[satz]

Just a general suspension query/discussion...

Is it the spring stiffness or the shock stiffness that plays a more important part in ride comfort? I know they both play their part, but which is more critical in ride comfort? Leaving aside any other changes (like bushes, etc)

Scenarios:

1. driving slowly on cobblestone road.

2. hitting shallow bumps at low speed.

3. hitting shallow bumps at higher speed.

4. longer dips at higher speed.

The spring will take the 'initial' impact, right? But when does the shock stiffness come into it if its main role is to damp out the bounce of the spring

I'm thinking spring stiffness won't make too much difference in example 1, but will in 2 and 3.

If you have to choose between them, is a stiff spring/softer shock more comfy than a softer spring/stiff shock combo?

And is a softer progressive spring more likely to hit the bump stops compared to a stiff spring?

cheers

[dleccord]

dampers: koni yellow sports.

[satz]

would Koni yellow with H&R lowering springs give a better ride than, say, Eibach pro kit springs with Bilstein B8?

[YoungBlood]

Suspension travel, spring rate, rebound, compression, and your definition of comfort are all a factor

[feuer]

TIRES.

Originally Posted by YoungBlood

your definition of comfort is the main factor

^

[SpartaEvolution]

This is a very broad subject with a huge number of variables, most of which are over my head, but being a recovering spring engineer I can speak to the last question: 'is a softer progressive spring more likely to hit the bump stops compared to a stiff spring?' TL;DR A softer progressive rate spring will bottom out faster than a similarly rated linear rate spring.



Progressive springs are not nearly as progressive as they are made out to be. The reducing coil pitch gives them a fairly dramatic look, but it really doesn't do too much in the grand scheme of things. I'll try and illustrate my point through the use of the maths:

Say you have a 100 pound/inch coil spring with 0.250" wire Ø, 10 coils, and a 10" free length. This gives you a coil pitch of 1.000", resulting in 7.500" of displacement and 750 lbs of load when the spring reaches it's solid height (aka bottoming out). Keep in mind thread pitch is from the center of the wire in coil x to the center of the wire in the next coil y, so the actual gap between the coils is (x - y - wire Ø). In this case with 1.000" pitch and 0.250" Ø wire, the starting distance between any two coils is 0.750"

Now say you have the same general spring, but with progressive coils. Instead of a uniform 1.000" coil pitch, the 1st and 2nd coil have a pitch of 0.350" (0.100" distance between coils), 2-3rd = 0.450"(0.200"), 3-4th = 0.550"(0.300"), and the rest have a pitch of 1.2"(.900") for a total FL of 10.05".

As you begin to compress the spring, the spring rate is 100 lb/in until the moment that the first coil gap closes. Since we have 10 coils, when the first coil closes after .100" of COIL displacement, the rate will increase by the ratio of coils lost. In this case, that's 1 coil out of 10, or 10%. Since the load is distributed through the spring, each coil will be displaced the same amount, so 0.100" of coil displacement doesn't occur until 0.900" of total spring displacement, which is equal to 90 lbs.

Once the first coil is closed, the spring rate rockets all the way up to 110 lb/in, and each coil gap is 0.100" smaller. The next coil closes after another 0.100" of coil displacement, or 0.800" of total displacement, because we lost the first coil gap. 0.800" displacement at 110 lb/in = 88 lbs for a total of 178 lbs after 1.7" if displacement.

Having now lost two coils, the spring rate goes up by another linear ratio of coils lost. This time, it's 1 of 9 coils, or ~12% more than 110 lb/in, for a new rate of ~123 lb/in. The next coil (don't worry, we're almost done), will close after another 0.100" of coil displacement, or .700" of total displacement = 86 lbs for a grand total of 264 after 2.4" of displacement.

Are we having fun yet?

Since all the progressive coils are now closed, the rest of the spring will reach coil bind in a uniform fashion. With 1 of the remaining 8 coils now inactive, the 123 lb/in rate will increase to ~139 lb/in for the remaining 5.1 inches until coil bind. With all said and done, the grand total weight to reach coil bind is 959 lbs.

Now let's look at the numbers. 959lbs vs 750lbs for the regular spring!? That's is over 20% more weight to reach coil bind! Sign me up! Not so fast! Let's look a the loading curve. Once the progressive springs were closed, you still had 2/3rds of your available spring travel to go, but that travel is done in a spring that is 40% stiffer than that smooth riding linear spring! If you wanted the rate during the bulk of the spring displacement to be closer to stock, say 110 lb/in (still heavier than 'stock', hint hint), you'd have to start with an 80 lb/in spring, which would allow for 776 lbs of total loading before solid, meaning you'd have to increase your usable spring rate 10% for a whopping 3.4% increase in load before hitting the bump stops.

Granted, the method of achieving that 80 lb/in initial rate would likely be an increase in coil count, which would raise the solid height, resulting in even less weight before coil bind, or a decrease in wire Ø, which would reduce the solid height, allowing more weight, but also more stress, and so on and so forth until 2013 end of days.

Anyways, we've got special forum pricing on our OE pads and rotors, PM for details

[Volasko]

Originally Posted by SpartaEvolution

This is a very broad subject with a huge number of variables, most of which are over my head, but being a recovering spring engineer I can speak to the last question: 'is a softer progressive spring more likely to hit the bump stops compared to a stiff spring?' TL;DR A softer progressive rate spring will bottom out faster than a similarly rated linear rate spring.



Progressive springs are not nearly as progressive as they are made out to be. The reducing coil pitch gives them a fairly dramatic look, but it really doesn't do too much in the grand scheme of things. I'll try and illustrate my point through the use of the maths:

Say you have a 100 pound/inch coil spring with 0.250" wire Ø, 10 coils, and a 10" free length. This gives you a coil pitch of 1.000", resulting in 7.500" of displacement and 750 lbs of load when the spring reaches it's solid height (aka bottoming out). Keep in mind thread pitch is from the center of the wire in coil x to the center of the wire in the next coil y, so the actual gap between the coils is (x - y - wire Ø). In this case with 1.000" pitch and 0.250" Ø wire, the starting distance between any two coils is 0.750"

Now say you have the same general spring, but with progressive coils. Instead of a uniform 1.000" coil pitch, the 1st and 2nd coil have a pitch of 0.350" (0.100" distance between coils), 2-3rd = 0.450"(0.200"), 3-4th = 0.550"(0.300"), and the rest have a pitch of 1.2"(.900") for a total FL of 10.05".

As you begin to compress the spring, the spring rate is 100 lb/in until the moment that the first coil gap closes. Since we have 10 coils, when the first coil closes after .100" of COIL displacement, the rate will increase by the ratio of coils lost. In this case, that's 1 coil out of 10, or 10%. Since the load is distributed through the spring, each coil will be displaced the same amount, so 0.100" of coil displacement doesn't occur until 0.900" of total spring displacement, which is equal to 90 lbs.

Once the first coil is closed, the spring rate rockets all the way up to 110 lb/in, and each coil gap is 0.100" smaller. The next coil closes after another 0.100" of coil displacement, or 0.800" of total displacement, because we lost the first coil gap. 0.800" displacement at 110 lb/in = 88 lbs for a total of 178 lbs after 1.7" if displacement.

Having now lost two coils, the spring rate goes up by another linear ratio of coils lost. This time, it's 1 of 9 coils, or ~12% more than 110 lb/in, for a new rate of ~123 lb/in. The next coil (don't worry, we're almost done), will close after another 0.100" of coil displacement, or .700" of total displacement = 86 lbs for a grand total of 264 after 2.4" of displacement.

Are we having fun yet?

Since all the progressive coils are now closed, the rest of the spring will reach coil bind in a uniform fashion. With 1 of the remaining 8 coils now inactive, the 123 lb/in rate will increase to ~139 lb/in for the remaining 5.1 inches until coil bind. With all said and done, the grand total weight to reach coil bind is 959 lbs.

Now let's look at the numbers. 959lbs vs 750lbs for the regular spring!? That's is over 20% more weight to reach coil bind! Sign me up! Not so fast! Let's look a the loading curve. Once the progressive springs were closed, you still had 2/3rds of your available spring travel to go, but that travel is done in a spring that is 40% stiffer than that smooth riding linear spring! If you wanted the rate during the bulk of the spring displacement to be closer to stock, say 110 lb/in (still heavier than 'stock', hint hint), you'd have to start with an 80 lb/in spring, which would allow for 776 lbs of total loading before solid, meaning you'd have to increase your usable spring rate 10% for a whopping 3.4% increase in load before hitting the bump stops.

Granted, the method of achieving that 80 lb/in initial rate would likely be an increase in coil count, which would raise the solid height, resulting in even less weight before coil bind, or a decrease in wire Ø, which would reduce the solid height, allowing more weight, but also more stress, and so on and so forth until 2013 end of days.

Anyways, we've got special forum pricing on our OE pads and rotors, PM for details

Haha see how complicated your question is OP!! That was just one part too!

[chris@strutmonkey]

The quick answer is BOTH. And the most important thing is that they need to match. If you have a firmer (higher spring rate) spring, you should have a firmer (higher compression/rebound rate) shock to match. So, the answer to the "soft spring/firm shock" or "firm spring/soft shock" is NEITHER. Both are poor choices. Best to decide how you like your factory suspension (when it was new!) and what you want to improve. You can adjust ride height (higher, same, or lower) and ride feel (firmer, same, softer) and get a suspension kit that satisfies both. Sometimes that will not be possible, e.g. alot lower and softer. Key is to get components that match each other well.

Originally Posted by satz

Just a general suspension query/discussion...

Is it the spring stiffness or the shock stiffness that plays a more important part in ride comfort? I know they both play their part, but which is more critical in ride comfort? Leaving aside any other changes (like bushes, etc)

Scenarios:

1. driving slowly on cobblestone road.

2. hitting shallow bumps at low speed.

3. hitting shallow bumps at higher speed.

4. longer dips at higher speed.

The spring will take the 'initial' impact, right? But when does the shock stiffness come into it if its main role is to damp out the bounce of the spring

I'm thinking spring stiffness won't make too much difference in example 1, but will in 2 and 3.

If you have to choose between them, is a stiff spring/softer shock more comfy than a softer spring/stiff shock combo?

And is a softer progressive spring more likely to hit the bump stops compared to a stiff spring?

cheers