trying to understand spring rate here....
05-04-16, 12:13 PM
#1
Driver
Thread Starter
trying to understand spring rate here....
a question that I am having a hard time to understand...
Why does coil over use a much higher spring rate than spring/shock combo?
e.g.
stock and lowering springs are in the range of 4.5 to 7k range
but even the "soft" BCR coilover is 10/8k, with people pushing to 14/10k normally
How should I compare ride if I am going from a stock shock/tein stech spring to a 10/8k BCR coilover?
Thanks in advance
Why does coil over use a much higher spring rate than spring/shock combo?
e.g.
stock and lowering springs are in the range of 4.5 to 7k range
but even the "soft" BCR coilover is 10/8k, with people pushing to 14/10k normally
How should I compare ride if I am going from a stock shock/tein stech spring to a 10/8k BCR coilover?
Thanks in advance
05-05-16, 08:13 AM
#2
Stiffer spring will result in feeling the road more. It also reduces body roll in a turn, which can result in quicker turns without losing traction. A little more road feel can be a good thing, depending on your goals and desires. A lot more is going to result in fatigue on longer drives.
A lot of people here put in stiffer springs so they can lower the car more. The stiffer spring obviously don't compress as much over smaller bumps. Drive directly into a curb at moderate speed and it is going to compress no matter what your spring rate.
10/8 is not likely to be a problem, but you haven't stated your goals. Lower the car? Improve handling? Increase road feel?
There are several with stiffer springs than mine, and mine can feel kind of rough on poor roads (which we have a lot of here, especially in the spring). I have lowered the car very little, but can still bottom out. However, it has felt pretty stable at auto-X and track day.
A lot of people here put in stiffer springs so they can lower the car more. The stiffer spring obviously don't compress as much over smaller bumps. Drive directly into a curb at moderate speed and it is going to compress no matter what your spring rate.
10/8 is not likely to be a problem, but you haven't stated your goals. Lower the car? Improve handling? Increase road feel?
There are several with stiffer springs than mine, and mine can feel kind of rough on poor roads (which we have a lot of here, especially in the spring). I have lowered the car very little, but can still bottom out. However, it has felt pretty stable at auto-X and track day.
05-05-16, 10:41 AM
#3
Driver
Thread Starter
Thanks for your reply
I do understand how spring changes a car when comparing directly in the same category (lowering spring vs lowering spring, coilover vs coilover)
What I am having a hard time understanding is why in general a coilover spring rate seems to be much stiffer in number than just lowering spring?
like my example, a 7k lowering spring is resulting a rough ride while for coilover the softest I have seen people use is at 10k/8k area. So I am lost in how I should compare ride with lowering spring to ride with coilover.
I bought my 350 used with stock shock and tein stech springs (about 6k spring rate iirc) and I find the ride not comfortable for long ride. I do plan on switching to BCR but I am lost in terms of what spring rate I should aim for. It seems by default they come with 10k/8k combo, but a lot of members are commenting that being too soft and needs to go 12k/10k or even 14k/10k.
I do understand how spring changes a car when comparing directly in the same category (lowering spring vs lowering spring, coilover vs coilover)
What I am having a hard time understanding is why in general a coilover spring rate seems to be much stiffer in number than just lowering spring?
like my example, a 7k lowering spring is resulting a rough ride while for coilover the softest I have seen people use is at 10k/8k area. So I am lost in how I should compare ride with lowering spring to ride with coilover.
I bought my 350 used with stock shock and tein stech springs (about 6k spring rate iirc) and I find the ride not comfortable for long ride. I do plan on switching to BCR but I am lost in terms of what spring rate I should aim for. It seems by default they come with 10k/8k combo, but a lot of members are commenting that being too soft and needs to go 12k/10k or even 14k/10k.
05-05-16, 11:14 AM
#4
I'll fully admit that I am not an expert here, but a couple of things to consider:
Dampers (shocks, struts) and springs have to be a matched system to perform well. For a standalone lowering spring, the manufacturers are at the mercy of whichever damper you have on the car. The manufacturers have to live to the lowest common denominator (ie worn out stock shocks). Since a stock shock, let alone a worn out stock shock can't control a high spring rate, they have to make them softer. It is a game of making the spring rate high enough that you don't bottom out, and low enough that the car doesn't become a pogo stick. A matched damper can better control the motion of a stiffer spring, so a stiffer spring can feel as comfortable as a softer one. This is much of the reason coilovers have much stiffer springs, the damper is able to control the spring and you don't get the bouncing that a softer spring on a mismatched damper gives you.
The other thing to keep in mind is that the spring rates quoted are static measurements; you put a given load on the spring (10kg) and it compresses a given amount (1mm). Hitting a bump isn't a static load, it is an impact load. Obviously stiffer, is stiffer, but you can't necessarily determine from the spring rate exactly how that spring (and damper) is going to react to an impact load. This is one of the reasons many people recommend Swift springs with coilovers. I'm speaking in generalities here, but for a given impact load a Swift spring will react more quickly than a cheap Chinese spring, which in turns means the ride feels smoother.
Dampers (shocks, struts) and springs have to be a matched system to perform well. For a standalone lowering spring, the manufacturers are at the mercy of whichever damper you have on the car. The manufacturers have to live to the lowest common denominator (ie worn out stock shocks). Since a stock shock, let alone a worn out stock shock can't control a high spring rate, they have to make them softer. It is a game of making the spring rate high enough that you don't bottom out, and low enough that the car doesn't become a pogo stick. A matched damper can better control the motion of a stiffer spring, so a stiffer spring can feel as comfortable as a softer one. This is much of the reason coilovers have much stiffer springs, the damper is able to control the spring and you don't get the bouncing that a softer spring on a mismatched damper gives you.
The other thing to keep in mind is that the spring rates quoted are static measurements; you put a given load on the spring (10kg) and it compresses a given amount (1mm). Hitting a bump isn't a static load, it is an impact load. Obviously stiffer, is stiffer, but you can't necessarily determine from the spring rate exactly how that spring (and damper) is going to react to an impact load. This is one of the reasons many people recommend Swift springs with coilovers. I'm speaking in generalities here, but for a given impact load a Swift spring will react more quickly than a cheap Chinese spring, which in turns means the ride feels smoother.
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