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Motion Pro Uni-Sag Accuracy

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I bought the Motion Pro Uni Sag tool a few weeks ago. Great looking tool, easy to setup and all but I am questioning its accuracy. When using this tool on an already known correctly setup suspension, this tool consistently will read too little sag, by quite a bit.

 

Referring to Race Tech or mostly any sag how-to references, most are saying measure to a Vertical distance. The Uni Sag measures are at quite an extreme angle since it mounts to the axle and seat bolt. I will measure vertically with a measuring tape and get correct sag. I will then mount on the Uni Sag and find readings low, way low. 

 

Am I doing something wrong? Is the tool indeed inaccurate?

Edited by stavendirtbike

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I always measure vertical.

My buddy has an RM250, the manual says use the seat bolt. His sag is "off" by 50mm- 50mm  sag with the rider on board-  using the seat bolt method.

 

If we use the seat bolt measurement, his suspension would be way too stiff.

IMO- measuring from the seat bolt has a sharper angle, hence the lower sag numbers.

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yeah, that what I'm sayin too! I'm reading this thread and the whole time I'm thinking, BUT BUT BUT FC SAYS.... We need to know the truth

 

At this point slowgs2001, I am going off what the suspension builder who actually built and setup my suspension (Factory Connection) for sag measurement technique. It is very annoying getting so many different variables as to vertical vs non vertical measurements. Each suspension builder's how-to's, factory manual instructions, how-to's from fellow riders are all at one end of the spectrum or the other when it comes to this.

 

Quite annoying since it is beat into our heads that SAG IS CRITICAL! My theory: go by either 1. The methods in which your suspension builder uses or 2. The bike's factory service manual method if you don't have suspension revalve or services from an outside company. Ironically, both the Suzuki factory manual method and FC's methods of sag measurement are in agreement; measure from the SEAT BOLT. 

 

Also, talking with the Factory Connection rep who was at my local track yesterday, we verified that the sag on both my bikes were spot on at 108 using the good old fashioned tape measure. Again, my Motion Pro tool reads 90. Factory Connection claims they did some testing with Uni-Sag and Solo Sag type tools and found them to just not be anywhere near as accurate as a measuring tape. Too much room for error. Getting on and off the bike causes the tool marker to move slightly (there goes a few mm's). How it mounts into the axle can also have slight movement (there is another few mm's out the window), also, there is some "stiction" within the tool itself. Measuring tape is tried and true. Just need another person there with you.

Edited by stavendirtbike
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I'm really glad I saw this. I have recently had a my first revalve from factory connection and I set my sag to 108 but I did it vertical from my axle nut to a dot I made on the back of the rear number plate. So going by what you guys are saying I'm probly running much more sag than I think most Likely a lot more than 108. 108 is what I'm shooting for too start with cause that's what factory connection recommended. Am I correct in thinking I'm running more sag than I think? Thanks.

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I'm really glad I saw this. I have recently had a my first revalve from factory connection and I set my sag to 108 but I did it vertical from my axle nut to a dot I made on the back of the rear number plate. So going by what you guys are saying I'm probly running much more sag than I think most Likely a lot more than 108. 108 is what I'm shooting for too start with cause that's what factory connection recommended. Am I correct in thinking I'm running more sag than I think? Thanks.

 

What bike MTrain? Visit the FC website. They have several photos of different bikes of where the sag measurements should be made. ALL are from the seat bolt! 

 

http://www.factoryconnection.com/sag/

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So it does show them measuring from the seat bolt I have be measuring to the very back of the number plate where it kind of comes to a point I put a dot there with a marker it's almost directly above the axle nut. I'm gonna have too get out there and measure soon I'm very curious. If I'm understanding you guys I could be running way more sag than I think I am.

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The vertical method would be the only consistent method in my opinion. Every brand bike will have a different seat bolt or fender bolt location which could dramatically change the angle. I also think the swingarm arc movement follows a path more in line with a vertical point above it.

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The vertical method would be the only consistent method in my opinion. Every brand bike will have a different seat bolt or fender bolt location which could dramatically change the angle. I also think the swingarm arc movement follows a path more in line with a vertical point above it.

 

I will be trying the vertical method and comparing how much different the readings are between the two. I will also adjust to the recommended sag via the vertical position and see how the bike responds to it.

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