Measuring sag by yourself?

adouglas · April 3rd, 2012, 08:39 AM

I want to set my preload properly, by measuring sag. I've done some homework and understand what preload adjustment actually does... that's not what this post is about, so please hold the advice on that front, thanks.

This is about getting a measurement if you don't have a willing assistant handy. I'm helper-challenged. Hard to round up anyone.

Conventional wisdom is to unload the suspension and measure it (easily done by putting a jack under the shock linkage while the front is up on a stand), then get on the the bike while wearing all your gear, have a helper stand it up while you assume the position and measure again. Sag is the difference between the two measurements.

Instead of using a helper, why can't I just put the bike on a track stand and hop on? Assuming I can figure out a way to get a measurement while on the bike, I can't think if any reason why this would not work.

Anyone?

Alex · April 3rd, 2012, 10:12 AM

Quote:

Originally Posted by adouglas

Assuming I can figure out a way to get a measurement while on the bike, I can't think if any reason why this would not work.

I think that's about it. If you can get around that issue, seems like you should be able to get a decent reading.

adouglas · April 3rd, 2012, 10:33 AM

Thanks.

Somebody sells a device for this purpose, marketed to dirt bike riders. It's stupid-expensive.

I'm taking inspiration from it, though. I'm thinking of this:

1) Fasten a Sharpie under the tail, in a defined/stable/repeatable spot, facing outboard. Maybe tape it to a dowel and tie the dowel under the tail. Something like that.

2) Fasten a strip of wood or PVC pipe to the swing arm/axle in a defined/ stable/repeatable spot, with said strip/pipe extending vertically.

3) Unload the suspension, wiggle pipe/wood against sharpie to make a mark.

4) Get on the bike, bounce the suspension to settle it. Then reach around, grab the wood and wiggle it so the sharpie makes a second mark.

5) Measure.

Alex · April 3rd, 2012, 11:19 AM

Wouldn't it be easier to offer a beer to the individual in the next-door cell to help out for a few moments?

kamikaze · April 3rd, 2012, 11:47 AM

Quote:

Originally Posted by Alex

Wouldn't it be easier to offer a beer to the individual in the next-door cell to help out for a few moments?

Werd. Beer is the universal currency.

cuong-nutz · April 3rd, 2012, 01:25 PM

Sorry, I don't know where sag is measured at but couldn't you just put a zip tie around a fork and shock and measure the difference after it moves?

adouglas · April 3rd, 2012, 01:29 PM

Quote:

Originally Posted by cuong-nutz

Sorry, I don't know where sag is measured at but couldn't you just put a zip tie around a fork and shock and measure the difference after it moves?

If the rear suspension had forks then sure.....

In fact the zip tie trick is exactly what I intend to do for the front, since I've just ordered a set of preload adjusters.

The problem as I see it is that just sitting on the bike doesn't quite give you an accurate reading. You have to bounce the suspension and let it settle. That will make the zip tie move beyond where it winds up. If I can't find anyone to help it'll have to do, I guess.

alex.s · April 3rd, 2012, 03:10 PM

use one of those locking tape measures. set the lock half-way on and secure the base to the ground. position it so the tail pushes down on the end of the tape measure (the rear passenger peg is good for this), but cant pull on it. sit on the bike. get off bike. observe reading.

if you need to bounce your shock to get an accurate sag reading (if going down vs going up is more than 5mm difference) then your fluid needs changing or your valving is clogged.

adouglas · April 3rd, 2012, 03:19 PM

Quote:

Originally Posted by alex.s

use one of those locking tape measures. set the lock half-way on and secure the base to the ground. position it so the tail pushes down on the end of the tape measure (the rear passenger peg is good for this), but cant pull on it. sit on the bike. get off bike. observe reading.

Brilliant!

duckracer · April 3rd, 2012, 05:10 PM

For the front I just use the old tie wrap trick, hell I never even remove the tie wrap! For the rear when no help is around I use a dowel taped vertical to the tail section. Loosely tie wrap the bottom end of the dowel to the track stand leg so it can slide, but not too loose. Then take a second tie wrap and put it loosely on the dowel even with the top of the tie wrap on the track stand. Then with all your gear either worn, or setting on the tank sit on the bike. the lower tie wrap will push the upper tie wrap up. get off the bike and remove all the gear. now just like the forks you measure the gap between the two tie wraps and that is your sag.

April 3rd, 2012, 08:39 AM	#1
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Measuring sag by yourself? I want to set my preload properly, by measuring sag. I've done some homework and understand what preload adjustment actually does... that's not what this post is about, so please hold the advice on that front, thanks. This is about getting a measurement if you don't have a willing assistant handy. I'm helper-challenged. Hard to round up anyone. Conventional wisdom is to unload the suspension and measure it (easily done by putting a jack under the shock linkage while the front is up on a stand), then get on the the bike while wearing all your gear, have a helper stand it up while you assume the position and measure again. Sag is the difference between the two measurements. Instead of using a helper, why can't I just put the bike on a track stand and hop on? Assuming I can figure out a way to get a measurement while on the bike, I can't think if any reason why this would not work. Anyone?

April 3rd, 2012, 11:19 AM	#4
Alex ninjette.org dude Name: 1 guess :-) Location: SF Bay Area Join Date: Jun 2008 Motorcycle(s): '13 Ninja 300 (white, the fastest color!), '13 R1200RT, '14 CRF250L, '12 TT-R125LE Posts: Too much. Blog Entries: 7	Wouldn't it be easier to offer a beer to the individual in the next-door cell to help out for a few moments? __________________________________________________ Montgomery Street Motorcycle Club / cal24.com / crf250l.org / ninjette.org ninjette.org Terms of Service Shopping for motorcycle parts or equipment? Come here first. The friendliest Ninja 250R/300/400 forum on the internet! (especially Unregistered)

April 3rd, 2012, 01:25 PM	#6
cuong-nutz RIP Alex Name: Cuong Location: Houston, TX Join Date: Apr 2011 Motorcycle(s): '10 250r, '09 265r Posts: A lot. Blog Entries: 2	Sorry, I don't know where sag is measured at but couldn't you just put a zip tie around a fork and shock and measure the difference after it moves? __________________________________________________ HalfFast Racing Team Serving Greater Houston Area Riders:WFO Riders MotoHouston HPC CMRA Ride Smart Fastline Lone Star Track Days

April 3rd, 2012, 03:10 PM	#8
alex.s wat Name: wat Location: tustin/long beach Join Date: Sep 2009 Motorcycle(s): wat Posts: Too much. Blog Entries: 5 MOTM - Oct '12, Feb '14	use one of those locking tape measures. set the lock half-way on and secure the base to the ground. position it so the tail pushes down on the end of the tape measure (the rear passenger peg is good for this), but cant pull on it. sit on the bike. get off bike. observe reading. if you need to bounce your shock to get an accurate sag reading (if going down vs going up is more than 5mm difference) then your fluid needs changing or your valving is clogged. __________________________________________________

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April 3rd, 2012, 10:33 AM	#3
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Thanks. Somebody sells a device for this purpose, marketed to dirt bike riders. It's stupid-expensive. I'm taking inspiration from it, though. I'm thinking of this: 1) Fasten a Sharpie under the tail, in a defined/stable/repeatable spot, facing outboard. Maybe tape it to a dowel and tie the dowel under the tail. Something like that. 2) Fasten a strip of wood or PVC pipe to the swing arm/axle in a defined/ stable/repeatable spot, with said strip/pipe extending vertically. 3) Unload the suspension, wiggle pipe/wood against sharpie to make a mark. 4) Get on the bike, bounce the suspension to settle it. Then reach around, grab the wood and wiggle it so the sharpie makes a second mark. 5) Measure.

April 3rd, 2012, 05:10 PM	#10
duckracer ninjette.org member Name: Randy Location: Ofallon, Mo Join Date: Dec 2011 Motorcycle(s): Ducati 1098 and 04 Ninja 250 race bikes Posts: 60	For the front I just use the old tie wrap trick, hell I never even remove the tie wrap! For the rear when no help is around I use a dowel taped vertical to the tail section. Loosely tie wrap the bottom end of the dowel to the track stand leg so it can slide, but not too loose. Then take a second tie wrap and put it loosely on the dowel even with the top of the tie wrap on the track stand. Then with all your gear either worn, or setting on the tank sit on the bike. the lower tie wrap will push the upper tie wrap up. get off the bike and remove all the gear. now just like the forks you measure the gap between the two tie wraps and that is your sag.