Spring rate suggestions

[triniemi]

2350lbs door car, 100inch wheelbase. 56% front (1316lbs) 44% (1034lbs) back. What spring rate should be used up front?

[triniemi]

Anybody?

[gearhead1011]

Need more info. Is it a strut or a-arm front end? If it is a-arm is it coil over or oe style? The front spring rates are a lot harder to calculate than the rear because the location and angle of a coil over on an a-arm suspension has a huge effect on the spring rate.

[triniemi]

It's a strut car.

[TopspeedLowet]

300# if you have enough platform threads to hold the car up. You have a very front heavy car, but the short wheel base may over shadow the initial hook up problems that you are about to experience with that scale report. The rear will like the lightest spring you can use to hold the car up to plant the tire better. If you have run this car already and have no issue with hook up, then the lighter spring in the rear may cause you to drive into a wheel stand and would prefer a stiffer rear spring. The front spring rate was chose to help transfer weight to the rear by storing more energy. This is the best I can do with the little info you have provided for us to evaluate. Ladder bar crap likes different rear rates so if you are a 4 linker guy you should be in the pocket or at least real dam close.
Good luck in 09

[triniemi]

Sorry for the light info. It has a 4-link. The front end seems to be way too tight now, less than 0.5" front end travel. When two guys (about 400lbs) steps on the frame, the front suspensions doesn't get down at all, it feels like a solid mount car.

Springs now are 7" tall installed at 6" height. I need to get the springs measured (I think I will do it at our gym :D ) so I will know how stiff they are. Inside diameter 2.5", outside 3.5", the spring wire is 0.5" thick and there are 6 active coils.

Few videos: http://www.youtube.com/results?search_type=&search_query=triniemi&aq=f

[gearhead1011]

I used a 250 lb 8 inch spring on mine with a front weight of 1109 lbs. I would think a 275-300 lb. spring would be about right for yours. Hypercoil shows both 7 & 8 inch springs and you would have to determine which length your struts should use.

[triniemi]

Ok, thanks.

Would this be a good spring? http://store.summitracing.com/partdetail.asp?autofilter=1&part=HAL%2D7%2D300&N=700+4294846689+4294787535+4294787580+4294791589+ 115&autoview=sku

My struts can hold maximum of 7" spring (free lenght).

How much I should preload it initally? 1" , 2", maybe 3"? Or should I just adjust my for the same ride height that it was with stiffer springs and try it for few passes?

[TopspeedLowet]

Ride height is all that matters, that is the basis for the spring calculation. Pre load is incidental to spring rate at ride height, it is not an independent adjustment. The lower the spring rate the higher the platform will need to be and the stiffer the spring rate the lower the platform will be. On your struts you should have about 3/4" of shock ram showing before it hits the bumper at ride height. If the spring were too light you will bottom out the shock when the platform is maxed out to it's highest adjustment. The amount of compression the spring has at ride height vr's it's free height is the springs pre load. The spring you asked about is a 300# spring that fits the description you gave for your strut.

[triniemi]

I measured the current springs (at our gym :D ). The spring took 400lbs to compress it one inch. Way too tight? Free lenght is 7" and they were installed at 6". I'm considering to order the 7" free lenght 300lbs springs. Can I now calculate how much I should preload the 300lbs springs to achive the same ride heigh?

[TopspeedLowet]

I measured the current springs (at our gym :D ). The spring took 400lbs to compress it one inch. Way too tight? Free lenght is 7" and they were installed at 6". I'm considering to order the 7" free lenght 300lbs springs. Can I now calculate how much I should preload the 300lbs springs to achive the same ride heigh?
each spring needs to hold up about 658# per side according to your scale report. So if your car was at the correct ride height meaning 3/4 +- shock ram showing above the bumper with the dimensions you just gave, then the new springs will require a higher setting to maintain the ride height. Go 658 divided by 300 = preload in inches to hold 658# that is 2.19 at ride height not what the platform needs to be. You have left out the spring ride height or strut travel dimension for the calculation. If you want to guess, the platform may need to be 3/4" higher than it was. Remember that you can easily change the spring platform when you lift the car back off it's feet. I would recommend that you try the 3/4" higher or 5.25" at ride height and take a look at where you ended up on your ride height. Unless you are installing this strut on the moon where you don't have an oppertunity to adjust it, you might just need to make one final adjustment to get it perfect and I feel that the work is worth the time.
Sorry I can not give a more pointed answer with the info available, but you should be in good shape from here wont you?
Good luck in 09

[triniemi]

There is about 1.5" of shock ram showing when the car is at the ride height with the current 400lbs springs. I could drop the nose a little, but not more than 0.3" or the headers will touch the ground. Do I need to get taller front tires if I want to drop it more with new 300lbs springs or is there another way to get the shock ram showing only 0.75 inch?

[TopspeedLowet]

There is about 1.5" of shock ram showing when the car is at the ride height with the current 400lbs springs. I could drop the nose a little, but not more than 0.3" or the headers will touch the ground. Do I need to get taller front tires if I want to drop it more with new 300lbs springs or is there another way to get the shock ram showing only 0.75 inch?
Yes you should buy taller front tires, You have used up the travel or the strut at ride height which will prevent pitch rotation like a solid suspension does. I like to run the strut on the bumper on the cars I build, but the 3/4" figure is what Rick Jones and others recomend for ride height set up. You may even be able to use a 275# spring to aide in weight transfer if the spring will hold up the car which I am sure it would based on the last info you reported.
I just had this notion to ask you, The engine weight is in the car when you are checking this isn't it?

[gearhead1011]

It depends on how much total travel the strut has. Most racing struts only have a total of 1 1/2" of travel from fully extended to the snubber. If that's the case with your struts with 1 1/2" showing now your strut is "topped out" or close to it. It might be that someone has tried to raise the car from the ride height it was built for which is a difficult thing to do with a strut car. If there is no extension left in the struts with the car at it's desired ride height you will need to either lower the car, use a bigger tire or change the strut mount.

I would recommend using the hypercoil spring. They're a much better spring than the springs you linked to. They're a little more expensive but worth it. You can buy them from strange. I noticed the springs you linked to are priced each so double the price they have there.

[triniemi]

I just had this notion to ask you, The engine weight is in the car when you are checking this isn't it?

Yes, the weights include everything. Car race ready, fueled full and me sitting in the car.