Well when you consider the stock 4 cylinder spring was 370 to 400 lb rate (in the stock location), I don't feel 250 lbs for a coil over is bad. Excerpt - Official Ford Mustang 5.0 Technical Reference and Performance Handbook : 1979-1993  -  Bentley Publishers - Repair Manuals and Automotive Books If this is a true coil over strut and spring combination, I am guessing you would like it at 250lbs. Lighter is recommended by a lot for drag racing (<175lbs).

 

I have Strange coils up front with MM CC plates and 12x200 springs. They are way too stiff. I have a set of 175lb. springs sitting in the garage to try next.

Sounds like I'm in a similar boat as you. I'm fairly confident the 175 spring will give me what I'm looking for, in a mostly street driven car.

 

Im running 250s street only...i think it feels fine...doesnt ride like a cadillac but i dont want it to lol

 

^agree^
I've had both 225# and then 250# over Bilstein HD's and I'm very happy with the ride quality,and the roads up here a like wagon trails.
That said,there is no way I would run anything more than a 275# spring on the street(depending on wheel/tire size).The folks that are recommending 300#-325# springs for a street driven vehicle must have some really nice roads to drive on or a spine made of Titanium.

You should really be converting to "wheel rates" to get the proper split front to rear when choosing your springs.Changing to a much softer front spring may necessitate a change of rear springs and vice versa.
For as close as I care to calculate I have wheel rates of 225 lb/in. front and 204 lb/in.(median) rear with my current setup which to me represents a good balance front to rear.
Coil-Over Suspension Frequently Asked Questions

 

Given the motion ratio difference, you can't compare a strut/coil-over spring rate with the rate for a spring in the stock location... The stock location requires a MUCH stiffer spring because of the leverage.

Weight, front/rear balance, wheelbase, etc are similar between my car and the fox bodies. I run coilovers in front (traditional MacPherson strut set up) - 275 lb/in. My aftermarket "sport springs" were about 180 lb/in. Stock was about 150 lb/in. While the spring rate is significantly higher than stock, the ride quality with the 275 Eibachs and Koni Sports is MUCH improved compared to the sport springs/Bilstein HD's that were on before. While firmer and more taut, because of the increased rate and MUCH higher damping rates of the Konis, all bumps are one and done. Bumps are quieter and motions much more controlled. I add this only to point out - increased rate/damping does not necessarily mean there's a penalty to ride quality.

 

As Michael noted, the only way to compare spring rates is to covert to the wheel rate (WR). WR is what the tire sees. This WR conversion takes into account the motion ratio of a conventional spring location and that of a C/O location.

For discussion purposes, lets take a conventional FRPP "C" spring at 650#. The WR of that spring is 163# (rounded). The WR of a 250# C/O spring is 225#. As you can see, the C/O has a higher WR despite a lower rating.

With that said, because of where the C/O is mounted, it reacts much faster with less friction than a conventional spring effectively causing a better ride. Thus one can run a higher WR with a C/O and get a better ride than the equivalent WR conventional spring.

 

Damn, I'm running 275's in my fox and they feel/ride fantastic. Way better than the Saleen and FMS springs I've ran in the past.

 

I've got 175s but think they're still a little too stiff.may try 150s this winter.

 

ive got 125's and love it!