SKINNY verses FATS

Submitted: Friday, Mar 18, 2011 at 22:25
ThreadID: 85085 Views:5237 Replies:7 FollowUps:13
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HI ALL
What is your thoughts on skinny tyres verses fat tyres in sand dune country
I notice that MICK O is running fats are they better?
Cheers Reggy 2
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Reply By: Mick O - Friday, Mar 18, 2011 at 23:16

Friday, Mar 18, 2011 at 23:16
A can of worms Reggy. No, actually it’s horse for courses. I don’t actually consider my tyres “fats”. I’m running 285/75-16’s (33” in the old). Member Jaydub is running 305/75-16’s (35”) which I call Phat! I’m a fan of a tubeless tyre as it makes temporary repairs fairly easy where as a tubed tyre on splits is a totally different kettle of fish in the repair and get going stakes (pardon the pun). To my mind they (tubeless) also offer a great deal of flexibility in dealing with varying terrains. In sand you can achieve a hell of a lot with a thin tyre providing you know what you’re doing with tyre pressures and your vehicle is not overloaded. Of course having a greater footprint provided by a wide tyre helps in sand. The reality is it’s all about the sidewall strength.

I’m no expert on MRF’s but I’ve seen the consequences of their use combined with improper use and hard country. It’s not a pretty sight. For a definitive appraisal about “thin” tyres have a look at Mick Hutton’s tyre articles on the Beadell Tours website. He’s a bloke who knows just what a tyre is capable of. Again, his main priority is the toughness (robustness) of the tyre in dealing with crappy conditions as you so often encounter in off track work. Sidewall strength is again a key factor he comments on. You can’t reduce pressure and ‘bag’ a tyre out if the sidewalls aren’t strong enough.

If you're going to be running over pristine dunes as a recreational activity, then wider tyres are probably a good option for you. If you're going to be crossing vegetation and stake infested dunes of the Australian deserts, somewhat more consideration is needed. My tyre choice is based on the type of travelling I do, the loads I carry and the terrain I carry it over not forgetting my ability to fix the damn donuts as well. My experience has led me to the Toyo and I’m very very happy with it.

Toyo Open Country MT - Review


Cheers Mick





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trip would doubtless be attended with much hardship.''
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Follow Up By: phil300 - Friday, Mar 18, 2011 at 23:25

Friday, Mar 18, 2011 at 23:25
I found for soft sand a taller skinny tyre down to about 10 psi works better than a fat tyre.
Tall skinny tyre gives a longer narrower print were a fat tyre gives wider print which has to move more sand.

cheers Phil.
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Follow Up By: Crackles - Saturday, Mar 19, 2011 at 00:39

Saturday, Mar 19, 2011 at 00:39
Fats may have more sand to move Phil but they also have a greater surface area meaning improved floatation for a given pressure. Having run both skinny & fat over the years either can be successfully used in sand dune country given the appropiate pressures with often no clear winner between the two. What does give a distinct advantage is a larger diameter tyre with greater clearance all round & less rolling resistance. Most impressive tyre I've seen on sand was a 37"x12.5 on the Madigan.
Cheers Craig.............
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Follow Up By: Rockape - Saturday, Mar 19, 2011 at 08:25

Saturday, Mar 19, 2011 at 08:25
Reggy,
not trying to hi-jack your thread, I just want to share something re Micko,s rims.

A good while back there was a warning from the mines department about those rims. The centres of the rims were cracking and collapsing.

Also we use this product or a similar one on our truck and bogger tyres, it works well, a side benefit is the tyres are easy to get off.Tyre seal

Have a good one.

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Follow Up By: Ozhumvee - Saturday, Mar 19, 2011 at 09:41

Saturday, Mar 19, 2011 at 09:41
Rockape
Mick has already done that to couple, threw one out of bed too ;-)))
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Reply By: AlbyNSW - Saturday, Mar 19, 2011 at 08:51

Saturday, Mar 19, 2011 at 08:51
Isn't it all about which ones look the best when your travelling around the bigsmoke on the blacktop ???? LOL
AnswerID: 448626

Reply By: Robin Miller - Saturday, Mar 19, 2011 at 09:09

Saturday, Mar 19, 2011 at 09:09
Wether its fat or not depends on vehicle weight mainly Reggy2 check out white paper below.

If I had 285 on my Patrol I'd consider them fat.

Either way some loose all round , consider the landcruisers with 90mm offset between front and rear axles - they have a much bigger frontal wave and consequent resistance in sand , and greater chance of hitting a stake - all this is completely un-necessary


http://www.expeditionswest.com/research/white_papers/tire_selection_rev1.html

Also there is a massive amount of uncooberated talk about this stuff , hence why we do so many on the ground comparisons.


In the picture below is a petrol 80 series running skinny 7.50 tyres - cause he could follow us anywhere with them.
I think we were onto our second cup of coffee before every combination of trying to get up this steep sand hill was tried and he gave up.





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Follow Up By: ob - Saturday, Mar 19, 2011 at 14:10

Saturday, Mar 19, 2011 at 14:10
Hi Robin,
Every combination.......did you try a different driver?

ob
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Follow Up By: The Explorer - Saturday, Mar 19, 2011 at 18:35

Saturday, Mar 19, 2011 at 18:35
Were the hubs in? :)

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Follow Up By: Robin Miller - Sunday, Mar 20, 2011 at 09:35

Sunday, Mar 20, 2011 at 09:35
Hi Greg

They are constant 4wd and no hubs to lock.

Pretty straight forward case I thought - this vehicle was only one outside the reccomended range as per white paper - and it couldn't do the job.

Has since gone to 235/85/16 , not a bad choice.

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Follow Up By: The Explorer - Sunday, Mar 20, 2011 at 11:44

Sunday, Mar 20, 2011 at 11:44
Oh - thats right - I only ever had the STD 80 diesels which had hubs.

Anyway - tyres. I dont think it is 100% conclusive that the width of the tyres was the issue in this case. Sure the tyres are "skinny" but the inability to get up this particular hill was more likely to be because the required lenght of footprint couldnt be achieved, even by letting the tyres down to the minimum safest level (assuming you let them down to say at least 12psi?). Doubt if you measured this characteristic of the tyre in question so there is no way you can eliminate it as a potential cause. The lenght of footprint largely defines how good a tyre performs in sand not its width.

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Reply By: get outmore - Saturday, Mar 19, 2011 at 10:08

Saturday, Mar 19, 2011 at 10:08
recently had to pull out an identical vehicle to mine exept he was running 33x12.5 tyres to my 235 tyres didnt matter how myuch we lowered his pressures he still went straight down and i pulled him out twice before giving up and just towing him off the beach

to show off i actually drove around him
sand was very soft but the fats were no match for my skinnies

what this pic doesnt show was my tyre tracks going right around him here



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Reply By: ob - Saturday, Mar 19, 2011 at 14:08

Saturday, Mar 19, 2011 at 14:08
Hi Reggy
Purely my experience, I have 2 sets of rims. One standard 16" split with 235/85x16 10 P.R. Hankook's for what I would call rough country.
One set 15"x8" steel rims fitted with Bridgestone 10.5x15 tyres.
The splits go on if I am going to be doing mainly outback travelling (yes some sand dunes) and the 15's if doing a beach fishing trip.
I have a trolley jack and rattle gun to change them before I go.
Rattle gun to remove ONLY.
The "skinnies" do work ok in sand but the "widies" work better IMHO.
Yes I adjust pressures to suit conditions and slow down a lot if required.
Oh ...the vehicle is an old but trusty HZJ75 Landcruiser. So not exactly infested with horsepower..........lol

ob
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Follow Up By: Jack - Saturday, Mar 19, 2011 at 17:51

Saturday, Mar 19, 2011 at 17:51
ob,

I think the 10.5x15 would lower your gear ratios and allow your 1hz to rev a bit more - giving the feeling that the vehicle goes better.


Jack
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Follow Up By: The Explorer - Saturday, Mar 19, 2011 at 18:13

Saturday, Mar 19, 2011 at 18:13
Hi

Yes - but do the wide tyres work better on sand because they are wider or because of some other factor ...like for example they produce a longer footprint when let down. In reality nothing to do with width but another characteristic of the tyre ..which just happen to be wider than the ones that dont work as well.

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Reply By: Member - Phil G (SA) - Saturday, Mar 19, 2011 at 14:36

Saturday, Mar 19, 2011 at 14:36
Gday Reggy2,
Most people have opinions on this, and they often differ because people have different experiences. I'll assume you mean desert sand dunes rather than coastal. I travel in groups of usually 6-12 vehicles and it gives a good opportunity for comparisons.

Width doesn't matter 2 hoots.....DIAMETER does.
A 205R16 (740mm diameter) doesn't go as well in soft sand as a 750R16 (810mm diameter) all other things being equal.
A 285/75R16 (835mm diam) goes better than a 10R15 (770mm dia).

But most vehicles I travel with are Landcruisers with either 750R16, 235/85R16, 265/75R16 or 285/75R16 which are the most popular sizes and the first 3 are the same diameter. The skinny 750's go everywhere the 265's go.

I also have a strong preference for tubeless - if anyone stakes a tyre, we are going again in 5-10 mins after plugging it on the vehicle. With splits we stop for 30mins smoko while the wheel is changed and then someone spends an hour at beer o'clock patching it. And its really annoying when the thing's gone flat from tube fatigue at low pressures, or the valve got ripped out from the tyre turning on the rim.

My head always says 235/85R16 on 6" tubeless rims is ideal for the desert, while my heart says 285/75R16 on fat mags :-))
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Follow Up By: Member - Porl - Saturday, Mar 19, 2011 at 18:34

Saturday, Mar 19, 2011 at 18:34
uhm okay Phil so you recommed go the skinny really tall tyres so you can bag them down to much longer footprint (in ordinary language)?
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Follow Up By: Member - Phil G (SA) - Sunday, Mar 20, 2011 at 20:24

Sunday, Mar 20, 2011 at 20:24
Gday Porl (didn't you used to be on the Prado forums years ago?)
Yes I forgot to state the obvious, and its the longer footprint (from both lower pressures and bigger diameter) that makes a difference.

Sorry to see your ex-Hilux in your profile - hope nobody was hurt. Hilux is a dilemma because they are a big vehicle with undersized skinny tyres (205R16) - If you upsize to 235/85R16 you put the gearing out by 7%. In between you can get 215/85R16 in a few brands but I doubt you can get LT construction in that size.
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Follow Up By: Member - Porl - Sunday, Mar 20, 2011 at 20:50

Sunday, Mar 20, 2011 at 20:50
Hi Phil

Yes I had the prado and was well obsessed but I never used it much and as the kids came along used it less and every day I'd look at this $40k vehicle sitting there as I rode my bicycle to work thinking what a waste - so I acted on it and sold it for 2/3rds and bought a hilux for a 1/4.

That ended with 2 trees, I was fine but the seatbelt cut into my 6yr old daughter and she spent 6.5weeks in hospital with misdiagnosed severed bile duct. Long story. She is sort of fine.

Have Rodeo now, just something different you know, something with ABS and a lower center of gravity (and a much better and more careful driver)

Thanks for the reply.

I got Rodney with Cooper AT's and I am not impressed with them.

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Reply By: Member - reggy 2 (VIC) - Saturday, Mar 19, 2011 at 21:40

Saturday, Mar 19, 2011 at 21:40
HI ALL
Thanks for your response I have been running 235x85 x16 on most trips but doing off tracking in dune country I just needed other people's thoughts looks like I will stay with the same
Thanks again Reggy2
AnswerID: 448673

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