Need help from lowering experts

[cj847]

I have a 68 that I bought already lowered. Needless to say, I don't know for sure what I have. My concern is the front suspension. I think it is 2.5" spindles and about an inch off of stock springs (or could be aftermarket) They measure 8.75 to 9" installed. This is a very mild lowering compared to what is on this board. Tires are 235/75/15. Shocks are new but are cheap blue monroes.

Here is the problem. When I drive over a "hoop de do", the front suspension doesn't bottom on the bump stops, it bottoms out on top of the tire. This is very dangerous if you are not expecting/slowing for a hoop de do. PS> the bump stop is missing on the side that bottoms first. But, a lot of rigs on this board have cut their bumpstops and mounts off.

Are most mildly lowered truck running aftermarket or no inner fenders?

[leftybass209]

My 72 is dropped on 2 1/2" spindles, and 2" springs in front. Tires are 255 60 r17's which is a 29" tire.

It rubbed when i first dropped it on one side. Found out that very little was tightened up properly under there. After going through all the inner fender bolts and making sure it's all tight, no more rubbing, whether going over bumps or not... it's actually very well manageable.

Core support mounts and body mounts can also cause issues with tires rubbing if they aren't in good condition.

[pjmoreland]

I have 2-1/2" drop spindles with a front disc brakes, along with 1" drop springs on my truck. The disc brakes widened the front end by 3/4" per side. I was running 15x8 Rally wheels with 255/60R15 tires, and I was having the same rubbing issues you're having when hitting dips in the road. This was even with stock bump stops installed. I ended going with 15x7 rims and 215/70R15 tires in the front, and it has solved the rubbing problem.

[dagnabbitt]

I'd say 235 75 15s are a pretty tall tire for truck that has been lowered possibly 4 inches.

[cj847]

All good points. After posting I started thinking that some of the disc kits widen the stance. Also, not sure of the backspace on the aftermarket rims. I did not think about the body mounts being a factor. I will check all of this over the next few days.

I am actually glad to hear others have had problems as it doesn't seem anyone brags about the problem with their awesome looking lowering job... lol.

[SCOTI]

A 235/75-15 is almost 29" tall so that is part of the issue (tall for a 4" front drop).

Bump-stops not helping limit travel is compounding the increased travel range making the inner wheel well the 'stop'.

Shocks w/too little dampening can be a contributing factor. Better mono-tube shocks can help depending on the current shock quality (age & quality).

If it has a coil cut from original springs, the spring rate can be too low for the drop amount + tire height combo. If you want to keep that tire height, you might need to step up to a higher rate drop spring which will help on compression.

Swapping a drum truck to stock discs widens the track width.
Drop spindles can slightly widen the track width vs. stock disc spindles.
Tires can make contact sooner depending on the actual final track width of the total package so the aftermarket wheel back-spacing is also a possible factor.

[Palf70Step]

As mentioned a 235/75 is a tall tire, 29" essentially. Most are using a a 26 or 27" tall front tire for lower trucks. That couple inches makes a huge difference for things like rubbing when turning or bounching.

[dagnabbitt]

This is just speculation but I think the guy that lowered it had it set up nice for himself but he liked his rims and tires so much that he kept them and threw the tall ones on when he put it for sale. I myself tend to sell my trucks with “roller” tires. It’s so much trouble to find wheels with the right backspacing and tires I like. Try a smaller tire for sure, that rubbing looks pretty mild and it might be solved.

[cj847]

I am learning a lot that I either haven't seen in other threads or skimmed over.

I've seen so many of these trucks with 235/75's that I ASS-U-MED it was close to the factory size. But now I see 215/75 = G78.

I learned long ago that any change from factory will potentially cause problems (ie radical cam = stall converter and electric vacuum pump, etc,etc.; big tires on a jeep = lower gears+ bigger axles + bigger brakes, etc, etc.)


Thanks for all the input.

[Ben IV]

I'm running 235/75/15 tires on steelies with 2.5" spindles and 2" springs with no rubbing issues and I've hit some bumps hard enough to rub the driveshaft on the upper rear crossmember or whatever it's called. I'm guessing your cut springs and cheap shocks are a contributing factor as well as wheel offset. Shocks would be the Cheapest thing to start with. I'm using kyb gas a just Shocks $37 bucks each for fronts on rock auto right now.