Thread: help with spring rates please.

i just fell into the canyon scene(very fun btw). i got D2 coilovers on my '91 B13 SE-R with a rear ST sway Bar. the previous owner set it up to be a drag car. i was just wondering what spring rates you guys would suggest for canyons. he gave me an extra pair of springs for them i think he sed they were 10k springs or sumthing likw that. anyways what rates would you guys suggest for canyons and handling? all help will be appriciated.

http://www.d2racing.com/content/products/springs

thanks

First things first. What type of car are we talking about here?

b13 with a ST rear sway bar. (edited #1 post)

Stupid company and their stupid spring rate units. Kilograms? Thanks a lot assholes. How far per x kilograms?!

If you want an extreme street setup that will be really rough on bad roads but kick ass on the canyons you should aim for 500 lbf/in (that's pounds-force per inch) in the front and around 350 lbf/in in the rear. Assuming the D2 coilover dampers can handle those rates. I'm guessing they can. Mike Kojima runs these rates on his street car.

If you want something to use on the canyons only you could probably go as high as 1,000 lbf/in in the front and 700 lbf/in in the rear for a rock solid ride. Who knows if the D2 coilovers are up to this. I'd ask them.

I see you'll have to order in "kg", so here's some conversions:

1,000 lbf/in = 14.594 N/mm
700 lbf/in = 10.216 N/mm
500 lbf/in = 7.297 N/mm
350 lbf/in = 5.108 N/mm

I'm assuming their "kg" crap is really Newtons per millimeter, but who knows?! Get the info from D2 directly so you can compare.

Edit: I just found that when you click the "view Applications" link they list the units as Kg/mm. Hang on...


Source: http://forums.maxima.org/4240073-post20.html

So...

1,000 lbf/in = 79.1 Kg/mm
700 lbf/in = 55.37 Kg/mm
500 lbf/in = 39.55 Kg/mm
350 lbf/in = 27.685 Kg/mm


That doesn't seem right at all. D2 only sells 3.5 - 21 Kg/mm springs... =/

thanks for all the help.

Spring rates are expressed in pounds per inch. So, if you have 200 pound/inch springs that means if you load the spring with 200 pounds it will settle 1 inch. "Pound feet per inch" doesn't make any sense. For conversion, 1 kg equals 2.2 pounds and 1 inch equals 25.4 mm.

For mixed application (street and track) most folks use about 300 lb/in front and 200 lb/in rear springs with a B13 with no more than 1 inch drop. Anything softer is going to bottom out, and anything harder is going to compromise ride (more the case with factory-style springs, coilovers vary). I'm not saying that you should not use stiffer springs -- just know what you are getting into.

I'd recommend that you try to hook up with some local forum members to ride in cars with a variety of suspensions before making a decision.

Stupid website for using Kg without any indication. I am assuming it is kgf? Otherwise they fail.

Bill, he meant lbf as in pounds force, not pound feet. And also the 1 kg to 2.2 lbs conversion is referencing pound mass to kg mass, not kg force, so you would need also to multiply by 9.8 before it could be used in a spring rate. Since on earth 1 lbm = 1lbf, those are interchangeable.

Spring rates or spring constants are expressed in the amount of force it takes to compress the spring a certain distance. Pounds are a unit of weight (or mass in a pinch), not force.


I apologize, I did mean pound-force. I've edited my post.

this is some confusing stuff. lol... i got so much to learn
thanks for all the help guys!

Confused, I am. Is kg force the same unit of measurement as the Newton?