Good tutorial for measuring for custom rearend?

[matty b]

Hey, Was trying to see if anyone had a good how to on correctly measuring for a custom width rear end. Looking for something that has pointers on everything I should take into consideration when doing this. I need to get this right the first time so any help here would be awesome.

[matty b]

ok maybe Im not as clear as I should be. Im planning on putting a 10" wide rim with 4.5" backspacing. Im trying to figure what I should take into account when measuring. Like any clearances I should remember to consider so that my wheels wont rub or sit in the wrong spot. I havent got the wheels yet so I have to wait but once I get them Im wondering how much clearence between to fender lips and the inner tubs ect. I had come across a magazine article that had info like this but I cant remember which one it was. In it I remember he had all these different measurements that he took when he was narrowing the rear end. Im wondering if I should just take the stock width and just subtract the difference in wheel offset. If any of you can chime in regarding this it would sure help out with me doing this right.

[MrQuick]

Its always good to have a base and a stock rear end is a good start.

Now, I like to buy the rims and tires that I know fit and make the rear end fit that. Its easier for me to do it this way now.

Good rule of thumb for clearance:

17"+ rims 45 series and under.
rear~ 1" inner 1/2" outer

You can get closer but I like to maintain that as a minimum if I can.

[matty b]

ok that sounds good. I just ordered my wheels from frank and lisa at prodigy theyre Boze Mesh with gunmetal centers and brushed machined hoops. 17x7 4" bs fronts and 17x10 4.5" bs rears. I gotta wait for them so Im just trying to figure out how I should set the rears up so that I measure them with correct clearences. Im thinking I should buy my rear rotors so I have that dimension figured into the equation as well. Thanks for the tip on that :twothumbs

[matty b]

ok I actually found the article in the magazine, it just so happens that I had that mag in the waiting room at the shop. Its the Feb 2008 issue of Rod & Custom. In it the following dimensions were taken into account:

Overall Car width, outside fender to outside fender
Brake standout for rear end
Rotor thickness
inner wheel mounting surface to insside tire bulge
Fender Clearence inner and outer

I knew there were quite a few measurements to take into account, thankfully I found the article. Makes life a bit easier when you have info like that. Thanks MrQuick for the help though ;)

[Josh]

Basically you will be taking the rear end out of the car, setting your wheels with tires in the wells right where you want them, lower the car over the wheels then measure inside to inside wheel mounting surface. This is the total width of the rear you will have made.

[Damn True]

Don't you need to take into account the brakes?

They will reside between the flanges and the wheel mounting surfaces.

[Josh]

The total width of the rear means brakes, rotors etc. When you know what you are going to run, add all the demensions into the equation including axle stick-out and what is left is the housing width.

[matty b]

yeah I listed that all out from the article. It is a very in depth article for what you would think is seemingly easy. It was written for someone that needs it correct with no real margin for error. The article was based on the premise that setting the tires in there isnt always spot on. MrQuick gave the most crucial dimension I ddint have and that was what the clearance between the inner and outer fenders should be. All other dimensions can be ascertained with just a tape measure, a mounted tire and wheel and either the rotor or a for sure dimension of the rotor. The author said that you find the center line of the axle and drop a plumb bob from each fender and that spot. Then with a tire mounted on the wheel you are going to use, measure the width of the tire bulge by laying the wheel on its side and lay a straight edge over the tire and measure from the ground to the straight edge. This gets the over all width of the tire. Then you measure from the wheel mounting face to the tire bulge of the tire the same way you measue wheel backspace. Then measure the outter fender lip thickness and the distance from the inner wheel well to the inner edge of the outter wheel well. With these measurements of the car you can more or less center up the tires in the wheel wells on paper with the correct clearance on each side of the wheel and then its simple subtraction to get the actual axle width. If you measure these correctly the axle should theoretically fit perfect the first time.

[astroracer]

Most custom rearend suppliers have good work sheets to use to set up your housing width.
This is Alstons'
http://www.cachassisworks.com/worksheets/fab9_instructions.pdf
Lots of good info with instructions.
Mark

[Josh]

Matt,
You are correct. Theoretical is a good word to use. After you work it all on paper, do the actual set up with the wheels in the wheel wells. If the end result is the same you will know your spot on. This will also rule out any "unforseen clearence issues" that are bound to occur. Good Luck!!!

[matty b]

Most custom rearend suppliers have good work sheets to use to set up your housing width.
This is Alstons'
http://www.cachassisworks.com/worksheets/fab9_instructions.pdf
Lots of good info with instructions.
Mark

go figure that I look at chassisworks site all the time and never came across that. Good find on that.

JOSH, yeah I would never go off just one or the other, having it on paper and checking it against the actual car is the only way you can be dead on that its right, but at the same time just setting the wheels in there doesnt get all the measurements exact more of a rough measurement opposed to an exact one. Thanks alot for all the very good info though. Cant wait till I get my rims so I can move along with this but in the mean time I guess I can get all the info I need to do it right. Thanks again though