Spring Rates

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Revision as of 08:12, 28 March 2013

Wether using stock-diameter springs or small-diameter coilover setups, choose your spring rates for your style of driving. Datsun 1200 in stock form uses 89.6 lb/in front springs, and a rear leaf spring of 109 lb/in. The front spring rate is best for comfort, while the rear spring rate is stiffer to allow for loading and rear seat passengers. Some racing applications will want far far stiffer spring rates.

Overview

Remember that the stock spring rate is 91 pounds/inch, so 250 pound springs will result in a very stiff ride, suitable for track racing with a lowered car. Not recommended for bumpy surfaces such as public streets or off-pavement racing. For street use, consider 175 pounds the upper limit.

Front Spring Rate

Datsun 1200 in stock form uses 89.6 lb/in front springs, which is the best for comfort. The stock suspension if in good shape results in a smooth comfortable ride. It is not bouncy if you have original specification strut-shocks in good condition.

Lowering

Lowering the car decreases the suspension travel. This increases the probability of bottoming out. Therefore, heavier springs are called for to help prevent bottoming out. This causes a stiff, uncomfortable ride but is the price paid for the good looks of lowering. It also requires a shock different from stock specification.

See main article: Lowering

Autocross

For autocrossing, 250 lb/in rate is what many use. The tight turns at speed want a flat ride, and comfort is not important in rallying. Keeping the car composed with quick directional changes are what's important.

Dedicated autocross: 250 lb/in with A12 or 275 lb/in with A14/A15

Part-time street/autocross: 175 lb/in springs

Gary_P says:

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On my street/autocross 1200 I'm running 250# springs in the front. They seem to match up with the rear leaf springs nicely. If you stiffen the front with higher rate springs and/or stiffer anti-sway bar you will need to add a rear anti-sway bar, preferably an adjustable one so you can balance the handling of the car.

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Rally

For off-tarmac rallying, on dirt or gravel or other loose surface,

Circuit Racing

Benny:

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I currently run a kings spring 275 lbs 180mm free length spring in my track car and a 5kg/mm generic [280 lb] 180mm free length in my streeter with a tender spring. I would say that its [streeter with 280lbs] just a tad too firm for the street. 4kg /mm [220 lb] would be better.

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Drag Racing

For drag racing, soft springs are called for with an 80/20 shock. This allows the front end to rise up, transferring maximum weight to the rear.

Rear Spring Rate

Sedan,Coupe: 109 lb/in
Van:         137 lb/in
Truck 4-leaf:149 lb/in
Truck 5-leaf:203 lb/in