How to test the rear spring
04-14-2005, 01:42 PM
#1
Melting Slicks
Thread Starter
How to test the rear spring
I realize this is a sour subject and the sagga continues for some of us.
I feel the rear sits reasonably OK. I believe it is around 29", which I can live with. However; to get at the height I had to use 10" bolts and the spring and nuts are well below the rim. I'll try and remember to post a couple of pictures.
Anyway, I thought of a way to possibly figure out if this spring will ever work and thought some of the DIY 'engineers' may be could add some input if this procedure is in the ballpark.
Raise the car on jack stands and loosen the nuts on the spring bolts just until there is no load on the spring. Next would be to measure from the bottom of the rim to the floor and measure from the bottom to the nut to the floor. Then subtract the nut measurement from the rim measurement. This is the distance the bottom of the nut would be from the rim.
The spring I have is the 330lb composite. I have never tested these, so I am assuming that the end of the spring will move 1" for every 330lb of force applied to it. Although I do not have the exact weight being place on each rear wheel, I think it is safe to guess around 850lbs. Therefore, that weight will flex/compress the spring approximately 2.5".
If the above calculated nut to rim distance is less than 2.5", then the nut should be above the rim when the weight of the car is on the spring. If the distance is greater than 2.5" than it will be below the rim.
What have I missed or is the whole reasoning wrong and not applicable?
I feel the rear sits reasonably OK. I believe it is around 29", which I can live with. However; to get at the height I had to use 10" bolts and the spring and nuts are well below the rim. I'll try and remember to post a couple of pictures.
Anyway, I thought of a way to possibly figure out if this spring will ever work and thought some of the DIY 'engineers' may be could add some input if this procedure is in the ballpark.
Raise the car on jack stands and loosen the nuts on the spring bolts just until there is no load on the spring. Next would be to measure from the bottom of the rim to the floor and measure from the bottom to the nut to the floor. Then subtract the nut measurement from the rim measurement. This is the distance the bottom of the nut would be from the rim.
The spring I have is the 330lb composite. I have never tested these, so I am assuming that the end of the spring will move 1" for every 330lb of force applied to it. Although I do not have the exact weight being place on each rear wheel, I think it is safe to guess around 850lbs. Therefore, that weight will flex/compress the spring approximately 2.5".
If the above calculated nut to rim distance is less than 2.5", then the nut should be above the rim when the weight of the car is on the spring. If the distance is greater than 2.5" than it will be below the rim.
What have I missed or is the whole reasoning wrong and not applicable?
04-14-2005, 02:25 PM
#3
Drifting
Member Since: Mar 2003
Location: Canberra AUSTRALIA
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St. Jude Donor '05-'06
Originally Posted by mandm1200
I realize this is a sour subject and the sagga continues for some of us.
I feel the rear sits reasonably OK. I believe it is around 29", which I can live with. However; to get at the height I had to use 10" bolts and the spring and nuts are well below the rim. I'll try and remember to post a couple of pictures.
Anyway, I thought of a way to possibly figure out if this spring will ever work and thought some of the DIY 'engineers' may be could add some input if this procedure is in the ballpark.
Raise the car on jack stands and loosen the nuts on the spring bolts just until there is no load on the spring. Next would be to measure from the bottom of the rim to the floor and measure from the bottom to the nut to the floor. Then subtract the nut measurement from the rim measurement. This is the distance the bottom of the nut would be from the rim.
The spring I have is the 330lb composite. I have never tested these, so I am assuming that the end of the spring will move 1" for every 330lb of force applied to it. Although I do not have the exact weight being place on each rear wheel, I think it is safe to guess around 850lbs. Therefore, that weight will flex/compress the spring approximately 2.5".
If the above calculated nut to rim distance is less than 2.5", then the nut should be above the rim when the weight of the car is on the spring. If the distance is greater than 2.5" than it will be below the rim.
What have I missed or is the whole reasoning wrong and not applicable?
I feel the rear sits reasonably OK. I believe it is around 29", which I can live with. However; to get at the height I had to use 10" bolts and the spring and nuts are well below the rim. I'll try and remember to post a couple of pictures.
Anyway, I thought of a way to possibly figure out if this spring will ever work and thought some of the DIY 'engineers' may be could add some input if this procedure is in the ballpark.
Raise the car on jack stands and loosen the nuts on the spring bolts just until there is no load on the spring. Next would be to measure from the bottom of the rim to the floor and measure from the bottom to the nut to the floor. Then subtract the nut measurement from the rim measurement. This is the distance the bottom of the nut would be from the rim.
The spring I have is the 330lb composite. I have never tested these, so I am assuming that the end of the spring will move 1" for every 330lb of force applied to it. Although I do not have the exact weight being place on each rear wheel, I think it is safe to guess around 850lbs. Therefore, that weight will flex/compress the spring approximately 2.5".
If the above calculated nut to rim distance is less than 2.5", then the nut should be above the rim when the weight of the car is on the spring. If the distance is greater than 2.5" than it will be below the rim.
What have I missed or is the whole reasoning wrong and not applicable?
Is the spring rate truly linear on a composite spring? The first inch may take 330LB but does the next inch also take 330LBs?
Do you have a bolt long enough? When I installed my 300LB VBP I needed to compress (push up) on the spring a little to get the bolt in. I think you wil need a 11-13 inch bolt to experiment.
Getting a longer bolt doesn't solve the problem. I went through 3 springs. The only way to get the car to sit right is to put on a VBP spring OR a steel spring that has been arched right. I have a 300LB VBP. Car handles like a dream and sits well on the road.
I have 17" wheels now so I could lower it (by adding longer bolts) if I wanted. Those with 15" wheels are messing with mecahnical forces if they use 10" bolts on 15" wheels with 60-70 profile tires.
I just hope no-one gets hurt driving at high speed by the bolts taking out a tire during a sudden avoidance turn or the like. In a straight line on a smooth road there may (MAY) never be a problem.
04-14-2005, 02:40 PM
#4
Le Mans Master
Originally Posted by mandm1200
Raise the car on jack stands and loosen the nuts on the spring bolts just until there is no load on the spring.
What have I missed or is the whole reasoning wrong and not applicable?
What have I missed or is the whole reasoning wrong and not applicable?
You cannot loosen the nuts until there's no load on the spring - when the spring is unloaded you're way off the bolt....
04-14-2005, 02:49 PM
#5
Melting Slicks
Thread Starter
Originally Posted by RedBad1979
You cannot loosen the nuts until there's no load on the spring - when the spring is unloaded you're way off the bolt....
04-14-2005, 03:01 PM
#6
Le Mans Master
Originally Posted by mandm1200
It's been 6 months or so; I don't recall if the spring hangs down lower than the 10" bolts. That may be the case with the multileaf steel spring and 6" bolts.