Wayne Ellison

I am in process of buying a 2018 GC and want to run 32" tires if they fit W/O a lift. But that is not my question. I don't want to have a larger spare than will fit in the spare wheel well! When I run the smaller OEM spare (7.8% smaller in diameter) will the computer apply the brake to that wheel and if so, can I disable the entire ABS system for the short period I have the spare installed? Nobody at several JEEP dealers can supply the answer.

rgr4475

Don't know how the 2018 brake system works but can't you just pull the fuse for ABS?

Wayne Ellison

I agree, pulling the fuse or removing the power to the ABS controller should work, even if it somehow generated an error code to the ECU. I could reset the ECU, when the "real tire" is re-installed. I see so many GC with big tires, with the spare on the roof or on a tire external tire carrier, I thought there must be more to this than meets the eye? I understand having a "big" spare if one were to get a flat way out in the rough country, but my GC will never see much more than rough dirt roads.

Bugout4x4

Man... Once again... Another case of automotive engineers not caring at all about the fruits of their labor and how it is going to affect the customers by creating hardships. Looks like in their mind you are just supposed to just call a tow truck and not even carry a spare or be able to help your own self.

dave1123

Car manufacturers are only required to supply a spare tire by the NTSB. Size is not specified as long as it allows the vehicle to be driven. Most are molded with "50 miles at 50 mph max" on them. Just enough to get you off the highway.

I have a tire that was replaced on a road hazard warranty, so I kept it during the last new set. I wanted a full size spare. I got out my spare and found the rim is a 17X4.5 while my road wheels are 16X7. Now I need a full size rim as well! The spare is only about 1.5" shorter than my road tires. IDK what the tire is, but it's got to be a 50 or 60 series.

andrewmp6

Dave a lot of new cars are sold with out a spare anymore,They give you a can of basicly fit a flat and a air compressor.And its all brands doing this now from gm to hyundai,What i find odd most cars have the spare tire well but nothing in it lol.

5-Speed

Both my newer cars have spare tires. One is a 2015 and the other is a 2017. Both spares are the same diameter as stock but only 5" wide. The only time I have seen a car not come with a spare is when it comes from the factory with "run flat" tires.

My concern to the OPs original question is if he runs 2 different size tires, it might hurt the diff. Does it have a limited slip in it? Is it an open diff? Something completely different?

dave1123

It's my understanding the diffs are open, but the traction control uses ABS sensors to check for wheelspin and apply the brakes on that wheel to shift power to the other one. That must be a real PITA for stoplight drags!

I think this is a cheaper way than using electric control on the diffs.

Jon Walter

You dont want ABS. You stop in a shorter distance w/o ABS.

I have wired up an ABS on/off switch in cars but they were all pre 2000.

I am not sure if the Diablo tuner turns off Traction Control in the WK2.

Days of brake controlled 4 wheel drifts are gone. A controlled 4 wheel drift was my preferred way to negotiate on/off ramps in the snow.

dave1123

YES! I want complete control of the car, not have the car make decisions FOR me! The Feds think we're stupid. Well, some people are.

I drove my 67 SS Camaro in the winter and some people told me I was crazy and I was going to kill myself. Not if you know how to drive it. Muncie 4-speed, 4.10 Posi rear, and big honking Firestone Town&Country snows.

omegaman1986

hey there, I have the same question on my end. Driving a 2005 jeep grand Cherokee WK and just put 32s on it. It's got the Quadra trac II system. Here is a quote I found on Wikipedia:

"When it senses a left-to-right speed differences between wheel hubs BTCS can apply each of the vehicle's brakes independently, similar to anti-lock brakes, enabling Quadra-Trac II's open front and rear differentials to offer limited-slip capabilities."

this confirms open diffs

"There is also an electronically controlled variable lockup clutch pack that can apply progressive 0 to 100% locking across the center differential."

seems like the transfer case can lock power to front / rear but I'm not sure if this feature could damage the transfer case running one smaller tire. Any transfer case guru's out there know if running one smaller tire would damage the NV245 transfer case?

i am wondering still if turning off traction control would disable the BTCS. I would think it would.

https://en.m.wikipedia.org/wiki/Jeep...-drive_systems