How do you measure that thing called sag? - SV650.org

15-02-07, 10:43 AM

I have tried searching for this with no luck.

My K1 skips over bumps when cornering at fairly low speed. Front seems to have a mind of its own! I've been reading the threads about changing springs and oil and stuff, and they also talk about measuring 'sag'. What is sag and how do you measure it?
Cheers
John

timwilky · 15-02-07, 10:54 AM

sag, is how low on the suspension the bike & rider sits. To my way of thinking it should be about 1/3rd of the available travel.

15-02-07, 03:39 PM

My 2001 curvy has about 110 mm of fork travel and the books say to start with around 20 - 30 mm of sag with the rider sat on the bike, feet on pegs.

15-02-07, 05:31 PM

Quote:

Originally Posted by petevtwin650

My 2001 curvy has about 110 mm of fork travel and the books say to start with around 20 - 30 mm of sag with the rider sat on the bike, feet on pegs.

So is the procedure:

1. sit on bike with feet on pegs and mark where front suspension compresses to. And then:
2. jack up bike so that front forks lift off ground and measure how far the forks have 'stretched' ?

is that it?

John

Lissa · 15-02-07, 05:59 PM

Can you read this?

15-02-07, 06:07 PM

Quote:

Originally Posted by Lissa

Can you read this?

Yep I could read that and I thank you very much for it - John

Lissa · 15-02-07, 06:10 PM

You're welcome John.

It was Pete really, he forgot to log me out and log himself in

Biker Biggles · 15-02-07, 06:14 PM

Call me old fashioned,but I don't think that's right.
I think static sag is the difference between fully extended and the level the bike sits at under it's own weight.When the rider gets on you get another level which is rider sag IIRC.Static sag can be adjusted by shimming the springs or preload adjusters,but the rest is dependant on spring rates,so requires new springs to adjust.I stand to be corrected though.

Lissa · 15-02-07, 06:20 PM

That was copied from Race Tech's information sheet that came with our new springs. I hope it's right, as that was the system we followed.

timwilky · 15-02-07, 06:39 PM

The printout is pretty much how I understand sag to be measured. My understanding is that static sag is both bike and rider and is static as it is a statically applied load.

The displacement as a result dynamic load on the suspension as a result of actually riding would be meaningless unless it was recorded over a track and then the overall suspension adjusted to suit that track. Not practical for road riding.

15-02-07, 10:43 AM	#1
ejohnh Guest Posts: n/a	How do you measure that thing called sag? I have tried searching for this with no luck. My K1 skips over bumps when cornering at fairly low speed. Front seems to have a mind of its own! I've been reading the threads about changing springs and oil and stuff, and they also talk about measuring 'sag'. What is sag and how do you measure it? Cheers John

15-02-07, 10:54 AM	#2
timwilky Member Mega Poster Join Date: Mar 2004 Location: Not in Yorkshire. (Thank God) Posts: 4,116	sag, is how low on the suspension the bike & rider sits. To my way of thinking it should be about 1/3rd of the available travel. __________________ Not Grumpy, opinionated.

15-02-07, 05:59 PM	#5
Lissa Just Ballast Mega Poster Join Date: Feb 2006 Location: Rugby, South Mids Group Posts: 4,381	Can you read this? __________________ If It's Too Loud, You're Too Old! I'd Rather Have Two Big Bangs Than Four Little Strokes

15-02-07, 06:10 PM	#7
Lissa Just Ballast Mega Poster Join Date: Feb 2006 Location: Rugby, South Mids Group Posts: 4,381	You're welcome John. It was Pete really, he forgot to log me out and log himself in __________________ If It's Too Loud, You're Too Old! I'd Rather Have Two Big Bangs Than Four Little Strokes

15-02-07, 06:14 PM	#8
Biker Biggles Member Mega Poster Join Date: Jan 2005 Location: Barnet Herts Posts: 5,070	Call me old fashioned,but I don't think that's right. I think static sag is the difference between fully extended and the level the bike sits at under it's own weight.When the rider gets on you get another level which is rider sag IIRC.Static sag can be adjusted by shimming the springs or preload adjusters,but the rest is dependant on spring rates,so requires new springs to adjust.I stand to be corrected though. __________________ On a clear day we stand there and look further than the ordinary eye can see.

15-02-07, 03:39 PM	#3
petevtwin650 Guest Posts: n/a	My 2001 curvy has about 110 mm of fork travel and the books say to start with around 20 - 30 mm of sag with the rider sat on the bike, feet on pegs.

15-02-07, 06:20 PM	#9
Lissa Just Ballast Mega Poster Join Date: Feb 2006 Location: Rugby, South Mids Group Posts: 4,381	That was copied from Race Tech's information sheet that came with our new springs. I hope it's right, as that was the system we followed. __________________ If It's Too Loud, You're Too Old! I'd Rather Have Two Big Bangs Than Four Little Strokes

15-02-07, 06:39 PM	#10
timwilky Member Mega Poster Join Date: Mar 2004 Location: Not in Yorkshire. (Thank God) Posts: 4,116	The printout is pretty much how I understand sag to be measured. My understanding is that static sag is both bike and rider and is static as it is a statically applied load. The displacement as a result dynamic load on the suspension as a result of actually riding would be meaningless unless it was recorded over a track and then the overall suspension adjusted to suit that track. Not practical for road riding. __________________ Not Grumpy, opinionated.

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