1984 m1028 fender trimming and tires?

i have an 84 m1028 and its currently sitting on 285/75r16's. i'm looking to get bigger tires and don't mind fender trimming, but i don't know just how big of a tire you can fit on a stock m1028 with fender trimming only, or any other cheap/ free mods i can do to accomplish fitting tires 35in or taller basically the bigger the better,im trying to avoid adding any lift to it. i don't mind skinny tires or wide tires, i would almost prefer wider tires like 15.50. just how big can i go with fender trimming only? what backspacing of wheels work best, when do i need anything different than the stock wheels? any help would be appreciated, i have looked but cant seem to find exactly what i'm looking for regarding this, thanks for any replys. sorry if im

Next time try to post in the correct forum, and use capitalization(these are the rules).

If you scroll down this page, you can see some similar threads that may help.

A search for "fender trimming 35" in the cucv forum may help.

Alright, sorry about not capitalizing and posting in the wrong place. I thought it would be fine where I posted it but my mistake. Any other suggestions for fitting 35s AND larger with no lift and some fender trimming or modifications are still appreciated.

Also if anyone has pictures of doing this and pictures of their trim job with the big tires that would be helpful as well.

Good to see all the support on this so far.

Does anyone have any ideas on how to add speakers and subwoofer and radio in a m1028? With there being little space to work with I am kind of stumped on what to do to make a subwoofer fit somewhere. I already have some so i figure i should try to get use out of them instead of just letting them sit. I toyed with the idea of switching to bucket seats to make room in the middle of the cab but do not know if there is another solution i just havent thought of yet. Are there stock seats that would be a direct bolt in, in place of the stock bench seat? Thanks.

Sarcasm, yeah that will help get results. You may be limited in the responses because many folks aren't really looking to saw up their truck. With that said, I have seen a 70's suburban with 40" tires and no lift. Have you clicked on any of the links at the bottom of the page?

There are spots for 4 speakers built into the truck but nothing for a subwoofer. Buckets may be the only way unless some crafty person makes a tapered sub box to fit behind the seats on the ledge.

Sorry, I'm not trying to be sarcastic. I appreciate any input so far. I have tryed to click on the links at the bottom already. I have not seen any posts about what I am describing so far. I do not post on forums very often because I do not usually get a response or not a very friendly response, maybe I just do not know how to word things properly on here but I am trying to be polite as possible. Sorry if I offend anyone that is not my intention. :/

No worries. I assure you that you can run 37" tires with just trimming. Fit and trim, fit and trim until clearance is gained. The sub is all you, I don't run sound systems in my trucks.

Ok, any advice on the wheel to use such as what backspacing. Is the stock backspacing ideal and if so what is the stock wheel specs. I think they're 16 tall by 6.5 wide do not know the back spacing for sure though. If I was to change to a stock 16.5 from a different truck to have different tire options, should any stock wheel work so long as it is the 8 lug chevy pattern? Thanks.

Try searching www.Fourwheeler.com and www.4wheeloffroad.com online sites for there articles on military pickups. They have both done articles on them.

Also keep in mind that the CUCV's are civilian Chevrolet full size pickups with modifications for the military. Most of the tire/wheel combination info for 1973-1988 full size pickups there will apply to your CUCV. The off road mags are an excellant source of info if you're planning to do it in the dirt or mud. They will have more info about sound systems to.

I hacked my fenders to fit 37's on Ford steel wheels with no lift. The tires rubbed the firewall area during turning. I replaced the front springs(stock), HD shacles, & bushings. Raised front 2-1/2" and no more rubbing.

Alright thanks, maybe I will have to stick with something smaller than a 37 then if i don't want to buy new springs or anything then.

If you stay with an 11 inch wide tire or less with an 8 or 9 inch rim that has either 4 or 4.5 inches of back spacing you can put 37's on without trimming (may have to trim the inside lip of the fender but not the outside. When you go wider or have less back spacing, that is when your tires will rub. The wheel wells are fairly large on the truck but the cut outs or small. An 11 inch wide tire will stuff inside the fender a 12 + wide tire will not.

My recommendation would be to do an ORD zero rate giving one inch of lift and moving the front axle forward 1/2 to 1 inch and it will eliminate the firewall rub and allow you to only trim the front of the front fender if any trimming is needed.

when you add the zero rates you can flip your u-bolt's.

kiss the 15.5 inch wide tires good by, they have to be really small with a lot of lift to clear fenders. The weight of these trucks do not require a tire that wide. A taller skinny tire will serve you better.

good luck

One problem I'm having is finding a tall skinny tire. The only thing I found I might be able to order is a 9.00-16 ( I think Sigma) Power King Premium Traction tire but I'm not sure yet if the local dealer can get them or not.

The stock backspacing on stock rims is intended to align the wheel's center-axis to the center of the bearings in the spindle/axle. If you change your tire/rim size, you would want to keep the same off-set as using an incorrect offset will add a cantilever force to the spindle/axle, which will eat up your bearings faster (normal life is around 10 years or so depending on usage, bad offset could reduce that to 2 years or less).

The offset thing is one of the reason most tire places don't want the liability related to wheel spacers any more (some people put on "what fits", without checking if it's "right").

Recall on your trimming though that the cab floor is one limit point, so move the wheels both ways, and at maximum suspension extension and compression (include some fudge factor) - lest you have rubbing on a hard turn when you hit a bump at speed.

Ok I'll jump in here and add a few comments. Gotta pay attention and make sure I capitalize correctly.

I suggest you re-think adding larger tires with just fender trimming alone. While that may look cool cruising through Sonic on Saturday evening, it will get you in trouble when you get into some serious off road situations. As long as you stay on flat pavement, fender trimming will accommodate the larger tires. However the first time you are off road and need to cross a ditch at an angle, those trimmed fenders will cut your nice big tires to pieces. I learned this lesson the hard way back in 1972. You see, when you traverse uneven ground, ARTICULATION is required of the truck's suspension in order to maintain ground contact by all four tires. Using the aforementioned ditch example, when one wheel dips down into the ditch and the wheel on the other end of the same axle does not, the frame flexes and drives the higher wheel still higher into the fender opening. Unless you have completely removed your fenders, they will indeed be forced into the higher tire by ARTICULATION and those sharp edges left by trimming will make short work of the tire. If this were to happen at Sonic it would be easy to change the tire and get home safely. But if it were to happen 37 miles from civilization in SW Wyoming while trying to extract a nice buck, only to find out your spare was flat, and it was -10 degrees and snowing, and cell phones had not been invented yet, well, you get the idea what deep dodo you would be in.

I recommend that you consider a mild lift kit, simple fender trimming, and moderately-sized tires while keeping ARTICULATION in mind at all times. This has been done and discussed on this forum more times that you can imagine. And as long as you refrain from being sarcastic, and remember to always use proper capitalization, these folks on SS will help you out.

Hope this helps.

Thanks for the replies. I know articulation is a big factor, I just wanted to keep cost down by not doing a lift, the truck sits pretty high stock as it is. Also if I do lift it I wouldn't be able to lift much because most of the local trails are very tight and in alot of situations the roof is already being rubbed by branches and trees already. The last thing i would want to do is build this big badass mud truck that I can only use off road if I trailer it to a park with no trees and just mud pits. I am not being sarcastic here, I am just saying with this big of a rig to start off with keeping it "small" would be better..for now. I already have a lifted jeep I can beat the crap out of if I want to, this truck is now my daily driver so trying to not mod it too much unless its something practical. For me, I'm hoping if I go up to 35's it will increase my mpg from like 11.5 to maybe 12 or 12.5, but also be better when using it for hunting since my current tires are pretty worn, and a nice new mud terrain 9.00-16 I think would look good, why not go a little bigger on the tire from the current 285/75r16's if I plan on getting new tires in the future anyways? Like I said, thanks for the help so far, I guess I've got alot to consider and think about still though before I actually do put up the cash. On a side note, I told my wife I wanted to upgrade the exhaust on my m1028 but she told me she didn't want me to be spending a lot of money on it. So I just cut the exhaust off at the mufflers and put turn downs on it to see if that would be good enough. So far I like it, not as loud as I thought it was gonna be. Kinda sounds like an old Camaro or something now.. OH yea, Sharecropper I really like your truck, wish mine looked as nice.

tim292stro said:

The stock backspacing on stock rims is intended to align the wheel's center-axis to the center of the bearings in the spindle/axle. If you change your tire/rim size, you would want to keep the same off-set as using an incorrect offset will add a cantilever force to the spindle/axle, which will eat up your bearings faster (normal life is around 10 years or so depending on usage, bad offset could reduce that to 2 years or less).

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I'm not disagreeing with the bold sentence... But, the back-spacing doesn't affect the bearings as much as one would think. Sure, in theory it will But, in real life... it doesn't. UNLESS you have other issues that contribute to early bearing failure. Most common issues are, bearing pre-load is incorrect, lack of grease and/or incorrect grease, dirt and debris (water included)... etc. The bearings can handle the minor offsets/Backspacing etc... If everything is correct you'll bend a rim before hurting the bearings... The weak point should be directed towards the kingpin Nylon bushing. Just my two cents.

Define minor . I'd define that as keeping the wheel load center within the two bearing races - and further, if you take the measurement between the two bearing race centers and divide it by three, your wheel load center should not fall outside the center 1/3 of that measurement.

Wheel offset can have much more effect than you might consider on a daily driven-vehicle. On axles like the Dana-60, your bearing spacing is only 4" center to center - this would mean that you only have about 1-5/16" wiggle room total (+/-21/32" from "ideal"). If you are at the edge of the center and outer 1/3, the outer bearing will take approximately 2x the load of the inner bearing. If the wheel load center is at the outer bearing race center, the outer bearing it actually taking 100% of the wheel load, while the inner bearing is only mostly keeping the spindle straight. Further out than the outer bearing race center, and it starts to multiply the load on the bearing and re-increase the load on the inner bearing.

This is simple leverage, and I think it's worth repeating one line from my last post here:

tim292stro said:

"...The offset thing is one of the reason most tire places don't want the liability related to wheel spacers any more (some people put on "what fits", without checking if it's "right")..."

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