[Boley]

Hi,

Firstly is a 285/75/16 size tyre a 33inch? And, do you experience any performance dips when fitting these size tyres? i read somewhere that if you fit 33's to a turbo'd vehicle its the same as removing the turbo?? (performance wise im talking). Has any one gone bigger like from maybe a 265/17/16 to a 285/75/16 and been dissapointed with performance?

Cheers.

 

[Youngbloke]

Boley,

I run 285/75/R16 Wrangler MT/R on my GU with a 2.8 engine. I haven't noticed any dramatic change in performance for what it's worth, but I also have had the gas injection and exhaust done. Some steep hills start to become a bit quicker on the decline, but these tyre's have just proved themselves each time (mud / snow / slop) so well worth it I reckon.

 

[Deccers]

I have no idea what dimensions my tyres are. But I have a 2000 3lt n went from 21" AT-R's to 33" Bighorns and noticed a pretty big difference with the take off. But getting a 3" zhaust pretty much fixes that issue.

Cheers

Deccers

 

[SpiderM]

I have no idea what dimensions my tyres are. But I have a 2000 3lt n went from 21" AT-R's to 33" Bighorns and noticed a pretty big difference with the take off. But getting a 3" zhaust pretty much fixes that issue.

Cheers

Deccers

I'll bet it was a big difference, with 21's I don't think you would have gone anywhere!

I was told that, for Patrols, rule of thumb is 10% power loss per 1" on radius.
Believe me, turbo with 33's is not like 31's on an N/A.

 

[EagleBay]

Yes 285/75 16 is a 33 but sizes can vary slightly between manufactures.
I had 265/75 16's on and just put on some 285/75 16 MTZs and havent noticed any performance drop, too early to tell if fuel consumption will be affected.

My ZD30 D22 lost a bit of power when going from 31's to 32's and dropped approx 100km per tank

 

[truckster]

On a dyno going from 265 to 285's lost 20kw of sniff and 100nm of torque. Same car, same day.

 

[forbsy88]

i have 33's on my 4.2 turbo ute and have not noticed any power loss at all and still getting same fuel usage as i was with the standard 265/75R16. still goes up steep hills in 5th no probs.

 

[Deccers]

Sorry I meant 31"s haha. That would be driving on golf buggy tyres (which would be quite funny to see). Likewise regarding the fuel economy. Only had them on my truck before I went sideways.

Cheers

 

[dan-0]

Look at my signature. I have noticed about %15 less power and 1Lt per 100kms worse in fuel. BUT the Patrol looks tough.

 

[heyhey]

I noticed it, it is slightly a significant difference in power loss but nothing you can't live with. I live in the hills and I can still pull 110km/h up 300m of steep hill. Not too much difference in fuel as dan-0 said aout 1L/100km different. But my favourite thing on road about the larger tyre diameter is my speedo is spot on km for km.

 

[Brunsy]

100nm of torque? thats more than I would have thought. Truckster was that with a ZD or your TB45?
I never even noticed the difference on my GQ 3.0L but then again it never had much go to begin with.

 

[JohnH]

31" travels 97.4" in one revolution and a 33" travels 103.8" or 6.6% further. You would loose circa 7% power at the wheels.

 

[Morejandal]

I have a 33's on my truck and it goes great. Can't compare as it had 33's when I bought it, but compared to my old GUIV with 32's it feels much the same.

 

[Graham99]

Tyre size

31" travels 97.4" in one revolution and a 33" travels 103.8" or 6.6% further. You would loose circa 7% power at the wheels.

How does that math work?

Yes the wheel travels further, but the circumferential diameter is not the driver. The torque required to turn the wheel at the new radius to apply the same force to the road would be the driver IMHO.

Agree about the loss of power and the speedo being more accurate though.

 

[Brunsy]

7%??? all you have done is quantify the percentage of rolling diameter increase, this is not a direct correlation to torque applied at the wheels.
But I can appreciate what you are trying to work out, those calcs will tell you how much your speedo will go out by.

 

[geordie4x4]

Surely there is also more to the feeling of power loss than just the increase in tyre diameter.
Tread pattern and hense friction will add a bit to the power loss. So too will how you drive the car and how loaded it is i.e. towing a trailer.

I went from standard GU IV, 17" wheels with 275/65x17s (with road orriented AT tread) to Procomp X terrain 285/75x16". they were bigger diameter, much chunkier tread and almost 10kg heavier per wheel. The drop in power was immediatly noticable. The biggest difference was when towing a trailer as it was just on the edge of struggling with the bigger tyres and extra load.



I then fitted a 3" Taipan exhaust, Diesel gas, Rapid chip etc and the difference was not a problem as it now had more power at the wheels than standard with standard tyres.

I have since fitted Mickey T ATZ 285/75x16 which have chunky AT tread but far better rolling resistance than the X terrains, and now it still far better than a standard one on standard tyres.

 

[zoom0001]

100nm of torque? thats more than I would have thought. Truckster was that with a ZD or your TB45?
I never even noticed the difference on my GQ 3.0L but then again it never had much go to begin with.

That would be from a 4.2TD.

Couple of graphs of 265's versus 285's on a GU 4.2TD same day, same vehicle.

 

[EagleBay]

Thats a fairly big drop, did you notice it?

 

[De-Lux]

don't forget the fact that taller tyre will increase the vehicle height, thus increasing the wind resistance

 

[badgu82]

i went from 265/75/16 to 37/12.5/16 its a bit off a difference, mind you its wasnt as bad as say maybe a stock car. mine has roller turbo big pump and big water too air cooler setup. but yeah ya still feel a bit. i also run 4.625 gears and full manuel auto. oh i also run 33,s as daily drivers at times and there pretty good all rounders. there muddys also.