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Setting Sag ?


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#31 jse

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Posted 30 April 2012 - 08:53 PM

Nope. You have just given a bunch of wooly nothings for a person to work from........ And now someone who has no (zero, zip, nada) idea what to do will mess about, get it wrong, and think it is fine.
The guy asked for help, so give it to the mm - it isn't that difficult to screw the the spring adjuster and get it accurate.
When the person has learnt a heap about suspension they'll start adjusting further.
Oh, and why is our bike suspension setup different to a mx or road bike ?..... Oh and don't worry about jetting, bar position, tyre air pressure, riding technique, etc....... it's only trials after all. Flipp'n heck.


O.K., I think I get your point (although you lost me on the last sentence), I'm yapping about "theory" and what this guy needs is information concerning "practice".

First, contact your dealer and get the actual suspension travel measurements, front and rear, for your particular make, year and model. Figuring a third of that is easy. It will also depend on the type of fork, so they are not all the same, for instance a TECH fork has about 165mm of travel and a 40mm Marzocchi has about 177mm of travel.

Measuring the fork setting is fairly straight-forward (measure on the tube) but rear setting is a little tricky. The rear wheel does not move straight up and down, it moves in an arc around the axle pivot, so you measure from the center of the rear axle to a point, maybe 4-5" forward of straight up on the fender (the measuring tape is canted forward at the top), which will give a little more accurate measurement.

When you measure sag on a RR or MX bike, it's usually butt-in-the-saddle. A Trials bike does not have a "saddle" per se, and I like to set sag with the rider standing up and placing enough weight on the bars to mimic the approximate stance he/she would use riding (if you don't weight the bars, the front will probably be closer to 1/5th travel). If the sag is close, the bike will lower and raise front/back equally when the rider bounces, also placing weight on the bars in the process.

Does that help a little?

Jon

#32 copemech

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Posted 02 May 2012 - 04:30 AM

O.K., I think I get your point (although you lost me on the last sentence), I'm yapping about "theory" and what this guy needs is information concerning "practice".

First, contact your dealer and get the actual suspension travel measurements, front and rear, for your particular make, year and model. Figuring a third of that is easy. It will also depend on the type of fork, so they are not all the same, for instance a TECH fork has about 165mm of travel and a 40mm Marzocchi has about 177mm of travel.

Measuring the fork setting is fairly straight-forward (measure on the tube) but rear setting is a little tricky. The rear wheel does not move straight up and down, it moves in an arc around the axle pivot, so you measure from the center of the rear axle to a point, maybe 4-5" forward of straight up on the fender (the measuring tape is canted forward at the top), which will give a little more accurate measurement.

When you measure sag on a RR or MX bike, it's usually butt-in-the-saddle. A Trials bike does not have a "saddle" per se, and I like to set sag with the rider standing up and placing enough weight on the bars to mimic the approximate stance he/she would use riding (if you don't weight the bars, the front will probably be closer to 1/5th travel). If the sag is close, the bike will lower and raise front/back equally when the rider bounces, also placing weight on the bars in the process.

Does that help a little?

Jon


Soo, if i hit a bump does the bike go down or the suspension go up?

How do I measure the true distance travelled in an arc with a tape measure?

Stop it Jon, Stop it! You are driving me nuts! You gotta understand the fact he does not have a spring! He is screwed! Done, Finished, Caput, Totally fecked!

Now since I am soo friggin observant, I think I have an easy solution to all this. For all the teccy geeks, just use your smart phone to get the angle of the lower part of the swingarm which is basically straight and just below the axle. This measure would be common among bikes of the same make, and could easily be replicated reguardless of point of measure. I might roughly estimate that in a perfect world of 1/3 sag with rider this would put the line at near level.

I figure a real smart fella might figure out that with a little more sag, it lowers the CG of the bike in relation to the axle height, which adds stability more than the simple change in steering geometry.

Now Y'all go figure all that out and let me know what you come up with. :beer:
Ride it Like it was one of your old Girlfriends, If you still remember how!

#33 nzralphy

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Posted 02 May 2012 - 07:19 AM

Now since I am soo friggin observant, I think I have an easy solution to all this. For all the teccy geeks, just use your smart phone to get the angle of the lower part of the swingarm which is basically straight and just below the axle. This measure would be common among bikes of the same make, and could easily be replicated reguardless of point of measure. I might roughly estimate that in a perfect world of 1/3 sag with rider this would put the line at near level.


So some motor cycle engineer develops the swing arm length or piviot point to adjust how your bike rides and gets traction...........

.........and you set the swing are to "near level" (+ve or -ve ???)

Very scientific.

Edited by NZRalphy, 02 May 2012 - 07:20 AM.

I'm not half as good as I think I thought I was...

#34 ham2

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Posted 02 May 2012 - 01:58 PM

:popcorn:
For the last time...it's not 'SUPPOSED' to have a seat.
There are two types of men in this world:-
1) Those who are Geordies and..
2) Those that want to be.

#35 jse

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Posted 03 May 2012 - 02:19 AM

Stop it Jon, Stop it! You are driving me nuts!


Copey,
It's what I live for...........:)

As I mentioned before, this is ballpark stuff and if you really care about setting up your
suspension, you will make changes (one at a time) and judge the results accordingly.

It's not rocket science but it can be time consuming to do correctly.

Jon

#36 copemech

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Posted 03 May 2012 - 02:46 AM

So some motor cycle engineer develops the swing arm length or piviot point to adjust how your bike rides and gets traction...........

.........and you set the swing are to "near level" (+ve or -ve ???)

Very scientific.


Yea, and I am also old enough to prefer a rear end with a bit more cush in it!

Engineers dno not have to ride the things!

I may decide to change things on the day! Muddy trial, rocky trial, varies with the sections. This goes for the front as well. :beer:
Ride it Like it was one of your old Girlfriends, If you still remember how!

#37 nzralphy

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Posted 03 May 2012 - 08:06 AM

Copey,
It's what I live for........... :)

As I mentioned before, this is ballpark stuff and if you really care about setting up your
suspension, you will make changes (one at a time) and judge the results accordingly.

It's not rocket science but it can be time consuming to do correctly.

Jon


Yeah I know what you mean, but how do you tell someone "where the ball park is" .....you tell them accurately. Now they will have somewhere to work from.

Phew I had enough. Again. :icon_salut:

Ralphy

Phew

Edited by NZRalphy, 03 May 2012 - 08:07 AM.

I'm not half as good as I think I thought I was...

#38 fatbastard

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Posted 03 May 2012 - 01:11 PM

All you advice never helped him one bit .

He was still ***** on Sunday .




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