Looking for a little help looking over my shoulder on this one. 51 chevy p/u Ordered up a tci leaf spring kit to drop the rear of my truck. Really nice product, they claim its nets 4" drop. I would like to go a little lower so i mocked up some three inch blocks. I plan to run 15" steel wheels which measure out to 16-1/4" overall diameter (as it would relate to scrub line) As i see it, with the 3" block that i have mocked up, My scrub line is right at zero.. . Correct? Seeing that drop springs below the axle shouldn't have any effect on axle scrub line. Just seems odd to me after seeing so many of these AD trucks around with 3" blocks. Looking at this, it seems the most block i can safely run is 2". Can someone confirm my math? Thanks in advance!
I believe I am correct is saying that on the tape measure you are showing in the picture, at 8.125" is the bottom of your wheel. (16.25" diameter divided by 2 equals a 8.125" radius) Really nothing should be below 8.125" except tire. If your tire was completely flat, you'd still have some rubber lower than 8.125", so any metal wouldn't contact the ground.
Easier to tell with a wheel on it. But yes cut the threads and it will help, or even a 2 inch block will make a difference. As for understanding scrub line. Imagine the car going down the road and getting a flat tire, when that tire is flat and on the rim anything on the ground is at or below scrub. So yes, springs under the axle could violate that line.
i don't think you and me have the same definition of scrub line, are you taking in consideration the diameter of the rim?
Exactly Doctor Detroit. There is a shock mount tab hanging off the bottom of the u-bolt plate on the front left of the picture right around 8-1/8th" Half of the 15" steel wheel overall diameter measures out to 8-1/8th as well. Please ignore the threads hanging lower, they will get cut to the right length once the wood blocks and green slime are replaced with steel solid blocks and a ford 8.8.
Ok you need to have 8 1/8 from the axle center minimum 8 3/8 would give you a little wiggle room. I think that you would be alrght with the 3" blocks but those are some numbers for you to work with. By the way only amatures neglect to trim the bolts once everything is pulled up tight. If you don't use long nuts you can actually end up with about 3/4" below the axle plate, maybe as little as 5/8". Ok I said that wrong, 8 1/8 would be your maximum length from axle center to longest hanging down part. I hate it when that happens. You are less than 7" to the plate so with nuts and washers I think you would still have an inch of clearance.
Yeah you are a little dicey. As mentioned normally you would have the tire to add a bit of height if it was flat but if it comes apart and you are left with just the rim it is going to be close. Guys that thing that looks like a bolt at the left side of the plate is the shock mount so he isn't going to be trimming that down.
Thanks for the help guys! I think i am pretty solid on the theory, just wanted to make sure i wasn't overlooking or over-thinking.
If I'm reading the tape right. If you can keep the nut and washer at 3/4 thick you will be 3/4 from scrubing (the u-bolts) with no tire.
Oh hell ya, if i swap it with the one from the other side the orientation is the exact same with the tab being up. Hah no fab, and i might possibly be able to run the shocks that came in the kit. This would give me 3/4" scrub line buffer with 3" blocks... I think i'm cool with that. Thanks man!
what is the diameter of the rim? not the tire size , but the actual OD. i just measured some 15" Americans and the OD is a hair over 16"
It seems that you have it figured out and what you have will work. I have seen u-bolts used the other way, they fit in a small grooved plate that fits against the spring and the nuts are on top with a axle tube sadel. Also if one tire were to come off and you were running on the wheel, the rear end travels up toward the otherside. If you were right on the scrub line, you may gain say 1/2 or so depending on how close the spring is to the axle.
could also have the eyes on the spring reversed (if they aren't already) and that will give you another inch lower without affecting scrub line. Also if spring hangers face down, you could flip them up, again not affecting scrub line. And like was already mentioned, flip the lower shock mounting plate from left side to right side, then upside down - or cut it off and re-weld it where it needs to be.
Give some thought about moving the axle back about an inch and a half farther back than stock. It will then look centered in the wheel well. Rich
Yep, thats where the 8.125" i got came from. Pretty sure the spring kit was supposed to move the centerline, but its on my list of items to check. Thanks! Thanks for all the other advice too guys! This is my first build to this extent and i appreciate you all looking over my shoulder!
One last question for anybody looking... Do you think this will require a small c-notch? Ive got 4" clearance to the frame with obviously no weight on it.
I would call the company who made the springs and ask them first. It looks like you may need one once there's weight on it. Don't forget to put a tiny bump stop on it or when it does bottom out it'll rattle your teeth.
Funny 'legal' story about scrub line, California 1959: I had a full-fendered '26 T tudor sedan, on a '30 Model A frame...looow in front, 8.20 X 15 rears, 5.50 X15 fronts. Cop stops me, says I'm too low, he's gonna have to measure it. He measures my front apron below radiator, it's about 5"...then he goes to the REAR, and measures the ground to the bottom of the wheel. (7" or so) I ask him how the front's gonna drop if the back goes flat. He opens a code book, (freshly printed) and reads: "No part of the vehicle shall be lower than the highest rim." Scrubbed my plans for the night...I was adding leaves! (just to get it checked off)