3/4 Drop - wheel fitment

[77GMC454]

I will be lowering my 77 C15 LB 3" in the front 4" in the rear, but need to know what backspacing/offset I will need on a 15x10 wheel. I want to keep the tires inside the wheel wells, and do not want to worry about the tires rubbing. I am new to this, and have not been able to find a straight answer on what will fit. I am thinking about 275/60/15s. Please let me know if anyone has done something similar and what has worked. Thanks for the help!

 

[J Knight]

If your using 10's on front and rear you cant tuck the front. You need 5in bs in the rear to tuck but you cant go more than 4in bs in the front or your wheel won't fit.

I will suggest a better wheel tire combo.
15x8 with 4in bs
245/60/15 or 255/60/15 tires
15x10 with 5in bs
295/50/15 or 275/60/15 tires.

Another combo that will work if you want same size all around.
15x8 with 4in bs
275/60/15 tires.

 

[77GMC454]

Thanks, John! Good information. I was assuming 10s would not be the best idea in the front, so I am glad you suggested another route.

Thanks again!

 

[J Knight]

No problem. Here's another tid-bit of info fyi....a 3.5/5in drop is less work (in the rear) than a 2/4in drop.

 

[newmexicosaint]

I second this.

If your using 10's on front and rear you cant tuck the front. You need 5in bs in the rear to tuck but you cant go more than 4in bs in the front or your wheel won't fit.

I will suggest a better wheel tire combo.
15x8 with 4in bs
245/60/15 or 255/60/15 tires
15x10 with 5in bs
295/50/15 or 275/60/15 tires.

Another combo that will work if you want same size all around.
15x8 with 4in bs
275/60/15 tires.

While I really like the 10" wheels all the way around it just doesn't work. 275/60's are too tall (IMO).

I did the 10"/8" combo on mine and love the Street Rod Look! I did 295/50's in back and 255/60's in front. My ONLY regret is that I didn't go to the 245/60's in front. To the sharp eye the 255's are a pinch taller sidewall than my 295's.

 

[77GMC454]

Gene - what backspacing did you do? how far is your truck lowered? Thanks

 

[newmexicosaint]

The backspacing on the 10" wheels are 4.75". I did a "ghetto" drop on mine. I cut one coil off the stock front spring and that gave me almost 3" and in the back I pulled 2 leafs and did a 2" drop shackle and that gave me 3.5" in the back. The back of the truck still needs at least 2.5"-3 in the back for my liking. I am looking to put a 12" wheel in the rear but will most likely force me to go to a custom 2 or 3 piece wheel.

The front wheel is 3.75" b/s.

 

[titomars]

The backspacing on the 10" wheels are 4.75". I did a "ghetto" drop on mine. I cut one coil off the stock front spring and that gave me almost 3" and in the back I pulled 2 leafs and did a 2" drop shackle and that gave me 3.5" in the back. The back of the truck still needs at least 2.5"-3 in the back for my liking. I am looking to put a 12" wheel in the rear but will most likely force me to go to a custom 2 or 3 piece wheel.

The front wheel is 3.75" b/s.

I did the same thing in the rear on mine. I bought mine with drop springs in the front. I would like another 1 to 2 inches in the rear and about the same in the front. I run 15X8's front and 15X10's in the rear. The tires don't rubs currently.

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[EdMailhot]

If your using 10's on front and rear you cant tuck the front. You need 5in bs in the rear to tuck but you cant go more than 4in bs in the front or your wheel won't fit.

I will suggest a better wheel tire combo.
15x8 with 4in bs
245/60/15 or 255/60/15 tires
15x10 with 5in bs
295/50/15 or 275/60/15 tires.

Another combo that will work if you want same size all around.
15x8 with 4in bs
275/60/15 tires.

i personally don't like the look of 275's on a 10" wide rim. i would do the 295's in the back on a 10" rim or go 275's if I did an 8" rim in the back. but that's just me.

 

[77GMC454]

J Knight - I should have listened to you about the drop. I decided to go with spindles, shackles, and hangers for a 3/4 drop. I did go with the 15x8s with 275/60. They look great on the truck and give it a little more muscle.

I have been working on and off for almost three weeks on the rear suspension components and it seems like every time I get somewhere I hit a road block. So far, I have spent almost a full day removing rivets (I did not remove the box or gas tank, so I expected to have issues). Then I could not get the spring eye bolt out of the bushing, so I decided to replace the bushing. The first one came out easily, but I have having space constraints again with gas tank. The drivers side shackle bolt is also rusted in similarly to the hanger bolt. My neighbors are likely a little sick of me yelling at the truck...

Anyway, now that I am closer to completing the rear drop, the spring eyes are not lining up with the mounting holes in the hangers. They are about half an inch to and inch too far back.

Any ideas?

 

[J Knight]

Lol! Hope the grinding was fun.....

Anyway, if you loosen the shackle bolts you can get enough play to line up the leaf spring to get the bolt in.

 

[77GMC454]

I thought I had finished the rear end and then when I took it off the stands I realized the leaf springs were hitting a bed support beam. There is one in front of the shackle and one behind the shackle (with about a 6-8 inch), so it looks like the cutting wheel is coming back out next weekend. I really hope the front spindles go a little more smoothly! At least I will not have to break any rivets free...

 

[smoothandlow84]

I thought I had finished the rear end and then when I took it off the stands I realized the leaf springs were hitting a bed support beam. There is one in front of the shackle and one behind the shackle (with about a 6-8 inch), so it looks like the cutting wheel is coming back out next weekend. I really hope the front spindles go a little more smoothly! At least I will not have to break any rivets free...

Ah hah...I came across having to notch the bed support beams too when I installed my 5-7 drop on my 84 c10.

As far as installing the sindles up front...definately go with a larger than 15" rim up front or you will have clearance issues between the inner rim lip and the lower a-arm. The p.o. of my truck ran 15" rims and gouged the lower a-arms... when I acquired the truck, the first item to be done was ditch the oem rally 15" rims and install 20"×8 up front and 20"×10 out back. The 2"drop spindles were on the truck when I took over. I have since installed 3"drop coils and removed the overload leaf for a lower stance and softer ride. The rear end also has a flip kit and drop shackles. Another item to consider is to make sure that the tires you use are rated for the weight of the truck. Too many people run incorrect tires NOT rated for the truck. Safety first..blow outs suck on lowered trucks, and they always happen at the worst possible time. Spend a little more for the correct rated tires now instead of replacing fenders and sheet metal later (or worse).

I am running 295 40 r20 in back and 255 45 r20 in front