Jump to content

Why shorter shock with lowering springs?


turbogrill
 Share

Recommended Posts

Hi,

Bilstein makes a Sport and a HD version of a shock, they are identical in terms of stiffness but the only difference is that the EXTENDED length of the shock is shorter.
They say it's for lowering springs.

But why does that matter? I would think you always want longest shock travel possible? The rest position of the shock will depend on the spring length/stiffness. So making it shorter only helps when the spring is unloaded. And it never is...

 

https://www.good-win-racing.com/Mazda-Performance-Part/61-0530.html

 

 

Link to comment
Share on other sites

12 minutes ago, turbogrill said:

Hi,

Bilstein makes a Sport and a HD version of a shock, they are identical in terms of stiffness but the only difference is that the EXTENDED length of the shock is shorter.
They say it's for lowering springs.

But why does that matter? I would think you always want longest shock travel possible? The rest position of the shock will depend on the spring length/stiffness. So making it shorter only helps when the spring is unloaded. And it never is...

 

https://www.good-win-racing.com/Mazda-Performance-Part/61-0530.html

Our car is lowered so far that we only have about 1" of damper travel before it bottoms out at static ride height. I'm guessing that in full unloaded body roll it only goes a couple inches the other way. Yet, the shock can extend like.. 10 more inches. Total shock travel is a function of how far your suspension moves, which is a function of how stiff / soft your springs are. For us, shock travel in excess of about.. 3" in total is pointless, so I guess my question is: why are you concerned with long shock travel when, I assume, you would never see long shock travel except when you have it up on jacks? I would love it if our shocks were shorter as it would make suspension removal / maintenance / reassembly / etc. a little easier.

  • Like 2
Link to comment
Share on other sites

6 minutes ago, enginerd said:

Our car is lowered so far that we only have about 1" of damper travel before it bottoms out at static ride height. I'm guessing that in full unloaded body roll it only goes a couple inches the other way. Yet, the shock can extend like.. 10 more inches. Total shock travel is a function of how far your suspension moves, which is a function of how stiff / soft your springs are. For us, shock travel in excess of about.. 3" in total is pointless, so I guess my question is: why are you concerned with long shock travel when, I assume, you would never see long shock travel except when you have it up on jacks? I would love it if our shocks were shorter as it would make suspension removal / maintenance / reassembly / etc. a little easier.

I was just thinking in general that more travel is better. If you could get longer spring with same spring rate and move the spring attachment point downwards then that would help with more travel.

 

But I guess you make a good point, they travel is reduced 0.5" so probably won't matter in most cases but makes it easier to deal with!

Link to comment
Share on other sites

1 minute ago, turbogrill said:

I was just thinking in general that more travel is better. If you could get longer spring with same spring rate and move the spring attachment point downwards then that would help with more travel.

 

But I guess you make a good point, they travel is reduced 0.5" so probably won't matter in most cases but makes it easier to deal with!

What do you mean by 'travel'? My damper could have 15" of total travel on a bench, but it only sees 3" of travel on the race car. Changing that 15" to 10" or 5" doesn't change the fact that when it's on a race track, it only sees 3" of travel.

 

What you are saying with spring attachment point is something that I have thought of before but I don't know enough about dampers to know if it matters.... you are saying "would it be better if I was using the middle 3" of the damper's range of motion rather than 3" of motion closest to where it bottoms out"? No matter where you attach the spring, if the spring rate doesn't change, you're getting the same travel.

Link to comment
Share on other sites

24 minutes ago, enginerd said:

What do you mean by 'travel'? My damper could have 15" of total travel on a bench, but it only sees 3" of travel on the race car. Changing that 15" to 10" or 5" doesn't change the fact that when it's on a race track, it only sees 3" of travel.

 

What you are saying with spring attachment point is something that I have thought of before but I don't know enough about dampers to know if it matters.... you are saying "would it be better if I was using the middle 3" of the damper's range of motion rather than 3" of motion closest to where it bottoms out"? No matter where you attach the spring, if the spring rate doesn't change, you're getting the same travel.

 

After thinking about it the 0.5" extra travel is pointless in most cases (with the points you made)

 

It could be beneficial in some case if you had coilovers with variable length springs.

 

Edit: and if you could add offset on the top hat to make it longer. Lots of ifs...

 

 

Edited by turbogrill
Link to comment
Share on other sites

If your present shock is bottoming out, you'll get some high instant loads to the tires and shock mounts. Getting a shorter shock will prevent that.

 

You have to decide whether you need a shorter shock but generally if you're lowering a car for racing, get the shorter shock.

  • Like 1
Link to comment
Share on other sites

2 hours ago, mender said:

If your present shock is bottoming out, you'll get some high instant loads to the tires and shock mounts. Getting a shorter shock will prevent that.

 

You have to decide whether you need a shorter shock but generally if you're lowering a car for racing, get the shorter shock.

How will a shorter damper help that? The 1" of travel is set by the springs?(Longer spring or stiffer spring will give more travel but higher ride height)

Link to comment
Share on other sites

Just now, turbogrill said:

How will a shorter damper help that? The 1" of travel is set by the springs?(Longer spring or stiffer spring will give more travel but higher ride height)

Are we talking fixed spring height or adjustable, if everything is open then it is a whole diffent story. If everything else in your suspension is capable of more than 1" of travel but you are limited to that 1" because of shock length and you can adjust your spring mounting height or spring length then you can gain travel without effecting ride height before the shock bottoms out. When this happens you effectively have a solid metal rod in there. Been there/done that. Once the shock bottoms out the spring just becomes added weight, everything becomes defined by the length and stiffness(material not compression/rebound stuff) of that shock. 

 

Think about having the same overall length but adjusting everthing else in there to make it have more travel. Shock comperssion/rebound ratios can stay the same, spring rate can be the same (even if length and/or mounting height changes) and ride height, but usable compression and rebound distances can increase.

 

I seem to remember in the early days of Spec Miata a successfull builder in the North East giving advice about setting ride height, etc.. He would suggest setting it just high enough that the bump stops would prevent the shock from bottoming out at full compression. Using this theory, if you shorten your shock but keep overall length the same you can use your bump stops (which are believe are free) to create a progessive spring rate as you approach the limit of compression but help prevent other bad stuff such as bottoming out the shock or coil bind...

Edited by Throoster
mostly added last paragraph
Link to comment
Share on other sites

1 hour ago, turbogrill said:

How will a shorter damper help that? The 1" of travel is set by the springs?(Longer spring or stiffer spring will give more travel but higher ride height)

 

So the travel limit could be: coil bind or shock bottoming out. if you have a new spring that lowers the static height 1 inch, you took 1 inch of bump (compressive) travel out from the lowered static height (assume shock and wheel travel 1:1). the shorter shock means a shorter compressed length, not always travel. you gain bump travel and reduce droop travel (extension).  

 

on lowered cars, you need to gain some of that bump back via a shorter bumpstop and/or shorter compressed length shock.

Edited by chbright
Link to comment
Share on other sites

4 hours ago, chbright said:

 

So the travel limit could be: coil bind or shock bottoming out. if you have a new spring that lowers the static height 1 inch, you took 1 inch of bump (compressive) travel out from the lowered static height (assume shock and wheel travel 1:1). the shorter shock means a shorter compressed length, not always travel. you gain bump travel and reduce droop travel (extension).  

 

on lowered cars, you need to gain some of that bump back via a shorter bumpstop and/or shorter compressed length shock.


That would make sense, but with the Bilstein it's the extended length that differs. Compressed is the same. I guess it's only to make life easy

Link to comment
Share on other sites

10 hours ago, turbogrill said:


That would make sense, but with the Bilstein it's the extended length that differs. Compressed is the same. I guess it's only to make life easy

OK I  now see your issue, it appears we are talking generic stuff and you are asking about specific parts. . Looking at the figures from https://www.good-win-racing.com/Mazda-Performance-Part/61-0530.html those shocks looks to be almost identical. I would be interested in overall length in addition to compressed and extended lengths.  From Bilstein they do not appear to be shorter, but rather "...performance upgrade to OE dampers designed to be paired with aftermarket lowering springs..." I will bet they are identical in almost every respect, just different valving.

 

You may get better results from taking a deeper dive into the Bilstein motorsport catalog and find one that is the right legnth and mounting for your application instead of going with the generic upfitter parts listed for your vehicle.

 

 

Edited by Throoster
spelling/grammer
  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...