The Tuesday Tune Ep 20: Preload Adjustment - Video
Coil springs require a certain amount of preload to hold them in place securely, but how much should you run? This week on the Tuesday Tune, we go right back to the basics to take a look at the function of a preload adjuster and its purpose, as well as the carryover mentality of preload adjustment from the motorsport world to mountain bikes.
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Thank you for another educational video.
Aludes to nothing, but gives away everything
Thanks Again !!! can't say it enough .
concrete example. I don't bottom out too frequently, my bike has good grip and feels really comfortable, front to back balance is pretty good, I'm 76kg with full gear on and rock a 2015 Boxxer Team with the medium coil installed (only drawback, the bike isn't super dynamic cause a little soft and I have to work a bit much to throw it from turn to turn).
I do have two preload spacers installed, one being the minimum otherwise there's slack.
One of my complaint is I find the front a little bit low in the really steep sections when my weight is completely over the front. As I'm not asking for more bottom out resistance, is preload a good solution to help keeping the front a bit higher as it adds a bit of resistance force (Obviously, It would be detrimental to small bumps sensitivity)? Would adding low speed compression be a better option?
I read that too much preload could lead to top out klunk when the wheel lives the ground. I can hear a slight top out sound nothing too bad really (and my rebound isn't that fast), is it normal?
Thanks a lot,
Benjamin.
I'd imagine this is largely personal preference, but curious how you think about air vs. coil on any given bike if you had the choice...advantages vs. disadvantages
I'm going to try a disc of rubber/plastic first, something to keep the spring from rattling around that won't get destroyed by the force involved.
@VorsprungSuspension I was under the impression that preload only affected sag not bottom out force as once the force required to move past the preload the rate of compression is the same.
Or to ask it another way, if the 2.25" shock in this video was mounted with a 2.25" spring instead of 2.35", would any preload be possible without spring binding when the shock damper bottoms out, ie. do you always need a longer spring free stroke than shock damper stroke if you did want the option to run some preload?
Thanks.
Something else that I would like you to cover in a future episode is tires: how they can be used and tuned like a suspension and mostly how they interact with the rest of the suspensions found on a bike (fork and rear shock, just in case... ;-) )
1. The stated rate on one or both springs is not accurate
2. Something was changed (preload, damper settings, tyre pressure, whatever) when the springs were swapped
3. Placebo. When you've paid $300 for a spring you're quite inclined to go looking for improvements whether they exist or not - plenty of people will tell you that their titanium spring feels plusher or whatever, but it just isn't the case.
I'm totally a bike nerd. mostly in suspesion- not only produts, but also philosophies behind linkage systems etc. However, and that is weird, i'm kind of every bike except mine kinda nerd, so I'm running 2006 26" XC bike, with full XT group and air shock. I even like my Avid SD V-brakes! (maybe cause i'm 125Ib guy, so almost everything locks my wheels and is powrful enough for the type of flat terrain i live in- Poland, 12 miles below the beaches of the Baltic sea). I switched to them from Hayes Nine and Simano deore brakes, that was too powerful in my opinion, and, as a poor engineering student I don't have money enough to buy some modern brakes with a proper modulation.
Getting to the point, I'd like to suggest You a topic, that is barely touched: shock stiffness/flex and how do links deal with unwanted forces, that are applied to the bearings/ Let me explain what i'm thinking about for some time now, and what i can only imagine, how works (i quit being a bike mechanic two years ago, when i found a job in automatics/teaching/programming and machine vision systems- I was at a hospital for two months, so i'm unemployed now, but i work on my engineer degree, so after few months i'll b bak on trail, probably with my wallets not so empty as now
We can see a whole sea of coplicated linkage systems, and the forces on links are being transmitted on the frame mostly through the shock. Thats right. But what we can see is that those links are in some angles, that varies, as shock goes through its travel, sometimes changes at those angles are about quarter of a turn, so that is rather much. As the back whel is sucked by roots etc it creates forces that not only alter suspension action, but also create stress on bearings, and of course, shock itself. What gives me some headache in comparison between those two above is this, that link, that compresses the shock almost never compresses it exactly in the straight line that can be drawn between eyelets, it almost always compresses the shock, with a force, that's vector is slightly (or more often not so slightly) rotated basing on this line. This causes stress on bearings, bushings, frame elements, and ofc shock itself. I know that we can alter some kinematics by making use of this, but it's a comromise between desired characteristics and material stress. And last: as we know, shocks are being compressed, but those frame elements, that links, that pushes them, are also kinda try to bend them in some way, cause forces go in a lot of directions. Air shocks have almost always wide shaft, while coil shocks has that few milimetres thin shafts. Im almostust sure, that it can be bent to some point (alloys are rather elastic, so it comes back to it's original form after compression). Is it true? How this can alter suspension performance/ I saw some old Yeti DH models, that compressed shocks in straight line with a weird kind of rail or sth. What can You say about this problem?
Second thing: vectors of forces in frames cause some issues, as forces aren't parallel (or perpendicular) to them, so is there a way to avoid it? (bearings are being worn-out, stress on frame members etc.)
Didn't know that pull shocks are ridden because of counteracting a shaft flex, but it seems very clever (more than rail- based suspension designs