Quote:
Originally Posted by lowside67
A lot of this information isn't really correct. For example, the firmer spring has more coils, which is why it has less usable stroke (travel before coilbinding).
http://www.swiftsprings.com/products...lover-springs/
Your car may never hit the bump stops but that doesn't indicate anything about your spring rates being ideal. You could have far too much bump travel and not enough droop, or far too high of a ride height, or a dozen other things. |
You're right about the springs. Sorry for the misinformation. Admittingly, I made the assumption before looking at the very swift site I referenced lol. I just know from experience that 4k was too soft and caused binding in 7" lengths. That is probably why ycw gives you 9" springs with their 4k rates... Since 6k 7" swift springs have 4.2" of travel, that means I would experience coil bind BEFORE bottoming out my suspension since I have over 4.2" of strut travel. I do not have any coil bind, so I am not even using all of my available bump travel. My 255 200tw tires don't produce enough mechanical grip to warrant increasing roll resistance IMO.
Strut stroke is independent of ride height adjustment on coilovers... 6k does seem ideal. A 6k spring lands you right in the middle of that stroke given the cars sprung corner weights (700lb) (700/336 =~2" of static travel) with the close to 1:1 motion ratio up front. That is about 50-60% bump and 40-50% droop travel given 5" of strut travel. I can't imagine anyone else's coil-overs being much different since they all have around ~5" of strut travel.
A stiffer 8k spring would result in 700/450 = 1.5" of static compression. Meaning, I would gain another 1/2" of bump travel (70% of available travel) I don't need. I would end up reducing droop travel (30% of available travel) to the point that I would probably be lifting wheels. Not a good thing. If I wanted to go any stiffer up front I would do it with swaybars to work around the coilovers.
Then again, I may not have super accurate suspension travel measurements. If I found that I only had 4" of total travel then I might consider moving to a 7k spring to maintain a bit more bump travel than droop. At 4" of travel, a 6k spring would put me at 50/50 instead of 60/40. The drawback of that might be that I don't have enough mechanical grip up front to make use of this stiffer springs...
Quote:
Originally Posted by lowside67
Springs and bars are also useful for speed of weight transfer and that's why I am going up in spring rate - the car is far too slow to transfer weight in transient events.
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I disagree with your comments about weight transfer. These cars are high COG and short wheelbase. There is actually very good weight transfer which makes them easy to toss around. Spring rates/swaybars have no affect on how quickly weight transfers. Springs rates/sway bars DO affect the distribution of weight (dynamic cross weight) under transition load (e.g. does weight shift forward in roll or rearward? Or, will the car be neutral, understeer, or oversteer?). Rebound and driver input (steering, acceleration g's, and braking g's) dictate how quickly the weight transfers. COG and wheelbase dictate how much weight transfers to the outside wheels in transition.
The ideal car would have 0 weight transfer. However, that's impossible since cog will always be above the ground lol. To go faster you need to be as smooth as possible with inputs to avoid abrupt weight transfer. You can reduce weight transfer to the outside wheels by reducing COG and widening the wheel base. The inside wheels will carry more weight and overall grip will be improved. This is one of the drawbacks of all the rear tire fitment being inboard. You won't be square with the front which pokes more. If you want weight to transfer quicker then simply use harsher steering inputs lol... make sure you turn rebound down too. That does not sound like an easy or fun car to drive though.
Stiffening the suspension would:
- reduced suspension travel (helps prevent dynamic changes in camber and toe)
- improve responsiveness (driver input is more direct to the tires with the drawback that you may ask more than the tires can provide)
- allow the car to ride lower without bottoming out (leads to less weight transfer if you've reduced the cog)