Rear springs...what to run?

[Slick_89_Hatch]

I am trying to figure out what rear springs to run on my car. I have 10" 275lb springs up front on my coilovers and I find the rear end will sag with the car in motion. I think I need to move to a stiffer rear spring. When the car is sitting, ride height is good, but when it's moving it is too low. Currently have Pro Kit's in the back. I was thinking of something like a H&R race spring but looking for idea's. Drop is not so much of a concern as I have height adj control arms.

[Parkway Ford Lincoln SVT]

Beware of too much rear spring rate in a Fox unless you have a torque arm or 3-link. Acceleration grip is easily lost with springs that are much stiffer than stock.

[Slick_89_Hatch]

Good to know, thanks Ed! Any recommendations? I have a set of Steeda sports I will try, the rates appear to be the same though. Is the "sag" partially because the coilovers have very little give?

[RedSN]

275 sounds like a lot of spring up front.

[Slick_89_Hatch]

So ive heard.....i should have went 225 which would still be more than enough and a little more comfortable on the street although the 275 doesn't ride too bad.

[tulowd]

selecting proper spring rate has to do with 3 things; besides having shocks that can control the springs properly:

intended usage - street cruise, drag, road course, slalom etc
tire grip available - need stiffer springs with stickier tires cause they send greater forces into the chassis
car weight bias / distribution; adding blower or other front weight means you need more spring rate

All of this needs to be converted into a common denominator. Quoting front coil over spring rates vs rear conventional springs directly is meaningless. \

Wheel rate is what matters; then everything can be compared on the same scale. Front to rear balance is obviously important.

http://www.maximummotorsports.com/faq_coilover.aspx

http://www.maximummotorsports.com/tech_front_susp_coilover.aspx

http://www.maximummotorsports.com/tech_rear_susp_coilover.aspx

[ZR]

Your not far off on the fronts, especially if you like a lil spirited driving tossed into the mix. If more compliant ride is what your after, dropping even 25lbs make a substantial difference. Given the price point of c/o springs, not all that expensive to experiment. I've also noted considerable differences in results using long vs short versions of the same rate c/o springs.
Rears, best to figure out exactly what your after before moving forward. Fact the Pro kit springs are too soggy, given their ridiculous inconsistency kit to kit, not surprised. Seeing most, but not totally consistent results, from either Maximum Road & track or H&R spring kits.
Almost forgot, when running Bilstein + coil overs on the front of the cobra, ran 275lb on the street / 350 for lapping days (tried every spring from 225-350lb plus few in more than one overall length). Could not stand the ride of anything over 275 on the street. Fast forward to upping the game to Koni adjustables this year, current all use front springs are 475lb combined with 650lb rears. Ride is firm but well on the side of comfortable. Never would have dreamed it would even remotely decent with spring rates that high. Maybe even more important that the springs you choose, shocks your using to control them.
Was always pleased with the Bilsteins but wish I'd gone with Koni's from the get go. Also wish I'd not messed around with so many conventional style springs and jumped to coil overs from day one. Few can believe how well mannered a coil over equipped Fox and beyond stang rides on coil overs, not just for the race track or ultra performance driving, great choice for the Sunday cruizer.

[Slick_89_Hatch]

Thanks Rick. I actually find the 275's are not too bad. My Illumina's seem to handle them pretty well too. I am currently not that concerned with the springs upfront, for the most part im pretty happy with them. If the Pro Kit's are known to be a bit soggy, I may try swapping in the Steeda sports I have and go from there. I like "spirited" driving on the street, primary use is a good street handling car. It does see the occasional drag stip day and eventually road course for a little fun. As it sits the car was hitting 1.7's at St thomas all day with MT ET Street radials. If I had the coin I would do a rear coil over conversion.

[ZR]

I think your on the right track, especially given the fact you already have them and not a big deal to swap n try out.
Have fun.

[RedSN]

Your not far off on the fronts, especially if you like a lil spirited driving tossed into the mix.
With the soft Eibachs in the rear?
What I meant in my post was that the 275's are too much for the current setup.

If it were me, and budget allows, I would be putting a coil over kit in the rear as well, and matched to the front. As tulowd said: it's about balance and intended use.

street use, occasional drag strip, eventually road course.
That's a tall order for a single setup to handle.

[Slick_89_Hatch]

With the soft Eibachs in the rear?
What I meant in my post was that the 275's are too much for the current setup.

If it were me, and budget allows, I would be putting a coil over kit in the rear as well, and matched to the front. As tulowd said: it's about balance and intended use.

street use, occasional drag strip, eventually road course.
That's a tall order for a single setup to handle.

I know im asking alot...lol....it won't be perfect at anything but pretty good at all 3 would be great :) Aside from the sag it works very well on the street and not bad on the drag strip either!
As far as road coarse, just want it good enough to have a little fun as an inexperienced driver. I'll swap in the Steeda's and see if that helps.

[ZR]

With the soft Eibachs in the rear?
What I meant in my post was that the 275's are too much for the current setup.

If it were me, and budget allows, I would be putting a coil over kit in the rear as well, and matched to the front. As tulowd said: it's about balance and intended use.

street use, occasional drag strip, eventually road course.
That's a tall order for a single setup to handle.


No, good if the rear is matched up to the front.