Drum to Disk swap resulted in tire hitting fender! :fry:

[ben88]

Hi Y'all,

I just completed a Drum brake disk swap on my 68c10 step side, Using the stock 68 Upper and Lower control arms, stock front spring, 73 and up spindle, caliper, disk, spindle. I also used the 73 and up front steering linkage.
I know that 31x10.5x15 are big tires but now when I hit a bump or go around a corner to drastically the tire rubs on what I think is the outside fender. What I am trying to figure out is if there is a extended bump stop that will essentially make the truck bottom out before the tire hits.

This is my first truck and I have been working on it since I was 16, since that was only 4 years ago I am looking for some aged advice.

-Ben

[ben88]

I should also mention that the wheels are 15x10 which widened the tires a bit, I plan on running 295/50/15 in the future but I have to save some $$ first hahaha.

[geunther]

I think the combination of the 10" wide wheel and what appears to be some negative offset is causing you the issues.

[toolboxchev]

Originally Posted by ben88

I should also mention that the wheels are 15x10 which widened the tires a bit, I plan on running 295/50/15 in the future but I have to save some $$ first hahaha.

I do not believe its the tires, most obvious the wheels and the change in offset. You could always fabricate a new stop with an adjustable height. That would be trick!

That is the great thing about these trucks, inexpensive modification fixes with improvements.

[67ChevyRedneck]

I don't know how much wider the track width is on the 73+ trucks, but if I remember correctly the 71/72 spindles push the wheels out about 3/4" per side compared to the 67-70's, which is why GM widened the rear axles of the truck in mid 1970.

You have quite a few things happening (all of which I'm sure you know.) The tires are too large, they stick out too far, and your springs and/or shocks are likely a little worn.

Do you have a sway bar?

[ben88]

I unfortunately do not have a sway bar but I am very interested in getting one, I have heard that it improves the handling quite a bit. The wheels have a backspacing of 3 3/4. The 295/50/15 will have shorter profile which will probably improve the issue but I really like the look of a filled out fender and a wide tire. Also I think the shocks are stock from the factory.

[Xeen]

That is correct the disc brake package moves the wheel out 3/4" on each side for a total of 1.5" and there is where the problem lies.
You can fix this issue by spending money, CPP offers a "Modular" drop spindle that will lower the front end 2" and bring the wheel in 3/4" to get you back to the same geometry as the original drum brakes.
If you decide to buy them you will also need to buy their GM disc brake bracket so you can bolt up the caliper, that's the modular part, they have different brackets for different brands of brakes, GM, Wilwood, Baer, etc.
Make sure you order the correct year modular drop spindle, they make both parts for 1967-70 ball joints and 1971-72 Ball joints.
Here is the link to their website.
http://www.classicperform.com/Chevy-Truck.htm

[GASoline71]

295's up front? That is a really wide tire for the front. 295's out back... sure... but you need a smaller tire up front unless you wanna do some body work on the fenders.

Gary

[Xeen]

Some further thoughts.
I just noticed you installed 1973 spindles which is fine CPP makes the modular for 1973-87 too, the part number is "CP30106-4" so on to other things.
The 10" wide wheel is the real problem here these trucks were never designed with the intention of having a wheel that wide on the front, I don't think anyone even manufactured wheels or tires that wide for passenger cars and trucks in 1968.
If you would have installed 8" wide front wheels you wouldn't have run into this issue, I know the disk brake track width isn't something you knew about so don't beat yourself up about it, a little money can put out this fire.
The one thing I'm not 100% sure on because you didn't mention it, is the 73' spindle a 2.5" drop spindle or is it stock, if it's a drop spindle then the modular will work perfect but if it's stock I'm wondering if the tire will clear the inner fender lip with the 2" modular drop spindle because the tire will be closer to it, you will need to measure to see if the 3/4" you are going to gain is enough.
I know you don't want to spend more money and you just bought spindles but the good news is you can sell those spindles once you swap them for the modular and recover some of your money, I say some because the modular system is more expensive.