Feed Back on 17" Tyres

[wardh]

As I have indicated in my previous post My D3 is a about to run out of Factory Warranty. Its also nearing time to fit new tyres and I am still unsure which way to go and more the hardest question what is legal in Qld.

I know this has been raised before but there are some questions I have that I feel members of this forum have first hand knowledge and experience of.

I have the 17" dia by 7" wide rims (which I wish to keep) on my D3 s vehicle and raised King Springs.

1 I like the idea of the 265/70 17" size tyre. (My reasoning is improved ground clearence and sand work) I am aware of the spare tyre issue and this is not a problem. My local tyre dealer has expressed concern that although that size tyre is wiithin the rim fitment width, he feels it is too wide and will compromize the handling of the vehicle when fitted to that width rim

Any comments from anyone who has fitted a 265/70 17 tyre on a 7" rim. Handling issues. Performance Gearing etc.

2 Another option is 255/65 17 this would keep the overall diameter of the tyre the same as the currently fitted 235/70 (won't improving clearance) but again would it adversly affect the handling. Also I have not been able to find a Light Truck build tyre in an ATR pattern in this size

245/70r 17 LT seems to be the easiest solution. But again not a lot of choice in tyres. Pirelli Scorpion, Cooper HT. Whats the opinion out there. is there any real advantage in a 265 width in comparison to 245.

Most of my driving is on bitumen and graded dirt roads. (will soon be pulling a 20ft van, also still have my boat) Off road is mainly sand (still love camping and fishing) and the occasional short venture on rocky maybe washed out tracks if no alterative route.

I avoid the serious off road stuff and rather find an easier way from A to B having spent years of being paid to go serious 4x4 driving (amazing where you can go with a fire up your tail) as a Forest Ranger prior to my retirement (I apologise now if anyone out there ever bought one of my ex gov vehicles :( )

Thanks in advance for your practical advice and comments

Howard

[chuck]

Your tyre dealer must be on drugs.
The 18" tyres are 255mm wide standard.
Your car could have been optioned with these wheels.
This makes the 265mm x 70 x 17 tyres 10mm wider & less than 50mm taller.
This is then a legal modification in most states & complies with the new Dotars Code of Practice.

Whilst I do not yet have a D3 I fitted 265 x 75 x 16 tyres to my D2 - this has done nothing but improve handling etc.

I am hoping to buy a D3s soon & the first modification I will do is fit a set of 265 x 70 x 17 tyres probably MT MTZ's or BFG MT KM2's.

Hope this helps.

Regards

Chuck

[rmp]

265/70 17 is 40mm over std and therefore not legal in Qld, and I'm pretty sure you'll have clearance issues.

The minimum rim width for such a tyre is typically 7.5" so your 7" are too narrow and thus not a legal fit anyway. Plus you'll slightly confuse the ESC with an incorrect speedo reading.

255/65/17 -- Bridgestone D694 LT. Will be fine on your 17x7.

245/70/17 -- Cooper STT for example.

Wider tyres handle better onroad, narrower better off and better in the wet. But a very marginal difference between 245-265 so choose based on price and availability.

[rmp]

en a legal modification in most states & complies with the new Dotars Code of Practice.


...which unfortunately, is not yet formally adopted by any state.

[Graeme]

I have earmarked Pirelli ATRs in LT245/70-17 as my everyday tyre when I get a D3 or D4 if it takes 17" rims.

[rovers1952]

Am now running Cooper S/T 245/70R17's and seem excellent at $335.00 each. However, a bit noisy at suburban speeds but ok at freeway speeds, and as good as anything in the rough stuff. These as far as I know are max legal in Qld and OK here in NSW.

[wardh]

rpm (Robert)

First thanks for the information.

Regarding Rim width, most manufacturers in there tyre specifications will quote a recommended rim width and a minimum and maximum rim width fitment for a given tyre size. Tyres (tubeless) as I understand and have reseached are engineered/made to fit within a range of rim widths that ensures the bead seals and holds the tyre when pressurised. Outside of these specifications the tyre could detach fail or suddenly deflate, not a good thing to happen.

The other interesting thing is that if a given size tyre, say our 265/70 is fitted to a 7" wide rim and measured for overall width then fitted to the 9" rim and measured again for overall width the tyre is not 2" wider. There is very little difference. There are charts available that will tell you what the percentage of overall width change will be when you apply the diameter, aspect ratio and rim width.

The 265/70r 17 tyre fitment rim width range is 7" to 9" with a recommended or ideal rim width of 8".

The rims I have will therefore take a 265/70R tyre but the fitment is at the narrowest end of the scale. This is what my local tyre dealer is pointing out and concerning him and is why I am trying to find out what effect that has if any.

The other thing I noticed was you quoted a Bridgestone D694 255/65 17 in a Light Truck construction. I had these tyres in 245/75 on my D2 and they were terriffic. I have checked the Bridgestone web site but it does not list that size in a LT construction.

Can you or anyone confirm Bridgestone make a D694 255/65R 17LT as I would seriously consider that tyre again

Thanks

Howard

[rmp]

Correct re rim widths. I got the 7.5min from another 265/70, may be different for different manufacturers but generally they're the same. The rim width has no effect on tyre width at all. If a tyre is approved for fitting on a 7" then it'll work and be legal.

Sorry my mistake on the Bridgestone. Try Cooper HT, ST and ST-C, General AT2. Maxxis S-1.

[gghaggis]

I'm unsure of the legalities of 265/70/17 tyres in Qld - in many other states, they are legal (within 50mm). But as far as compromised handling and width clearance issues, many of us here in the West have been running this size for 3 or more years as a daily tyre. No handling issues have been reported (and note that in the US they fit 285-width tyres with no modification). Tyres of choice in this size have been BFG AT, Mickey Thompson ATZ or MTZ, Maxxis Bighorn and Cooper STT. These are all fitable on the 7" rim.

Cheers,

Gordon

[rmp]

Good to know there's no clearance issues. The laws vary from state to state, Vic and NSW are +/- 15mm, SA is 50mm for 4WDs as an example.

Whichever tyre you buy ensure your rim width is approved for it and that is tyre-specific. You don't want to explain to your insurance company why you were running a 7" rim on a tyre approved for 7.5-9 for example.

[chuck]

If narrower tyres work better off road then why do all the highly modified
4x4's run wide tyres?

Regards

Chuck

[rmp]

If narrower tyres work better off road then why do all the highly modified
4x4's run wide tyres?

Regards

Chuck

Because they run very tall tyres, like 35s or 37s and you need a reasonable width for that sort of diameter. Look at the Defender, other similar offroaders, they're on the likes of 235/85/16. I know of one very successful offroader driver, multiple champ, who runs the narrowest 35s he can.

[gghaggis]

If narrower tyres work better off road then why do all the highly modified
4x4's run wide tyres?

Regards

Chuck

In competition, you run at very low psi - all other things being equal, the wider tyre will mold to the surface (rocks etc) better, as it has a greater internal volume. And of course, the greater width can span cracks/holes/ruts better.

Cheers,

Gordon

[rmp]

Threads that start discussing tyres tend to be very long, especially those that cover the relative merits of narrow vs wide.

Some points -- a wide tyre has the same contact patch as a narrow one, all else being equal, it's just a different shape. Narrow tyres have a longer contact patch, shorter ones wider. Both are oval shaped not rectangular.

The contact patch is a function not of width, but of tyre volume, weight and tyre pressure. However, the tyre construction has much to do with how a tyre's contact patch changes as these factors change.

A wide tyre spans a wider area than a narrow one, which is why they aren't so good in the wet; say a 285 has to move an area 285mm wide of water out of the way for maybe 140mm of tread length, whereas a 235 cuts a path only 235mm through the wet and its long contact patch, maybe 180mm then has a relatively dry road to work with. That principle applies offroad too in the wet as it often is. Wide tyres also run more risk, offroad, of not sitting flat to the terrain. Not an issue onroad, where width is an advantage (in the dry) for various reasons like tyre slip, penumatic trail, steering response which is why sports cars have wide tyres. And the longer contact patch of a narrow offroad means if you are driving over say a stone the tyre can bend over it like a mini tank-track because it's long (like the spanning point, but the other way around). Wide ones can't do that as well; you could argue they could do much the same laterally, but tyres are designed to work with ALL their tread on the ground, not part of the tread of the ground. Hence my general point about narrow, tall tyres being good offroad. But like everything offroad there will be the odd occasion where wide is better. The wider tyre will have a greater internal volume than a narrow one, but to achieve the same contact patch you'd air down further so it would be the same in the end. The bigger the volume of the tyre, the more you have to air down to get the flexibility and reduce loss of traction through bouncing. Those Icelandic 4X4s run virtually no psi but their tyres don't look flat as there's such a huge volume of air there, same as a smaller tyre but it's not compressed into a 245/70/17 or similar.

There's lots more to say but in reality the differences between D3 tyre widths aren't massive and offroad the driving technique, quality of tyre and pressure etc will make the difference, not whether you're running 235 or 275.

Comp trucks are a bit different to D3s as they run beadlocks on very large tyres which usually have incredibly stiff sidewalls (they're no fun to remove off rims), and the tread patterns they use are very aggressive.

[Leo]

A touchy subject! Personally, i find that the D3 works much better in soft sand on wider tyres, better on road handling as well, better in mud (some types) and much better on rocks.

Narrow tyres work better in snow (generally speaking, but again, depends on type of snow) and aquaplane later.

Sure there's somebody out there who will feel the oposite is true. :lol2:

P.S. I don't see why a narrow tyre, of same compound, diameter and sidewall height as a wide tyre should have a longer contact patch.

[rmp]

A tyre's contact patch is only ever as wide as its tread width. Any bulge is only on the sidewalls. Therefore a wide tyre has a wider contact patch. *

Given a contact patch is a function of weight, construction and pressure if a tyre already has a wide patch then those forces don't result in a CP as long as if it were narrower, it just doesn't elongate as much. This can be measured. A long contact patch is not great for on-road driving which is one reason why sports cars don't go in for narrow tyres.

Two tyres of the "same compound, diameter and sidewall height" but one narrow, one wide are not the same, because the wider tyre will have a greater volume of air. This means for a given vehicle weight it should be run at a lower pressure, and that in itself can give benefits offroad as the tyre bounces less (but there are disadvantages too). However, it's a disadvantage onroad because you want high pressures for high speed road work -- and that's why low-profile wides, not high-profile wides, are common for sporties as these tyres have a relatively low volume of air thus are run at high pressure, but have the on-road advantages of a wide tyre.

The direct comparsion would be two tyres of equal diameter and construction, but different widths, and of equal internal volume. This would require the narrower tyre to have a smaller rim diameter.

It's also clear what a compromise tyres are!

* assuming it's flat to the ground, and the pressure plays a part too, at really high pressures for example there the contact patch doesn't extend to the sides of the tyre etc etc....

[Pedro_The_Swift]

for what its worth,,
a narrow rim is also protected better by the tyre,,

the wider the rim, the more exposed it is to damage.