Need coil spring/ride height help

[mbrew2]

OK, I guess a made a classic mistake. When I replaced the front suspension on my 73 vert I installed a set of Scott Drake 1" lowering springs and KYG gas-adjust shocks. Ride is so harsh its almost like a solid suspension when I hit bumps - jars the whole car. I just spoke to Eaton Springs for their help. Their stock spring is rated at 292 lbs, their performance spring is rated at 362 lbs. According to Scott Drake spec the spring I put on is 600 lb.!!!! going to go with Eaton performance spring but need help with how much drop to get. They offer -1, -1.5, and -2 in springs. Problem is, I like the stance of the car with Drake springs but I think they dropped the car more than 1". To find out what to order, I need to find out the factory ride height. I'm running 225/60/15 BFG's on the front and it measures approx 25 inches to the fender lip the way it sits now. Any help or advise would be much appreciated. Got to get these thing changed before it knocks everything on this old vert loose.

 

[Don C]

You can go here to get the factory ride heights

https://www.7173mustangs.com/thread-underbody-dimensions?pid=298050#pid298050

 

[Hemikiller]

I recommend that you ditch the Gas A Justs before going to different springs. If you want a more factory ride, try the KYB Gr-2s, they're about $80 / set of four from RockAuto. I just swapped mine out last weekend and the ride difference is amazing.

As far as Drake's springs, I seriously doubt that they are 600lb rate. any time you see a spring listed as "620", it's because the wire diameter is .620", not because they have a 620lb rate. I bet the tech gave you some bad info. The 73 Mustang springs were all right around 300lb rate for non-CS cars, and upwards of or slightly over 400lb rate for CS equipped cars, equipment load out and engine dependant.

If you give me your original engine, trans type, A/C, P/S or not, I can get you the original Ford part #.

What did you use for rear springs?

 

[mbrew2]

I recommend that you ditch the Gas A Justs before going to different springs. If you want a more factory ride, try the KYB Gr-2s, they're about $80 / set of four from RockAuto. I just swapped mine out last weekend and the ride difference is amazing.

As far as Drake's springs, I seriously doubt that they are 600lb rate. any time you see a spring listed as "620", it's because the wire diameter is .620", not because they have a 620lb rate. I bet the tech gave you some bad info. The 73 Mustang springs were all right around 300lb rate for non-CS cars, and upwards of or slightly over 400lb rate for CS equipped cars, equipment load out and engine dependant.

If you give me your original engine, trans type, A/C, P/S or not, I can get you the original Ford part #.  

What did you use for rear springs?

The 600 lb/in rate was what is listed in the catalog for spring rate. All I know is that its way too stiff for this car. Your factory rates above are very similar to the information I was given from Eaton.

1973 convertible, 351 2v, FMX, A/C, power steering.

I think you are right about the KYB shocks combined with these springs. That was also a recommendation from Eaton. I have not changed the rear springs but am running the KYB shocks on them too and and they're Ok on the rear. 

Looking for a little stiffer feel for the front, just not bone-jarring. Thats why I though The Eaton 362lb springs might be a good compromise - something between factory stock and CS equipped spring rates.

 

[Hemikiller]

I see that in their catalog, again, I have my doubts. I'd like to get some measurements on those to see what they match up to.

Stock springs for your car:

C9OZ-5310-F - 8.5 coils, .630" wire, 16 5/8" free length , 1900 lb load

Moog crosses that as the 8350 spring, but the specs are off - 16.64 free length, .65 wire and 2117 lb load for a 345l lb/in rate.

A closer replacement is the Moog 8330 w/ 16.625 free length, .620 wire. 1809 lb load and a 290 lb/in rate.

Competition suspension spring for your car is Moog 8356 - 15.05 free length, .650" wire and 1900 lb load, with a 418 lb/in rate

I've always jsut trimmed my coils to get the ride height I wanted. The "1" lowering springs" are so arbitrary as to be completely useless. Drop an aluminum intake and set of head on a car and it's going to ride higher. Most of us has reduced the weight of our cars in some respects.

 

[mbrew2]

I see that in their catalog, again, I have my doubts. I'd like to get some measurements on those to see what they match up to.

Stock springs for your car:

C9OZ-5310-F - 8.5 coils, .630" wire, 16 5/8" free length , 1900 lb load

Moog crosses that as the 8350 spring, but the specs are off - 16.64 free length, .65 wire and 2117 lb load for a 345l lb/in rate.

A closer replacement is the Moog 8330 w/ 16.625 free length, .620 wire. 1809 lb load and a 290 lb/in rate.

Competition suspension spring for your car is Moog 8356 - 15.05 free length, .650" wire and 1900 lb load, with a 418 lb/in rate

I've always jsut trimmed my coils to get the ride height I wanted. The "1" lowering springs" are so arbitrary as to be completely useless. Drop an aluminum intake and set of head on a car and it's going to ride higher. Most of us has reduced the weight of our cars in some respects.

Thank you for this information! I really appreciate your effort.  As to the car - It does have an Edelbrock intake and I have replaced the factory air with a simple Sanderson style compressor and system from Classic Auto Air. My estimate would be at least 100 lbs off the nose. The guy at Eaton also asked specifically about modifications from factory. Based on this information, he suggested springs for a non-ac car. He also suggested, as you did, that the best thing would be to buy stock springs and cut them to get the ride height I was looking for. They even have a tutorial on their website for cutting springs. Basically, they say cut, drive hard, check ride height, repeat as needed. Problem is, I have gotten older and have health issues that prevent me from doing this myself and I'm afraid that hiring a shop to go through this would be cost prohibitive. 

Tomorrow I will try to take some measurements from the frame as shown in my shop manual, probably at the front bumper arm mounting hole. According to the diagram, factory spec is 11.91". According to Marti, car came with E70/14 which is real close in diameter to the 225/15 on the car now. Hopefully, this will give me some idea of how much the car is lowered and I can go from there.  At this point, I am willing to give up some in ride height for improved ride.  Never ridden in a car with CS suspension so I really don't know how stiff a 418 lb rate is, which is why I am leaning toward Eatons 362 lb spring as sort of half-way between stock and  CS specs. Also will ditch the Gas-adjust shocks. Eaton suggested Qal (sp?) adjustable shocks which are ridiculously expensive or Eldebrocks as an alternative. I'll probably go with the lighter KYB as you suggested. 

Again, thanks for your help. I'll try to take some measurements of the Drake springs when I get them off - #coils, wire dia, and free length as close as I can and relay the info to you.

 

[mbrew2]

Well, after several conversations with Gary at Eaton Spring, I ordered a set of custom 1" drop competition springs to replace the Scott Drake springs.  Not actually sure of the spring rate but we talked about somewhere around 450#.  Daylight and Dark! Car actually rides/drives like it has a suspension now but still feels "planted". Firm but not bone-jarring. Still running gas-a-just shocks but they don't seem to be a problem. Wire size difference and length between Eaton and Drake was dramatic.

Funny (and scary) thing was that the poor guy who did the swap didn't have a clue as to how to  change out the springs. The shop that I took it to does a lot of work on classic cars but this guy was used to working on struts, not top-loaded springs on our cars. Fortunately, this is a shop that allowed me to hang out in the shop while he was working on the car. At first, I didn't want to be one of those know-it-all guys that intervenes in others business but when he put it on the lift, dropped the wheel, and started to use a 4' prybar to try and dislodge the 600# spring, I was sure somebody was about to get hurt. I stopped him and told him that I had to use a spring compressor to put those things in and that was scary for me but not nearly as scary as that loaded spring coming out and bouncing all over the shop. Finally, an experienced guy came over to help him and explained the process. Took poor guy 5 hours to swap out 2 springs but he managed with no injuries. I was physically and emotionally exhausted standing by his side the whole time helping hold things, guide things in place, etc. But, now he knows how to do it safely.

 

[Stanglover]

I'm not sure if you have read on old post of mine about my front end replacement kit I bought from Scott Drake.

In a nut shell, this 'kit' was listed for the 71-73 Mach 1, no A/C. It did not say anything about auto or manual trans, i.e. weight difference.

When I got it and took it to my local shop to install, it was found that while all the components were quite good and installed without issue, the springs they include were not. My 'guy' did have a spring compressor, but taking out the original springs scared the crap out of him. Putting the new springs in scared him even more. On these, the wire gauge was thinner, but the height was 2" more. Thinking the old springs had sagged, he put them in. When the car was back on its wheels, the front end pointed skywards, way too high (by 2"). When I contacted the vendor, they agreed to take the springs back although, as it was a kit, not supposed to.

I contacted Eaton Springs to get the correct specs for MY car. The old springs turned out to be still right on spec for height and not distorted at all, so I had them put back in. I too use KYB Gas-A-just shocks all round no problem. I also have a 1 1/8" anti sway bar up front and a 7/8" on the back, so yes, my ride is very firm, but not outrageously hard. I did replace my rear springs with Grab-A-Trak standard eye 4 1/2 leaf springs to help stop spring wrap-up. These also turned out to be Scott Drake crap and I needed to install 1" lowering blocks because they sat 1 1/2" higher. They have settled somewhat, but still not enough to take the blocks out. I still may order a correct set from Eaton Springs, but when money permits.

Point here, buy the best from the start.

Geoff.

 

[Mister 4x4]

Great information all! ::thumb::   

Thanks for the follow-up and sharing the information about the different springs.

I'd bought a Super Suspension Kit from Laurel Mountain Mustangs (before they closed, apparently), and I think I have those same springs you got from Scott Drake - they're supposed to be the 1" drop springs, but are so stiff they have almost no give (even with the engine back in, and 3 250lb+ guys standing on the cross members, we couldn't get the car to bounce any at all).  Now I'm just thinking about pulling the springs altogether and going with a set of Aldan American coilovers.

https://aldanamerican.com/product/coilover-kit-ford-mustang-1971-front-450-lbs-in-sku-m1sbf2s/

My big question would be: do I get the 550lb- or 450lb-rated springs for the best ride/handling?  I have a 351C-2V with lots of performance goodies, aftermarket A/C, AOD, RAAMat, subframe connectors, 7/8" rear sway bar, and Lakewood slapper traction bars.  The suspension is otherwise basically stock (KYBs, 5-spring leaf packs, etc.).

The car drives fine (as far as I know - since it wasn't running when I bought it, I have no comparison), but I didn't get the 1" drop I was looking for, and if there's benefit to getting rid of the overly stiff springs, that's what I think needs to happen (I'd hate for it to shake itself apart and/or cause other damage because it essentially has truck springs instead of actually what it really needs).

 

[mbrew2]

Great information all! ::thumb::   

Thanks for the follow-up and sharing the information about the different springs.

I'd bought a Super Suspension Kit from Laurel Mountain Mustangs (before they closed, apparently), and I think I have those same springs you got from Scott Drake - they're supposed to be the 1" drop springs, but are so stiff they have almost no give (even with the engine back in, and 3 250lb+ guys standing on the cross members, we couldn't get the car to bounce any at all).  Now I'm just thinking about pulling the springs altogether and going with a set of Aldan American coilovers.

https://aldanamerican.com/product/coilover-kit-ford-mustang-1971-front-450-lbs-in-sku-m1sbf2s/

My big question would be: do I get the 550lb- or 450lb-rated springs for the best ride/handling?  I have a 351C-2V with lots of performance goodies, aftermarket A/C, AOD, RAAMat, subframe connectors, 7/8" rear sway bar, and Lakewood slapper traction bars.  The suspension is otherwise basically stock (KYBs, 5-spring leaf packs, etc.).

The car drives fine (as far as I know - since it wasn't running when I bought it, I have no comparison), but I didn't get the 1" drop I was looking for, and if there's benefit to getting rid of the overly stiff springs, that's what I think needs to happen (I'd hate for it to shake itself apart and/or cause other damage because it essentially has truck springs instead of actually what it really needs).

I am super pleased with the 400#+ springs I got from Eaton and would suggest you give them a call. They are very helpful in helping you choose a spring just for your specific car mods and your needs.

The ride now is firm but nowhere near bone-jarring. With the Drake springs, I honestly felt like this old convertible was going to break in half when I hit a rough spot. Like having a solid front end with no give at all.

I looked at the Aldan coilover kit and also one from another manufacturer that I can't remember right now but decided against going that route. Saw a video on installing the Aldan unit on an earlier Mustang and it didn't have enough adjustment to lower the ride much below stock. Also, surprisingly, read a bunch of not so favorable reviews about the shocks.

Whichever way you go, if your present springs are as stiff as mine were, you'll be glad you got rid of them.

 

[Don C]

I believe the 550 pound springs would put you in the same situation the Laurel Mountain springs did, a ride like a buckboard.

The 450 pound springs should be plenty stiff, I wouldn't go less than 400s.

 

[jeff8877]

mbrew2,

I have used the Scott Drake 1" lowering springs on both my 73 Mach 1 and my 72 convertible. Both have factory competition suspension and are all stock in the engine compartment including original A/C. The rear springs on both cars are the correct Eaton factory springs. Both cars have factory rims and tire sizes. The 72 has the exact size tires as on your car and my front ground to fender lip is 25 3/8". The 73 sits a bit lower but that is because it has the factory 14" rims and the 72 has the factory 15" rims.

As others have said, I highly doubt these are 600 lb springs. My cars both have a nice ride and I would not say it is stiff or harsh at all. Both cars also have KYB GR all the way around. I was looking for a slight rake front to back and this produced the desired result on both cars.

I would try switching out the shocks first and see if that works. Good luck!

 

[Hemikiller]

Do you still have your Drake springs? I'd love to get the dimensions on them to calculate the actual spring rate. Lots of people seem to have issues with the springs from them, probably too much of the "fits all" mentality.

 

[Mister 4x4]

He actually changed out the Scott Drake springs for some more appropriate springs from Eaton, and is much happier. 

Unfortunately, changing out shocks won't do anything to change the ride height - probably won't have much effect on the actual ride itself either, depending on how stiff the springs are.

 

[mbrew2]

Do you still have your Drake springs? I'd love to get the dimensions on them to calculate the actual spring rate. Lots of people seem to have issues with the springs from them, probably too much of the "fits all" mentality.

I do. If you can guide me on what to measure I will do the best I can to get you the information. I'm curious too.

 

[Hemikiller]

First, measure the 'wire' diameter as accurately as you can, as this is a critical measurement and paint thickness can make a difference. It's preferable to use a dial caliper or micrometer if you have one available.

Then measure the ID and/or OD of the coils parallel to the top of the spring that seats in the shock tower. Again as accurately as you can. These are not such critical measurements as the wire diameter, but if you let me have both they will provide a cross check for the wire diameter measurement given above.

Next, I need the free length, or overall length of the spring.

Finally, count the number of 'active' coils. Do not count the ground portion of the spring, start where it is touches the next coil.

I've often thought that companies screw up the calculations because Ford's spring-on-upper-arm suspension essentially removes half a coil from the "active coils" in the calculations.

 

[mbrew2]

First, measure the 'wire' diameter as accurately as you can, as this is a critical measurement and paint thickness can make a difference. It's preferable to use a dial caliper or micrometer if you have one available.

Then measure the ID and/or OD of the coils parallel to the top of the spring that seats in the shock tower. Again as accurately as you can. These are not such critical measurements as the wire diameter, but if you let me have both they will provide a cross check for the wire diameter measurement given above.

Next, I need the free length, or overall length of the spring.

Finally, count the number of 'active' coils. Do not count the ground portion of the spring, start where it is touches the next coil.

I've often thought that companies screw up the calculations because Ford's spring-on-upper-arm suspension essentially removes half a coil from the "active coils" in the calculations.

OK, here's what I have so far: wire diameter measured in several different coils = .71 to .715, free height = 13 3/8",  # of coils = 8

 

[mbrew2]

First, measure the 'wire' diameter as accurately as you can, as this is a critical measurement and paint thickness can make a difference. It's preferable to use a dial caliper or micrometer if you have one available.

Then measure the ID and/or OD of the coils parallel to the top of the spring that seats in the shock tower. Again as accurately as you can. These are not such critical measurements as the wire diameter, but if you let me have both they will provide a cross check for the wire diameter measurement given above.

Next, I need the free length, or overall length of the spring.

Finally, count the number of 'active' coils. Do not count the ground portion of the spring, start where it is touches the next coil.

I've often thought that companies screw up the calculations because Ford's spring-on-upper-arm suspension essentially removes half a coil from the "active coils" in the calculations.

OK, here's what I have so far: wire diameter measured in several different coils = .71 to .715, free height = 13 3/8",  # of coils = 8

If any of these measurements look odd to you, let me know and I'll try again. Old eyes don't see as well as they used to. I stared coil count at the end of the approx. 1/2 coil at the bottom of the spring to where it lined up with the next coil and so on. When I got to the flatter, top of the spring it worked out that there was close to the same distance between the last coil and the top so I counted it as a coil too. If it helps, space between coils is apprx .88

 

[Hemikiller]

Wow - .715" wire diameter, no wonder the springs were so stiff. Can you also give me the OD of the spring itself?