JustinOlson Posted January 2, 2007 Share Posted January 2, 2007 I've been reading “Engineer to Win” by Carroll Smith. In the suspension section he talks about loaded length and free length of springs. “Another side of the same coin is the fact that we wish to be pushing each of our tires into the track with as much force as we can arrange at all times. IF a spring is so short as to uncouple in some combination of droop and roll, then that tire is unloaded at a time when the spring could have been loading it. This can lead to such things as partial loss of traction at one end of the car and inside wheelspin.” I’m curious what free length is acceptable so that the springs stay engaged at full droop. I’m looking at running the following combination. I want to run 8” rear springs to get the spring collar above my rear tire. Will this give me trouble? Any suggestions? Front: 250lb/in Hypercoil 10” free length 2.5” diameter spring Koni 8611 5” threaded sleeves 17”X9” wheels Suspension Techniques 25mm ARB Techno-Toy Camber Plates Adjustable TC rod Adjustable Control Arm Rear: 275lb/in Hypercoil 8” free length 2.5” diameter spring Koni 8611 5” threaded sleeves 17”X9” wheels Suspension Techniques 19mm ARB Techno-Toy Camber Plates Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 2, 2007 Share Posted January 2, 2007 I've read that same book and I thought that was a funny thing for him to say at the time, but then I thought that you really have to put that comment in context. If you have a lot of droop like just about any Z with coilovers, then you have to get A LOT of air for the spring to come completely uncompressed. If you were driving a formula car with 3" of travel and the spring could come off of the perch at the top of that travel, that would be a problem and I think that's what he's talking about. Quote Link to comment Share on other sites More sharing options...
briann510 Posted January 2, 2007 Share Posted January 2, 2007 Our rear springs we have (I think they are MSA lowering springs), are free well before the wheel is even all the way off the ground (when I jack it up for instance) which I dont like at all. Id like to find a spring that still has some pressure on it even when suspension is fully unloaded. I also need to stiffen the rear suspension alot more than it is right now. It has Tokico HP struts currently, so the first step is to get rid of those and use Tokico Illuminas set on #5 I suppose. The car is not road raced, only street driven and 1/4 drag raced so it needs to really have the rear stiffened up as much as possible while retaining the current ride height. Right now at really hard launch the left halfshaft goes to its end of travel. I need about 1/4" or so more travel in it or stop the suspension from going that much farther to bottom the halfshaft out. Im about ready to just move the whole diff 3/4" to the right and kiss all these left side being so short problems goodbye. For those who havnt followed my previous diff posts, when we changed to 4.38 gears, the diff carrier fat spacer had to be moved to the opposite side making the left side even a shorter distance than stock between the side diff flange and stub axle flange which is presenting all sorts of problems with that sides cv or halfshaft length being too long and bottoming out. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 2, 2007 Share Posted January 2, 2007 Just about any lowering spring is going to be loose like that. Again, unless your doing Dukes of Hazzard style jumps, it really doesn't matter. Quote Link to comment Share on other sites More sharing options...
briann510 Posted January 2, 2007 Share Posted January 2, 2007 Yea no daredevil air jumps in this car. Quote Link to comment Share on other sites More sharing options...
johnc Posted January 2, 2007 Share Posted January 2, 2007 One thing people forget is that Carroll Smith was writing mostly from the perspective of an open wheel car and an unequal length control arm suspension. Essentially an ideal suspension. In our strut based suspensions things are more limited and we have to work with what we've got. Both the front and rear suspensions, while the car is on the road and in a corner, are droop limited by the ARBs. Looking at suspension droop while the car is on a lift has little relevance to the actual droop available while the car is on the ground. On the inside wheel in a corner, the rebound force of the spring and weight of the suspension corner is matched by the compressive force of the ARB. That is the droop limit and is inches above the free hanging droop limit (assuming the shock is taken out of this discussion). This should also give us a clue as to why bigger ARBs are not always better. Quote Link to comment Share on other sites More sharing options...
JustinOlson Posted January 2, 2007 Author Share Posted January 2, 2007 Thanks for the insight into this. Does my setup look ok? I'm not trying to conquer the world, but just want a solid setup that is adjustable. Regards, Justin Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 2, 2007 Share Posted January 2, 2007 Looks fine to me. Should be a fun dual purpose car. Quote Link to comment Share on other sites More sharing options...
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