Lowered 1974 C20 8 Lug

[Miguel2b]

Hello, my project is a 1974 GMC C20 LWB. It has a 454 engine with a Corporate 14.

I plan on lowering with a 6"/8" drop kit from switch suspension. I want to run a set of Bart wheels with stretched street tires.

I was thinking of the 15" x 10"(8 Lug) with 3.5" backspace. I want the rim flush with the body.

Do you guys think the wheel will clear the front brakes, and the drum brakes in the rear?

Thanks,

 

[Dave M]

No idea what Bart wheels are and I'm not really into lowered trucks anyway, but how about a bit more of an intro' and a few happy snaps of your truck. Welcome to the forum.

 

[AyWoSch Motors]

Welcome from New Mexico.

And yes, I agree with Dave m, pics and explanation please.

 

[Miguel2b]

Here are some pictures of my truck. It is a 1974 GMC Sierra Grande. It came with a 454 engine and a th400 transmission. I am the second registered owner on this. I am from Los Angeles.

 

[Catbox]

I would assume that these are the wheels you are looking at....

You must be registered for see images attach

On the fitment, I am not sure as the wheels on my truck are 8 inches wide and still inside the fenders.
For comparison, here is my truck on a set of American Wheels that are 16 x 8 with a set of 265/75/16 tires on it. The tires are 31.5 inches tall.

You must be registered for see images attach

It feels like you want to run a much shorter tire on yours though.

 

[Dave M]

I'm a fan of the factory rally wheels, (I think that's what you call them) these are the 8" rims.

 

[Corvette Ed]

Welcome to the forum from East Tennessee.

 

[1973c10]

Welcome from Oregon

 

[John Nes]

Hello, my project is a 1974 GMC C20 LWB. It has a 454 engine with a Corporate 14.

I plan on lowering with a 6"/8" drop kit from switch suspension. I want to run a set of Bart wheels with stretched street tires.

I was thinking of the 15" x 10"(8 Lug) with 3.5" backspace. I want the rim flush with the body.

Do you guys think the wheel will clear the front brakes, and the drum brakes in the rear?

Thanks,

In regards to the front drop, what’s in their kit for the front? Spindles n springs I guess? Any more than a 3” drop via drop spindles and your outer edge of your lower A arms will catch on a 15” wheel, I wanna say I’ve read that you’re gonna have to go up to like a 17” or maybe 18” wheel for clearance. You can grind on that outer edge/lip on the A arm for clearance but I’d just go with a tubular or dropped control arm. 6in drop, with that wheel n tire set up gonna be hell on them ball joints lol…
As for backspacing, I got 10” wheel with 295’s, and a 4 or 4.5 backspace (i forgot what Detroit steel made
For me) and I can barely fit a finger between the wheel arch and the tire.

Was bout to get some **** from Switch for my 73 3/4ton but read the fine print n saw that the same drop kits won’t work with a cab chassis truck ‍… oh well lol

 

[Babs]

You must be registered for see images attach

 

[OldBlueDually]

Welcome @Miguel2b from MN. VERY cool looking truck! Love the deep inset grills of the early ones.

I too purchased a 6/8 drop from Switch Suspension. It all went in well for me. I have a 76 GMC 1 ton. For some pics of those pieces from switch, and how they go in, you can check out my build thread. Not sure what page those pics are on, but you will see them.

https://www.gmsquarebody.com/threads/76-gmc-crew-long-box-dually-gotta-get-it-on-the-road-again.29806/

@John Nes I have a dumb question here for you. In your last statement you mention the fine print from Switch, what is "cab chassis truck"? And why won't their kit work? I am curious to know

 

[BRetty]

Hi Miguel, welcome to the forum from a fellow Angeleno. Your '74 is awesome, that two-tone orange-on-orange rocks! But the best thing is that you are smog-exempt, you won't just have your vehicle effectively outlawed like a whole lot of diesel trucks suddenly are.

Other good stuff: Lots of the major performance and aftermarket suppliers are still nearby here in SoCal (just not in LA, can't have actual *industry* here anymore), you still see great old cars and trucks on the streets just about *hourly*, often driven by guys with decades of low-rider stories to tell, and any part you might need is probably within 20 miles, sitting in some dude's backyard in Sylmar, or Fontana.

The bad: Enjoy it now, before California just bans gasoline, or makes it illegal to own any vehicle more than three years old (commercial trucks, already), or some cities just ban all vehicles (Santa Monica, where they think their artisinal produce and drugs will be delivered by drones, and the nannies and gardeners can just ride donkeys (from Montebello)) or Los Angeles is just looted and burned to the ground.

Sorry, I got a little off-topic.

My only substantive advice is: the roads in Los Angeles are old, sprawling, and in amazingly bad shape. My truck is dropped 4.5/6, and although I adamantly steer and swerve around the many hazards I know about, I still scrape my control arms and my fuel tank once a week.

BRetty

 

[John Nes]

@OldBlueDually cab chassis trucks were produced for going right to work. To my knowledge, and i could be slightly off, they rolled off the line with no bed, essentially just the cab on the chassis (front clip obviously there too) and were customized/outfitted with the owners choice of bed. I.e. mine which has a long wheel base enclosed utility bed.
You can see if it was a cab chassis truck based off the vin. Also you can see the renderings of them in the service manuals as well.

Now, as to why the CC trucks and switch suspensions 6/8 kit isn’t compatible, I haven’t the slightest lol.

 

[OldBlueDually]

@OldBlueDually cab chassis trucks were produced for going right to work. To my knowledge, and i could be slightly off, they rolled off the line with no bed, essentially just the cab on the chassis (front clip obviously there too) and were customized/outfitted with the owners choice of bed. I.e. mine which has a long wheel base enclosed utility bed.
You can see if it was a cab chassis truck based off the vin. Also you can see the renderings of them in the service manuals as well.

Now, as to why the CC trucks and switch suspensions 6/8 kit isn’t compatible, I haven’t the slightest lol.

OK!! Whew, I got a bit worried there...well, my kit is already installed but I thought "ah crap, I need to know this info now just in case!"

Thanks for explaining. I learned something new while at work today, now I can go home