Lowering with staggered 18's 20's

Help Support 7173Mustangs.com:

Caleb Z

New member
Joined
Jan 25, 2017
Messages
4
Reaction score
0
Location
US
My Car
1971 Hardtop
Multipart question:

71 Hardtop, H engine

Ultimately, my goal is to lower the car slightly, do 18x8's on the front, and 20x? On the rear.

So, here's the questions:

1. Do I just get the lowering springs for front and rear off eBay? What am I missing here?

2. The only springs I see on eBay are like a 1" drop. That doesn't seem like much, but maybe it's enough?

3. If I go with 18x8 on the front, what are the specs I need on the wheels? 4.5" backspace with 0 offset?

4. On the rear, I would like to do 20's, but I'm not sure what width I can fit or what backspacing and offset I'd have to have.

5. When it comes to tires, with the lowering of the car, what's my max overall height of the wheel/tire that I can fit? Someone was saying 28". Is that a STRICT 28", or would something like 28.5" fit? I have seen ppl say that 245's will fit on the front, and 315's on the rear, but idk if that's with it being slightly lowered.

Sorry for the extended question, but I look forward to any help I can get on this. Thanks!!

 

20louie06

Member
Joined
Jan 27, 2017
Messages
16
Reaction score
0
Location
Tulare
My Car
72 Mustang coupe
302/C4... for now
Well since no one else has chimed in I'll tell you what I would do if I was going the same route you are.

I would start by cutting the front springs (I know it's not recommended) maybe 1/2 a coil. I believe the springs that are offered only drop the car 1". To lower the rear you would need lowering blocks. One thing worth mentioning. If the springs you have now are the original ones from 1971 they might be sagging already. Getting lowering springs might not change the height if that's the case. I'm not sure on the wheel specs. I'll have to look at mine to be able to compare. It's all about backspace. I test fit a 20x10 with a +35mm offset just for kicks and with the proper spacing it could work. Maybe a 0 offset. The tire on that wheel was a 275/35 I believe. The tire I have back there now is a 29" tire (ordered wrong size) and it doesn't have any issue on the stock suspension. I re did my entire suspension last year btw. I think you need to ask yourself what do you want more, A lowered car or big wheels. Not saying both can't work but I think you should do the most important thing first. Big wheels fill out the wheel gap nicely but could make the stance look bad so lowering might be necessary. I have seen it done before though.

 

Caleb Z

New member
Joined
Jan 25, 2017
Messages
4
Reaction score
0
Location
US
My Car
1971 Hardtop
Thank you so much for your input! I'm just getting into this Mustang thing, so all the input I can get is great! My car was a one-owner car, and literally EVERYTHING is still original. My boss is encouraging me to leave it all alone, and keep it as stock as possible. He says it will have more value if I leave it original. I sure don't want to devalue the car. I'm sort of stuck on which way to go, but I may just go back with the original tire size.

 

luxstang

VIP Members
Staff member
Moderator
Joined
Dec 23, 2010
Messages
6,619
Reaction score
78
Location
Luxembourg / Europe
My Car
1972 Mustang Convertible
Ok, I'll have to chime in with the link to previous posts as I have done all that.

Rim size is usually not the issue as it's the overall diameter you need to keep in mind, The bigger the rim, the lower the tire.

There is a slight difference on how the tires will behave according to their sidewall ratio.

Here's what I mean: I have 15x7 Magnum 500 and 18x9 rims. Both rims are sitting in the exact same spot in the wheelhouse (Backspacing etc).

I either use a 255/60/15 or a 255/45/18 tire and they are both the same diameter (27.05) and tread width, so I should be ok, shouldn't I?

Turns out, I'm not ok! The 15 inch rims and tires fit, the 18 inch rims and tires rub slightly although the tread is the same width, it's in the same position and the tire is the same diameter. That is because the bulge the 15 inch tire creates makes it less "square" than the low ratio 18 inch tire. And it's that square corner that rubs slightly.

But my car is lowered a lot.

Keep in mind that the lower your tire ratio is, the more they will look like stage coach wheels and the lower your car will have to sit to compensate for that.

27 inch is a good average, don't go any smaller or they won't fill the wheel wells correctly.

If you just put big rims on and keep the stock height it won't look good.

The bigger the rims, the more the lines of the rims and the wheel wells will clash, which sometimes makes for weird looks.

The one inch lowered 620lbs coils are a good start but as soon as you go bigger than 17 inch it won't look good.

I have those and cut one complete turn off. That brings the car down considerably (think twice about long tube headers!) but the look is correct.

Here's more info:

http://www.7173mustangs.com/thread-lowering-1971-convertible-how-low?pid=285636#pid285636

 

Caleb Z

New member
Joined
Jan 25, 2017
Messages
4
Reaction score
0
Location
US
My Car
1971 Hardtop
luxstang,

Thanks for your input! I love the look of your car! I know you have played with the sizes and stance quite a bit. I have never thought about the squareness of tires based on their ratio, the way you described it, but it makes perfect sense to me. I will definitely keep that in mind!

 
Joined
Apr 27, 2012
Messages
4,756
Reaction score
77
Location
Nashville, Tennessee
My Car
1973 Q code Mach 1
I did a 1" drop in the front with the same 680 coils. With 17 wheels, it is hard to find a tire taller than 26" and I don't think I could have the car sit any lower without making it hard to drive on the street as a result of how my headers hang down.

In the rear, 1" lowering blocks are an easy modification that can be reversed with ease. Be aware that lowering blocks do change the leverage on the rear axle spring perches. Most blocks are aluminum and hollow. If you can't find solid aluminum blocks, you might want to cut a piece of steel tubing to the height of the block and glue it to the inside of the block. I also added welded in wedges between the axle and the spring perches after I tore the perches up. Use good quality U bolts!!!

Note: my signature Pic is prior to lowering either end

 
Last edited by a moderator:

zsmith71

Member
Joined
Feb 5, 2015
Messages
10
Reaction score
0
Location
California
My Car
1971 Mustang
I am in the process of installing 620 1" lowering springs and 5 leaf reverse leaf springs on my convertible. Once I finish I will post some pictures.

Luxstang: thank you for your advice over the holidays.

Z

 
Top