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Discussion Starter #1
Does anyone have P265/60-18 tires on a stock P38? I am about to go to the tire shop to put on some Cooper Discoverers and would like to see if there are any issues or if I should stick to the 255/55. I don't think I can find the 255/60 size.
Thanks in advance.
Alfredo
 

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Re: Urgent question--Sorry Tire related

I used to run 255/60r18s with stock suspension.
It was drivable on the bumpstops but would rub under cornering.
Yours would only be 10mm wider and 12mm taller, they should work but someone has had slight issues
http://www.RangeRovers.net/outfitting/t ... .html#alt2
 

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Discussion Starter #5
Re: Urgent question--Sorry Tire related

Thanks for the replies.
I had read the Official P38 Tire Size post, but it wasn't clear to me if the 265/60 tires were used with the stock suspension.
This morning, I did have the Cooper Discoverer H/T plus installed in the 265/60R18 size, to replace some worn General Grabber UHP 255/55R18.
I am about to embark on a 1300-plus-mile trip from Laredo, Tx to Amarillo, Tx and back, leaving in a few minutes, in fact. I will update when I return to see how these new tires behave.

kmagnuss, sometimes it takes me awhile to remember the initials, so, if you don't mind, what is FTW? I am sure that as soon as I see it I'll slap my forehead, it will be so obvious.

Thanks again.
 

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Re: Urgent question--Sorry Tire related

For The Win!
 

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JACK'S GRANDAD
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Re: Urgent question--Sorry Tire related

kmagnuss said:
FTMFW!!!!!
And explain that one in long hand without getting a vacation.... :lol:
 

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JACK'S GRANDAD
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Re: Urgent question--Sorry Tire related

Cheater.... :lol:
 

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Discussion Starter #11
Re: Urgent question--Sorry Tire related

UPDATE: Sorry for the length.
Well, I did the first half of the trip yesterday (Laredo to Amarillo).
The ride seems softer but still firm (nice), more absorption of the road bumps. It also seems that it was a quieter ride.
We got rain from about Junction to Canyon (about 300 miles or so), sometimes pretty heavy. Did not bother them at all, even at 75 or so mph.
The only thing I noticed is this: last year, on the same trip, my average mpg was pretty close to 15 (I get around 11 mpg in mixed city/highway everyday driving; I can't figure out how some guys get 15 to 22 mpg, I have tried everything). This year, with the new tires, I was averaging again just under 15 mpg, even reaching speeds of 80 mph (legal in some counties) until I hit the rainstorms. You could then see the mpg just dropping, giving me approximately 14 mpg during the drive through the rain. All this values are from the dashboard message center (I now have an iPhone application called Gas Cubby, and it reported 13.6 mpg.)
I like this tires so far. I have a 1995 4.0 and it is running on 265/70R16 Cooper Discoverer ATRs bought about 4 or so years ago. they are still going strong and and have lots of life left. In fact, when we bought them the guy at the tire store told my son and I that we were going to be amazed at how these tires would last and perform. He was very right. I hope these new tires perform as well as the old ones did.
We'll see how they behave on the way back.

I don't know how to edit the title so it no longer says "urgent". Can someone please tell me how to do it?
 

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Re: Urgent question--Sorry Tire related

I can´t comment on the tyres but I might be able to offer some advice regarding your poor fuel economy.
Over here in New Zealand the open road speed limit is 100 kph (about 62mph). I am regularly getting about 21mpg on trips in my 1995 4.6 (117,000k) on long trips and I use the cruise control as much as possible. That gets rid of the human element on the ´loud pedal´. I have heard many similar stories to yours about poor economy - mostly from peolpe who tend to be heavy footed on the gas.
Without wishing to offend I would like to suggest that you drive conservatively and accelerate modestly (don´t bury your boot to the floor) and use the cruise control when you are on a steady state situation on a motorway. Maybe stick to about 60mph and see how it goes - you will hopefully be pleasantly surprised. Of course what sort of load you are carrying or towing, as well as how much hill work, will make a difference but these things are just my experiences so they might be worth a try.
One last thought - your American gallons are smaller than our Imperial ones so your figure of 15mpg equates to about 16.8 for us. My 21mpg will be about 19 for you.

Good luck
 

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Re: Urgent question--Sorry Tire related

Two reasons your mileage has gone down.

1. The new tires are bigger, so they're heavier.
2. The new tires are bigger, probably by about 8%... so when your odometer says you went 500 miles, you actually went 540. That probably makes up for the difference.

C. Wind direction and strength may have played a part as well.
 

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Discussion Starter #14
Re: Urgent question--Sorry Tire related

Rowant: No offense taken. I know I have what over here is known as "lead foot", but still I thought I would get a bit higher mpg.
I do use the cruise control on highways, especially here in Texas where you can travel as much as 800 miles and not leave the state. Still, at 75 to 80 mph though. We in our family are not used to traveling at 60, as we are 150 miles from anywhere.
I have three land rovers, a 94 Discovery I (~10 mpg on 235/70R16s), a 95 4.0 (~11.5 mpg on 265/70R16), and the 99 4.6 (~11 mpg on the old tires) (mixed driving). I have tried driving as conservatively as possible (getting honked at for not accelerating fast enough from a stop light), but never did I see the kind of mileage reported here. I am aware that I must sacrifice mpg for the kind of driving I do.

Kmagnuss: I realize and agree with reasons 1, 2 and C. In fact, I had planned on researching the outside diameter of the tires to determine the change in the speedometer and odometer readings. As a physicist, I am well aware of the effect of these variables and am even waiting to see the return trip results. This will allow me to better compare mpg since my reported figure for last year was for the return leg (I was towing a fully loaded U-haul on the way up), to remove changes in altitude and other variables.

I did not have any sort of significant load on the truck, myself, my wife (or, as someone here says SWMBO) and a couple of suitcases. I also didn't feel much of a strong wind, although, since it was dark, a steady wind may have been hard to detect.
Anyway, I will update after the trip back. Thanks for the replies.
 

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I've taken the urgent off.

265/60r18 equates to a theoretical diameter of 775.2mm (30.519685"). Theoretical as tread pattern may alter this slightly.



If you want to do an economy run the bear in mind the following.
.Aerodynamic drag increases with the square of speed, so 90mph has four times the drag of 45mph. Roof racks, spotlights, mirrors, a-bars are all bad for economy because of increased drag.
.More energy is used changing speed than running at a constant speed, a dual carriageway with roundabouts is worse for economy than a motorway despite comparable cruising speeds.
.The computer averages economy over time, when was the last time you hit the reset button?
.Revs are bad for economy, very gentle acceleration is good.
.EFI engines use no fuel on the overrun, plan ahead and don't brake for junctions.
.Ditch all excess weight.

Good luck.
 

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I run bfg a/t 265/65/R18 (FTGDMFW) and I get 13.9-14.6 mpg (91 octane, 10w30 oil genuine filters ) with all around driving and I keep up on maintenance.

Some mild rubbing but not nearly as much as when I had 285/60/R18's
 

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FWIW... don't forget that a Scottish gallon is 1.200 times larger than a Texas gallon

Oh my golly gosh... is that possible? 8-0= :lol: :lol: :lol:

So, 21 miles per Scottish gallon equals 17.5 mp(Texas) gallon

similarly 15 mp(Texas) gallon is 18mp(Scottish)gallon

sleep peacefully !
 

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Discussion Starter #18
Tim thanks for taking the urgent off.
I press the "i" button until the message center reads "computing mpg" at every fillup.
.More energy is used changing speed than running at a constant speed, a dual carriageway with roundabouts is worse for economy than a motorway despite comparable cruising speeds.
Took me awhile to translate, but I agree. :)
EFI engines use no fuel on the overrun, plan ahead and don't brake for junctions.
I try, although police may not agree with you. :)
.Ditch all excess weight.
What if she insist on coming along? :lol: :lol:
Of course that last comment was in jest (she may read this).

Thanks all for the replies.
 

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Discussion Starter #19
UPDATE...

Got back into town yesterday evening. Approximately 1550 miles traveled. On the way back, the message center read from 14 to about 14.7 mpg while using the cruise control at the 75 mph mark.
As mentioned before, the slightly larger tires create a discrepancy in the speedometer reading and the actual speed. Someone mentioned 8%. It is more like 4%. I arrive at this from two sources: first, the police officer that stopped me for clocking 78 on his radar gun (thankfully, and for the first time in my life I got away with a warning, all other times I got a speeding ticket) and then an iPhone app called GPS by MotionX which also reported about 78 mph using GPS calculations.
Adjusting for this, my average miles per gallon (US) for the return leg of the trip was around 15.
Also, in the parts where I was force to drive around 60 mph, mileage did increase significantly, sometimes to almost 17 mpg.
Tires behaved beautifully and seem to absorb road bumps better than the old 255/55s. For total of US $571 for all four mounted and balanced, I think I came out alright.
 
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