Spring rate f/r relationship question - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 4 Old 06-27-2011, 10:00 AM Thread Starter
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Spring rate f/r relationship question

I want to significantly increase my wheel rate. If I am currently satisfied with the f/r balance (I'm not quite) should my increase keep the same wheel rate specific number Difference (such as 100 lb/in less in the rear) or should I increase each end by a percentage of wheel rate?

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post #2 of 4 Old 06-27-2011, 01:18 PM
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If the weight distribution is 60:40, you'd want the front wheel rate to be 1.5X that of the rear.
Notice that is WHEEL rate, so you have to factor in spring rates to achieve those wheel rates.

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post #3 of 4 Old 06-27-2011, 02:00 PM
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If it's flat ride pitch behavior that you're talking about maintaining, you'd probably need to increase the rear wheel rate a little bit more than proportional to the front wheel rate. IOW, a front wheel ride rate increase of 33% might need a rear wheel ride rate increase of, say 40%. This is more of a street-driving consideration.

If it's a matter of roll stiffness and lateral load transfer that you want to hold constant, you should also consider the effect of the stabilizer bar(s) and roll center heights. In this case due to having a much stiffer front bar a 33% increase in front wheel ride rate should only need a smaller increase in rear wheel ride rate in order to maintain that balance.


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post #4 of 4 Old 06-28-2011, 08:47 AM Thread Starter
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Thank you guys for the replies. This is a track only car so more roll stiffness is my desire while maintaining the amount of understeer that I currently have. The car is a 98 cobra with factory swaybars as far as I know. Front springs are conventional 800's and rears are 350's (torque arm). Down south tracks tend to get bumpy so I need to keep that in mind. I am considering going coilovers all around with something north of 400 lb/in springs on the front. If I go 425 on the front then 300 on the rear should be an equal increase per percent of wheel rate. Since I know how the car handles now I believe I would do better to work off this vs. A 1.5 factor. I feel like a small move towards oversteer would benefit this car so based off Norm's comments going with a 425/300 setup may be a good starting point as it may make the f/r relationship be a little more stiff on the rear.
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