OEM Offset/Backspacing/C'Bore For '04 EXT

[kcb58h]

I can't find these specs for a 04 LS 2wd EXT. The stock alloys were 17s when I swapped them for these 18s. (A/R Marins, no spacers).
Oops. Bad Move.
I want to got to 16s. (285/75/16) Even if I can get custom drilled 6x5, I think I'm gonna need spacers, right?
I am woe to admit I knew nothing about a counterbore spec.
Were the base wheels 16s?
If anyone can help, it would be much appreciated.
The numbers would be great, a site reference even greater.
Happy Trails

[BC backroader]

I believe that the stock rims on the EXT models are 17", due to the larger brake rotors used on them. My stock 05 EXT has 245/65/R17 tires. Another owner recently posted that he was able to fit 265/70/17 on his, which should be close to the same overall dia. as what you have on now. Check the tire size calculator at the top of this forum.

[kcb58h]

Thanks. Someone else just told me the same thing about 16s. I've been reading about SWB guys swapping their rotors out for EXTs for sometime now.. I shoulda remembered. The Contis I took off were 245/65/17 as well. Remember- these 265/65/18 (31.6) fit with no rubbing issues with just a 2" level kit..
With 3"LM and 87s I'm thinking I can go 285/70/17 (32.8") on 17x8.5 5.38"BS 12mmOS and 1.50" spacer/adapters. (That adds up to that ridiculous 50mmOS).
And I think that's pushin' it without a body lift. (+1.2"dia./+.75"w)
Have you seen this one?
http://www.willtheyfit.com/
Happy Trails

[BC backroader]

That's a nice comparison chart in your link, but the critical point in our suspension is the location of the upper ball joint, which is why we need spacers, or the unobtainium wheels with less backspace and the right bolt pattern for our oddball 6x127, when we go wider/taller with the tires. I'd really like to go to 31.5" tires, but to keep the trans. happy, given my wimpy 3.42 gearing, I'll only go up to 30.5" and save the cost of new wheels and/or spacers, as well.

[kcb58h]

That UBJ observation is absolutely onthemoney. It would seem the GM engineers got together and asked, "How can we make this thing as difficult to modify as possible!" I mean 6x5? Really?
BCb - Are you restricting your max.tire dia. strictly on your 3.43 gears? From what I've gathered, 3.43 gear guys are concerned about premature tranny wear if they go with 31.5+ tires. But I've never read "Got my 33s and the tranny went south in six months". (BTW - There's nothin' wrong with the South.)
5 years & 30k miles on my 31.6s and 3.43s and have noticed a shift hiccup occasionally. (Once a month, maybe when I'm driving aggressively). My experience may not apply, however - 2wd.
I think it would be a mistake to limit your tire size singularly based on gear sizes.
I would like to know what more seasoned ORTB members have to think.
Happy Trails.

[BC backroader]

kcb58h, there are a number of considerations in my choice, as this truck is my dd/family vehicle, so cost, reliability, and accessability for my mobility challenged wife (very bad back) all enter into it. She's the reason that the TB still has running boards, which are a PITA in the bush. The 2.5" lift/level gave me the extra clearance I needed for 95% of the logging roads and trails I run, so I don't need a whole lot more from the tires, other than better gravel/mud traction.

There are definitely more seasoned members here with experience on our trucks, that's why I'm here too, though I've probably been 4x4ing longer than most of them have been alive.

[navigator]

Kc, many of us have a scangauge (or torque pro) to monitor tranny temps. Before my tranny cooler running 32s and 3.42 gears I would see temps approaching 220 on flat highway in the summer. Even with the cooler, towing my bass boat in OD or beach driving in 4-hi it would again run close to 220. On the beach it ran a bit cooler in 4-low but was still closer to 210. Hi temps is a killer of transmissions. I don't think 220 is that bad but I would prefer them closer to 200. If you did a poll among lifted guys, I think several have had tranny issues. Now with 33s, 4.10s and a cooler I am running 190-195 most of the time.

Where you live and what you do and I expect each truck is a little different . I think it is important though to know what your tranny temp is. It running cooler might allow you to get 300k miles vs 175k miles.

[kcb58h]

Chris-that's hard data I can use. Thanks for taking the time to post it. Just when I resolve one issue it seems 2 more arise. I'm ok with swapping out my 3.42s for something smaller when I put on 33s, but I didn't think all the way to 4.10. Towing, as you mentioned, is also a critical factor. So much to consider....
Happy Trails

[navigator]

If you are going through the trouble to gear swap for 33s, go with 4.10. I would prefer 4.56.

[navigator]

Sorry, forgot you are 2wd. Not as big of a deal to swap just the rear.
Unless someone practically gave me the 3.73 or the 4.10 was a huge difference in cost, I would still go with the 4.10s.

[kcb58h]

Gracias, nav. It would have been easy not to follow up on that. It really is hard to take every variable into account. I can't decide if it's more like a algebraic expression or a chemical formula. Leave one factor out and the rest of the "equation" is moot. I'll research a part decision for months thinking it's how I want to go, and in the 11th hour stumble across a post telling me why it ruined this guy's ride! And that's a post 4 YEARS old!
I'm still having doubts 2857017s (32.8) will fit w/o body lift or radflos. Currently with 2656518s (31.6) my 87s and 3"LM (3.76"x1.47)=5.5" lift @ wheel in front. RC .75" spring isolator, orig. '83 spring and 2" LM in rear makes 2.75" in back. No winch. No custom bumper.These same 31.6s have been trouble free with a 2"RC for the last 5 years. A 1.2" increase in diameter sounds tiny until you roll those tires side by side. And I'm not scalping my bumper.
Still scanning build threads for ideas hoping no one left anything off....
Happy Trails

[navigator]

I think Trailx (James) and Ncislandrunner(Rory) are both running 33's with no body lift. Look up their build threads.

[navigator]

A lot of time the extra width has as big of an impact on rubbing as the height. Changing your backspacing/offset is also a big influence. I think James and Rory are both running stock wheels.

[v7guy]

I run 33s on my envoy with some basic fender trimming... the envoys require a bit more than the trailblazer due to their smaller wheel well opening, 32s are the limit in my experience before you have to start cutting front fender sheetmetal. If you do cut the front fender some self adhesive fender trim from your favorite auto parts store does a nice job of not making it look like shit. You'll also need to trim up some of the fender liner, but again, really not a big deal.

As Chris said, if swapping gears and looking at 33s I would just go to 4.56s. The highway manners are perfectly reasonable. My envoy has 4.10 gears with 33s and I easily pulled 5000lbs through the mountains of CT with no issues other than the obvious of it taking a bit to speed up and slow down. 4.56s would have raised the RPM a couple hundred, but nothing significant and it would give a lil extra grunt for acceleration. Of course these comments are from driving an envoy with 33s and 4.56s... I'm not just guessing.

[kcb58h]

To Fellow ORTB Friends -

Thank you all for the lively discussion. I should have never wasted site space with my initial post.
I just saw TrailX's explanation of the BS/OS of the TB wheel in the "Wheels and Tires" forum.
The forum I visit the most.
How totally f***n embarrassing.
Can I petition the Moderator to delete my post?;)
The kicker is, I remember reading T-X's post backinthday!
This is just another reminder for me to READ, READ, READ before thinking a post will do the trick.
Thanks also for the references of members with similar (33s, no BL) builds. I have also found builds that spec BS/OS of their aftermarket wheels. Good baseline numbers if you can get feedback on performance.
Happy Trails