Lower 69 Mach

Uh... ok... that is definitely a statement... Did you have a question or did you just want to let us know?

you could lower a stock hieght stang about 2" before it get close to any issues.

69 mach said:

Yes it was a question.I have a 69 mach that I am restoring.I am about to rebuild the front and rear suspenson .How is the best way to lower and is it nessary to replace the springs and shackles.

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If you are really rebuilding the front and rear supsensions you should replace all four springs, sort of part of the rebuild if you ask me. I do not think the '69 needs any geometry adjustments (like the Shelby drop) for either a 1 or a 2 inch lowering but I'll let the 69-70 guys speak about that.

I would suggest you buy springs that are already lowered rather than cut the coils yourself and install blocks. If you've ever tried to cut spring-steel you'll know what I mean. You can buy leaf springs that have the "eye" relocated which will lower the car better than those ghetto spacers.

A very popular thing to do it to lower the front 2 inches and the rear only 1. The rake of the body is barely perceptible and adds to the already aggressive '69 styling if you ask me.

Deciding if a lowered car is okay for your streets depends on your streets. My biggest problem is going to be getting up the first 8 feet of my driveway

What kind of headers if any are you planing on running? My Hooker Super Comps hang down VERY low at stock ride height.

Just something to think about.

You've got several options for lowering the car, but how far is up to you and depending on what you feel is adequate road clearence. I've lowered my Mach a bit by lowering the front and rear both by approximately an inch, but still feel there it sits a bit high.

As for your options, much of what Edbert said is correct. For the front, assuming you want to maintain the stock suspension design and most components, you can:

1) Do the Shelby drop on the upper control arms... this lowers the upper arms an inch, but typically only gets you max of 1/2" (if any) lower. The main goal of this mod is to improve suspension geometry. The price is right: FREE!

1a) 1.75" version of the Shelby drop using Pro-Motorsports negative wedge kit... This is the one I did and it did lower the car about 1". The further lowering of the upper arm requires the use of the negative wedge kit, but the benefit is that you get significantly improved suspension geometry (near perfect according to Pro-Motorsports). Cost: $270ish (just for the kit, upper arms not included).

2) Lowering springs... These will typically lower the front end about 1", and benefit is that these are a higher rate than the original springs. Combine the higher rate and lower stance, and it should improve handling a bit. Cost: under $100 easy.

2a) Cut your current springs... this is a viable option assuming you have access to a cutoff wheel (do not use a torch!!!). Its a trial and error process... remove springs, cut 1/3-1/2 coil, reinstall, see how it sits, repeat until car sits as low as you'd like. Cutting springs will also increase the rate, making them a bit stiffer, which again, should be good for handling. Cost: FREE!!!

3) Air ride suspension... I mention this because it often gets overlooked. Its expensive, and while handling is usually ok, its not designed for that reason. Still its totally adjustable, so you can raise or lower your car as needed.

4) Drop spindles... I've never seen anyone use these, but they are available and lower the front approximately 2". I hear prices are relatively reasonable, but don't know specifically.

For the rear, your options are pretty limited if you're using the original suspension design...

1) Lowering leafs... these come in mid-eye or reverse-eye. I used the mid-eyes and I got about an 1" of lowering. I suspect reverse-eyes would get you another 1/2" or so. These come in 4 or 5 leaf configurations, so you can opt for higher rates for better handling if you want. Cost: under $200.

2) Lowering blocks... this is a tried and true method, used for years on the street and in racing. I've seen lowering block kits with 1" and 2" blocks. They bolt inbetween the axle and the springs, thus essentiall racing the axle in the chasis, providing lowering. Cost: under $30.

I think that is about it... One tip though: if you're rebuilding the suspension, decide now if you're gonna do springs or the Shelby drop, because now would be the time to do it. Otherwise you'll have to do a ton of work later and pay for yet another alignment. Prior planning can save tons of both.

Hope this helps... Good luck!

I was planning on doing the Shelby drop and using 1" lower 620 pound springs on my '70 Mach... will that work? On the rear I was planning on going with 5 leaf mid eye.

Another option for improving suspension geometry is the Global West upper control arms www.globalwest.net.

Darren
'70 Mach 1

I was thinking, just to add to the mix of shelby drops and such. If you are lowering the front about 2 inches, would the shelby drop still be a good idea, or would you get too much negative camber?

Route666 said:

I was thinking, just to add to the mix of shelby drops and such. If you are lowering the front about 2 inches, would the shelby drop still be a good idea, or would you get too much negative camber?

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as i understand it, anything past those 1" lowering springs is too much for the shelby drop. the negative wedge kit would be worth the money if you want it lower.

darkBuddha: how would cutting the springs increase the spring rate? you aren't changing the properties of the metal, just making it shorter. 500 lbs to compress 1 inch is still 500 lbs to compress 1 inch. shorter springs should be a higher rate so that you don't bottom out the suspension.

i say just save yer pennies and get something wild like the strut kit from Fat Man, you can do 2" or lower depending on the struts. come one, it's only money!!

burnout289 said:

darkBuddha: how would cutting the springs increase the spring rate? you aren't changing the properties of the metal, just making it shorter. 500 lbs to compress 1 inch is still 500 lbs to compress 1 inch. shorter springs should be a higher rate so that you don't bottom out the suspension.

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Not correct... Spring rate calculations are based on a number of factors, including the shear modulus of the wire, wire diameter, coil diameter, and THE NUMBER OF COILS. Specifically, the formula for spring rate is as follows:

rate = ( wire diameter^4 * shear modulus ) / ( coil diameter^3 * number of coils )

There are a number of web resources that explain the formula and have calculators for estimating spring rate. Here is the one I use:
http://faq.f650.com/FAQs/SpringRateFAQ.html?wireDia=.495&coilDia=2.712&numCoils=3&rateValue=1072

I hope this clarifies the reason cutting coils increases spring rate.

1" drop

Before I lost it to the Ex, I did a 1" drop on the SCJ.

I did the 620 front coils like above, but with the 428 and headers, speed bumps and big holes were definite problems afterwards. With all that motor weight, and lowered, it loked cool, but had the trade-offs.

Out back, I did the mid-eye spring, set for a 1" drop. I wanted to keep the rear down too, since I did alot of open track with the car, and was trying to avoid as much forwards weight transfer as possible.

Do a full suspension re-do, to compliment your work. 1" lowering worked fine on the Mach.

BTW, 1400 posts!!!!

I will hopefully take pictures of my car and post them this weekend. My mods are in my sig.

DarkBuddha said:

Not correct... Spring rate calculations are based on a number of factors, including the shear modulus of the wire, wire diameter, coil diameter, and THE NUMBER OF COILS. Specifically, the formula for spring rate is as follows:

rate = ( wire diameter^4 * shear modulus ) / ( coil diameter^3 * number of coils )

There are a number of web resources that explain the formula and have calculators for estimating spring rate. Here is the one I use:
http://faq.f650.com/FAQs/SpringRateFAQ.html?wireDia=.495&coilDia=2.712&numCoils=3&rateValue=1072

I hope this clarifies the reason cutting coils increases spring rate.

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oh. my bad.

it's like having a bit of steel pipe. Say you had a 2 foot bit of 2" diametre steel pipe (0.25" sidewall) and tried to bend it, now imagine the pipe is 20 feet long, it would bend a lot easier. Same principle with the springs.

Route666 said:

it's like having a bit of steel pipe. Say you had a 2 foot bit of 2" diametre steel pipe (0.25" sidewall) and tried to bend it, now imagine the pipe is 20 feet long, it would bend a lot easier. Same principle with the springs.

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it just seems like that wouldn't come into play when it's in a straight line... i dunno. i like physics, tho, so i want to figure this out! i'll play with that formula more....

it's the same deal, the spring is longer, until you cut some, then it is shorter. The fact that it is coiled only impacts the packaging, and the length. The spring could be a straight bit (like leafs) but packaging sucks for that, hence why coils are what are used now.

Ok why not start with the 600# spring if the spring is going to get stiffer when cut off and do the shelby drop . Approx 1 1/2 " lower now in front.Then us 4.5 mid eye leafs plus maybe 1" spacer then cut the front spring if needed.The car is a 351 W stroked 393 and will just be driven on the highway not raced but I want the lower look as long as I don't drag on speed bumps.Ride is probably just as important as handling.But will I really give up that much in handling.