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Author Topic:   Checking spring rates
xhubby
Dirt Freak

Total posts: 376
posted May 24, 2004 07:11 PM  
Me again. What is the correct way to accurately check spring rates? Can different brands be checked the same way? We have Afcoil & Hypercoil. Thanks.

joeyi
Dirt Roller

Total posts: 20
posted May 25, 2004 04:23 AM  
check your ride heights if any side is lower than use the spring system in the toolbox or find someone with a spring checker lol

xhubby
Dirt Freak

Total posts: 376
posted May 25, 2004 04:49 AM  
I've got access to a spring checker, just wasn't sure how many inches to compress the spring to get the an accurate reading.

sulley
Dirt Roller

Total posts: 9
posted May 25, 2004 05:14 AM  
Spring rates are per inch of travel. I usually put 100lbs of load on the spring then compress an additional inch. Then subtract the 100lbs of preload I put on the spring to get your actual spring rate. Seems to work pretty well for me.

nvracer
Dirt Maniac

Total posts: 127
posted May 25, 2004 07:50 AM  
To check a spring rate, compress the spring 1" check the pressure, compress the spring 1" more, check the pressure. Subtract the 2nd reading from the 1st reading that is the spring rate.

zeroracing
Dirt Forum Champ
Total posts: 1875
posted May 25, 2004 09:35 AM  
that is the correct way, to preload it one inch and then take that reading, then add 1 more inch, and take that one, then subtract the two.
but do not be to worried if your springs are not the exact same as they are supposed to be. it takes about 10,000 to get a really accurate spring checker, but a cheapy whould be close.

xhubby
Dirt Freak

Total posts: 376
posted May 25, 2004 10:40 AM  
Thanks guys. I knew it was something like that, but just wasn't sure.

c21
Dirt Forum Champ
Total posts: 521
posted May 25, 2004 10:46 AM  
I've had great luck with an electonic scale pad sitting in the shop-press.

additionally, for open-ended springs, sometimes it helps to sit it in a lower control arm and then set both on the scale pad (in your press).

c21

juliaferrell
Dirt Freak

Total posts: 370
posted May 25, 2004 12:04 PM  
DTT

rocket36
Dirt Freak

Total posts: 209
posted May 28, 2004 07:57 PM  
the scale pad is what we use too. once you've preloaded the spring one inch, just zero the scales and compress another inch. if you zero again and compress another inch, you shouls end up with a similar reading (unless you've got progressive rat springs). be very care full when compressing springs though, in case they come out. we made a cup and mandrel to hold ours safely.

xhubby
Dirt Freak

Total posts: 376
posted May 28, 2004 09:51 PM  
We checked 3 springs. One of them came right off of the car, the other two had set for at least a year. We ran them down 1", then went 2", then 3". At 2" it doubled on poundage, & at 3" it added the weight of the spring again. (ie: 200 lb spring-200lb @ 1", 400@2", 600@3"). We checked each spring three times. One thing we did notice was that the spring that came right off of the car was consistant all three times. The two springs that had been sitting for a year lost about 10lbs on the 2nd, & 3rd time we checked them. One was a 225lb that read 225 on the 1st time & 115lb on the 2nd & 3rd time, & the other was a 200lb that read 200 on the 1st, & 190 on the 2nd & 3rd time. Maybe old springs are alot like us old racers, they get a little stiff if they set around too long. LOL.

rocket36
Dirt Freak

Total posts: 209
posted May 28, 2004 11:07 PM  
the 200lb-400lb-600lb is good. a 200lb spring means it will take 200lbs to compress one (each) inch. if you DON'T zero your scale the 2nd inch should read 400lb and so on.

carolinafast
Dirt Full Roller

Total posts: 72
posted May 28, 2004 11:30 PM  
interesting..my theory is check every spring the same way same checker every time and don't freaf out when your readings don' t
match the tag

xhubby
Dirt Freak

Total posts: 376
posted May 29, 2004 08:05 AM  
carolinafast, I hear ya. I was surprised that they were as close as they were. I think most spring manufacturers mention a + or - 10% tolerance, or something like that.

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