# School me on coil spring preload/sag...



## nojoke (Apr 15, 2008)

I just picked up my 1st DH rig Long story short, I ran up on a Ironhorse Sunday 08 model awesome condition, very clean bike, everything was tight, low mileage, good component group etc for a good price (yes I know they are out of biz now). It has a Fox DHX 5.0 Coil on the rear with a 9.5x3" stroke. 

I am about 200lbs geared up and it came with a 350lb spring, the rider I bought from was alot smaller. It seems to go past the target sag area of 30% when I set the shock up with not cranking the shock coil. I know that max preload on spring is recomended 2 full turns upon engagement. 

My question is, what are the drawbacks of running this spring cranked up to create the correct sag if rebound can be controlled correctly with rebound settings? What else I am effecting in the range of travel by running an excessive preload?

Lastly what size coil spring should I be running with my weight of 200lbs? I was thinking in the 450-500lb area?


Thanks
Allen


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## Uncle Six Pack (Aug 29, 2004)

nojoke said:


> My question is, what are the drawbacks of running this spring cranked up to create the correct sag if rebound can be controlled correctly with rebound settings? What else I am effecting in the range of travel by running an excessive preload?
> 
> Lastly what size coil spring should I be running with my weight of 200lbs? I was thinking in the 450-500lb area?
> 
> ...


Rebound has little to do with it... there are few problems with excessive preload.... topping out the suspension (excessive rebound could be a band-aid on this problem, but will lead to other probs), possibility of coil-bind at full travel, and preloading a coil spring does not change the spring rate.

You must start with a spring rate that is the correct ballpark, then think of preload as a way to fine tune the ride height. It sounds as if the 350 is no where near what you need.

I don't know about the leverage ratio of the Sunday or any unusual sag characteristics of a DW, but I would assume that for a 200 lb rider, you are looking at a 450, maybe 500... at least with either of those, you should get good sag within a couple of turns (unlike the 6-10 or so turns I am assuming you need with the 350).

Personally, I like running the least preload possible on my shock, then I will add 2 turns for pedally terrain with big rocks to help avoid pedal strikes. The DW is a little different, though... you probably want to find the sweet spot for your sag and pretty much keep it there.

Other sunday riders could probably point you in the right direction for your weight, but good old proportions should get you close.... if the other rider was maybe 160 and a 350 was good for him (assuming he had it set-up correctly), then a 450 would be close for you.... if he was like 140, then more like a 500 for you.


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## m3t4w0rm (Aug 1, 2010)

http://www.tftunedshox.com/info/spring_calculator.aspx

Might be of some help.


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## nojoke (Apr 15, 2008)

Thanks for the input guys. The guy that came off the bike was about 160, so he was lighter. Thanks for the spring link.


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## Rock Climber (Jul 25, 2007)

http://www.ridemonkey.com/forums/showthread.php?t=168138

you can get lost in that thread, but has lots of great info


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## essenmeinstuff (Sep 4, 2007)

Couple things

Pre load is not a fix for the wrong spring rate. You can change your ride height with preload, but the spring will still compress at a 350lb per inch rate, ie yes you might have the right sag using a lot of pre load, but you will still blow through your travel.

Also lots of preload means that to get the shock to move you need to overcome the preload force first. Lets say you add in 50lbs of preload, you need to then have an impact of 50lbs or more to even get the shock to move, compared to the right spring with zero preload, where any small impact will make the shock start to move. Ie when you are unloading your weight, skimming stuff etc if you have no preload, then the wheel will track the ground better and "try" to maintain traction, if you have lots of preload, its like a hard tail at that point and bouncing off stuff instead.

Setting sag is meant as a measurement/confirmation of the correct spring rate, using preload to get this is basically cheating lol


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## nojoke (Apr 15, 2008)

essenmeinstuff said:


> Couple things
> 
> Pre load is not a fix for the wrong spring rate. You can change your ride height with preload, but the spring will still compress at a 350lb per inch rate, ie yes you might have the right sag using a lot of pre load, but you will still blow through your travel.
> 
> ...


Thanks for the info, that makes alot of since in regards to preload vs compression rates and how it will blow thru the travel just as quick no matter how you set the coil spring up, its still a 350 no matter which way you flip it.

Thanks again!.


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## Dougie (Aug 29, 2004)

Sunday's usually run lower spring rates than most other DH bikes. I'm 155-160ish and I run a 300lb. spring on my Sunday. 

Take a look at that Sunday thread on Ride Monkey. It's a wealth of information to say the least.


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