# Pre load adjustment?



## NismoGriff (May 15, 2011)

So my bike has the SR Suntour XCT-V4 80mm shock on it. It doesn't have a lockout but it does have the preload dial. My question is, how do most of you determine how to set your preload? On this particular shock the knob turns to a point that it seems to click and then turns again. I haven't tried to turn it till it stops completely because I am wondering if it is even supposed to turn passed the 'click'. Anybody care to 'splain it to me a little more?


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## jeffgothro (Mar 10, 2007)

Yeah, I need to know too...better yet, is there a way I can turn the knobs on all my shocks so they are at there stiffest settings or as close to lock out as possible??

I have 

RS SID LT
RS Judy Carbon
RS Judy DH


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## AndrwSwitch (Nov 8, 2007)

The way a preload is supposed to work is that it compresses your spring. This doesn't actually change the spring rate. (Or, shouldn't in theory; real life is different but not that different unless the engineer really ****ed it up.) It does reduce the sag in the fork.

Hooke's law - Wikipedia, the free encyclopedia

I don't determine my preload, I have an air fork.  With a coil fork, you'd do it based on how much sag you want. Depending on use, people go for anywhere from 15% to 40% or so. 15% would be for someone using a short-travel fork. You don't want to give up the little travel you've got. 40% (could be an overstatement here, I'm more of a XC guy myself) would be for a DH fork, so that the fork extends into dips as well as it soaks up hits.

There "shouldn't" be a way to get preload to behave like lockout. But if you have enough movement in your preload to get past the spring's linear region, (shouldn't be possible, on a well-designed fork...) all bets are off.


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## NismoGriff (May 15, 2011)

Ok, so since this fork only has a knob on one side and it is a coil spring, I'm assuming the preload capabilities are handled by one side of the shock. How about the number of turns? I just don't want to start cranking on this thing clockwise or counterclockwise expecting it to stop only to find out I have damaged it. Is there some sort of mechanical stop in them typically?

I did notice the first time I was doing little bunny hops, I could feel the fork extending before the front wheel would come off the ground. I assume this is the 'sag' you are referring to. After I rotated the preload a couple of turns, this didn't seem as noticable. I'm about 235-240 lbs at the moment.


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## AndrwSwitch (Nov 8, 2007)

I'd say read the manual if I thought there was one.

You could take it apart and have a look at how the mechanism works. Better forks have oil in them, so make sure you're ready for that. I don't know if it's an issue with Suntour's products, though.


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## NismoGriff (May 15, 2011)

AndrwSwitch said:


> I'd say read the manual if I thought there was one.
> 
> You could take it apart and have a look at how the mechanism works. Better forks have oil in them, so make sure you're ready for that. I don't know if it's an issue with Suntour's products, though.


I haven't found anything in the literature that talks about that. I've been poking around on the web some also and can't seem to find anything. I'm probably overlooking it.


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## AndrwSwitch (Nov 8, 2007)

LOL, you're probably not.

Most people see that fork as a placeholder for the "real" fork. It's not very well documented, and good luck finding parts.


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## NismoGriff (May 15, 2011)

AndrwSwitch said:


> LOL, you're probably not.
> 
> Most people see that fork as a placeholder for the "real" fork. It's not very well documented, and good luck finding parts.


Yea, I know it's not the greatest, funny thing is, it's the same fork that was on some of the brand name bikes that I was considering for $200+/- more with most other components being the same. The more I tweak the adjustments and get the brakes broke in the better it feels. I've been out 3 times and only logged a little more than 20 miles and none of it has been on trails yet, but I've been messing around hopping over curbs and stuff just trying to get a feel for the shock. I doubt it's going to give me any real comparison to trail riding though. I do notice a little bit of bounce when I am standing up pumping the pedals hard but it's not awful. Still, you would think somewhere, they would talk about the adjustment limit of this dang fork, lol.


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## AndrwSwitch (Nov 8, 2007)

I wouldn't stress out about damaging it.

I think one of two things is going to happen, depending on how it's assembled. Either you'll hit a hard stop or you'll get to a point where the preload just doesn't do anything.


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## NismoGriff (May 15, 2011)

So, I messed around a bit with this last night. I turned it counter clockwise and it did hit a mechanical stop point. I turned it clockwise and the more I turned it the harder it was to turn which makes sense because I am putting tension on the spring. I never turned it clockwise till it stopped, just till it hurt my fingers to turn it, lol. I doubt I will ever need to preload it any more than what I had already turned it as it seemed very stiff at that point. It basically feel like it has a 'notch' indicating every 180 degree turn of the knob.


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## AndrwSwitch (Nov 8, 2007)

Could you feel any difference in the ride, or measure a difference in sag, between the two extremes?


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## NismoGriff (May 15, 2011)

AndrwSwitch said:


> Could you feel any difference in the ride, or measure a difference in sag, between the two extremes?


I didn't ride it because I just happened to be out in the garage and remembered that I wanted to look at it. I did notice a slight difference in sag when I sat on it and it also felt a little stiffer when just pushing my weight down on the handlebars.


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## seanpr123 (Jul 9, 2012)

Just wanted to say thanks Nismo, was trying to figure out the limits of my fork myself without breaking anything and your research helped.


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