Front SAG


8 replies to this topic
  • godov

Posted May 29, 2013 - 01:55 AM

#1

Hi,

This may be a stupid question bur here it goes anyway:

- Should front race SAG be setup? I've done the back, but didn't find much info on the front...
- For the rear it should be between 100-115mm. What about the front?
- How is race Sag set-up on the front?

Thanks everyone.

  • Krannie McKranface

Posted May 29, 2013 - 05:28 AM

#2

Front sag is such a pain make changes with, it's just about ignored by the average rider.
It requires shims on the springs, and if it's a closed cartridge fork, that means dissassembly of the forks.
I've only run into problems with front sag being way off when the wrong forks springs are are used, like putting YZ springs in WR forks (some YZ springs are longer, reducing sag), or when companies like ProAction or Smart Performance pre-load the springs too much (I'm not sure why).

Mixing fork spring rates (a different spring rate in each fork to create a 'custom' spring rate) is usually all that is needed:

The Dwight Rudder method:

[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]I have come up with a formula that I use for setting the suspension up on my bikes. This info was collected the past few years from several different tuners and applied. I have broken this down into a formula using percentages of available travel so this will work on most any bike. (KTM PDS is slightly different but close). I thought I would share this knowledge with you.[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Your shock spring preload should be less than 10mm on linkage suspension but not less than 5mm. You don't want to over preload a weak spring as you will just get a harsh ride that still will allow hard bottoming. I usually shoot for about 5mm preload on fork springs. If you have the right spring.[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]You can figure your correct sag numbers by using percentages. That way you can get the correct springs for you and your bike. Base these percentages on the available travel front and rear with a variance of + - 3 mm.[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Front suspension static sag should be 14% ( available travel in mm X .14 = static sag in mm)[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Front suspension rider sag should be 25% (X .25 = Rider sag)[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Rear suspension static sag should be 11% of available travel (X .11 = static sag)[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Rear suspension rider sag should be 34% of available travel (X .34 = rider sag)[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Using these principles you can figure the correct sags for any bike and thus the correct springs without guessing and compromising.[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]Once you get the springs set correct you can get the forks and shock revalved if need be. I usually like to take 20-25% of the high speed compression out with the correct spring rates. I am an offroad racer / rider. [/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]I usually leave rebound stock or change according to the replacement springs. I usually will change rebound one click per .2 kg. on rear shock. If I go up on spring rate say from a 5kg to a 5.8kg , I will go in 4 clicks. That is a good place to start. After setting rebound and spring sags (and getting correct spring rate installed). I find a G out or a ditch that I can jump into and expect to bottom front and rear at same time. I will back off compression till I am bottom softly front and rear. NOT DRIVING FOOTPEGS THROUGH YOUR FEET OR METAL TO METAL BOTTOMING.. Just bottoming softly. Then I go back in about 2 clicks to compensate for heated suspension. I then will ride extensively to see if I need to go in or out slightly to fine tune. Damping I find is a very personal thing it you take the time to dial it in. I like a plush and compliant suspension but not wallowy. Many times lately I find that I have to go down on fork springs and up on shock spring rates. I weigh 180-185lbs and ride a 2011 Husqvarna WR150. It came with .42kg fork springs. That is what my KTM 525 / 530 had in the front forks. For sure there is a big difference in weights. I tried .44kg on my 525 and the bike would not turn. The bike should settle into the corner front and rear when turning. My bike would not settle. The forks were way off static and rider sag. I was on the cusp whether to go to a .38kg or .40kg. If I were 10lbs lighter I could have used a .38kg. But as it stands the .40kg allowed my sag numbers to work perfectly. 40mm static and 75mm rider. With the correct sag rates the bike is not nearly as tall feeling. Much easier to throw a leg across. Turns perfectly and is very stable on straights. I am very happy with the results. Use the formula and you can get the perfect spring rates for you and your bike. Don't ride the bike till you are satisfied you have the correct spring rates as most shops will exchange unused springs for different rates. If you ride with them they will look used and can't be sold as new. I think you will be very happy with the results if you don't compromise.[/background][/font][/color]

  • GuyGraham

Posted May 29, 2013 - 09:30 AM

#3

There's too much stiction on the forks to get accurate sag figures
measure it, then measure it again and your results will vary hugely

  • SurfaceToAir

Posted May 29, 2013 - 01:06 PM

#4

I am stokedyou posted this. I have been doing research around too, and its hard to find any info. Though tons on the rear.

In my case, I am about to put stock springs into the front ( just did the back) since the PO had RaceTech springs in there for a 185 lb rider. I am 165-170lb. He also had it revalved with Racetech valves, though I dont know which ones.. And no idea about the shims, etc.. Hoping I can just put the stock springs in, not adjust (what is left of ) the oil, and hopefully it will be good. Hopefully the springs are the same length, etc.. Hope hope hope..

And knowing hope is not a strategy, I am wondering if swapping the springs is even a good idea.. Will see.

cheers-
Dustin

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  • Krannie McKranface

Posted May 29, 2013 - 06:06 PM

#5

I am stokedyou posted this. I have been doing research around too, and its hard to find any info. Though tons on the rear.

In my case, I am about to put stock springs into the front ( just did the back) since the PO had RaceTech springs in there for a 185 lb rider. I am 165-170lb. He also had it revalved with Racetech valves, though I dont know which ones.. And no idea about the shims, etc.. Hoping I can just put the stock springs in, not adjust (what is left of ) the oil, and hopefully it will be good. Hopefully the springs are the same length, etc.. Hope hope hope..

And knowing hope is not a strategy, I am wondering if swapping the springs is even a good idea.. Will see.

cheers-
Dustin


Instead of following the front sag thing, I just follow the front to rear spring ratio thing.
RaceTech posts the matching springs to use when you change the rear.
So, if you get the rear sag perfect, there is a matching spring for the front listed, to make the front perfect.

  • godov

Posted May 30, 2013 - 01:02 AM

#6

Great help Krannie! But you know, after reading your post I decided I should get some professional help...

I've done the rear, but the front is just too much for me...

I contacted a company which uses racetech material and do a lot of work for professional enduro and Dakar riders (http://www.rnm.pt/index.asp?p=306).

I'm guessing that for around $400 I will have top of the line material and the best fork setup I can get.

What's your opinion everyone?

Thanks

  • Krannie McKranface

Posted May 30, 2013 - 12:19 PM

#7

Great help Krannie! But you know, after reading your post I decided I should get some professional help...

I've done the rear, but the front is just too much for me...

I contacted a company which uses racetech material and do a lot of work for professional enduro and Dakar riders (http://www.rnm.pt/index.asp?p=306).

I'm guessing that for around $400 I will have top of the line material and the best fork setup I can get.

What's your opinion everyone?

Thanks


So, you are saying that you have changed the rear spring, but did not revalve, and are now going to change the front springs, and revalve?

You will be out of balance.............the stock rear shock is already waay under valved on re-bound...

  • godov

Posted June 08, 2013 - 12:42 PM

#8

No, i just adjusted sag on the rear. But have now decided to leave it all to the pros.
I guess it will be better that way!
We'll see!

  • godov

Posted June 13, 2013 - 06:36 AM

#9

Race tech stage 2 mod completed. Can't wait till the weekend! :)




 
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