Suspension Theory

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4/27/2020 7:33 AM
Edited Date/Time: 4/27/2020 7:34 AM

Anyone have any recommendations for good reference material on learning how to revalve? I like to tinker, and I’m tired of spending ungodly amounts of money for revalves.

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4/27/2020 7:53 AM

Look up the Race Tech Suspension Bible. That’s what everyone I’ve talked to has recommended.

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4/27/2020 8:17 AM
Edited Date/Time: 4/27/2020 4:28 PM

I learned by installing my own gold valve kits back in the 90s as well as the RT suspension bible and spend some time on Thumper Talk there is a plethora of info there!

Also I learned this the hard way, take some time to understand the differences of shim thickness, a .12 is about 3 times stiffer than a .10!!! My suspension was soooo stiff on small chatter but great on big hits and I got lost in adjusting my mid valve in all different configurations. Turned out one day I was on Thumper Talk and a random post said “remember the blue KYB shims are .12 not .10 so that makes a big difference” I was using a analog micrometer and couldn’t really tell the difference and ordered a digital... I’ll be damned half the shims in my Mid Valve and compression stack were .12 shims 🤦‍♂️

I went back and re installed the original stacks I had in all .10 and it was rideable again and worked well! It’s little stuff like that, that will drive you insane but when you learn from your mistakes it’s rewarding!!!

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Never try to argue with idiots; they will only bring you down to their level.....and being more experienced, they will beat you at their own game!

2020.5 KTM 450 SXF FE
2006 KX250

4/27/2020 8:36 AM

Awesome, I’ll order that book. Thanks guys.

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4/27/2020 10:20 AM

Paul Thede's books

Introduction/Theory to fluid dynamics (rent a book from your local library and learn the basics)

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4/27/2020 2:00 PM
Edited Date/Time: 4/27/2020 4:27 PM

https://thumpertalk.com/forums/topic/1124437-dyno-data-–and-what-it-tells-us-about-how-to-tune-a-shim-stack-and-control-the-shape-of-the-damping-force-curve/

This thread on TT made me feel pretty stupid for awhile... when it all starts to make sense you read it again and have this look on your face and realize you don’t get it!

Photo

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Never try to argue with idiots; they will only bring you down to their level.....and being more experienced, they will beat you at their own game!

2020.5 KTM 450 SXF FE
2006 KX250

4/27/2020 2:15 PM

CSAR FE wrote:

Anyone have any recommendations for good reference material on learning how to revalve? I like to tinker, and I’m tired of spending ungodly amounts of money for revalves.

Getting into suspension and re-valving is only half of it if you're not a good test rider and can't ride a bike and feel it needs less or more of something you will just be another shim stacker and be totaly lost

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4/27/2020 3:24 PM

a couple of things I've learned that took a bit of time to learn but were very important:

The mid valves in forks can be very restrictive. A lot of the harshness on chop - assuming you have a reasonable spring rate- is the mid valve being toooo stiff. So if you're getting too much feed back on chop... sharp edged stuff with the forks; Try opening up the float and lighten the mid valve. A mid valve change has more effect then a base valve change (pull one shim from the mid value and you'll feel it.. the base valve you'll barely notice it). Make big base valve shim changes as a result. My mind set now is to go with higher oil levels in the forks and softer on the valving to get the small bump compliance I want... I tune till the forks is too soft then add stuff back in... Vs staying too stiff. I want that small bump compliance and will give up some bottoming resistance. Especially for off road.

On shocks pay attention to the pivot shim size. That is the last shim in the stock.. the smallest diameter one. Changing the piviot shim can effect the entire stack.

I setup shock initial compression to be softer then stock most often. Often I will put in a bleed shim between the shock piston and the first shim that will be big enough in diameter to cover the piston (compression side). Why? That little bit of bleed helps the bike track under power. The shock moves a bit freerer and hooks up better. This is similar to drilling out the bleed hole in the shock piston (if there is a hole). It can be undone too. Some of the best shocks I've ever valved had this done to them and they hocked up... clawed at the ground. I've put a few bleed shims in too... Had to do this to a KTM 350 due to the stock linkage setup. To get the bike to move on small chop. Yes you can go too far and it will blow through. But you need to experiment and find these points. You'll learn alot about what you like and don't like.

On shock rebound: I like my high speed rebound to be stiffer then stock. When the shock is deep in the travel I want it coming back SLOW from a hard hit. Now, I m not hitting super cross woops etc... this is mainly for off road which is where I spend most of my time. I go for cross overs higher up in the rebound stack to let the shock move in the first part of the stroke for compliance - then stiff up the high speed part of the travel to control it.

Note: I don't go near a supercross track... so none of what's above would apply there. Supercross is a different animal and I have nothing to add to setup for that.

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4/27/2020 4:09 PM

The RT book is good for theory, but it doesn’t cover anything on shims or revvalving.

There’s an Ohlins shop manual floating around on the web, has some good info about shim selection and the math to convert to different size shims.

Restackor is a computer program that can help graph and plot shim changes, There is a ton of info on the site as well.

TT suspension form has been the biggest help to me, I don’t really know anything.

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4/28/2020 8:29 AM

As an extuner, I can tell you that most of the info these guys are throwing out is good. But even if you have the mechanical know how, books on theory, etc, the biggest thing to do to be successful is testing. And as someone mentioned, you do have to have some skill. Don't have to be a pro by any means but good enough to tell the difference when yo make change. And you have to be willing to go back and tear it down again (and again and again). Suspension work is messy and smelly.

I have looked at the restacker program though I never bought it. It looks like it could be a benefit. I guess one question is.....are you just doong this ofr yourself and a possible living?

Race Tech used to include valving charts in their God Valve kits but they no longer do so. Many will debate the good or bad of Gold Valves but they are still an excellent place to start ofr the DIY guy.

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4/28/2020 10:06 AM

CSAR FE,
Lots of good advice in here!

One thing to note, as Honda65 said "And you have to be willing to go back and tear it down again (and again and again)."

Honestly, once you do it a few times, you can do it FAST. But it IS messy!!! You will be much more inclined to dive into it if you have a proper, dedicated work space to do suspension and contain the oil that will be flying around.

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4/28/2020 10:55 AM

Thanks for all the advice gents. This is making for a great thread. Please keep it coming.

Not doing this for a living, just for me personally. I’m in the military and move around a lot, so sometimes my suspension needs change with the terrain and in some cases exceeds what I can adjust for with the clickers.

I’ve been riding for a long time and am in tune with how to adjust my suspension and set up my chassis, but translating that to a valving change is a blind spot for me.

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4/28/2020 11:19 AM

CSAR FE wrote:

Anyone have any recommendations for good reference material on learning how to revalve? I like to tinker, and I’m tired of spending ungodly amounts of money for revalves.

I had a discussion with Graeme Brough a few months back about suspension valving and set-up

He kept reminding me that it's a black-art and One needs to have an open mind. Do not be afraid to experiment.....that applies to everything on the bike.

Trend monitoring - it crucial to document everything you do in a note book and use the data as a references going forward.

There are suspension tuning books and DVDs out there.

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Non Gratum Anus Rodentum

4/28/2020 12:07 PM

Don't have to be a pro by any means but good enough to tell the difference when yo make change. And you have to be willing to go back and tear it down again (and again and again). Suspension work is messy and smelly.

What this gentleman said above is very true. I 100% agree. I did some work on a friends bike - he's pretty darn fast - and the only feed back he could give me was "it feels different". I was like... "huh.... ahh... need more info than that".

You also have to know what you like. Or at least are willing to experiment to find out what you like. I like stuff that absorbs chop. I don't like getting pounded by sharp edged chop. So I set the bike up to adsorb that stuff first and foremost.

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4/28/2020 12:11 PM

I think this would be a good place for you guys with the knowledge to define some key terms or jargon used with suspension setup. For example, “set the float”, and things of that nature.

Thanks again. You guys are awesome.

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4/28/2020 12:13 PM

CSAR FE wrote:

Thanks for all the advice gents. This is making for a great thread. Please keep it coming.

Not doing this for a living, just for me personally. I’m in the military and move around a lot, so sometimes my suspension needs change with the terrain and in some cases exceeds what I can adjust for with the clickers.

I’ve been riding for a long time and am in tune with how to adjust my suspension and set up my chassis, but translating that to a valving change is a blind spot for me.

Yeah, man, I'm with you. I read the Race Tech book then went over those threads in Thumpertalk multiple times till it started sinking in. Finally dove into my CRF450. After a few tries, I had the forks feeling really good (to ME). Absolutely no way can I say I am a suspension tuner as that would be an insult of the highest order to those guys that can do that work for other people but it was immensely satisfying to do my own bike myself.

Like Boomslang said, keep a notebook and make lots of notes and keep track of every little change. It will start to make sense. Also, keep in mind there are many ways to create a valve stack that will get similar results.

Boomslang- do you have that photo of your suspension bench set-up?

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4/28/2020 12:17 PM

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4/28/2020 12:20 PM

PTshox wrote:

Don't have to be a pro by any means but good enough to tell the difference when yo make change. And you have to be willing to go back and tear it down again (and again and again). Suspension work is messy and smelly.

What this gentleman said above is very true. I 100% agree. I did some work on a friends bike - he's pretty darn fast - and the only feed back he could give me was "it feels different". I was like... "huh.... ahh... need more info than that".

You also have to know what you like. Or at least are willing to experiment to find out what you like. I like stuff that absorbs chop. I don't like getting pounded by sharp edged chop. So I set the bike up to adsorb that stuff first and foremost.

I quote you here - "he's pretty darn fast - and the only feed back he could give me was "it feels different". I was like... "huh.... ahh... need more info than that"

A common blady problem and one needs to dig deep to find the patience.......

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Non Gratum Anus Rodentum

4/28/2020 12:32 PM

FWYT wrote:

Yeah, man, I'm with you. I read the Race Tech book then went over those threads in Thumpertalk multiple times till it started sinking in. Finally dove into my CRF450. After a few tries, I had the forks feeling really good (to ME). Absolutely no way can I say I am a suspension tuner as that would be an insult of the highest order to those guys that can do that work for other people but it was immensely satisfying to do my own bike myself.

Like Boomslang said, keep a notebook and make lots of notes and keep track of every little change. It will start to make sense. Also, keep in mind there are many ways to create a valve stack that will get similar results.

Boomslang- do you have that photo of your suspension bench set-up?

No my friend, I'm not a suspension tuner although at one point I worked under Graeme Brough and Grant Reynolds. I've pretty much been with one rider for the last 13 yrs. We out-source our stuff.

Ill dig up some old photos of our sus department from back in the day.

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Non Gratum Anus Rodentum