How low is too low for lowering springs?

[jzepp]

How low is too low for lowering springs for a daily driver SN95 mustang? Should i stay around 1.5" or is that pushing it also? Should the spring rates be increased as you lower the car to prevent bottoming out? What spring rates are too much for a daily driver?

 

[97gt-svt]

When I first bought my car it had homemade:nonono: lowering springs that were supose to be 2.5 inches, the ride was horrible it was almost to bad to drive on the street. I put 1.5" lmm springs on and it rides great. just my .02

 

[jzepp]

97gt.........how is the 1.5" for driving daily? any exhaust scraping or anything? Is the ride comfortable or slightly harsh with the 18's?

 

[JasonSnake]

most of the roads in my area are smooth so I have no problem with harsh ride. But it can get harsh on crappy roads and 18"s and I'm runnin the Eibach Sportlines 2". Also, since I put on my catted UPR x-pipe, the cats hang a bit lower than the stock so I scrape those too over some speedbumps.

 

[jzepp]

Can anybody explain spring rates? The eibach sportlines have a close to stock spring rate.......why do people say they are harsh? then some people tell me to use H & R race springs for my 98 cobra convertible that are 750/850lb spring rate........isnt that a very high spring rate? or is it the lower you drop the higher the spring rate you need? i have bilstein shocks/struts that arent on my car yet but i want a decent drop of around 1.5".........eibach only has the pro-kit for my car that lowers 1.3",1.4"......i want a bigger drop. maximummotorsports tells me to use H & R race springs with a 1.25" drop but very high spring rates....they also have a road & track spring that lowers 1.5" with a spring rate of 600/780lb. front and 275/300lb. rear.........wont that be a better compromise for ride quality?

So, basically do you want a close to stock spring rate or should you go with a high spring rate when lowering?

 

[96RagTop]

The higher the spring rate, the less movement you will get out of the spring up and down.

When you lower the car you want higher rate so you do not have problems with rubbing.

 

[97gt-svt]

I love the ride, it great for everyday driving. It gives the car a better stance and it very comparible in ride quality to other mustangs with stock springs even with my 18"s. The exhaust only srcapes once in a while going into my friends drive way, but he has a unusally sharp angle and it barely scrapes.

 

[Ciotti]

Just to clarify the explanation of spring rates...

The spring rate is essentially the amount of force it takes to compress to spring, a higher spring rate will require more force/weight/a big ass bump to compress.

You definitely want a higher spring rate than stock when lowering the car or it will bottom out and slam the bump stops all over the dam place. When you lower a car you are taking away some suspension travel which would normally suck up that extra bit of energy when you hit a bit bump, thus the importance of raising the spring rate to eat up that extra energy.

You don't want the spring rate too high though on a daily driven car or the ride will be rough, BUT that also has a lot more to do with the dampening of the shocks and struts.

If you do a search on lowering springs or just springs on this board only you will get a TON of info on how everyone likes just about every different set of springs offered for our SN95's... Except for FRPP G springs which of course are the ones I am getting

 

[jzepp]

Ciotti............the FRPP "G" springs are close to Eibach pro-kit specs so essentially from what you said you will be bottoming out all over the place because of the light spring rates...i think they are in the lower 400 lbs. in front. I was going to get the Eibachs for my 98 cobra vert but it only lowers 1.3" or so.........the FRPP "G" springs say 1.5".........let me know what kind of drop you get and how the ride quality is?

Will there still be good ride quality with H & R springs in the 600 lb. range for up front?

 

[YardSpecial]

I ran H&R SS on my 02 Vert and LOVED the smooth ride (OEM stuts/shocks)
Was dropped 2 1/4 ! IMOP it was too low, but it drove great. Believe the MM CC plates where the key.

Here is the spring chart I used from Stang Suspension.com:

Stock Spring Rates
Model/Year Front Spring Rate (lb/in) Rear Spring Rate (lb/in)
Mustang GT/V6 Coupe 1994-2004 450 (linear) 210 (linear, solid axle)
Mustang GT/V6 Vert. 1994-2004 400 (linear) 185 (linear, solid axle)
Mustang Cobra Coupe 1999-2001 500 (linear) 475 (linear, IRS)
Mustang Cobra Coupe 2003-2004 600 (linear) 600 (linear, IRS)
Mustang Cobra Vert. 2003-2004 500 (linear) 470 (linear, IRS)
Mustang Mach1 Coupe 2003-2004 600 (linear) 250 (linear, solid axle)
Mustang Bullitt Coupe 2001-20022 600 (linear) 250 (linear, solid axle)

Aftermarket Spring Rates
Manufacturer/Part Info Front Spring Rate (lb/in) Rear Spring Rate (lb/in)
Ford Racing B Springs (M5300B) 425-530 (progressive) 200-300 (progressive, solid axle)
Ford Racing C Springs (M5300C) 650 (linear) 200-300 (progressive, solid axle)
Ford Racing F Springs (M5300F) 460-570 (progressive) 170-310 (progressive, solid axle)
Ford Racing G Springs (M5300G) 500-570 (progressive) 170-310 (progressive, solid axle)
Eibach Pro-Kit Springs (94-04 Mustangs) 425-530 (progressive) 200-300 (progressive, solid axle)
Eibach Sportline Springs (79-04 Mustangs) 425-630 (progressive) 140-295 (progressive, solid axle)
H&R Sport Springs (94-04 Mustangs) 490-575 (progressive) 205-250 (progressive, solid axle)
H&R Sport Springs (99-04 Cobra) 700-760 (progressive) 685 (linear, IRS)
H&R Super Sport Springs (94-04 Mustangs) 700-760 (progressive) 275-300 (progressive, solid axle)
H&R Race Springs (79-04 Mustangs) 750-850 (progressive) 260-280 (progressive, solid axle)
H&R Race Springs (99-04 Cobra) 750-850 (progressive) 770 (linear, IRS)
Steeda Sport Springs (79-04 Mustangs) 650 (linear) 200-250 (progressive, solid axle)
Steeda Sport Springs (03-04 Cobra) 720-780 (progressive) 650-790 (progressive, IRS)
Steeda Competition Springs (79-04 Mustangs) 750-850 (progressive) 250 (linear, solid axle)
StangSuspension Springs (94-04 Mustangs) 490-575 (progressive) 205-250 (progressive, solid axle)

 

[Ciotti]

By that chart the stock springs our Cobra convertibles have are probably the same ones the GT's have and are 400 up front and 185 out back.

The G springs are progressive in that they are wound in a certain way that the first bit of compression will be light(the first number) then as they compress further it becomes harder to compress(the second number)
They drop a lot less than the H&R's which I like as I don't want the suspension geometry in my front end to go to hell but they are a bit stiffer than the Eibach Pros which will hopefully be enough when coupled with a decent set of shocks to prevent the car from bottoming out yet still riding nice and smooth.

FRPP G's are 500 - 570 front and 170 - 310 in the back

So, with them being progressive, in order for these to bottom out it will take 570 worth of pressure up front vs. the stock 400 and 310 out back vs. the stock 185 so I'm pretty sure I won't have many problems with it bottoming but it does look like I'll be guinnea pigging them since I can't find anyone else that has them

Driving around here will be a real good test as our roads are awful and I'm having longtubes put on at the same time so I'll let everyone know.

 

[jzepp]

ok.......got ya........H & R's seem too low for me also.......i think 2" might be too low for a daily driver....i have a 98 cobra vert and there dont seem like many springs for the verts so i was gonna go with the Eibachs or FRPP "G" springs myself until a few of the guys at maximummotorsports.com said that the rear springs would be too light for a convertible. They have there own springs which H & R did the manufacturing on so i am looking at them.

They have a MM street spring which lowers 1.25" but is compared to the H & R race spring in spring rates...750/850lbs. up front. They also have MM road & track spring which is 600/780lb. in front and 275/300lbs. in back that lowers 1.5"..........i am thinking of going with those. Does this spring rate sound like it would be comfortable enough combines with bilsteins or would it be a harsh ride?

 

[Ciotti]

jzepp, they don't sound too stiff at all and 6 months ago when I was planning to set my car up heavily for autocross and road race I would have been all over those, but lately I'm realizing that since it's a daily driver and its FUN AS HELL to run it down the quarter at Atco, I want the rear springs to have a bit more squish to them so that I can get a bit better weight transfer off the line.

They're a lot stiffer than stock so I'm sure they'll be ok, the last thing I need with these AWFUL NJ roads especially the one I drive every god dam day to work is to have springs that are too stiff and will rattle me and the car to pieces