewhat comparable.

make of it what you will i.e. que the slating

[Anderzander]

I think he was trying to imply that he is an authority on all things Land rover because he has had a cover car I resisted telling him that I had one in 2006.

I didn't get that from his message ?

[bill van snorkle]

. Disregarding drive traction, which for a given terrain is a product of a tyres tread pattern, air pressure, weight supported etc, an easy example of the advantage of larger diameter tyres is this. Push or pull a wheelbarrow,or wheeled trolley with say 20" diameter tyres up against a vertical obstacle measuring up to 10'' in height, and there is a good chance that you can pull it up and over. Now try an 11" high obstacle and no matter how hard you pull, that trolley/barrow isn't going anywhere.So larger diameter tyres will conquer larger obstacles more easily.This is how the 'vertical obstacle' spec on true cross country vehicles performance data is determined.

The wide verses narrow debate is easily resolved by looking at the rear tyres on agricultural tractors. Effectively they are both 'wide' and 'narrow' in the same tyre, in that the deep widely spaced lugs provide a high ground pressure, just like a narrow tyre would, but when the terrain is very soft and deep, the large section of the tyre gives high floatation as sinkage occurs. almost the best of both worlds really, aside from the rapidly high wear rate of AG type tyres when used on hard surfaces.