Can someone explain shock spring pre-load
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Tourer
Joined: Apr 2010
Posts: 401
Likes: 2
From: Odenton, MD
Can someone explain shock spring pre-load
Just installed progressive 944s and have the pre-load set to the middle adjustment. I was thinking when the wife wants to ride I need to essentially extend the shocks which would decrease the pre-load. However, the installation instructions state that if excessive bottoming occurs you need to increase your spring pre-load, which shortens the shocks?? That does not make sense to me.
Am I thinking backwards on this???
Am I thinking backwards on this???
Seasoned HDF Member
Joined: Sep 2013
Posts: 5,372
Likes: 1,362
From: Aurora, CO
Just installed progressive 944s and have the pre-load set to the middle adjustment. I was thinking when the wife wants to ride I need to essentially extend the shocks which would decrease the pre-load. However, the installation instructions state that if excessive bottoming occurs you need to increase your spring pre-load, which shortens the shocks?? That does not make sense to me.
Am I thinking backwards on this???
Am I thinking backwards on this???
Yes, don't think length. Think tension. Pre-load puts more tension (hence the load that is pre) on them, making them stiffer (sort of).
Road Captain
Joined: Sep 2013
Posts: 687
Likes: 5
From: Maryland
Just installed progressive 944s and have the pre-load set to the middle adjustment. I was thinking when the wife wants to ride I need to essentially extend the shocks which would decrease the pre-load. However, the installation instructions state that if excessive bottoming occurs you need to increase your spring pre-load, which shortens the shocks?? That does not make sense to me.
Am I thinking backwards on this???
Am I thinking backwards on this???
Sort of. The preload doesn't shorten or lengthen the shock. It's an adjustment of the initial load on the spring...the preload.
Simplistically, less preload gives a softer ride because it allows you to use a softer portion of the spring wind, but it won't handle heavier weight as well as more preload will which takes you into using the beefier part of the spring wind. That's actually where the term "progressive" comes from...the springs get progressively stiffer as you add more load.
Less preload is sort of like running less air in your tires...while more preload is like running more air in your tires. Yes, there's way more to it than that...but increase the preload when your wife wants to ride with you. I used Progressive 7610Ps on my race bikes way back in the day...great shocks...good choice.
Last edited by Wheels24; Mar 16, 2015 at 08:29 PM.
Road Master
Joined: Jan 2015
Posts: 1,057
Likes: 10
From: SF Bay area
Say a spring has a 100 pound per inch spring rate and is 10 inches long. When installed it's preloaded 3 inches. It now has to see 300 pounds before it will start to compress. Take an identical spring and preload it 5 inches. It now needs to see 500 pounds before it will start to compress. Assuming both springs will go coilbound at 8 inches compression, they will BOTH be exerting 800 pounds of force. The only difference is that the 5" preloaded spring will not move under 300-400 pounds load and the 3" preloaded one will. The 3" spring will give a softer ride over small bumps because the 5" spring is like a rigid frame at that point.
The 5" preloaded spring will not bottom less under equal load.
Road Master
Joined: Apr 2014
Posts: 831
Likes: 10
From: Kentucky
Fat man on a air mattress. Mattress inflated to soft and he hits bottom. Not enough " support". Inflate tighter to support the weight.
Tighter your springs, more weight support.
Tighter your springs, more weight support.
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Road Master
Joined: Jan 2015
Posts: 1,057
Likes: 10
From: SF Bay area
Sorry, but this just is not true. Think about it.... how is compressing the spring with preload adjustment any different than compressing it with a passenger? It isn't.
The preload will just make the ride less "bouncy" with a heavier load as it will travel less.
The preload will just make the ride less "bouncy" with a heavier load as it will travel less.
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Joe Kucinski
Intermediate
Joined: Oct 2013
Posts: 45
Likes: 0
From: Toronto, Ontario
It's like Bikerscum said, the spring does not limit travel since it will compress the same amount regardless of preload, unless you preload more than your load. Spring preload is adjusted so that the bike sags to the midpoint of shock travel under the intended load, giving you maximum suspension travel as you ride.
Road Master
Joined: Apr 2014
Posts: 831
Likes: 10
From: Kentucky
Ok lol