Quote:
Originally Posted by ex o
Thank you Garrett for trying to be as unbiased in your post as possible. I agree with you on the sentiment that 10k is WAY too stiff for the front. I have experience with 10k Swift springs on a CKS kit and it was almost unbearable after a while. I eventually bought a set of 6k Swifts and it alleviated much of the stiffness. But I would go even further in saying that a 4k or 5k linear spring would work well with the BC Racing coilover.
It's important to note that BC Racing coilovers have a different methodology in dialing in ride height. Most coilover kits have a threaded shock body that lowers/raises the perch to get the determined ride height. The downside to this is that as you lower the perch, you are also subtracting from the shock travel (compression).
The way BC Racing (and Ohlins RT) coilovers dial in ride height is to lower the entire shock body into the carrier while the perch is set to a predetermined preload. The plus side to this set up is that you can lower the car to extreme amount while still retaining the full shock travel. The potential down-side of this set up is that you get less "droop" (especially if you use high rated springs on the front). Not "drop", "droop". In laymen's terms, droop is how much the wheel will hang when the suspension has no load on it, or decompression or rebound amount. Droop might not seem important, but it actually is when you're driving on the street (or rally racing for that matter). If you don't have enough droop, the car might fly over bumps as opposed to roll over them (literally, your wheel will be airborne. See attached pic of M3 GTR hitting curb vs Subaru STI rally car below). A good amount of droop will give you more traction on bumpy roads.
In my experience, putting a 10k spring on this kind of suspension set up pretty much eliminates all usable droop. So it's imperative that you get a reasonable spring rate; unless you only care about racing on a smooth track. To me, reasonable is 4k - 6k on the front and BC should have no problems valving their dampers to match that rate.
The point is that all suspension (even OEM) is a collection of compromises. But someone who is knowledgable can minimize the compromises and get closer to what they desire out of their suspension.
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I agree with most of what you are saying here.
For me personally depending on the piston design used in the damper to control it or where you set the damper I personally find 8-10kg under the front of these cars very streetable for a daily setup...but that is my own preference. I couldn't agree more with how all of this is a compromise and the best setup is one you pick out yourself making an informed decision. To be honest that's the entire reason I joined and now started posting was to try and help put the info out there and help the members make more informed buying decisions (regardless if its our products or someone else).
I think the word we are looking for is "sag". You don't hear this term as much in reference to cars but anyone familiar with motorcycle setups will instantly know what it is. When using a singular linear spring the distance the wheel could drop back down before the wheel lifts off the ground would be the same as the amount of sag the setup has- or the distance the cars weight compresses the spring. For illustration purposes we can average and round the weight of the front corner of f82 to around 950lbs. so if you were to use a 10kg spring (560lbs) the car would sag about 1.7 inches. (again I say roughly because there is number of other factors that should be considered if we were trying to get a 100% accurate number). So this 1.7 inches would be distance the tire/suspension could droop back down before the wheel raised off the ground if we went over a bump.
Simply lowering your spring rate to gain more droop is yet again another compromise and not something that always makes sense. A helper spring could be utilized to give more suspension droop in a setup that doesn't naturally have much (higher spring rates)....but I also wouldn't just add helpers to all setups as this add length to your spring setup which then takes away from wheel and tire backspacing (you can't run as big of a tire on factory fender car).
We also use helper springs a lot here for rwd setups built for drag racing. There is a number of worlds fastest (for a given chassis) street car setups we've build where helper springs are utilized for more travel. When rwd drag cars launch and get large amounts of weight transfer the extra travel down allows the front wheels to stay in contact with the ground (completely or more depending on the car) giving the driver more control allowing them to maintain steering control where it would otherwise be lost.
Companies who offer setups without independent preload and height adjustments usually add helper springs to their setup to maintain preload (and eliminate noise and other issues associated with drooping the spring to change ride height).
I agree rebound/droop is very important, but having a TON isn't always necessary and can sometimes have a negative impact overall.
Again it can't be stressed enough, there is no "best" without a context, and even then its very subjective. The best racing suspension is not going to be fun for the street or even work well (since it was setup for lighter car with more mechanical grip)...and the best street suspension will just bottom out all over the track in a full race car.