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Suspension setup: sag or bottom-out

2021 Views 10 Replies 8 Participants Last post by davec113, Jun 20, 2006

dbblackdiamond

Discussion Starter · Jun 19, 2006

Hi,

i have a quick question regarding how many psi to put in my rear suspension: do I use the 25% sag measure or the never-bottoming-out-but-use-up-most-of-the-travel measure?

The reason I am asking this question is that if I set the suspension so that I have 25% sag, then I loose about 20% of travel as on the trails I am riding the last 20% of travel never seem to get used. If I set it up so that I use most of the travel, but never bottom out, then my sag figure is about 30-35%. I know it is not an exact science, but as this is my first FS, I thought I would just ask.

Thanks a lot in advance.

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Homebrew

· #2 · Jun 19, 2006

The 25% is just a starting point. It's perfectly normal to adjust up or down from there based on preference. And it completely depends on the bike and intended use. For short travel, you might want to run less sag and longer travel, you can certainly get away with more sag. I wouldn't recommend the other way around though (i.e. long travel with less than 25%). But it's your ride and you can do whatever you like.

What bike though? You might try the mfg forums and see what others with your bike are using.

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eatdrinkride

· #3 · Jun 19, 2006

Like Homebrew said, 25% is a starting point. I often run more sag than that if I set out for a ride on a slow, technical trail with big stairsteps. I want 'cushy' on those days. I'll run less sag for faster, flowing days with some smallish jumps thrown is. 'Firmer' is better for me then.

As far as not bottoming out the shock....just ride harder

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dbblackdiamond

Discussion Starter · #4 · Jun 19, 2006

The bike is a C'dale Prophet 600 with a crappy Radium rear shock. I went the route you guys mentioned: I am trying to use as much of the travel as possible, as this is the reason why I bought the bike in the first place. My thought is that if I wanted to only use 3", I would have bought a 3" bike and not a 5.5" bike. Once I can do bigger jumps, then I'll firm it up again.

Thanks a lot.

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Jayem

· #5 · Jun 19, 2006

dbblackdiamond said:
Hi,

i have a quick question regarding how many psi to put in my rear suspension: do I use the 25% sag measure or the never-bottoming-out-but-use-up-most-of-the-travel measure?

The reason I am asking this question is that if I set the suspension so that I have 25% sag, then I loose about 20% of travel as on the trails I am riding the last 20% of travel never seem to get used. If I set it up so that I use most of the travel, but never bottom out, then my sag figure is about 30-35%. I know it is not an exact science, but as this is my first FS, I thought I would just ask.

Thanks a lot in advance.

Well, lets assume you have a marzocchi fork, and a fox DHX or progressive rear shock.

With this combination, you set your SAG first with spring rate, and then set the BOTTOMOUT with the oil height in the fork and the bottom-out knob on the rear shock.

If you don't have these adjustments, then "sag" goes out the window, you have to use the spring rate that keeps you from bottoming, period.

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derby

· #6 · Jun 19, 2006

Sag affects pedaling, handling too

Jayem said:
Well, lets assume you have a marzocchi fork, and a fox DHX or progressive rear shock.

With this combination, you set your SAG first with spring rate, and then set the BOTTOMOUT with the oil height in the fork and the bottom-out knob on the rear shock.

If you don't have these adjustments, then "sag" goes out the window, you have to use the spring rate that keeps you from bottoming, period.

This guy isn't bottoming with 35% sag. But that much sag reduces pedaling efficiency on his single pivot, and any bike (although will increase braking efficiency if balanced well with fork action).

For a new bike, I'd say use manufacture's recommended range of sag and adjust to suit riding style within or near that range.

Get a feel for how the bike geometry is designed to ride, then experiment outside recommended sag range to see if deeper sag rides better (as long as it doesn't bottom.)

- ray

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fsrxc

· #7 · Jun 19, 2006

dbblackdiamond said:
Hi,

i have a quick question regarding how many psi to put in my rear suspension: do I use the 25% sag measure or the never-bottoming-out-but-use-up-most-of-the-travel measure?

The reason I am asking this question is that if I set the suspension so that I have 25% sag, then I loose about 20% of travel as on the trails I am riding the last 20% of travel never seem to get used. If I set it up so that I use most of the travel, but never bottom out, then my sag figure is about 30-35%. I know it is not an exact science, but as this is my first FS, I thought I would just ask.

Thanks a lot in advance.

You're on the right track. Once you start tuning for travel on the trail, forget sag, just tune to use most of the travel, as long as it doesn't get too mushy (if that matters).

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Jayem

· #8 · Jun 19, 2006

derby said:
This guy isn't bottoming with 35% sag. But that much sag reduces pedaling efficiency on his single pivot, and any bike (although will increase braking efficiency if balanced well with fork action).

Sag reduces pedaling efficiancy?

That's quite a "blanket" statement there.

More sag means the suspension works better, reacts better to small bumps.

I run at least 35%, and it's plenty, err, "efficiant"...

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Blue Shorts

· #9 · Jun 19, 2006

Having too much sag can seriously screw up the bike's geometry.... especially while climbing. That will effect efficiency.

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derby

· #10 · Jun 20, 2006 (Edited)

Blue Shorts said:
Having too much sag can seriously screw up the bike's geometry.... especially while climbing. That will effect efficiency.

Yea, my Superlight would climb like poo with lowered air pressure in the shock and too much sag. It had a sweet spot of sag that pedaled my bike forward and uphill best and still absorbed bumps pretty well. The Profit

is pretty similar in high monopivot geometry.

My Tracer is more low and more rearward monopivot path type and was less affected by deeper sag when I tried that for a few rides, such as 35 - 40%, than more common and usefull, 20 -25%. But with deeper sag it had a more linear linkage rate range while pedaling and less usable compression travel, and so not much different climbing efficiency if I moved more forward to maintain climbing position over the bike. On the Tracer's Horst link, less sag, 20 -25% sag, still pedals noticeably more snappy with better bump compliance having more rising rate spring leverage effects in that most common use of pedaling bump travel and deeper travel compliance for bigger hits.

Interesting. I imagine a BB concentric monopivot would be nearly unaffected by a deep static sag setup, actually climb with more efficiency with less available squat and dynamic sag left to crush into when pedaling harder.

- ray

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davec113

· #11 · Jun 20, 2006

You can try different levels of sag, go with what works best... but if this is your 1st fs bike, it seems normal that you wont use all the travel with the bike set up correctly. It takes time to get to know the bike and what it can do... concentrate on your skills more than anything.

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