Lift and Tyres of your JK

[Nanook]

Originally Posted by hailey

Ok so im a complete noob here so feel free to have a giggle...

If i install a kit myself is it possible to get an engineering cert. Or do they have to do it themselves to certify it?

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You can do it yourself without certification in NSW if you don't go higher than 2".

[John Bernard]

MY08 Rescue green CRD Unlimited here. Ordered with the rear diff lock and front electronic disconnects. I'm only into mild off roading but now approaching my third set of tires at 160,000k. First were the 255/75R17 Wrangler silent armour and was pretty happy with them as a genuine 32" tire. Replacement time a few years back at about 75k, there were none in the country and I was steered towards 265/70R17 Khumo Road Venture that barely made 30" on the rims. Well its that time again and I'd like to go with a 33" tire but not a mud terrain. Was all set to order some Cooper ST Max in 255/80R17 but of course..." none in the country". Would have seemed an easy fix. Now I'd like to try the Toyo Open Country A/T but the size I'm looking at is 285/70R17. These tires will be on stock 7.5" rims. With limited off road use and the disconnects not being utilised, would this set up work. The tires come out at 11" wide on the wheel. This car is mainly a commuter these days with dirt roads and reasonably good tracks being the norm. Would I need to increase the bump stop length or not necessary unless I choose to use the disconnects?. The maths put it at 1" wider than what I'm running now and at 32.8" in diameter, about .8" larger than the stock tires the Jeep came with.
with thanks .. J.B.

[chris0375]

It's a bit hit and miss because it is very close. Some people will experience no rubbing. Others will. Depends on actual size of tyre versus published size. Depends how centred your axles are.

Get the tyres fitted. Flex it up a bit and then be prepared to fit bumps stop if required.

I do ask why you are going for a relatively large tyre when your usage would suggest you could get away with something smaller?

[John Bernard]

Originally Posted by chris0375

I do ask why you are going for a relatively large tyre when your usage would suggest you could get away with something smaller?

.. Fair enough question. I missed the ride quality ..and the height of the 32" standard Goodyear Wranglers. The ride became much more choppy on the 265/70's even though the salesman 'insisted' they were the same diameter as what I had originally. I gave up in the end and regretted it since. I know the gearing and torque can handle the 33" without issue and I originally wanted to source a 33" tire with either a 75 or 80 profile and around 265/275 but it appears there is no such animal in the 17" in an A/T. There appeared only the 33" BFG in the m/t and that really wasn't an option. The Cooper 255/80 seemed the ideal answer but once again...'no stock'. Hence my question about going wider to get height. I guess its a case of diminishing returns. Fuel economy in the 265/70s is not as good as the 32" Goodyears either. The Silent Armour looks like the safe fall back at this stage.. at least its the 'devil I know'.. but I'll always wonder how much better..or different the larger tire would have been.
.. thanks for your feedback

[bretto88]

Hi John, if you're after a 32-33" in AT bigger than a 265/70 there is a 275/70r17 a/t by Mastercraft.

I've just had them put on 6 months ago and they've done well on road, tracks and dunes. I selected this size instead of true 33" due to 3.21gearing and petrol torque, but with a CRD that's not an issue for you.


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[Paul-JK]

Originally Posted by John Bernard

The ride became much more choppy on the 265/70's even though the salesman 'insisted' they were the same diameter as what I had originally. I gave up in the end and regretted it since.

Check the load rating of the tyres. The choppy ride may be more to do with that than size. The OE Wranglers are passenger construction tyres which will give a softer ride. Not sure what your Chum's were but if they are LT construction they have stronger stiffer carcasses. Also many tyres in that size are E load rated so they are even stiffer again. With the stiffer carcass & higher load rating you'll need to run the tyres at much lower pressure to get the smooth(er) ride back as the JK doesn't weigh that much. I've had LT285/70/17 D rated tyres on mine and there is a significant difference in ride between the 32 psi I run them at and the 40psi that the tyre places like to inflate them to. There have been comments from tyre manufacturers that LT265/70/17s that are E rated could be run at 26-28 psi on road to reduce the choppiness of the ride (that was on a 4dr CRD JK).

[John Bernard]

More good information and thanks Paul. Every size I'm keen to try seems to be an LT construction anyway..but once again some are obviously stiffer than others. The Goodyears were fine on the road and respectable on gravel and rocks but hopeless in soft stuff for obvious reasons. While there are some tires geared towards 90+ % on road, I think they give up too much for that 'every now and then' foray into soft ground and rocks. BFG and Cooper both list a 275/70R17 in their a/t tires.. and Mastercraft also. Its not a 33" but it would be a lot closer , than what I've been running the last three years. Had heard good things about Toyo and the tread pattern looked impressive but once again the size options appear to be 265/70R17 or 285/70R17. I didn't want 'pizza cutters' but I'm not after the 'over endowed' look either and I'm guessing handling would suffer to a degree also. More homework needed I guess..