Suspension help
08-13-2008, 12:37 AM
#1
Suspension help I made a post about a few weeks ago and BMR responded (Thanks again). I have BMR dbl adj. LCA (race), relocation brackets (bottom hole), Spohn adj. tunnel mount tq arm, Eibach Pro kit, stock DeCarbon junkos, that sums up the rear. I recently put QA1 single adj. with 275# spring in the front. The front comes up good. I was told that I pulled a wheel for the 1st time tonight, but..... no new best for the 60'. I spin pretty much all the way through 1st cutting a best 60' tonight of 1.67. My best ever (stock struts, shocks, w/ Eibach pro kit) was a 1.54 on a 125 shot.
Does anyone know the spring rate for the Eibach Pro Kit rear springs? I know that I need to put a set of QA1 shocks on the rear. If I can't get this to hook on a 200 shot out of the hole, I may have to send it to someone that can get it dialed in.
Does anyone know the spring rate for the Eibach Pro Kit rear springs? I know that I need to put a set of QA1 shocks on the rear. If I can't get this to hook on a 200 shot out of the hole, I may have to send it to someone that can get it dialed in.
08-13-2008, 11:21 AM
#2
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Wow, 275 lb/in springs in the front seem really really soft. I run 600 lbs springs up front, but then again I am autocrossing, not drag racing, so take what I say with a grain of salt. However, both of us are trying to manage weight transfer, and the amount of weight transfer. It just happens that I am trying to manage left to right, and for and aft, while you are just trying to manage for and aft....
It's all about the speed of the weight transfer. Regardless of spring rates, and shocks, the same amount of weight will transfer during acceleration in a streight line or a corner. The springs and dampers just affect how FAST the weight will transfer.
In the case of drag racing you want the weight to transfer to the rear as quickly as possible, but you don't want the weight transfer to "overshoot" and spring back. This will be evident when the car hooks good off the line, but then looses grip shortly after.
Given your current setup, I'd start out by adjusting the your QA1's up front. Usually I start out at full soft, then do a run. I then increase the stiffness by a certain known amount, and do another run. I keep repeating this process until I reach the optimum setting. You will know that you've hit the optimum setting when further stiffing of the shock results in an increase in 60 ft time.
BTW, the Eibach Pro Kit springs are a progressive rate spring. Which is fine for ride, but sucks for handling. I can't remember what the two rates are. Regardless it will be much easier to tune a car with single rate springs.
One other thing to consider, a higher spring rate will transfer the load quicker because the body will not have to move as far to develop the load on the rear axle. Think about that for a second. If one has a 100 lb/in spring in the rear, the body will have to sink 5 inches to transfer 500 lbs of load. If a 250 lb/in spring was in the rear, then the rear would only have to move 2 inches to transfer that same load. The same, but opposite goes for the front. A higher rate spring in the front will shead weight faster because the body will not have to move as far.
The result, less engery will be consumed by the moving body, and more will be available to get you down the track...
It's all about the speed of the weight transfer. Regardless of spring rates, and shocks, the same amount of weight will transfer during acceleration in a streight line or a corner. The springs and dampers just affect how FAST the weight will transfer.
In the case of drag racing you want the weight to transfer to the rear as quickly as possible, but you don't want the weight transfer to "overshoot" and spring back. This will be evident when the car hooks good off the line, but then looses grip shortly after.
Given your current setup, I'd start out by adjusting the your QA1's up front. Usually I start out at full soft, then do a run. I then increase the stiffness by a certain known amount, and do another run. I keep repeating this process until I reach the optimum setting. You will know that you've hit the optimum setting when further stiffing of the shock results in an increase in 60 ft time.
BTW, the Eibach Pro Kit springs are a progressive rate spring. Which is fine for ride, but sucks for handling. I can't remember what the two rates are. Regardless it will be much easier to tune a car with single rate springs.
One other thing to consider, a higher spring rate will transfer the load quicker because the body will not have to move as far to develop the load on the rear axle. Think about that for a second. If one has a 100 lb/in spring in the rear, the body will have to sink 5 inches to transfer 500 lbs of load. If a 250 lb/in spring was in the rear, then the rear would only have to move 2 inches to transfer that same load. The same, but opposite goes for the front. A higher rate spring in the front will shead weight faster because the body will not have to move as far.
The result, less engery will be consumed by the moving body, and more will be available to get you down the track...
08-13-2008, 01:46 PM
#3
Try raising your lower control arms up a hole. What tires do you have on the car and what pressure do you have in them? If you want to give me a call we can run over your setup and see if we can figure out how to improve it. Our tech dept is open mon-fri 8:30am-6:00pm est.
