[TryHard]

hey well im getting some 33s stuck under the zook soon now my problem is i cant figger out what tyre choise i want to go with atm iv runing the 31x10.5 Maxxis bighorns and love them .. now what should i do i was thinking of just upgrading to 33x12 w/e it is but then il have problems with the tyres rubbing on the springs .. and need a bigger offset of spacers .. or i could run something like simexs .. they are skinner .. but what is better is the question ... u go higher u want wider ? ... ya ideas please thanks...

o bw this is mainly for rocks / sand

[Fatzook]

Wider is not the way. Zooks are so light. they really need a skinny tyre to get any decent ground pressure.

Having said that I have had 12.5's on a sierra and they've worked as well as mates on skinnies.

[TryHard]

Fatzook wrote:

Wider is not the way. Zooks are so light. they really need a skinny tyre to get any decent ground pressure.

Having said that I have had 12.5's on a sierra and they've worked as well as mates on skinnies.

see my problem haha cant pick im leaning towards skinnys

[pyrohamish]

Both tyres will give the same ground pressure, its just how its distributed.
Skinny is good for mud where you want to sink to the hard stuff, wide is good where you want to float around a bit more.

[nato78]

I think silverstone extremes come in 33x11.5, these are what I'm thinking about upgrading to

[Gwagensteve]

pyrohamish wrote:

Both tyres will give the same ground pressure, its just how its distributed.
Skinny is good for mud where you want to sink to the hard stuff, wide is good where you want to float around a bit more.

I think that needs some clarification.

I'm not sure which two tyres you are comparing pyrohamish, but ground pressure is kind of complex. if you meant "If both tyres will give the same ground pressure, its just how its distributed." Then your comments are spot on, but there's a bit more too.

The ideal footprint is as long as possible and as narrow as practical. It's not just an outright traction thing - two tyres of similar tread pattern but with different widths and heights will produce similar forward traction, where the width comes into play is in drivability. Long, narrow footprints offer the best throttle response and lateral control. How narrow you can go though is a bit dependent on what your driving, who your driving with, and how tall a tyre you are willing to run.

*I'll add that these comment refer to wet conditions. In dry conditions all of this stuff is pretty irrelevant, it's really just about diff clearance and carcass conformability- I know this isn't directly what you've asked, but it might be useful info for you and others*

I'll kind of break it down like this:

An aggressive 33 12.5, lets say, will generate acceptable traction through just chucking lots of crap out behind it. However, for the tyre to move forward, it has to grab 12.5" of dirt, roll it under the tyre, and spit it out. It's propelling the car fine, but the car isn't very fussed about staying in a straight line. back off the throttle, and as the tyre fills up with junk, you have a larger surface area on the ground and it skates.

A narrower tyre has to grab less ground so whilst ground pressure might be higher (which is good - like comparing footy boots to runners in mud) it also has less junk to clear from the leading edge of the tyre, and a longer area of contact, under these conditions think about a rudder - a long narrow rudder works well, but a square rudder doesn't work at all. 33 12.5's have an almost square contact patch, and that hurts directional control. This is also true in sand, where a wide radial is constantly pushing a bow wave of sand in front of the tyre, so the car is always try to drive out of a hole. Tall narrow tyres work well in sand- it's better to achieve the lower ground pressure with a tall narrow tyre at low pressure than a shorter wider tyre - it's much more efficient and more drivable, and we are always horsepower limited in a sierra.

Now here's a complication. If you drive lots of deep ruts, and your diffing out a lot, a narrower tyre, even if it's a bit taller, might not help. after all, if your on the diffs, you're stuck regardless. A wider tyre like a 12.5 can help you to get traction off the inside edges of the rut, so long as your overall width doesn't go too crazy. If the rims are heavily offset and you car is very wide, this doesn't work any more - you fall into the holes from all the big cars. It's hard to achieve this with a WT sierra, as the front springs have to be moved under the chassis like a NT to allow enough steering lock to run wide tyres without adding too much overall width.

I run 9/34 swampers. In any conditions where very deep ruts aren't a problem, I have plenty of forward traction, and the car is very controllable on slippery hills. Much more so than a wider tyred car. However, I'm on offset rims and my car is quite wide. In deep ruts, the narrow tyres drop right into the bottom of the rut and I struggle with diff clearance.

We have a couple of cars in the club with Q78 swampers. These are over 35" tall and about 10" wide. They offer good clearance and a good ratio of height to width, so they are quite drivable, but of the two cars, one is narrow, and one has much more rim offset and is much wider. As such, the tyres can't work off the inside of the ruts and the wider car doesn't do as well as it looks like it should in deep ruts.

We also have a couple of cars on 35" Krawlers, which are 13.5" wide. They are on 3.75" backspaced rims, (I dunno- I think that makes them +15?) and they totally own ruts because the tyre fill the rut up and they grab the insude edges. However, on slick surfaces these cars are hard to drive - they don't want to go straight at all, even though they have plenty of grip.

A 33 11.5 would be worth a go in an aggressive tyre like a silverstone extreme- but for rocks/sand I don't think it's going to be great.

BFG do a 33 10.5, I think you can get a BFG and a bighorn in a 255 85 16 (that's 33.3X10, on a 16" rim) but BFG"s are dear, and 16" rim sizes tend to have high load ratings that mean they don't work as well on a light car like a sierra.

There's also 34 10.5 LTB swampers, which seem to work quite well as an all round offroad tyre.

I wouldn't use a radial mud terrain tread like a bighorn at 33 12.5 on a sierra - to maintain ground pressure you have to go more aggressive in tread pattern as you go up in size or you loose bite, and the stiff radial tread doesn't like to conform on rock.

I don't have any other great ideas for the type of tyre though. Like I said, in dry conditions it's not hard to generate enough grip to get where you want to go, so it's mostly a flexibility and clearance thing, so from that point of view I reckon the real answer is beadlocks.

Steve.

[TryHard]

hmmm well i was looking at buying the silverstones .. i could just buy something like the bighorns and run low low tyre pressure with beadlocks

very helpfull info steve

[SuziBlu]

Steve, I agree whole heartedly in all bar the sand analogy, the taller the better, and, the wider the better.

If you have a tall wide tyre, aired down well, you will not be pushing a bow wave, simply because you are basically floating. I leave tread marks, others well tyred leave many inches of rut, lots of cars I see drag the diffs thru the sand, leaving huge ruts.

A narrow tyre will drop into the sand, and so IT will be pushing a bow wave, and that will drain power immensely.

I highly aggressive tall and wide tyre will eat other tyres for breakfast in the sand.

A mate I go out with will not go below 10psi with his 30x9s, or whatever, 30x9.5 ? cant remember, I have 31x10.5s, he has to be in 4wd, I only go into 4wd if I have fukd up badly and have a wheel up in the air.

I find that when holidays are on, and the beach is fukd by many people going down and not airing down properly, 12" ruts everywhere, the big wide tyres just baloon over them, where as the skinnier tyres will follow, and becomes hard to climb out of them.

This is why I want to go to rags, 33 x 13.5s for my play tyres (when i do the build and fit the 5.12s)

[Gwagensteve]

This has been discussed at length before. You're entitled to your opinion Suziblu, but it's not the only one.

A 33 13.5 isn't tall, it's short and fat.

Comparing the performance of one car with one size tyre at high pressure and your car on another size tyre at low pressure isn't a fair comparison.

I'm not going to discuss tyre design and sand performance with you at many more length Suziblu. You're happy with the performance of your tyres and that's great. Others wouldn't be.

Steve.

[TryHard]

hmmm so 33sx12 bighorns on beadlocks ? lower the tyres right down ? what u think ? there 33s will be mainly used on rock but i want do some beach driving as well ..

[SuziBlu]

Ok Steve, you offered an opinion, I offered an opinion, based on my own findings.

I put this in here, because like you say, mine is not the only opinion, as your is not, so I was offering another.

A 33 on a suzi is a tall tyre. many say too tall.

10psi is not high, its just higher than I run. You say skinny, I offered my observations on a skinnier tyre than I run, now you say that that is an unfair discussion, hmmm ok.

TryHard, sound like the go to me.

I run at 5psi on 8s and do not have beadlocks, and do the sideways dance all the time, but I only run on sand. When I go bigger on 10s I will be putting internal beadlocks on.

[Gwagensteve]

As discussed, I'm not a fan of 33 12.5's as a size, but to a certain extent that's based on us driving in wet conditions. At least with beadlocks you can run them at any pressure you like, 5psi should be a start. Make sure you have a fast compressor - there's lots more air in a 12.5 than a small tyre!

However, if you are currently widetrack, It gets hard to maintain useful steering lock with 12.5's and sensible backspacing. You might want to narrow track your front springs so you can run 3.75-4" Backspacing with an 8" rim and keep a handle on the overall width. The car will be more capable on more terrain (including on road) with less overall width, the steering won't beat you up as much, the car will drive straighter, and be less of a cop magnet.



Steve.

[oozuk]

Gwagensteve

thanks for your comments, i have been on a similar train of thought with tyre sizing and footprints but seen it proven (wide Vs skinny) i am currently running bias Claws 33x13.5 15 and i'm not a big fan of them, i am now deciding if the next set of tyres will be 33x12.5 or 33x10.5.

Might be going the 10.5's on beadlocks

[Gwagensteve]

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

[oozuk]

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

I i had done a guard chop prior to the body work but a 33' tall tyre is the limit for me. with the terrain up in qld and my Torque the rear axles will not stand a chance on Q78's

unless you willing to donate those fancy full floaters you've knocked up.....

[Fatzook]

oozuk wrote:

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

I i had done a guard chop prior to the body work but a 33' tall tyre is the limit for me. with the terrain up in qld and my Torque the rear axles will not stand a chance on Q78's

unless you willing to donate those fancy full floaters you've knocked up.....

Find an SV420 rear diff and I'll make you a SPOA shortened hybrid with full floaters when I make the diff for my ute.

Factory 4.6 rear and WAY bigger than the twigs you run now

[oozuk]

Fatzook wrote:

oozuk wrote:

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

I i had done a guard chop prior to the body work but a 33' tall tyre is the limit for me. with the terrain up in qld and my Torque the rear axles will not stand a chance on Q78's

unless you willing to donate those fancy full floaters you've knocked up.....

Find an SV420 rear diff and I'll make you a SPOA shortened hybrid with full floaters when I make the diff for my ute.

Factory 4.6 rear and WAY bigger than the twigs you run now

as tempting as that sounds.... i am flat out scratching the coin together for new rubber let alone to buy the GV parts, new air locker and the deep pockets needed for your excellent handy work

P.M. me what you would want to do something like that as i might win the lotto in the future, you never know

[Fatzook]

oozuk wrote:

Fatzook wrote:

oozuk wrote:

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

I i had done a guard chop prior to the body work but a 33' tall tyre is the limit for me. with the terrain up in qld and my Torque the rear axles will not stand a chance on Q78's

unless you willing to donate those fancy full floaters you've knocked up.....

Find an SV420 rear diff and I'll make you a SPOA shortened hybrid with full floaters when I make the diff for my ute.

Factory 4.6 rear and WAY bigger than the twigs you run now

as tempting as that sounds.... i am flat out scratching the coin together for new rubber let alone to buy the GV parts, new air locker and the deep pockets needed for your excellent handy work

P.M. me what you would want to do something like that as i might win the lotto in the future, you never know

Ahh come on! I thought my prices were farely reasonable considering the quality you get

R&D and experimental work rates are considerably cheaper too

[stockman]

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

What brand are the Q78's? Is there a website?
I have tried googling it but it just brings up forums.

[alien]

go 33x10.5 KM2s... or 32x9.5 simex if you're doing mud only.

[oozuk]

Fatzook wrote:

oozuk wrote:

Fatzook wrote:

oozuk wrote:

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

I i had done a guard chop prior to the body work but a 33' tall tyre is the limit for me. with the terrain up in qld and my Torque the rear axles will not stand a chance on Q78's

unless you willing to donate those fancy full floaters you've knocked up.....

Find an SV420 rear diff and I'll make you a SPOA shortened hybrid with full floaters when I make the diff for my ute.

Factory 4.6 rear and WAY bigger than the twigs you run now

as tempting as that sounds.... i am flat out scratching the coin together for new rubber let alone to buy the GV parts, new air locker and the deep pockets needed for your excellent handy work

P.M. me what you would want to do something like that as i might win the lotto in the future, you never know

Ahh come on! I thought my prices were farely reasonable considering the quality you get

R&D and experimental work rates are considerably cheaper too

haha no disrespect intended, your twinstick gear is great value and i would of looked at some of your gear when i was building oozuk but twinstick didn't exist then and generally i'm a bit of a tightass..

when your thinking of doing a hybrid rear floater diff, let me know and we can discuss it further.

[MrRocky]

have some flipped 15x8's in the shed same as running 2" wheel spacers on f100 offset just getting dust on them ,
maxxis bighorns in 32x11.5 should be good enough for 99% of situations compared with 33's they are my pick for the best all rounder tyre sand, rocks and mud in perth anyway

[Fatzook]

oozuk wrote:

when your thinking of doing a hybrid rear floater diff, let me know and we can discuss it further.

Will do. Might work out that we can trade work anyway, as I'll need some airlockers fitted and lapped in new housings anyway.

I'll let you know

[oozuk]

stockman wrote:

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

What brand are the Q78's? Is there a website?
I have tried googling it but it just brings up forums.

Q78 = super swamper TSL 35x9.5 15

[oozuk]

alien wrote:

go 33x10.5 KM2s... or 32x9.5 simex if you're doing mud only.

33x10.5 KM2s are my 1st choice but Bighorns in the same size seem good value for money....also sorry for the hijack

[Gwagensteve]

oozuk wrote:

stockman wrote:

Gwagensteve wrote:

Q78 FTW

I would have thought you car would be spot on on some '78's

Steve.

What brand are the Q78's? Is there a website?
I have tried googling it but it just brings up forums.

Q78 = super swamper TSL 35x9.5 15

They're a bit chubbier than that- 35.5"X10" measured. - doesn't sound like much but they're miles bigger than a 9/34.

I can't remember whose, but they are bigger than some 37's

They are available for 16" rims too - same overall size.

Load range C - once bedded in, they flex well on a sierra.

Steve.

[boostedbrick]

Ive only done one trip on my Silverstones, there a 33x10.5 and found them much nicer than the 31x10.5s that i had. Even with just 4.9s and stock diffs that size just felt like a easier tyre to drive with.. Been taller helped alot with diff clearance and didnt have a noticable effect on stability. Personally i would have gone with a 9.5 but then the silverstones are a skinny 10.5. Time will tell i guess with more off road work.

[SuziBlu]

Steve, 35s bigger than 37s, kewl, so if I put on these, 37s, for engineering purpose, then put on 35s, Im way under, sounds good to me.

Who ?? or, what are they.

[shane1992]

dude my 33x12.5 go fine, ive put the pressure down to 12psi and its crawled up heaps of big rock ledges with open diffs.

[shakes]

Gwagensteve wrote:

lots of stuff re tire sizing

Steve.

Was talking about this exact thing the other night with a mate over a beer... You validated our thoughts on it all exactly!! makes me feel a little better.