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Another SAG question...

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So after my last issue with my suspension I had a question about SAG.

In Keith's videos he says you want 20-30% of suspension travel front/rear for track 30-40% road... My issue isn't which percentage but the difference between front and rear.  Let's say I chose 30% do I set 30% on front and rear?  Or is it independent; because for those that offer mm or in. travel settings always recommend more SAG in the front for some reason; like 35-40mm in the front and 30-35mm rear for road.

I understand it's just a baseline and eventual setting will depend on how you ride and how the bike feels to you.  I'm just trying to get an understanding of the baseline for now as I've been tweaking it slowly after every ride to see what I prefer.

If I go based on specifications on the bike (2012 Honda CBR600RR) then the front suspension travel is 110mm while the rear is 129mm; so any % I take would make the front shorter SAG.

A little insight please...

Also currently I prefer a little stiffer front on my bike because the front stock forks are and loves to nose dive every chance it gets; I think I have it close to where I want it so it's not that bad.

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As in the videos.  Setting sag allows the bike to stay within the "sweet spot" of the springs motion.  This prevents the shock from bottoming out or topping out during the regular conditions of riding.  Many riders will adjust the sag to be more in the front and less in the back to help the bike "turn in" better in high speed cornering situations.  Preload only sets the amount that the spring is loaded and is not really intended to affect stiffness.  Even though it "kinda" does when you compress the spring enough but you risk bottoming out the suspension (and crashing) if you run out of spring travel.  If you want to affect the suspensions stiffness you probably should look at replacement springs.  A different spring rate might give you the feel that you are looking for. 

There are a number of companies out there that can help you do a basic setup on the bike to get you close to where you want to be for around $50.  (replacement springs are extra if you have to adjust the spring rate).  I would find a local track day with suspension service and have them give you a basic setup.  Often times many of the technicians are quite willing to chat with you about suspension so they can give you great advice on your specific model bike.  They likely have lots of experience working with your specific year and model and know what riders typically run into on those setups.   

I personally don't tinker with my own suspension very often.  I have done it once on an older bike but I have found that the professionals can always give me a workable setup that requires very little adjustment and performs way better than I could do on my own. 

Something to keep in mind as well.  Most suspension professionals will tell you that you need a suspension refresh every year or so of track riding.  You may get a considerable performance increase just by getting the suspension on your bike rebuilt if it's not been done before.  I recently had the Ohlins suspension on my 2013 RR serviced for it's yearly service and was rather amazed at how much improvement I got after the rebuild.  Shocks and forks have rubber parts inside that wear and deteriorate over time.  Especially if the suspension is moving a lot and getting hot. 


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Already rebuilt the suspension, which it needed badly, I understand the reason for sag... Question is about why most just suggest a value, and what is based on, vs Keith's video on sag suggesting % of travel.  There's a safe range and tweak based on personal preference... Paying to have it set isn't an issue, issue is with everyone doing things a little differently.

On the 06 and earlier CBR the front and rear travel is the same, the 07-12 the rear has more travel, if sag is independent of total travel then the initial value can be whatever those videos state, if it's dependent then...?

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My stab at it is that Keith works with so many riders and so many bikes that giving a percentage is more workable than giving numbers due to the range of available travel on different models of bikes. You could always do the reverse math and would derive to the same.

SAG numbers aren't set it stone, but they give you a starting point to work from with other adjustments and you actually may end up changing preload settings while tuning, which is what Dave Moss did with my bike- he checked sag first (I initially had no free sag making the rear too stiff) and after a couple sessions on track, preload was taken out by a few turns in the front.

Although you'd want to be precise in your measurement of sag it's still a ballpark figure based on percentage range of travel, which is what the manufacturers provide- a range.

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