How do I determine spring rates?
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Freshman User
Joined: May 2003
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How do I determine spring rates?
Hello.
I have to replace the rear springs on my 1991 Aerostar Sport standard bed.
The old ones: F19A-5534BA (door label spring code K B)
and are regular wound coil.
The replacements available: F19A-4434AB and are variable rate coil, from a mid90's Aerostar. 400 miles on 'em. (Difference is BA versus AB).
Question: I know they will fit, but am I replacing with a lesser spring that cant handle just a family of 4? Maybe some 1000#/100# tongue towing???
$10 for these, or $60 for the one-size-fits-all Moogs?
Thanks guys!
I have to replace the rear springs on my 1991 Aerostar Sport standard bed.
The old ones: F19A-5534BA (door label spring code K B)
and are regular wound coil.
The replacements available: F19A-4434AB and are variable rate coil, from a mid90's Aerostar. 400 miles on 'em. (Difference is BA versus AB).
Question: I know they will fit, but am I replacing with a lesser spring that cant handle just a family of 4? Maybe some 1000#/100# tongue towing???
$10 for these, or $60 for the one-size-fits-all Moogs?
Thanks guys!
Last edited by 1991Aerostar; Jun 19, 2003 at 02:39 PM.
Postmaster
Joined: Apr 2001
Posts: 3,818
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How do I determine spring rates?
I ran both those part numbers through an online Ford parts search and both came back as invalid part numbers. (???) (http//:www.fordpartsonline.com) You may want to take this question to your local Ford parts counterman and see if he/she can determine the application for the used ones. There were different springs for the standard, extended and E4WD versions that year along with commercial applications (ultility van versions, etc. with heavier duty spring rates.) Sorry, can't offer any more help than this. Perhaps others can shed some light on the situation.
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How do I determine spring rates?
Thanks Aero.
I did just that this afternoon and he said the numbers weren't in the database anymore. And he couldn't say how the rates may have differed.
He did offer teat they should work just fine so long as they're put in as a matched pair and weren't of seperate vans. He mentioned the specific numbers were really for replacing one spring out of the four corners on a specific car, say one in an accident.
I would like to know if they were out of a std, or 4wd or other just to know how they'll behave.
I find it interesting too how Moog can sell springs for 2wd or 4wd only. No other considerations. Perhaps I look too much into this spring rate thing. Heck, they all have the same ford parts numbers, just different suffix letters for the rates.
I did just that this afternoon and he said the numbers weren't in the database anymore. And he couldn't say how the rates may have differed.
He did offer teat they should work just fine so long as they're put in as a matched pair and weren't of seperate vans. He mentioned the specific numbers were really for replacing one spring out of the four corners on a specific car, say one in an accident.
I would like to know if they were out of a std, or 4wd or other just to know how they'll behave.
I find it interesting too how Moog can sell springs for 2wd or 4wd only. No other considerations. Perhaps I look too much into this spring rate thing. Heck, they all have the same ford parts numbers, just different suffix letters for the rates.
Postmaster
Joined: Apr 2001
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How do I determine spring rates?
Were I in your situation, I'd say, heck, for $10.00 a set, why not give them a try? Its a pretty easy swap out and likely as not, you will have equal or better capacity to what you now have. Just a thought.
Posting Guru
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From: PNW
How do I determine spring rates?
I too tried to find out spring rate data from the dealer and they were no help. The parts guys had no data. I was trying to get something stiffer since the stockers are sagging and seem too soft. Anyway, the Ford parts guy told me that all he could sell me were the ones that matched the spring code on the door jamb, nothing different than what it came with. Something to do with liability (just one more benefit we get from all those frivolous lawsuits and unscrupulous lawyers).
Junior User
Joined: Oct 2002
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How do I determine spring rates?
The spring rate chart should be listed in the factory shop manual, in the suspension section. The parts people at most dealers don't have access to info such as this.
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How do I determine spring rates?
Thanks 01 and all!
Since the Aero has 2 empty benches, and rarely a full load, I grabbed a set of NEW $15, AB rated, original Aerostar springs off eBay. I know they will fit my Aero, and shouldn't be far off the old BA rated springs. Since the only aftermarket coils were cargo type, which I would rarely use, I am trying the OEMs first to keep the soft ride. Ohio has lots of concrete expansion crack roads! As said earlier $15 won't break me, and its a easy install to experiment with.
Now for the fronts, Oy!
Since the Aero has 2 empty benches, and rarely a full load, I grabbed a set of NEW $15, AB rated, original Aerostar springs off eBay. I know they will fit my Aero, and shouldn't be far off the old BA rated springs. Since the only aftermarket coils were cargo type, which I would rarely use, I am trying the OEMs first to keep the soft ride. Ohio has lots of concrete expansion crack roads! As said earlier $15 won't break me, and its a easy install to experiment with.
Now for the fronts, Oy!
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Thread Starter
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Freshman User
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How do I determine spring rates?
Got the springs installed today. Both side upper retainer bolts broke off though. Had to drill them out and replace with Grade 8 bolt and nuts. Ride is just fine.
Fronts are next.
The whole right side had a nasty lean to it. Still some though. I figured the front were at fault anyway.
Installed FORD Class II hitch while I was at it. Works great. Thanks for all the info guys.
Fronts are next.
The whole right side had a nasty lean to it. Still some though. I figured the front were at fault anyway.
Installed FORD Class II hitch while I was at it. Works great. Thanks for all the info guys.
Cross-Country
Joined: Jul 2002
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How do I determine spring rates?
Look at the site http://www.cswnet.com/~carother/coil...calculator.htm
and you'll find an easy way to determine different spring rates using the wire diameter, coil outside diameter, and the number of active coils. I just calc'd my 96 AWD extended and the rears are 140 #/inch, which sounds like a reasonable answer. If anyone has the so-called "cargo" coils, I'd sure be interested in what the rates are on them. I'd bet they aren't very stiff. As a point of reference, the spring rates in the front of an old Corvette were up to 550#/inch, but the effective rate was probably half that due to the leverage of the A-arm acting on the spring.
and you'll find an easy way to determine different spring rates using the wire diameter, coil outside diameter, and the number of active coils. I just calc'd my 96 AWD extended and the rears are 140 #/inch, which sounds like a reasonable answer. If anyone has the so-called "cargo" coils, I'd sure be interested in what the rates are on them. I'd bet they aren't very stiff. As a point of reference, the spring rates in the front of an old Corvette were up to 550#/inch, but the effective rate was probably half that due to the leverage of the A-arm acting on the spring.
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How do I determine spring rates?
Sounds interesting. I just took a quick look at the site. But I have a question? What or how would you calc the rate of a variable coil? I mean the rears on my 91 had increasing diameter of wire from the top down. And 140#?inch sounds awfully light. The crown vic I was running ran with 710#/inch coils...
Not being contradictory
,, just trying to reconcile what I've seen. Thanks for the site.
PS. I just had reeplaced the BA rated coils with new (ford takeoffs) AB rated coils. The stood up better than the squished originals but they still sat on the first two loops that are rubber coated.
Not being contradictory
,, just trying to reconcile what I've seen. Thanks for the site.PS. I just had reeplaced the BA rated coils with new (ford takeoffs) AB rated coils. The stood up better than the squished originals but they still sat on the first two loops that are rubber coated.
Last edited by 1991Aerostar; Jul 25, 2003 at 06:12 AM.
Cross-Country
Joined: Jul 2002
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How do I determine spring rates?
Well, you have a point about variable-rate coils--it IS more complicated to calc these, and the calculation table I referred to doesn't account for this variation.
Actually 140 #/inch is right in the ballpark for typical rear spring rates. 710#/inch is not likely for anything this side of a NASCAR vehicle unless the axle has leverage on the coils such that the EFFECTIVE spring rate at the axle is much, much reduced (for example, if the coil is mounted on a trailing arm between the pivot on the chassis and the connection at the axle. Notice also that because the Aerostar rear springs are mounted on a trailing arm BEHIND the axle (and not between the pivot point and the axle), the effective spring rate at the axle is actually higher (my guess without measuring everything is 10-20%) than the rate for the spring itself.
Note also that any coils that are already compressed/touching when the vehicle is at normal ride height do not count as active coils.
Actually 140 #/inch is right in the ballpark for typical rear spring rates. 710#/inch is not likely for anything this side of a NASCAR vehicle unless the axle has leverage on the coils such that the EFFECTIVE spring rate at the axle is much, much reduced (for example, if the coil is mounted on a trailing arm between the pivot on the chassis and the connection at the axle. Notice also that because the Aerostar rear springs are mounted on a trailing arm BEHIND the axle (and not between the pivot point and the axle), the effective spring rate at the axle is actually higher (my guess without measuring everything is 10-20%) than the rate for the spring itself.
Note also that any coils that are already compressed/touching when the vehicle is at normal ride height do not count as active coils.
