285/70/17 or 285/75/17

what suspension you running?

 

I have 285/70/17 KO2's with a BMC and a very tiny bit of bumper cutting. Wish i went with 285/75 as I think mine looks slightly small. Also wish i had more offset.

 

"More" offset, or "less" offset?

Have you done a BMC, and are you prepared to bash your firewall in? Are you regeared?

 

you high?

 

Great question!

No.

I asked because negative offset (negative means less) pushes the wheels out. Or, did you actually want to pull them in?

The rest of the questions were just simple questions.

Edit: nevermind, I see you have a BMC.

Are you ready to do the cutting and other work necessary to clear ~34" tires?

Are you regeared? Or, are you prepared for your acceleration and fuel economy to suck (even worse)?

I'm asking because I have 295's and they don't clear the firewall 100%. And, although I don't have any issues, I could imagine some folks being unhappy with the performance without a regear.

On another note, good choice on the epic sidewinder!

 

Looks like on the other post he did do a BMC and cutting.

The regearing at 75 I can see an argument to go either way.

 

Ahh, I missed it about the BMC. Thank you!

 

Anyone who says they want more offset means they want more negative offset. Otherwise they would say they want more positive offset. You know this. you're just looking for reasons to post something.

Again you're just looking for reasons to post something because you didn't initially read what i posted.

already cut my body mount and my and my bumper to fit tires. also cut my bumper to fit the lopro.

I'll re-gear if i need to.

This is where you got me. I have no idea what you mean by firewall. When i think firewall i think the metal between occupants and the engine. Don't know. If i need to re-gear I'll re-gear. If i need to relocate the body mount I'll do that.

I think we're getting pretty far off topic from OP's post here. Just wanted to throw out there i think he should go with 285/75's. Looks better.

 

With all that lift, might as well go 35s

 

I ran 285/70/17 tires without removing the mud flaps or BMC. If you’re having to do all that, something is terribly wrong.

 

I don't think it's really off topic, because you're saying you wish you'd gone with 285/75's instead of 285/70's.

My point, even if I took a shitty route to get there (I'll admit it), is that it seems like anything above 285/70/17 requires a lot of extra work.

So, I would say that to anyone considering that jump.

Yes, you can get by without a regear. But, for example, I have to drive in S4 almost all of the time on 295's, unless I want the transmission to downshift nonstop.

Also, the tires rub on the firewall (fender wall? Maybe I'm using the wrong term) occasionally, usually while I'm having fun. This would be even worse with 285/75/17's. I don't think my 285/70/17's ever hit the firewall.

And, I could have been more direct about the offset question. But, the fact is that any negative offset is going to make the rubbing problems even worse.

This is what I'm saying. I'm pretty sure 285/70/17's can be cleared without much work. But, it's a tight fit.

Do you have the OEM mudflaps? Did you have to trim or adjust them?

 

Yes, OEM flaps. Just had the front fender nip and tuck. I think people are over complicating this, or they’ve got the wrong crew setting it up. This was when I had the 3/2 lift. I have since removed the lift and went back to 265’s.

 

So your panhard bar should be parallel to the axle. If it is angled, it needs to be corrected. I've seen it recommended at 2.5" of lift or more. I'm sure it varies per vehicle some, like everything else

 

I see a lot of people saying they didn't need to cut anything going to 285's. And then I look at pictures and it's pretty clear it will rub if it articulates while turning. After I put 285/70's on, with the steering wheel locked I rubbed on the front bumper and the mud flaps just a little with no articulation.

I didn't want to do any fender or bumper cutting so I went the other direction and did a BMC. Turned out I still needed to take a quarter inch or so off the bumper for no rub with full articulation.

 

I elected to not go with the upgraded panhard rod from Ironman at 2" lift. OEM one so far has been ok for me.

 

does your spare fit? I went 285/70 because I was afraid about the spare tire. I like the look of your tires way more than mine.

 

I don't see anyone really hitting the issue with the panhard bar here. The stock bar is a fixed length mounted to the frameand the axle and keeps the axle from moving sideways in either direction, or to say it in another way, keeps the axle centered.

When you put bigger tires on you also typically lift the car by replacing suspension. When you do that you push the axle down and further away from the frame. Taking a step back, when stock, the bar is flat, or horizontal. Again, because this bar is a fixed length it means that when your rear suspension articulates, the bar will move up and down depending on which side is going up and down. When it does this it will move the axle away from center; to the left or right. This is the problem.

If you use a stock panhard bar on a lifted vehicle you get the same effect on the panhard bar as you would if the driver side rear tire were to articulate down. The panhard bar connects on that side of the axle and will drop down to that side (lower on driver side and higher on passenger side) and will no longer be horizontal. What this means to all of us is the the axle will be pulled to the right of the vehicle and off center. Truck might not drive straight and tires might wear funny. And another thing happens...

So now you have an axle pushed to the right. Well what happens when the driver side tire articulates upward? Because again the bar is dictating right to left axle position and is fixed length, as the tire goes upwards the axle will be pushed towards center until the bar becomes horizontal. Then once past horizontal, the bar will angle upwards. When this happens, it will stop pushing the axle to the left and then pull it back towards the right. The worst case scenario on these is you hit little bumps on the road which pushes and pulls the axle back and forth, the suspension effectively fighting itself. This makes the rear end feel more stiff and will not articulate as smoothly.

I welded on the panhard bar correction kit (PCK) which allows a higher mounting point on the axle and brings the bar back to horizontal to avoid the right left fighting movements. Still, based on the mounting holes, my panhard bar is not perfectly horizontal, but pretty close, so I got the Ironman 4x4 adjustable bar, along with adjustable trailing arms, so the alignment shop could get the rear axle aligned best. But if the correction kit allows you to have a horizontal bar, then the stock bar should work perfectly. The kit i got allows correction for a 2 and 3" lift.

I felt a world of difference having the rear axle not aligned correctly and the panhard bar not close to horizontal. It bugged the crap out of me every time I drove until i got it fixed.

 

I still have a 285/70/17 as spare from my previous tire set up which is mounted underneath the trunk in the spare location. I haven’t tried to fit a 285/75/17 underneath yet so I am not sure if it will fit. If I get a flat, I will use the 70 temporarily until I get the 75 repaired or a new one mounted.

 

Thanks for explaining this so clearly, especially about the part where the suspension fights itself. I have a 1.5 in lift and didnt think it was necessary, although I recall it’s not parallel to the ground. If I ever get the correction bracket, now I’ll know why !

 

Keep in mind that running different size tires in 4wd will cause binding. I’m not sure it’s even a good idea to run them on the rear axle together while in 2wd. Putting the smaller tire in the front will give you the best chance at not breaking something.

 

you could always get an adjustable bar so an alignment can center the rear axle but it's probably not too far off. I mean...how many degrees off horizontal is it? and then i forget the math that would give us the change in distance per the length of the stock panhard bar. Can't be much.

 

An adjustable length panhard could center the axle, but it wouldn’t deal with the suspension fighting itself once it passes horizontal, correct?

 

correct - but a proper alignment would make it drive straight and not have the tires wear funny......which may or may not even be a problem in the first place.

 

Would rear axle misalignment show up under steer ahead and/or thrust angles? I recall mine came out pretty good post-lift.

 

I really don't know. When I did my lift I tried to match my adjustable rear control arms to about the stock ones and same with the panhard bar. My car didn't go straight and the rear end was a bit rough like i was saying before. The not going straight part could have been everything. First shop I went to miscommunication with me big time, 4wheel parts, and didn't align the rear at all. Nothing. So my rear tires ended up getting feathered slightly in 6k miles. But again that could be a combination of a the adjustable trailing arms being the incorrect length as well at the panhard bar.

 

Yes, I know. It would only be a temporary solution until a replacement or repair is done to the damaged tire. I really don’t want a spare tire carrier in the back so my other option will probably be mounting a 75 on the roof rack if it doesn’t fit underneath.

 

I've considered the roof rack option with mine. I just don't know how fun it's going to be heaving 90# on the roof.

Another, less popular option is to keep it in the cargo area. Of course, it eats up a fair amount of space. But, I've been making it work.

 

Yes taking down the heavy ass wheel and tire from the roof and possible more bad MPGs from wind drag while mounted on the roof surely will suck. I might eventually go with a swing out tire carrier but that would eliminate the rig from being able to fit in my garage. I don’t see myself keeping the spare inside my rig as an option. I love my trunk space.

EDIT: I guess mounting a spare on my roof rack would still eliminate it from parking inside my garage. I’d probably just use the spare 70 on the front and swap the bigger tire to rear temporarily if needed.

 

OK so. Bear with me. I didn't get the best look because it's wet outside and didn't want to kneel in the rain but...regarding the spare tire. Looks like there's a lot of space on both the sides. It lacks space in front and rear.

Front side (above panhard bar) has a bracket thing that looks like you could easily cut some off and maybe weld a piece of metal on.

When it's dry I need to measure it. Looks like it would get real close to the panhard bar but 285/75's look doable to fit in the spare area with some cutting.

 

The shop i use said they could make it fit by doing what your saying.