The 265/75 pro's and con's

[reida1991 Member Find all posts View Profile Close reida1991]

Hey guys,

Done a fair bit of reading on here about going up to 265/75 from 265/70 on my 01 GXL Turbo Diesel.

The vehicle has approx. 2 inch lift, so clearance should not be an issue. I'm after people's experiences who have gone from OEM to 265/75 on a DIESEL prado in terms of economy, acceleration, changes in speedo, towing performance etc. I want to go up in size for a larger selection of tyres, performance off the black top and hopefully save a few pennys.

Failing this, can someone link a thread I couldn't find on this topic?

Cheers



Thanks

[williade Avid PP Poster! Find all posts View Profile Close williade]

The main advantage of 265/75/r16 offroad is the slight increase in ground clearance (12.5mm) and better availability of new tyres in the event of blow out.

You speedo will be out by approximately 3% (eg when your speedo says 100kph, you will actually be going 103kph)

If your question about acceleration, economy and towing performance is asking for real world numbers, I think they will be hard to obtain. Obviously, they will have a negative impact on all of the above, but how much and whether it will really matter to you is hard to say. There are many more variables to consider and the increase in diameter between 265/70/R16 and 265/75/R16 is so small it would be hard to accurately measure the impact on the performance of the car.

[light5light Member Find all posts View Profile Close light5light]

It really depends on many factors to answer your question.

I think the impacts from changing size will be noticeable on not only Petrol but also Diesel.

I used Cooper LT 265/70/16 before, and now KM2 BFG 265/75/16.

The speed is about 5km different now (using GPS to compare).
Slightly feeling that the car is slower when start.
About 5% of fuel is used more also (which reduce about 5% of total kms done/tank).

Towing my caravan ~2T will be a little slower when start, and climb up hills. On flat roads is the same.

[Derb Senior Member Find all posts View Profile Close Derb]

Hi Boss. I don't know that it would be a positive move. Fuel economy would take a hit and you would most likely be out of top gear more often. JMHO. Cheers, Derb.

[Leethal Advanced Member Find all posts View Profile Close Leethal]

Matt, as has been posted already it is hard to get definitive information on running 265/75's.

If you are changing from "OEM" type tyres, that is highway or road type tread patterns in a 265/70 profile to an aggressive All Terrain or Mud Terrain 265/75 in a Light truck construction, then I believe the tyre type and construction are going to have a greater effect on performance and economy than the 70 to75 profile diameter change will have.

MT tyres in Light truck (LT) will increase consumption and decrease performance wether in 70 profile or 75 profile simply due to their increased rolling resistance, that said a MT tyre will give better traction off road and should have suffer fewer failures if travelling the outback etc.

A big advantage of the 75 profile tyre is the greater range of tyres available to choose from, the performance change from a 70 profile to a 75 profile in the same tyre pattern/construction would be minimal I believe.

Lee

[Guest Close Guest]

The rotational inertia of a tyre increases with mass and diameter. This will dull the performance of a car and increase fuel consumption as the engine needs greater effort to spin up a tyre where the weight is now heavier and further away from the rotating axis.

[longdog Member Find all posts View Profile Close longdog]

The speed is about 5km different now (using GPS to compare).
Slightly feeling that the car is slower when start.
About 5% of fuel is used more also (which reduce about 5% of total kms done/tank).

Are you sure? Are you using your odometer or scangauge to calculate your increase in fuel consumption? Don't forget that your odometer is now under-reading by 5% so your fuel consumption may not have changed at all.

[light5light Member Find all posts View Profile Close light5light]

Are you sure? Are you using your odometer or scangauge to calculate your increase in fuel consumption? Don't forget that your odometer is now under-reading by 5% so your fuel consumption may not have changed at all.

Pretty sure. A full main tank (90L) was running about 450km around city, now it is around 420- 425km only. Although circumstances change when you drive, but that should be right.

[reida1991 Member Find all posts View Profile Close reida1991]

Hey guys, thanks for the replies. The tyres I have now are bfg at. I'm looking at going to the Mickey Thompson 4 rib in 265/75. I'm gathering that the tread patterns are generally similar, so I shouldn't see much difference there I think. My main concerns are fuel economy and a drop in performance, however I am planning on going to a dpchip in the future which should solve the issue.

Thanks

[ken2m Junior Member Find all posts View Profile Close ken2m]

The speed is about 5km different now (using GPS to compare).
Slightly feeling that the car is slower when start.
About 5% of fuel is used more also (which reduce about 5% of total kms done/tank).

Another thing to remember when comparing fuel economy is that if you increase the circumference by say 5% you actually travel 5% more than your trip odometer so if you were getting say 15l/100km and you increased fuel consumption to 15.75l/100km you have not lost anything at all, except for acceleration and you may have to change down more often as per other posts. The other thing that may be better is the accuracy of the speedo which on mine is still -3% with 265 75 16.

[MDST Member Find all posts View Profile Close MDST]

I like more 255/85R16 tires. I know they are 33.3" and decrease even more the performance; more than 265/75R16 but, more ground diff clearence = less hit in the rocks.

Glen knows what I mean!

Cheers

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

Well according to my 2 GPS units (took one out of the other car to be sure), going up to a 75 profile, made the speedo spot on. The increase in tyre height is 12mm, so you only get 6mm in extra ground clearance.

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Yep when I changed up a profile on my 90's the speedo was reading 100% to my GPS. Performance wise you will definately notice it especially up hills, and in LOW range as well I noticed it wasnt as good, but very minimal in the low range department. As others have said just going from the standard OE tyre to even a A/T the rolling resistance you will notice. I found in some spots around town where I have been driving the same road for over 10 years where I use to roll extremely easy on the standard grandtrecks with out touching throttle and it would roll over the speed limit. When I had the A/T's fitted in some parts I would have to actually accelerate to stop it slowing as much and i always ran 40psi round town with the A/T's and even the standard grandtrecks........Cheers Steve

[tassie tiger Advanced Member Find all posts View Profile Close tassie tiger]

Hey guys,

I'm after people's experiences who have gone from OEM to 265/75 on a DIESEL prado in terms of economy, acceleration, changes in speedo, towing performance etc.

Thanks

Hi

We went from std to 265/70 (120 series) which is very similar to the change you are thinking (3%). We swapped the std grandtreks to goodyear wranglers. We have an auto and noticed a marked change in all the things you have asked.

Actual economy UP by .5 litre per 100ks.
Notable drop in performance.
Speedo out by 3%.
(Not sure about towing)
The big one for me was that the auto would now change into top earlier and this took the engine out of its power/torque band and you could feel it was 'hunting' a bit.

We fitted a dtronic and it brought it back to what it was before the tyre change.

To sum it up - I noticed the 3% change and if I had my time over I would stick with the std size. I think with auto TD's the computers are setup pretty good from the factory and dicking with them mucks the balance. Manual is not so bad I think.

I think next time I will buy some second hand steel rims with mud tires on them and swap them when going for a play. Bit of work but you can clean under the car properly when you take them off again - (thats looking on the bright side of life)

Cheers

Here is a link to an online calculator;

http://www.inawise.com/tyre-calculat...alculator.html

[williade Avid PP Poster! Find all posts View Profile Close williade]

The increase in tyre height is 12mm, so you only get 6mm in extra ground clearance.

The nominal increase in tyre height will be 26.5mm so the increase in ground clearance will be 13.25mm.