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[Front] Race Sag?

Discussion in 'The Garage' started by GoGoGavin41, May 11, 2016.

  1. GoGoGavin41

    GoGoGavin41 Waves to Moto Cops (and they wave back)

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    I've been messing around with my suspension which I have not done a lot of. On a 990 Adventure, so I can adjust rebound, compression, and preload.

    Currently at the "Standard" setting according to KTM. Assuming I'm measuring everything correctly, it looks like my rear is pretty good at 28%, but front is not so great at ~48% (shooting for around 30%). I usually hear people talking about "race sag" in reference to the rear rather than the front. Does this mean I need to crank up the preload in the front? Does cranking the preload mean I should adjust rebound or compression also? Does changing settings in the front mean I should change the rear? Yikes, this is complicated. Maybe I'll just ride it like it is...
    #1
  2. Mobil1

    Mobil1 Long timer

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    If you're happy with the damping the way it is already , you shouldn't have to change it with a change in preload. Preload is basically ride height. You're just adjusting the suspension where it sits in its stroke.
    #2
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  3. Hipster

    Hipster Long timer

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    If you weigh more then 140 lbs and are running the stock fork springs, you won't be able to properly set the sag. I weigh 180 lbs and I'm running 58 kg/mm springs, stock springs are 48kg/mm springs. Also, the sport setting for the suspension is a good starting point.
    #3
  4. JohnCW

    JohnCW Long timer

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    Yes, is the answer to that question, assuming you're measuring it correctly. But if loaded sag is 48% of your total suspension travel, well let's just say that's an unusual extreme. Don't want to be personal, but you would need to be a very large bloke, or someone has previously fitted very light springs to expect that outcome.

    I prefer the terms 'loaded' and 'unloaded' sag as they are self explanatory. Loaded sag is the same as 'race sag' (bike and rider weight) and equally applies to both the front and rear suspension. Unloaded sag (bike only) is generally called 'static sag'.

    P.S. Regarding does changing setting (I'm taking this to mean damping) on one end of the bike affect the other ....... you could nearly write a whole book on that subject.
    #4
  5. Hypermofo

    Hypermofo Been here awhile

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    What JohnCW said - race sag just means how much the suspension compresses under rider weight (including all gear and any kit you normally carry on the bike) versus static sag like John explained above. In my experience (YMMV) on most bikes you only set the rear sag as there is no way to really adjust the amount the forks "sag" (the fork pre-load doesn't have that great of a range of adjustment unlike the rear shock). What you're implying with your fork measurement is that your forks are compressing through half their total travel with just you sitting on the bike. If that's really the case you need higher rate springs (firmer). An easy way to check this is put a zip tie around one fork leg (the part that slides inside the other) get on the bike, then get off and take all the weight off the forks (center stand) then measure the distance from the fork seal to the zip tie and compare that to the available travel.

    FWIW What I suggest is check and make sure your forks are set correctly in the triple trees first - that the top of the forks are the correct distance above the top edge of the top triple tree (check your manual, correct could be flush to 10mm above).

    Once that's confirmed correct, set the fork preload in the middle of its adjustment range - back it all the way off then turn it in half way. Check your manual but it should be counterclockwise until it stops to back it off then clockwise 1.5 to 3 turns to half way). Don't worry about compression or rebound right now because that doesn't affect sag, just the speed of the suspension movement when it's in motion.

    Once that's done measure and adjust the "race" sag at the rear shock until it is in the correct range. Again check your manual but normally it is 30 - 40% of total shock travel.

    Note to properly measure "race" sag you first have to measure the distance the suspension extends (hangs down) with all the weight off the wheels i.e. on the center stand. Then take the bike off the stand and get on it ideally with your feet on the pegs (and all your kit) and re-measure the suspension compression at the same spot then subtract the two to determine your race sag. Adjust your shock preload and repeat measurements until you get in the desired range. If you back the preload all the way off and still don't get enough sag your spring is too firm, if you add the full amount of available preload and still have to much sag your spring is too soft. Note you don't really want the preload set at either extreme of its adjustment range - better to change springs so that it is in the middle of the range.

    Now that your sag is set correctly adjust the compression and rebound to the standard number of clicks on both the forks and shock. Check your manual to get the numbers - KTM usually provides number of clicks for "comfort", "standard", and "sport". Just be sure to turn the adjustments all the way counterclockwise until they stop. Then start turning them clockwise counting clicks until you get to the right number. Don't forget to adjust both the high and slow speed setting on your shock if it has both.

    Now for the fun part! Go ride your bike and find a stretch of road/trail that is similar to what you normally ride or plan to ride. Ideally something you can ride in 3 - 5 minutes and is easy to repeat. Ride it and see how your bike feels - too soft add in a click or 2 of compression, too firm back off a click or 2. Ride the same road/trail again, repeat until you get the ride characteristics you want. Just note 1 or 2 clicks makes a big difference and you should be able to get the results you want in a range of 4 - 6 clicks at most. Otherwise something is wrong - sag is off, spring rate is too soft or firm, etc...

    HTH and have fun!
    #5
  6. Hypermofo

    Hypermofo Been here awhile

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    [QUOTE="GoGoGavin41, post: 29395313, member: 147933" Does cranking the preload mean I should adjust rebound or compression also? Does changing settings in the front mean I should change the rear? Yikes, this is complicated. Maybe I'll just ride it like it is...[/QUOTE]

    One other thing... Not sure I directly answered your question above... Adjusting one thing doesn't mean you need/have to adjust the others but any one change will affect the rest. That's why I suggested above that you reset everything back to a standard setting and then start adjusting...
    #6
  7. Yinzer Moto

    Yinzer Moto Sloppy 300 rider Supporter

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    Front sag is impossible to set because the forks have too much internal friction to get a good reading. If you have 48%, it is way too soft. You will have to buy some new springs.

    As it was suggested above, put a zip tie on the fork and do some testing, you want it to bottom out on a hard hit but not bottom on a moderate hit. Your definition of the size of hit may be different than another person. To some a large hit might be a over shooting a 30' double to a flat landing, to others it might be a 6" log. On a road bike, you also want it to resist diving during hard braking.
    #7
  8. Hypermofo

    Hypermofo Been here awhile

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    Trailer Rail's is right on - there isn't a "correct" suspension setting - it is subjective to the riding style, type of riding, rider skill, and rider perception. It can be tedious, but get everything set to "standard" then go out and test, adjust, repeat. Just be systematic, write it down (you'll forget, trust me), make only 1 or 2 click adjustments to one setting at a time and after a bit of tinkering you'll be amazed at the difference it makes in your ride comfort and bike handling.
    #8
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  9. GoGoGavin41

    GoGoGavin41 Waves to Moto Cops (and they wave back)

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    Thanks for the feedback guys. Agree that I'll probably need new springs. Might even consider doing the whole deal with a revalve from a suspension shop. I do still have the Sport setting to try and I'll see how that feels before I do anything else probably.

    Just to be clear, to measure sag for the forks, I measured along the fork (parallel) unladen, then with just the weight of the bike [static], then with me and gear one it [laden]. My laden measurement was 48% of my unladen measurement. I am probably 190 with gear.
    #9
  10. Hipster

    Hipster Long timer

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    For heavy bikes like the 990, I skip the static sag and only measure race sag. Measure the forks at full extension (bike on center stand w/ wheel off the ground) then sit on the bike with feet on the pegs in full riding gear and pump the suspension a few times, have a helper steady the bike and measure the forks again.

    Here's one source for springs along with a few videos on basic suspension setup http://slavensracing.com/shop/fork-springs-wp48mm-43mm-x-465mm-for-ktm-wp/
    #10
  11. DC950

    DC950 Microadventurer

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    don't even think about having your suspension revalved until you have the right sag, which may or may not require new springs. Excellent dampening simply can't fully overcome the wrong springs and sag set up.

    Not that you are one of them, but it is astounding how many people on this site don't understand this. They would rather guess and throw money at something rather than spending some quality garage time with a tape measure and a spring chart.

    The comment above about front sag being impossible to set due to too much internal friction makes no sense.
    #11
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  12. GoGoGavin41

    GoGoGavin41 Waves to Moto Cops (and they wave back)

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    I tend to agree. It definitely seems to be the preferred train of thought in OC. My going down this route was in the interest of spending time rather than money on it, at least for now.

    I see you also have a Futura - I'm on my way to set the sag on mine right now.
    #12
  13. JohnCW

    JohnCW Long timer

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    Now I understand where the 48% is coming from. The way you've calculate it, isn't the normal way laden sag is expressed.

    First of all you need to know your totally suspension travel. You can either measure it with the springs out (fully extended less fully compressed measurements), or rely on the manufacturer's stated specification. You them measure your 'laden' sag as you've outlined above, and this measurement is expressed as a % of your total suspension travel. It is not expressed as a ratio between static and laden sag (using your terms) as you have done.

    There is a reason to compare the ratio of static and laden sag e.g. your 48%. But it is not for the purpose of setting laden sag. It is a 'rule of thumb' method for determining if your spring weights are in the ball park. You can set a correct laden sag with any spring weight (just alter the pre-load till its achieved), but the static sag will be widely out if the spring weights aren't in the ball park. I use the term 'ball park' because there is no such thing as the 'correct' spring weight, it all depends on road conditions, and rider preference.

    Typical front suspension sag setting are:
    Rider Sag - 30-35mm (25-30% of Full Travel)
    Free Sag - 15-20mm (60-70% of Rider Sag)

    If your free sag is 48% of the rider sag (assuming rider sag is set correctly and your measurements and methodology are correct), then this suggests your front springs may be too soft (pretty typical finding for the average older Western male).
    #13
  14. JohnCW

    JohnCW Long timer

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    Why? This could be interpreted as having the wrong springs in a heavier bike is less important than a light one. If I had to choose, its my heavier bikes I want to handle as best they can.

    A correct race sag can be set with ANY weight spring. Hasn't altered the fact the springs are still wrong. And a bike with incorrect springs will handle like shit (to use a technical term) no matter how you try and set sag or damping.
    #14
  15. shovelstrokeed

    shovelstrokeed Long timer

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    Tell me more about the location of "the holy city". If you are in the Vatican, I don't think I can help but if you happen to be in northern California I know a great suspension shop.
    #15
  16. GoGoGavin41

    GoGoGavin41 Waves to Moto Cops (and they wave back)

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    Sorry, might not have been clear. My first measurement is with the front wheel off the ground.

    I am in Charleston, SC. A bit far from NorCal.
    #16
  17. shovelstrokeed

    shovelstrokeed Long timer

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    But not to far from north GA. Give Race Tech a call. I know you want to DIY but trust me on this, there is a lot to getting the suspension right and piece by piece isn't the way to do it. At the very least, they can sell you a set of springs that will be pretty close to your weight requirements. Reports from friends who still race tell me that their stuff is good quality and they do know what they are doing. You might drop a grand or so but your bike is gonna handle like you never imagined it could.

    I mis-quoted the shop. Traxxion Dynamics is who you want.
    #17
  18. GoGoGavin41

    GoGoGavin41 Waves to Moto Cops (and they wave back)

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    Yeah, I was looking at their site yesterday. It's also cool that they're close to Highland park, I've been wanting to do a hare scramble there. Unfortunately though, my suspension budget is approximately $0.00 for probably quite some time due to various circumstances. I'm spending plenty a month just keeping the bikes I have rideable, nonetheless dropping $ on upgrades. This motorcycle stuff can get expensive!
    #18
  19. slackmeyer

    slackmeyer Don't mean sheeit. .

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    I'd read up on some of the suspension threads in orange crush. If you can pony up for new springs and oil ($100) at some point, you're going to have way way better performance than you have now. You don't need to spend $800 on revalving front and rear. At your weight, the front springs are way to soft, the front valving is too soft, the rear spring and valving are just fine for now. Some .58 springs and synthetic atf in the forks would do wonders.
    #19
  20. JohnCW

    JohnCW Long timer

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    Ok, then simply crank up the pre-load till its 30%. Haven't got external adjusters, or they can't get to that measurement, increase the length of the internal spacers inside the forks. Then check the static sag measure and compare it against the race sag measurement. Now you'll have a good idea if the spring rates are correct (if you didn't have enough adjustment on an external adjuster, you can guarantee they are to soft).

    P.S. The specifications on the internet say the long travel front end for your bike is 190mm. A 25% race sag would mean it should be about 47 - 50mm.
    #20