Disadvantages of Sports w/ Rubi 33's

[Deleted member 29479]

Brand new/addicted to the Wrangler community since January. I bought a Granite Sport S JLU and have been all over these boards since then trying to decide on what size tires to bump up to.

She's my daily driver but will see mild off-road use on nearly all of my off days. Mainly forest roads and farmland - only a few weeks with snow, but mud year round.

Can anyone tell me any serious drawbacks (short & long-term) of running the Rubicon wheels & 285/70r17 KO2's on the stock Sport? Thanks in advance!

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[Pig-Pen]

I have the exact same jeep as you and its on stock rubi wheels/tires. I took it on a trail on those wheels at stock height and then put stock rubi suspension on it and took it out some more.
No issues either way.

I can feel it slightly more sluggish and a little higher to get into the jeep but thats it

 

[Htfan]

I have the exact same jeep as you and its on stock rubi wheels/tires. I took it on a trail on those wheels at stock height and then put stock rubi suspension on it and took it out some more.
No issues either way.

I can feel it slightly more sluggish and a little higher to get into the jeep but thats it

Are you running the 8sp transmission? Some have said the transmission does not use 8th gear as much at high speed with larger tires. Also wondering if this is resolved with tire diameter update in JLU computer ...

 

[Strommen95]

Are you running the 8sp transmission? Some have said the transmission does not use 8th gear as much at high speed with larger tires. Also wondering if this is resolved with tire diameter update in JLU computer ...

I hit 8th all the time with 33s. Calibrating the tire size will do nothing for the transmission and shift points.

 

[blnewt]

OP, you'll be fine w/ that setup!

 

[Arrowhead]

I hit 8th all the time with 33s. Calibrating the tire size will do nothing for the transmission and shift points.

Have to strongly disagree with that. I've done the same swap and calibrating with a Tazer made a big difference.

 

[Strommen95]

Have to strongly disagree with that. I've done the same swap and calibrating with a Tazer made a big difference.

Placebo effect.

 

[Arrowhead]

Placebo effect.

Bullshit

 

[Strommen95]

Calibrating the tire size will do nothing for the transmission and shift points.

I've done the same swap and calibrating with a Tazer made a big difference.

Bullshit

That's the good thing about facts. It doesn't really matter if you agree or not. It's still true.

 

[Toniagp]

Brand new/addicted to the Wrangler community since January. I bought a Granite Sport S JLU and have been all over these boards since then trying to decide on what size tires to bump up to.

She's my daily driver but will see mild off-road use on nearly all of my off days. Mainly forest roads and farmland - only a few weeks with snow, but mud year round.

Can anyone tell me any serious drawbacks (short & long-term) of running the Rubicon wheels & 285/70r17 KO2's on the stock Sport? Thanks in advance!

I could tell no difference when I installed Rubicon wheels and tires on our JLUS(did not recalibrate anything) it ran and drove great!(3.6 Auto). Now running 35" Milestar Patagonia's on stock Rubicon wheels(it is now recalibrated) and do not see 8th gear as much but still do, and you would be hard pressed to tell the difference in normal driving.

 

[Arrowhead]

That's the good thing about facts. It doesn't really matter if you agree or not. It's still true.

So what has been your experience to say correcting the calibration for tire size has no effect on shifting? Do you think it should even be recalibrated for say 37's...40's? How about gear changes?

 

[rcpeters]

Good: Once recalibrated works great.

Bad: Dealer will use it as an excuse not to work on the Jeep if something comes up(unless you re-calibrate through the dealer)

 

[Strommen95]

So what has been your experience to say correcting the calibration for tire size has no effect on shifting? Do you think it should even be recalibrated for say 37's...40's? How about gear changes?

The transmission and the gears mated to it are what will effect shift points. Not what's calibrated for the speedometer. 3.45 is appropiate for 31-33 inch tires, 4.10s for 33-35s, 4.56s for 35-37s, etc. Regearing from stock gears needs to be calibrated for the transmission but tire size does not. Do I think you should calibrate for 37s on stock gearing?.. Yes but that's because the speedometer would be way off. If you have 37s calibrated but have stock 31.5 tires on the transmission is not going to be "confused". It's going to react to the tires physically on the Jeep. Good luck hitting 6th or 7th on stock gears with 37s just because you calibrated for it. Similarly a Sport with 33s will shift like a Sport with 33s regardless if 31.5 is what's calibrated or not.

Take a minute with the Tazer and switch to 245-75-17 again. Drive as you normally do. There won't be a difference. The transmission and gears with it react to the load it's dealing with. The only thing that will positively affect shift points when putting on extra weight(tires, bumpers, etc) would be higher gears and calibrating for those higher gears. Not tire calibration.

 

[Arrowhead]

The only thing that will positively affect shift points when putting on extra weight(tires, bumpers, etc) would be higher gears and calibrating for those higher gears. Not tire calibration.

Hey I don't want to get into a pissing contest, you seem like a reasonable person and all. But I really think you are missing the forest for the trees. The tire size ultimately effects your final gear ratio. Larger tires is just like hooking up a heavy trailer, it's additional load on the engine. Recalibating the ECM for tire size doesn't just correct the speedometer, it allows the ECM to apply more efficient shift points. It's just like the Tow / Haul mode in a lot of pickup trucks. You haven't changed anything on the drivetrain, but you're telling the computer you have a heavy load - so it adjusts the shift points accordingly. In the end, it doesn't matter whether you change tire size or gear ratio in the Tazer as long as the combination provides the correct final drive ratio it will allow the transmission to shift at the most efficient shift points. And BTW I agree, 8th gear will become less useful with larger tires (gearing remaining constant), but you've effectively lowered your final drive ratio so 7th might be a similar ratio as to what 8th was before.

 

[Strommen95]

Hey I don't want to get into a pissing contest, you seem like a reasonable person and all. But I really think you are missing the forest for the trees. The tire size ultimately effects your final gear ratio. Larger tires is just like hooking up a heavy trailer, it's additional load on the engine. Recalibating the ECM for tire size doesn't just correct the speedometer, it allows the ECM to apply more efficient shift points. It's just like the Tow / Haul mode in a lot of pickup trucks. You haven't changed anything on the drivetrain, but you're telling the computer you have a heavy load - so it adjusts the shift points accordingly. In the end, it doesn't matter whether you change tire size or gear ratio in the Tazer as long as the combination provides the correct final drive ratio it will allow the transmission to shift at the most efficient shift points. And BTW I agree, 8th gear will become less useful with larger tires (gearing remaining constant), but you've effectively lowered your final drive ratio so 7th might be a similar ratio as to what 8th was before.

We’ll agree to disagree. It’s not a pissing contest, this is a discussion forum and I appreciate the discussion.

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