Author Topic: How to reduce the shock sag?  (Read 1368 times)

0 Members and 1 Guest are viewing this topic.

Offline johnnyrebel

  • Street Triple Member
  • **
  • Topic Author
  • Posts: 92
  • Bike: '17 Striple RS
  • City / Town: Elgin
  • Country: scotland
How to reduce the shock sag?
on: September 14, 2019, 05:18:19 PM
Folks,
I'm 85kg and my RS seems to sag a fair bit when I sit on it. I'm far from being an expert so would the handling improve with less sag? If so how would I do it?
Thanks!

Offline RedBikeAgain3

  • Street Triple Master
  • ****
  • Posts: 440
  • Bike: 2015 ST ABS noneR
  • City / Town: Lincoln
  • Country: gb
Re: How to reduce the shock sag?
Reply #1 on: September 14, 2019, 07:17:45 PM
There is much written about suspension.
From my basic grasp you want some sag ie use of suspension travel with you on the bike - use a 1/4 to a third of the travel front and back to avoid topping out over bumps and at the back when braking
Mid third to half travel for normal brisk use, leaving 1/3 to 1/4 potholes, emergency stops etc.
Measure how far each axle travels against a fix point on the bike in line with the wheel travel. You are looking for sag with you on in the right range and in about the proportion front and back.
There are some good videos by Dave Moss?


Sent from my iPhone using Tapatalk
Yam DT80, Honda CB250RS, Yam XJ650, Suzuki X7, Kawa GPz500, Honda CB-1 (400), Yam FZS600 and now ... ST

Online tim.8061

  • Street Triple God
  • *****
  • Posts: 1974
  • Bike: Street Triple 09
  • City / Town: Gloucester
  • Country: england
Re: How to reduce the shock sag?
Reply #2 on: September 15, 2019, 08:55:58 AM
The only way you reduce sag is to fit a stiffer spring.

Depends on what you mean by "improve" - it won't feel as comfy.

Offline XCDC

  • Street Triple Member
  • **
  • Posts: 58
  • Bike: 18 765 RS
  • City / Town: Leicester
  • Country: gb
Re: How to reduce the shock sag?
Reply #3 on: September 15, 2019, 03:47:28 PM
Er, not really.  You can't make the spring bottom out any less without changing it, but you do alter the sag value by adding pre-load.

https://lifeatlean.com/teach-me-suspension-everything-preload/

My RS also had far too much sag when I bought it, I'm 90kg currently in kit and I had to wind the preload on quite heavily and add more damping to get the rear to the correct ride height.  You use a c-spanner on the pre-load ring to add more, which effectively raises the back of the bike so it's not as far into it's travel once you're sitting on it.

there's several guides on You Tube to explain how to do it, you'll need a couple of correct size c-ring spanners, a tape measure and a friend to help.

Offline JonyB

  • Street Triple Pro
  • ***
  • Posts: 199
  • Bike: Street Triple R 2011
  • City / Town: Wollongong
  • Country: au
Re: How to reduce the shock sag?
Reply #4 on: September 16, 2019, 04:01:34 AM
If you want to reduce SAG on the shock, you essentially need to add pre-load. To do this, you need to wind in the castlenut that locks in the shock spring, hence compressing the spring. Apologies but I'm not even sure if your bike has this adjustment or not. If not, than you'll be left with the option of getting a stiffer spring.

Now, in regards to changing SAG on the shock only and leaving the forks alone, I suggest that you check SAG of the whole bike and see if the bike is settling in a balanced manner when you sit on it or not. What I'm trying to say is that you can (in theory) reduce shock SAG too much and if the forks are too soft, you'll end up with a front end that will be too heavily loaded and this will affect your handling noticeably, especially under braking. Have a read of this https://racetech.com/articles/SuspensionAndSprings.htm and use this as a starting point.

Then, once you know that the SAG is ok or in the ball park, and once you checked that the fork travel is also ok, start thinking about what you can do with the damping to get you the balance between support and comfort that you're going for.

I'm a bit lighter than 85 kg, but I'd say that you can still adjust the stock springs to work with a rider of your weight, unless of course you ride hard and load the suspension very much.

Hope I'm not confusing you.

Ride to add life to your days, not days to your life.

Street Triple R 2011
ZX9R C2 (1999)
HEL || JayBee Biker Bits || STOMPGRIP || MOTUL

Online tim.8061

  • Street Triple God
  • *****
  • Posts: 1974
  • Bike: Street Triple 09
  • City / Town: Gloucester
  • Country: england
Re: How to reduce the shock sag?
Reply #5 on: September 16, 2019, 01:06:22 PM
Oh dear oh dear, do some people really think preload changes sag?? The trouble with forums is anyone can say any old rubbish. Preload just changes ride height ie the start point but the amount of sag when you sit on it doesn't change - that's determined by the spring. Unless its top or bottomed out then you have all sorts of problems, probably how to get your bike back out of the hedge you just pogo'd into. And ride height will certainly affect your handling but not necessarily improve it.

Offline JonyB

  • Street Triple Pro
  • ***
  • Posts: 199
  • Bike: Street Triple R 2011
  • City / Town: Wollongong
  • Country: au
Re: How to reduce the shock sag?
Reply #6 on: September 16, 2019, 08:20:56 PM
*Originally Posted by tim.8061 [+]
Oh dear oh dear, do some people really think preload changes sag??

Preload affects SAG. That's a given.

You believe I'm wrong?, ok so have a read of step 5 on the RACETECH bulletin... I'm no expert, but I'm convinced that RACETECH will know a bit better than most of us put together.

What Preload doesn't change is the stiffness of the spring.
Ride to add life to your days, not days to your life.

Street Triple R 2011
ZX9R C2 (1999)
HEL || JayBee Biker Bits || STOMPGRIP || MOTUL

Online tim.8061

  • Street Triple God
  • *****
  • Posts: 1974
  • Bike: Street Triple 09
  • City / Town: Gloucester
  • Country: england
Re: How to reduce the shock sag?
Reply #7 on: September 18, 2019, 03:24:03 PM
If the spring is too soft then winding on preload to set the loaded sag just means the unloaded sag is wrong as it will be less then spec. Then the suspensions tops out and you pogo into the hedge.

But carry on if that makes you happy.

Offline bazzer

  • Street Triple Master
  • ****
  • Posts: 824
Re: How to reduce the shock sag?
Reply #8 on: September 18, 2019, 03:48:57 PM
It does not change the spring rate, but it does change the total amount the bike sags and setting the sag is used to put the shock in the correct place to start with, so it can operate correctly.

You are correct that it will not change the the difference between static sag and rider sag values (unless you have zero static sag to start with)

It is an import part of making the suspension work properly.

However if you set your rider sag and you find you have zero static sag then the spring is probably too soft. If you have way too much static sag when setting rider sag then spring is probably too hard.


Offline JonyB

  • Street Triple Pro
  • ***
  • Posts: 199
  • Bike: Street Triple R 2011
  • City / Town: Wollongong
  • Country: au
Re: How to reduce the shock sag?
Reply #9 on: September 19, 2019, 04:25:57 AM
The question is: "How to reduce the shock SAG?"

By adjusting the Pre-load adjuster of the shock one will adjust the SAG, there's really no 2 ways about it. It will not change the stiffness of the spring (spring rate) as I noted before.

Whether or not one will be able to get to an intended SAG by simply adjusting the Pre Load adjusters, that's a different conversation.

I'm not saying that the spring currently installed will cater for all riders of all abilities and all types of riding however, I disagree with your view on it that is that the only way to reduce (or change) SAG is by changing the spring. This will only be the case if what the rider does (his ability / speed / weight / type of riding / etc.), requires the suspension and the installed spring to work in a way that falls outside the installed spring's usable range. Why else would suspension manufacturers give you the option to adjust Pre Load on shock and forks? My understanding is that it is to give the rider the option to adjust where in the spring's usable range he will be riding / using the bike.

I agree that if you find yourself winding in the pre load all the way in or all the way out to get to a specific SAG number, and / or if the bike has 0 static SAG (or very close to 0), than a new spring will most likely be required, BUT as a first step grab a measuring tape, check what the bike is doing under the rider's weight and also under the bike's weight (check the SAG), and then you can make an informed decision about where to go with regards to setting your suspension.
Ride to add life to your days, not days to your life.

Street Triple R 2011
ZX9R C2 (1999)
HEL || JayBee Biker Bits || STOMPGRIP || MOTUL