Suspension SETUP, a 'how to' guide...

PB Forum :: Mechanics' Lounge
Suspension SETUP, a 'how to' guide...
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Posted: Apr 30, 2020 at 7:46 Quote
There is a funny tendency in Moto GP and even Formula One where to best racers are often the worst at helping along product development. They get something they like for a particular track and just want to keep running it rather than continuing to "develop" it. I've read Sam Hill is kinda the same; he famously resisted going to 29er or letting Nukeproof alter the Mega's Med sizing because he had a platform that worked good enough for him. The dude could ride a stock Huffy better than most of us can ride a dentist's bike. But what also makes racers like Luis Hamilton or Valentino Rossi so good, is that they have a genius not only for racing but for also not losing track of their baselines when adjustments are made. On the other hand, there was a kid named John Kocinski who won 250 and Supebike World Championships, but was so bad at bike suspension setup, always trying to tweak the things, getting lost in it, frustrating himself and not performing as a result that no crew chief wanted to work with him. He was humiliated by the press and dropped hard from the GP circuit. Tuning is a dark art.
R-M-R wrote:
It's not always wrong to be fiddling with adjustments (watch any Fox video with Loris Vergier!), but you're quite right that many folks get lost in the adjustments, make things worse, blame the equipment, lose practice time due to fettling, and/or never trust the equipment because it's never consistent.

There's a hierarchy of suspension properties to prioritize; once those are sorted, the remaining variables become fine-tuning and finer-tuning.

Posted: Apr 30, 2020 at 9:15 Quote
The top World Cup DH guys are all fairly involved in the set-up process, with quite a range from those who are always tinkering to those who prefer consistency, even when they're deep into the world of telemetry (by mountain bike standards).

As much as Sam Hill has a reputation for not messing with his gear, he was a pioneer of "long and slack". For about half his time on the Iron Horse Sunday, he had a custom Large front with Medium seat-tube and a head angle not much over 60°. He was the only rider to get a custom Sunday ... except me, of course! Wink I stumbled upon a frame that was intended for him, but made with a Large seat-tube. This bike taught me why it's not always wise to emulate the pros: it's clumsy unless ridden extremely hard and fast; there's little overlap between my skill and the bike's optimal operating conditions.

Posted: Apr 30, 2020 at 16:44 Quote
There is a loose but useful way of thinking of the difference between low and high speed compression.
Lsc generally controls input from the top down, ie your bodyweight and rider inputs compressing the suspension. The more lsc you run, the more support you will have to push against while trying to move the bike around, and the more it will resist brake dive etc. The bike will generally feel stable and poppy instead of like riding a lurching waterbed. The downside being that it will feel harsher and more tiring to ride over rough terrain, and the tyre will not be able to track the ground as seamlessly.
Hsc generally controls inputs from the ground up ie. hitting rocks etc. Running over anything more significant than smooth undulations in the terrain will likely blow into the high speed circuit. The effect of adding hsc is more difficult to describe. Essentially adding hsc should mean you use less travel for a given hit. The more you add the harsher the bike will feel, but the more travel it will keep in reserve for bigger hits.
Low speed adjusters almost always control the size of an orifice which allows fluid to bleed through. High speed adjusters ideally adjust the stiffness of a shim stack, but more often simply add preload to a spring, which alters the blow off threshold. This isnt really a true high speed adjustment, instead controlling the amount of force required to open the high speed circuit.

Generally (true) hsc is reasonably set and forget. Find a setting that means you use near full travel for the biggest hits you regularly encounter. Then leave it there. You want to run as little hsc as possible without bottoming out too often.

Low speed is much more tuneable from track to track. This is the dial you should mess with the most. Generally the smoother and flowier the track the more lsc you run. The rougher the track the less lsc you can get away with. A stable and responsive bike is generally a good thing, so you want to run as much lsc as you can get away with without making the bike too harsh. The rougher the track, the less lsc you can run. Most other settings can generally be left untouched unless you are riding terrain conpletely different to your normal riding.

Posted: Apr 30, 2020 at 20:16 Quote
Excellent post. Thank you. I have probably been being to timid with my LSC adjustment, instinctively knowing what it does, but not knowing just what to do with so many clicks. It isn't like rebound or HSC which is pretty obvious to set; you know almost immediately within a couple clicks when you are in range. But 16 clicks of LSC was throwing me off; just have no experience with it. A few clicks of LSC didn't seem to make enough difference to know if I was headed in the right direction. What you said tells me I need to go from one extreme to the other (in a particular scenario) and I should find the right point. Sounds stupid to put it like that, but there is really a vacuum of real world tuning tips out there concerning micro adjustment LSC. So yeah, this was good to hear. Again, thanks.

gabriel-mission9 wrote:
There is a loose but useful way of thinking of the difference between low and high speed compression.
Lsc generally controls input from the top down, ie your bodyweight and rider inputs compressing the suspension. The more lsc you run, the more support you will have to push against while trying to move the bike around, and the more it will resist brake dive etc. The bike will generally feel stable and poppy instead of like riding a lurching waterbed. The downside being that it will feel harsher and more tiring to ride over rough terrain, and the tyre will not be able to track the ground as seamlessly.
Hsc generally controls inputs from the ground up ie. hitting rocks etc. Running over anything more significant than smooth undulations in the terrain will likely blow into the high speed circuit. The effect of adding hsc is more difficult to describe. Essentially adding hsc should mean you use less travel for a given hit. The more you add the harsher the bike will feel, but the more travel it will keep in reserve for bigger hits.
Low speed adjusters almost always control the size of an orifice which allows fluid to bleed through. High speed adjusters ideally adjust the stiffness of a shim stack, but more often simply add preload to a spring, which alters the blow off threshold. This isnt really a true high speed adjustment, instead controlling the amount of force required to open the high speed circuit.

Generally (true) hsc is reasonably set and forget. Find a setting that means you use near full travel for the biggest hits you regularly encounter. Then leave it there. You want to run as little hsc as possible without bottoming out too often.

Low speed is much more tuneable from track to track. This is the dial you should mess with the most. Generally the smoother and flowier the track the more lsc you run. The rougher the track the less lsc you can get away with. A stable and responsive bike is generally a good thing, so you want to run as much lsc as you can get away with without making the bike too harsh. The rougher the track, the less lsc you can run. Most other settings can generally be left untouched unless you are riding terrain conpletely different to your normal riding.

Posted: May 6, 2020 at 23:10 Quote
Hi guys. It is not a scientific question but if you stand next to your bike and push hard on the bars how much should your fork compress?

Posted: May 6, 2020 at 23:32 Quote
Depends how hard you push! If I hop up, lean over the bar, and really get my weight onto it, maybe two-thirds travel. If I just push down with my hands, maybe a third.

A better way to set up the fork is to track how it bottoms out:

• It should bottom out once in a while.
• You should never get a harsh "clang!" bottom-out unless something bad happens, like nose-diving off a drop or a big huck to flat.
• When the fork bottoms out, the impact should be about as much as your body could handle - i.e. you and the fork both max. out at about the same time.

Posted: May 6, 2020 at 23:49 Quote
Thank you very much.

Posted: May 7, 2020 at 0:04 Quote
gabriel-mission9 wrote:
There is a loose but useful way of thinking of the difference between low and high speed compression.
Lsc generally controls input from the top down, ie your bodyweight and rider inputs compressing the suspension. The more lsc you run, the more support you will have to push against while trying to move the bike around, and the more it will resist brake dive etc. The bike will generally feel stable and poppy instead of like riding a lurching waterbed. The downside being that it will feel harsher and more tiring to ride over rough terrain, and the tyre will not be able to track the ground as seamlessly.
Hsc generally controls inputs from the ground up ie. hitting rocks etc. Running over anything more significant than smooth undulations in the terrain will likely blow into the high speed circuit. The effect of adding hsc is more difficult to describe. Essentially adding hsc should mean you use less travel for a given hit. The more you add the harsher the bike will feel, but the more travel it will keep in reserve for bigger hits.
Low speed adjusters almost always control the size of an orifice which allows fluid to bleed through. High speed adjusters ideally adjust the stiffness of a shim stack, but more often simply add preload to a spring, which alters the blow off threshold. This isnt really a true high speed adjustment, instead controlling the amount of force required to open the high speed circuit.

Generally (true) hsc is reasonably set and forget. Find a setting that means you use near full travel for the biggest hits you regularly encounter. Then leave it there. You want to run as little hsc as possible without bottoming out too often.

Low speed is much more tuneable from track to track. This is the dial you should mess with the most. Generally the smoother and flowier the track the more lsc you run. The rougher the track the less lsc you can get away with. A stable and responsive bike is generally a good thing, so you want to run as much lsc as you can get away with without making the bike too harsh. The rougher the track, the less lsc you can run. Most other settings can generally be left untouched unless you are riding terrain conpletely different to your normal riding.

By running lsc do you mean open or closed

Posted: May 7, 2020 at 0:06 Quote
wellbastardfast wrote:
By running lsc do you mean open or closed

Closed, clockwise, firmer.

Posted: May 7, 2020 at 7:59 Quote
R-M-R wrote:
wellbastardfast wrote:
By running lsc do you mean open or closed

Closed, clockwise, firmer.

As rmr says.
More = closed, clockwise, firmer
Less = open, anticlockwise, softer

Same is true for all suspension settings

Posted: May 8, 2020 at 1:18 Quote
Hi all, I have tried to adjust my rear coil suspension. I cannot for the life of me twist it... I need to loosen it and extend the spring more. Is there a specific tool or just a method to do this easier please?

Posted: May 8, 2020 at 1:40 Quote
VargaL wrote:
Hi all, I have tried to adjust my rear coil suspension. I cannot for the life of me twist it... I need to loosen it and extend the spring more. Is there a specific tool or just a method to do this easier please?

Mine did this once I grabbed some channel locks and a cloth and wrapped the cloth around the preload nut and then grab it with the channel locks and turn it some sort of lube might help too

Posted: May 8, 2020 at 1:41 Quote
lube the threads with a thin oil and let it run into the collar. Leave it a day and try again.

Posted: May 8, 2020 at 2:05 Quote
cyberoptixs wrote:
VargaL wrote:
Hi all, I have tried to adjust my rear coil suspension. I cannot for the life of me twist it... I need to loosen it and extend the spring more. Is there a specific tool or just a method to do this easier please?

Mine did this once I grabbed some channel locks and a cloth and wrapped the cloth around the preload nut and then grab it with the channel locks and turn it some sort of lube might help too

Thabk you.


 
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