DH bike spring selection and sag setting

Discussion in 'The Adrenaline Factory' started by bing!, Sep 20, 2013.

  1. bing!

    bing! Active Member

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    Am injured right now and am off the bike.

    What better thing to do than start tinkering?

    I rode the bike the whole summer on a 400 lb coil because it felt better than stock. Now that it's the end of the season, I measured my sag and it's at 27% without gear. After 75 runs, I'm sure the coil is broken in.

    I just bought a 300 lb spring got 38% without my gear sitting down and 35% standing on the pedals. I have a 350 coil on its way.

    My question is, what sag do guys like riding. Do you measure sitting or standing? Is 40% too much?

    Consider that my bike has a very progressive suspension. It starts with an LC of 3.4 and ends at 1.4. Average is 2.66.

    References say DH sag is between 30 to 40%. The 951 is a bit confusing to dial in. I've had 5 springs for it. Two of them were horrible. The last 3 are pretty good. just gotta figure out which one I like best. Compared to the fork, it only took me two springs. The stock and the next one.

    Looking to do tests in a couple of weeks. Thanks!
     
  2. shwinn8

    shwinn8 New Member

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    I'm at about 35%. You should measure from the sitting position. Just have to keep tinkering with it till you find a spring that works best for you. My Straight 8 was set up for when I was about 130lbs. with a 400lb spring. I woke up one morning a few years ago weighing in at about 170lbs over night. I upgraded to a 550 spring and allll is good now! When setting the springs pre-load, start with a loose spring. Slowly tighten the adjusting ring until the spring stops jiggling around and give it an additional 1/4 turn. Sit on the bike as if you are riding it, feet on pedals and record the required data. If the math comes out to over 35% tighen the spring 1/4-1/2 turns at a time and repeat till you get to 30-35%. Most manufactures say not to go over 2 full turns on the adjustment ring. I use a sharpie to make a mark on the ring so I know how many turns I'm doing. Good luck! you'll get it!
     
  3. kazlx

    kazlx New Member

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    I always measure mine standing, because I don't ride my DH bike sitting down. I put much more weight on the fork. I try to get close to 30-35%, but a little either way doesn't really matter. The settings on the shock are much more imperative to get the rear end feeling good. You can use a spring calculator to see where you're at. How much do you weigh?

    The more you sag, the plusher the ride can be on small chatter, but you will run out of travel on bigger hits. A lot of it depends on terrain you ride. You could probably get away with 40% or more no problem at SS.

    http://www.tftunedshox.com/info/spring_calculator.aspx
     
  4. bing!

    bing! Active Member

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    You also can't balance on your bike on in the rearward biased attack position used for riding a dh bike :)

    Thanks for the link. I used Fox's rec. for purchasing the 300 coil. The TF calculator recommends 350, which is on its way.
     
  5. herzalot

    herzalot Well-Known Member

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    A common misperception is that DHers ride off the back. Look more closely. They ride with the chest over the bars at all times except when shoving the bike forward over drops. With such long travel and slack geometry, if you ride in the backseat, you will have very little control and even less speed.
     
  6. bing!

    bing! Active Member

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    True. I may have to lean more into the bars with the new spring. With the old spring, I would spin out too easily if I were riding with a front bias.
     
  7. 92se-r

    92se-r Active Member

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    Dh bikes should be measured in the attack position. 30-35%
     
  8. Garrett

    Garrett Active Member

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    I usually ride 25-30% in the rear and 15-20% in the front. I like to stand up, bounce a couple times to let the bike settle into it's travel, push the O-ring indicators against the dust wipers (or have a second person measure the I2I for a coilover shock) then carefully get off the bike and make a measurement. Also super important to do all of this with the compression fully open.
     
  9. McG715

    McG715 Active Member

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    That's a good point.. of course when you check out the bigger riders, they can appear to be riding in a rearward bias and still have that chest over the bars, especially if they have a short cockpit (like our Podiums do) :)
     
  10. surftime

    surftime New Member

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    So maybe this is why I dont have as much control as i want but dont go over the bars - sitting back instead of up over the front? or maybe this does not apply as much on a 5 inch bike

     
  11. McG715

    McG715 Active Member

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    I would think it applies to any descending.. but depending on the terrain, it's hard to put yourself out over the front and commit like that, but pretty sure the text book states to be out over the bars, bend those elbows, and keep force on that front wheel regardless.. easier said than done in some situations
     
  12. Formu1fan

    Formu1fan Slow Down, Slower Up

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    Even the steep stuff? I was always under the impression that you want to have your center of gravity over your bottom bracket, hence standing back when you start going down. I am kind of in the same boat as surftime, I feel like I would go OTB if I was in that super aggressive attack position.

    I guess re-reading Chris' comment made me realize that with a slack bike like that, it does help to ride a bit over the front. I noticed I wasn't getting full travel or as good of a ride when I rode in the backseat of the Glory I demoed.
     
  13. McG715

    McG715 Active Member

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    On the steeps is where it's needed most.. but that's tough to do sometimes.. easy to hang as far back as you can but with a slack front end you have little control.. I think by having weight centered over the pedals your chest would be over the bars or at least in that direction.. Chris, Greg and I were watching a girl at SS last Sunday from the chair and she was so far back, her butt was almost behind the rear wheel.. it was crazy
     
  14. McG715

    McG715 Active Member

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    This shot is from Strength In Numbers in the Whistler segment and every time I watch it I always think damn I'm never that committed to keeping that much force on the front wheel when headed into a steep roller..

    SIN 1.jpg
     
  15. surftime

    surftime New Member

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    when my 12 year old goes down steeps he usually is more forward than me. I am always back and he is up front - still maybe sitting up too high though. I am always yelling from behind "get back" to keep him safe. But maybe thats why he is riding so good, he knows something i dont
     
  16. McG715

    McG715 Active Member

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    When we were in Whistler this summer my son rode for a few hrs with one of their private coaches/bike guides/instructors.. and in watching his helmet footage afterward, the common theme of advice that they kept reinforcing on the gnarly stuff was to drive thru the legs, keep his knees a bit wider to stabilize his stance and keep elbows bent out over the bars..
     
  17. surftime

    surftime New Member

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    thanks - learn something all the time, thats why i like this forum.
     
  18. ridinrox

    ridinrox Well-Known Member

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    That was me...ha ha. J/K J/K

    A couple times riding w mtnbikej, we were riding down Barham (Oaks) from Deer and I would ride this side rock feature but had loose dirt after it; I kept loosing my front tire and crash (J would just bunny hop over me). He told me to put more weight on my front tire. Best advice!!
     
  19. McG715

    McG715 Active Member

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    Rox I've heard too many good things about your riding.. no way you'd look like this girl looked.. but yes you did get some great advice from mtnbikej.. did you put that advice into action to test the theory?
     
  20. ridinrox

    ridinrox Well-Known Member

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    Every time I ride. Loose dirt is still my nemesis!! Thanks for the kind words but if we ever get the chance to ride together you'll see my butt is usually hitting my back tire. (Laughing Face)
     

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