265 75 16's v 235 85 16's

[highrr]

Hi People,

I am new to this stuff so can anyone tell me what size would be better to run on my 1996 range rover?

Thanks

[mtb_gary]

highrr
My personal preference is for the 265/75/16 as a lot of the driving over here in the West is done on sand, so the additional footprint provides a bit larger footprint in the width. Both the tyre sizes are almost identical in circumference so no great benefit from either in that respect. I guess the question comes back to what terrain you wish to spend most of your time on.
For my P38 I run 2 sets of wheel/tyre combinations. I have the 265/75/16 Maxxis Big Horns for off road work and the Pirelli Scopion Zero's 255/60/18 for day to day road usage.
Another side benefit from the 265/75/16 is that they are also very common on the Jap cars and as such are readily available no matter where you are.
Gary

[highrr]

Thanks Gary, I'm leaning toward the 265 75 16 as they are more available

[Gippslander]

265/75/16 stuff up your diff ratios and you end up not being able to hold lockup in the converter under 90km for normal highway use as the tyres size increase is equivalent to a 9% increase in Tyre size from 29inch to 32 inch. I have fitted 265/75/16 Khumo mud Tyres and am now going to fit 4.1 : 1 diffs to get back my down hill braking as 4.1 : 1 gives me a 15% reduction so i pick up another 6% for down hill decent. It was good when i bought the car on 29 inch Tyre i could descend steep terrain without touching the brakes but since changing i have to brake a lot on descents which was not the case before. I live in Gippsland and have done a large amount of the High country to test the set up out. Hope this helps Gippsalnder

[mtb_gary]

Gippslander
I agree, the only problem after the bigger tyres is the hill decent. Where did you get your 4.1:1 diffs from (and roughly how much $$$)?
Gary

[Gippslander]

Hope to get them ordered in the next couple of weeks i am getting Ashcroft models and lockers to suit decided to go all out and hopefully get a good all round tourer with the lower diffs giving hopefully better fuel as stated and also looking at fitting extra fuel tank in wheel well as the new tyres do not fit anymore.:p

[mtb_gary]

You'll have to do a separate posting with the outcome. It will be an interesting project to follow. Good luck with the work, and take lots of pics :D
Gary

[PaulP38a]

The 4.1:1 diffs in mine are from Great Basin Rovers. Around $1K-1.5K for the pair. A must have if you run 33" tyres.

[Gippslander]

Thanks for that Paul do you think they are as good or better than the Ashcroft and do you have lockers if so what brand. I have tried to read up on these diffs and was going to go with Ashcroft gears and lockers thinking by going with a common manufacturer it might save trouble when going to install them and i would just have to get new bearings for the full rebuild.:eek: Also noted Ashcroft state 16% decrease in ratio but GBR say 12%.

[PaulP38a]

Thanks for that Paul do you think they are as good or better than the Ashcroft and do you have lockers if so what brand.

Dunno mate, Hardy put the GBR 4.1:1 diff gears in when I bought the beast from him in 2008. I do know that they are still going strong after me giving them a good beating. I have an ARB air locker in the rear that runs off the EAS compressor.

Key message back to the thread topic - If you are going to run big rubber on your P38, change the diff ratios to suit the new tyre diameter if you want to maintain control going down steep descents off-road.

Happy New Year all!

[benji]

Wouldn't the lower revs at highway speeds lead to better fuel economy? The 4.6 could easily do 2000 at 100kph.

Would you think Gippslander, that standard ratios would still be okay for the occasional jaunt up Butcher Country / Dingo hill etc? As I was planning to run a set of standard size road tires.

[Gippslander]

I was like you and thought the size difference would help but sadly it didn't i use a lot more fuel than before i realise the tyres drag more air as they are mud terrain and directional but all said and done i lost fuel economy. Yes you can do Butcher country and all the others the only problem is you use your brakes a hell of a lot more. Hope you enjoy the trip as i do every time i get away just expect to use more fuel and be careful on the steep down hills rest your brakes when you can.

[highrr]

I have gone the 265 70 17, I have a Gen 3 in it so it has awesome low down grunt, it has 4.11s and lockers and big vent brakes so my only issue was the clearance, but the manual bypass kit allowed me to pump it up, so I am happy.

[Keithy P38]

Got 17's on ur Rangie eh highrr?

Gippslander, are your figures based on the trip computer or measured kms versus pump litres? I have been getting better mileage in my P38 with the bigger tyres @ the pump.

[highrr]

Yeah got 17's on it, but don't like them, I bought 16's but the stud pattern was different so i am stuck with the 17's

[Gippslander]

Fuel usage is based on trip computer and across reference to GPS haven't gone right into it but i do believe it is worse off than before.

[Keithy P38]

Unreal! My trip computer says I'm doing worse - naturally because I've gone from 94kmh at indicated 100, to 100kmh at 100 indicated. By the GPS and bowser I'm about a litre per hundred better off!

[Gippslander]

According to my GPS i am doing 100 when speedo show 93 which is i would expect bigger tyres travel further per revolution and all. Fuel at best on flat highway shows 14.7 per 100 as compared to 11 per hundred before. :mad:

[Keithy P38]

Probably because your trip computer doesn't know you are actually travelling at 100 instead of 93!

Ill let you know in a few years when I upgrade to larger tyres again.

[ozscott]

Gearing aside the higher profile tyre will always be better in sand. It's not width, but rather length of footprint and the shallower and less aggressive approach angle of the taller tyre to the sand. Picture the wedge build up. And effort to roll a log through sand - you don't want that. The taller tyre gives better protection to the rim. All the above applies rock hopping etc. I have experimented with fat v tall skinnier on my D2 which is far heavier than standard and does quite a lot of beach towing and tall skinnier wins even on the heavy vehicles.

Cheers

[highrr]

fitted my 265 70 17s, who would have thought that commodore rims fit a P38, I wish I had a know that awhile back.

[Keithy P38]

Did you need to machine the centers? Last time someone fitted commodore rims to a P38 I recall the wheel centers needed machining to fit correctly?

[highrr]

factory one's do, but aftermarket one's don't need to be, BMW 3 series also fit

[Hoges]

Are they (BMW/Commodore wheels) rated for RR P38 gross mass?

[highrr]

The ones I got are, and the factory one's are, but I don't know about the aftermarket ones

[wayneg]

Did you need to machine the centers? Last time someone fitted commodore rims to a P38 I recall the wheel centers needed machining to fit correctly?

Thats correct, Someone over here in Perth did it, wassamipimpninga ( or something like that?). One thing thats not been mentioned is the fact that Landrover Rims have a stronger and bolder internal beading which helps the tyres to stay on at lower pressures. Tyre fitters hate them as its a PITA to get tyres on and off the rims. I would stick with the LR rims