Guys with lowered cars + 17" wheels...question

[atey950]

I have eibach sportlines, all other components are stock. Of course with the drop, my wheels lean inward at the top and I get really bad premature tire wear. I want to get the cc plates and get this fixed but here is my problem.

I'm running 17x8.5 wheels with 245/40 tires. It seems that when I go to install the cc plates, the top, outside corner of the tire is going to want to rub on the inside of the fender lip. I could go to a narrower tire, but I'm afrai it will look bad on the wheel.

I really like the stance of the car as it is now but it seems I might have to get different springs to raise it a bit. Any of you guys have a similar issue? The springs were already on the car when I bought it. I'm thinking the previous owner didn't really think this thru.

 

[larrym1961]

I have Eibach Pros on my '87 with a 245/45/17 tire. I have no issues with tires rubbing fender lips. Then again before I had the springs installed, I installed caster/camber plates before that was done which I understand is a must if the Mustang were to be lowered. Something else to consider also would be a set of offset steering rack bushings to help with "bumpsteer" that comes with a lowered Mustang.

 

[Riverart]

I have the Ford Racing B springs with 17X9 10th anniversary replicas with 255/40/17 tires. The setup sits pretty close to flush with the fender. The tires rub the fenders on large dips and my wheels rub when I turn on the control arms. I had the car aligned with no CC plates. Wear seems pretty good though i don't drive my Mustang much.

 

[91TwighlightGT]

Wouldn't an easy fix be to add a thicker isolator (assuming there is one there at all) to raise the ride height? That way you could still keep the same springs.

 

[atey950]

I have Eibach Pros on my '87 with a 245/45/17 tire. I have no issues with tires rubbing fender lips. Then again before I had the springs installed, I installed caster/camber plates before that was done which I understand is a must if the Mustang were to be lowered. Something else to consider also would be a set of offset steering rack bushings to help with "bumpsteer" that comes with a lowered Mustang.

that makes sense. according to eibach's website, the sportlines are .5" lower than the pro-kit. And, i was mistaken about my tire size. they are actually 245/45, not 245/40. When i get new tires I will go to a 245/40 and that will shrink the sidewall height a little. here's what i'm looking at now...

To correct the alignment, the top of the tire would want to move outward (towards the fender lip). Pretty sure it would rub.

 

[91TwighlightGT]

You are going to throw off your speedo a bit by making that change. The current size you are using is very close to stock.

http://www.miata.net/garage/tirecalc.html

 

[MFE92]

That's not a "correct" alignment for a lowered car. Put 1.25 degrees of negative camber in it, pay attention to the toe setting (0 to 1/16th inch total toe out), and it won't rub and they won't wear funny. If you stand the tires up so straight that they rub the fender lip, you're doing it wrong.

 

[atey950]

That's not a "correct" alignment for a lowered car. Put 1.25 degrees of negative camber in it, pay attention to the toe setting (0 to 1/16th inch total toe out), and it won't rub and they won't wear funny. If you stand the tires up so straight that they rub the fender lip, you're doing it wrong.

I need to do some homework on this. So you're saying the wheel shouldn't sit plumb? If you don't mind, I'd like to ask you a few more questions once I have the cc plates. I really need to wrap my arms around this.

Thanks for all of the replies.

 

[gearheadboy]

What does your premature wear look like?

 

[MFE92]

I need to do some homework on this. So you're saying the wheel shouldn't sit plumb?

It should absolutely not be straight up and down. First, at the risk of oversimplification, the tire needs to lean into a corner in order to generate the most traction. I can point you to several literary sources that explain why, or you can trust me However, as soon as it generates traction, the body rolls, and then what happens? If you have 1.5 degrees of camber, but 2 degrees of body roll, what do you have? half a degree of positive camber, and now the tire is actually pointing outward, onto the outside edge of the tire. Furthermore, there's a concept called "camber gain". That's where the tire gains more negative camber the more the suspension is compressed, according to its "camber curve". But in a strut suspension like these, camber gains at a decreasing rate. Put simply, when you lower the front end of a strut suspension like these, and you don't relocate any of the suspension pivot points, you set it up to lose camber relative to body roll.

Study this for a visual: http://www.miracerros.com/mustang/t_suspension.htm#Curve

Bottom line: You need negative camber, especially with a lowered mustang. Now it won't be long before some knuckledragger comes along and says "negative camber wears the inside edge of your tires". No, it doesn't. TOE wears the tire, and negative camber concentrates it on the inside edge. So be careful about your toe setting, make sure your tie rod ends and bushings are good, and set the front end to 1.25 degrees of negative camber, then forget about it.