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Correct it doesn't change the base spring rate, but it does change the initiation force from top out which is my point. The bike during aggressive fast riding over rough terrain will be reaching top out or near to it a lot of the time, if it didn't bike designers wouldn't aim for roughly a 30% wheel sag in the first place.
Ffs watch....

Oh and Dougal you know that graph in Andrextr's video when you said anyone can draw a graph...funny, because Steve has drawn the same one... So is Steve wrong too?
Steve tells you that preload sets ride height within the first 90 seconds of the video. He then goes on to say that targeting a sag percentage is stupid. Do you even watch the videos you post?
 

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And in one simple sentence you just proved you know nothing about the dynamics of riding a bicycle... You just compared a car, or a motorbike if you like to riding a full suspension mtb. No they are not the same thing and require different schools of thought, practically every suspension tuner worth his salt knows this.... That sentence right there Dougal is all I need to know, this conversation need not go any further.
No. I asked you a question to gauge your understanding. You didn't/couldn't/wouldn't answer it and instead tried to frame it as a statement meaning something you've just made up.

That's like a 4/10 trolling effort. I really hope you weren't serious.

do you mean the effect is neglectable and is overcast by other factors?
Yes. To give you an idea of the forces involved. It takes over 130kg to bottom-out my fork slowly. It takes more force for the air spring alone when compressed fast and then you bring in damper forces. You're seeing in excess of 200kg peak forces on the fork in my slo-mo video at about 10km/h.

6kg to break 2.5mm rear shock preload is nothing. A Bomber CR rear shock has over 30kg to break stiction and internal IFP pressure. That's without the spring.

I'm done here, godbless those who actually believe some of the crap he says and worse pays for his 'expertise'... This is my last post in this thread.
I am filled with skepticism.
 

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In a car or on a motorcycle the vehicle chassis etc makes up the majority of the mass and is all sprung... On a bicycle the rider makes up the majority of the mass, the sprung mass of the frame is relatively light weight compared to the spring rate and riders mass and the rider being detached from the frame means said riders weight is not always in sync with the sprung mass of the bike frame and therefore this means the riders weight is not 'always' sprung mass..aka dynamic. .
Have you ever heard of motocross bikes?
They tend to weigh close to what a rider does, and rumor has it they can be ridden pretty dynamically.
 
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"initiation force" isn't what you think it is.

You seem to think that a 400lb spring needs 400lbs to move at all, so a 450lb spring would need even more to get going. The higher rate spring simply moves less. That's why springs are rated in pounds per inch, or kg mm.

Trying to pretend the suspension engineer doesnt understand dynamics is pretty funny though. You missed the point about car springs and preload, not dougal.
 

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Discussion Starter · #585 · (Edited)
"initiation force" isn't what you think it is.

You seem to think that a 400lb spring needs 400lbs to move at all, so a 450lb spring would need even more to get going. The higher rate spring simply moves less. That's why springs are rated in pounds per inch, or kg mm.

Trying to pretend the suspension engineer doesnt understand dynamics is pretty funny though. You missed the point about car springs and preload, not dougal.
Jesus, you think I don't know what spring rate means? No I don't think any of what you wrote at all, I'm not dumb....the clue is in the name isn't it, pounds 'per' inch..

I'm saying spring prwload does require initiation, if you preload a 99'999lb spring or any spring rate by 50lbs, it will take 50lbs of force until it will start to compress and it's as simple as that, I'm not arguing how far or not a spring moves in terms of spring rate.

I find it ironic Dougal the suspension expert is liking your messages when you are completely wrong, it's not me that doesn't understand preload, it's you, and he doesn't understand how automotive preload has no relevance whatsoever to the mtb world.

For a start on a car a certain amount of preload is required to stabilise the chassis along with anti roll bars etc.. secoedly automotive and motorbike springs do not come in the vast range of rates generally that mtb springs do, you have 1 spring on a motorcycle that needs to suit both 140lb skinny dude and a 400lb fat ass.. that is why you set preload on motorcycles to maintain ride height and geometry as it's one coil to suit all.

Maybe actually watch Steves video I posted instead of still arguing, as he says at the start, this is 'REALLY BASIC STUFF'.
 

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Banshee Titan, Ragley Bluepig
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6kg to break 2.5mm rear shock preload is nothing. A Bomber CR rear shock has over 30kg to break stiction and internal IFP pressure. That's without the spring.
Just wanted to repeat this because Dan seems to have an aversion to reading anything at all

Although wasn't 6kg at the wheel?
 

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Banshee Titan, Ragley Bluepig
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Dan if the bump is small enough that it can't overcome 6kg of force, then is it even a bump?
 

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Just wanted to repeat this because Dan seems to have an aversion to reading anything at all

Although wasn't 6kg at the wheel?
Yeah 6kg at the wheel, 30kg at the shock. With a ~2.5:1 leverage that 30kg at the shock becomes 12kg at the wheel.

Dan if the bump is small enough that it can't overcome 6kg of force, then is it even a bump?
It might be the difference between @Danzzz88 gettomg 150mm and 155mm!
 

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Banshee Titan, Ragley Bluepig
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Out of interest how much does a Super deluxe have vs a Mara pro
 

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Discussion Starter · #590 · (Edited)
What is being ignored here is impulse, a shock force of 6kg due to preload at top out creating a sharp spike on initial impact is not the same as applying 6kg at a slow and steady rate. The reason suspension 'feels' like less force is transmitted to the rider is because it prolongs the time period the force is acting over.. the actual total force generated doesn't change apart from some being dissipated into heat by the damper... Of which the damper is doing nothing anyway until the preload force has been exceeded.
 

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Out of interest how much does a Super deluxe have vs a Mara pro
The IFP preload is pretty similar. Same internal pressure, similar sized shafts.
But the difference in friction is enormous. Today I dyno'd my spare RS SD Coil. It's got ~20kg of friction each way at change of direction. Which is exactly what you feel in a bench test even with the air can off a SD Air.
My dyno measures the IFP preload during calibration and subtracts that back out of the plots.
 

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The IFP preload is pretty similar. Same internal pressure, similar sized shafts.
do you know why the deluxe uses different pressures dependig on the model (with/without platform) but the super deluxe does not?

the deluxe rlr/rl/rt needs 500psi instead of 250psi in the deluxe r, but all super deluxe need 250psi.
 

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I'm saying spring prwload does require initiation, if you preload a 99'999lb spring or any spring rate by 50lbs, it will take 50lbs of force until it will start to compress and it's as simple as that, I'm not arguing how far or not a spring moves in terms of spring rate.
Thats not how that works. If you preload a spring 50 pounds, it'll take 50 additional pounds to move it an inch. One pound will begin to move the spring. This "initiation force" thing is something you're not understanding at all. Breakaway force has to do with friction from seals. The spring is nearly frictionless in compression, and starts moving once it has any weight applied at all. Preload is no different.

I know you're not arguing how far, but thats because you dont understand how springs work! Thats why I stated they're rated in force and distance. a 400 pound springs starts moving at 1 pound, just not very far. More or less preload determines how far.

You seem to think preload sets breakaway friction, which makes no sense. The video you yourself posted shows that preload sets height :lol:
 

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Discussion Starter · #594 · (Edited)
No it won't move an inch with an additional 50lbs it depends on the spring rate in that case how far it moves...

Here is an example.. say you have a 100lb/in spring and preload it 50lbs.. to move one inch will require 150lbs. Applying a force of 50lbs or less will not make the spring move at all.

Think of it like lifting a weight off the floor, if you have a 50kg dumbell, and apply 49kg of pulling force directly upwards it will not lift up or move at all.. what it will show if you placed in on a scale to begin with is the scale will now read 1kg but the dumbell will not move... You see the force on the scale changes but the dumbell doesn't move, it's common sense that if a scale is reading 1kg then something is moving down not up in the direction of the pulling force To lift the dumbell requires greater than 50kg, and to counteract the preload requires 50lbs force or greater.. I cannot believe Dougal was agreeing with you on this.

I'm gonna go find a calculator on the internet to prove it if I can find one.

Sorry you've got it all wrong.
 

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You can spend $5.99 on a fish scale and verify this yourself.

Yes, the spring in your example will absolutely move with less than 150 lb on it. It'll move half an inch with 75lb. 1/4 inch with 37.5lb, 1/8th inch with 18.75lb and so on. Literally any amount of weight will move it an amount.

For your other example, put the 50kg weight on a scale and pull up but not enough to lift it. Scale reads less. Same thing... And actually it's moving/flexing exactly the same as the spring, just much much less.
 

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Thats not how that works. If you preload a spring 50 pounds, it'll take 50 additional pounds to move it an inch.
thats completely wrong, it offsets the curve!

1925767


" In other words[...]you would have to put more than 17.5kg force on the end of the fork tube to create any movement at all. "
 

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I put no effort into this thought at all but curious about it's validity.

Wouldn't the force of your spring be identical at the same given sag point even with two different rate springs? Sag is just the equalibrium between weight compressing the shock and the spring pressing back. Whether you have a 400 or 450lbs spring if your sag is 30% the spring is pushing back with the same amount of force.

So one could stand to reason the effect on small bump sensitivity would be tiny between a preloaded 400lbs spring and a zero preload 450. The difference in spring rate will be more noticable the further it's compressed which will be important for aggressive riding.

Again didn't put much thought into this. My as well keep the thread going!
 

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Discussion Starter · #598 ·
I put no effort into this thought at all but curious about it's validity.

Wouldn't the force of your spring be identical at the same given sag point even with two different rate springs? Sag is just the equalibrium between weight compressing the shock and the spring pressing back. Whether you have a 400 or 450lbs spring if your sag is 30% the spring is pushing back with the same amount of force.

So one could stand to reason the effect on small bump sensitivity would be tiny between a preloaded 400lbs spring and a zero preload 450. The difference in spring rate will be more noticable the further it's compressed which will be important for aggressive riding.

Again didn't put much thought into this. My as well keep the thread going!
Forget sag a minute, yes sag will negate any preload effect when the weight has exceeded the preload force...I'm talking about a preloaded shock from full extension.. and he seems to think that a preloaded shock will start moving with any force whatsoever which simply is not true.
 

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Lots of wrong info here.

Preload is an offset. You have 50lbs of preload, it will take 50lbs of load before that spring moves.

No, 30% sag on a 400lb spring is not the same load as 30% sag on a 450lb spring.

Realistically, sag is nothing more then a check to see if your spring rate is roughly correct. On a dirt bike, this is more apparent because you have two types of SAG. One is the bikes weight alone, the second is with you on it. If you have too soft of a spring and then crank up preload to get the sag right with you on it, then the bike won't sag enough under the bikes weight alone. If you have too stiff of a spring then you have to back off preload to get rider sag right but then it sags too much under just the bike weight. It's nothing more then to see the balance between spring rate and preload is within the correct balance.
 

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Discussion Starter · #600 ·
Lots of wrong info here.

Preload is an offset. You have 50lbs of preload, it will take 50lbs of load before that spring moves.

No, 30% sag on a 400lb spring is not the same load as 30% sag on a 450lb spring.

Realistically, sag is nothing more then a check to see if your spring rate is roughly correct. On a dirt bike, this is more apparent because you have two types of SAG. One is the bikes weight alone, the second is with you on it. If you have too soft of a spring and then crank up preload to get the sag right with you on it, then the bike won't sag enough under the bikes weight alone. If you have too stiff of a spring then you have to back off preload to get rider sag right but then it sags too much under just the bike weight. It's nothing more then to see the balance between spring rate and preload is within the correct balance.
Exactly!
 
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