Ideal front wheel backspacing for a GENI - Lateral-g Forums

bucks69 · #1 12-29-2007, 08:25 PM

Hey guys if you were building your "ideal" road/street racer what would be the backspacing you would want on the front with a 17"x10" wheel And also an 18"X10" wheel? Also to go a little further what would the rear backspacing be for a 18"x12 and a 19"x12"? This is assuming you were going with a custom frame and could go with whatever size and backspacing you want. This is for a regularly driven street car if that helps any. Also please elaborate a little about your decisions please. Thanks in advance.

DriverzInc · #2 12-30-2007, 12:50 AM

Well, ideally, you would want to have a 0 offset on both wheels. Keeping things centered puts less stress on bearings and such. Ask any mechanical engineer, they'll tell you the same.

ProdigyCustoms · #3 12-30-2007, 08:23 AM

This could quickly turn into a huge technical discussion on suspension. But, short story, since longer is better for suspension arms, you would end up with a big possitive offset on your front wheels to make your suspension design better. But for looks most do not like the high positive offset wheels and want some "lip" on the wheel.

On a live axle rear it does not matter.

bucks69 · #4 12-30-2007, 10:07 AM

Thanks Jon and Frank. I appreciate the reply. So as far as looks go(performance second hand) what would be the suggested backspacing that you would consider when you would be doing your own car. This has been my brickwall on ordering stuff and I know I am overthinking this I just dont want to be wrong this early in...LOL
Thanks again

ProdigyCustoms · #5 12-30-2007, 10:16 AM

It depends. I am assuming you are mini tub? So we usually do a 6 to 6.25 backspace. Although I did buy a dozen custom 19" outer rims shells to be able to do a 6" lip on Lisa's Project EmptyNest which is right at 5" backspace or so. Looks KILLER! On the front, a 8" rim with 4 3/4 backspace is usually good on stock track width and give a nice 2" lip. Again, though if you are designing the front suspension from scratch, you would want to make the arms as long as possible, changing you backspace. Brake caliper clearance also will be a dictator here.

If you would like to talk through this you are welcome to call

four zero seven 832 1752
8 AM to 10 PM

bucks69 · #6 12-30-2007, 10:29 PM

Frank I will call tomorrow if you are open. And yes front track width is whatever I want it to be so I just need to know what a decent backspacing would be. I need that info to order, I also have to account for brakes and what that would do to the width needed. Thanks again

ProdigyCustoms · #7 12-30-2007, 10:34 PM

I will be around 8 AM to 5 PM eastern tomorrow. Our New Years Eve party starts in the afternoon so................................

**parsonsj** · #8 12-31-2007, 01:29 AM

Well, I'm certain this has been discussed before, but I'll weigh in with my thoughts.

In the back, wheel backspacing for a live axle style is just user preference. Lots of backspacing, neutral backspacing, etc. just doesn't matter that much. Reducing strain on the bearings via neutral backspacing isn't such a bad idea.

In the front is where the discussion gets interesting. Ideally, the wheel should be set up such that scrub radius (the difference between the pivot point established by the ball joint centerlines, and the center of the tire contact patch) is less than an inch. Modern suspensions with a KPI of 8-14 degrees usually need a wheel with a significant backspace. My clean sheet of paper design for my car used an 18x9 wheel with 7.375" of backspacing. Have a look at modern cars with oem wheels and you'll find that nearly all of them have "flat" wheels (not much exposed lip) for this reason.

For a brief discussion of this have a look here.

jp

bucks69 · #9 12-31-2007, 09:08 AM

Thanks for the link John.Now it wont pull it up for some reason. HMMM

James OLC · #10 12-31-2007, 12:23 PM

John's reasoning and his explanation in the PHR article is (as usual) bang on and reflects how we planned out the backspacing for our '67 - although we didn't have a clean slate to start with as we were already committed to a subframe and suspension design. In our case we ended up with 6.125" BS and an 8.5" wheel running a 255/35 18 tire. I do not think that this setup will work with all first gen's as it is dependant on a lot of different factors including control arm choices, spindles, and even tie rods, not to mention your subframe. It would have been ideal to go with more but this was the absolute maximum that we could accomodate in our configuration.