V85TT Rear wheel travel

[Sye]

Forgive the question but I'm having a bit of a senior moment I think 🤔
Rear shock travel is 102mm or just over 4", so to achieve 30% static sag the shock needs to compress 30.6mm. Simple so far, but...
The shock is mounted at an angle, so the rear wheel travel is not 102mm? So, measuring sag to the rear spindle means nothing unless someone knows what the rear wheel travel is.
A long shot I know but does anyone know the rear wheel travel on a V85tt please?
TIA, Sye

[Huzo]

Forgive the question but I'm having a bit of a senior moment I think 🤔
Rear shock travel is 102mm or just over 4", so to achieve 30% static sag the shock needs to compress 30.6mm. Simple so far, but...
The shock is mounted at an angle, so the rear wheel travel is not 102mm? So, measuring sag to the rear spindle means nothing unless someone knows what the rear wheel travel is.
A long shot I know but does anyone know the rear wheel travel on a V85tt please?
TIA, Sye

No Sye I don’t, but does it matter ?
Just set your sag @ 30% of full shock travel and you will have 30% of wheel travel won’t you ?

[Sye]

You are right of course Huzo but I don't have a second pair of hands to measure the shock length. I use a sag tool to get it right but this measures vertical wheel travel. I would guess that 45mm will be about right but that's 15mm over 30% of shock length.
You can tell me if I'm being dim, I won't mind. 😁
Edit, just had a thought, thanks Huzo. I can set up the sag tool at the same attitude as the shock, then use 30% of shock compression.

[Huzo]

Just before the geometry and math professors train their guns on me...
I’ll admit that the relationship between shock compression and swingarm rotation is not linear. As the angle between the shock and the swingarm increases upon compression, you will get less shock compression for each degree of swingarm rotation.
But the rate of change in the relationship will be indiscernible I’ll cautiously  suggest.

[Moparnut72]

Sounds like a related rates question to me. That was the toughest part of the calculus course I took in college, so I can be of no help.   
kk

[Caffeineo]

Rear Travel (in/mm)    6.7 / 170

Found on https://www.motorcycle.com/specs/moto-guzzi/touring/2020/v85/tt-adventure/detail.html

[egschade]

With the shock fully extended put a twist tie on the shaft and slide it down to the shock body. Lift the bike off the stand carefully so you don't bounce the suspension. Put it back up on the stand and measure how far the twistie moved. Can do the same with the forks...

[Sye]

Rear Travel (in/mm)    6.7 / 170

Found on https://www.motorcycle.com/specs/moto-guzzi/touring/2020/v85/tt-adventure/detail.html

That's exactly what I needed, thanks Caffeineo 

Rear wheel travel 170mm, static sag 51mm or 2".

[Vagrant]

Frame and suspensions
FRAME
Specification Desc./Quantity
Type High strength steel tube
Steering rake 25.7°
Trail 128.3 mm (5.05 in)
SUSPENSIONS
Specification Desc./Quantity
Front hydraulic telescopic fork diam. 41 mm (1.61 in)
Stroke 168 mm (6.61 in)
Rear Swingarm in die-cast light alloy with 1 shock absorber with adjustable spring pre-load and rebound damping.
Stroke 102 mm (4.02 in)

This is from the on line shop book. I think it's wrong! I set mine at 2" but it took 7-10000 miles to get that much.

[Sye]

Frame and suspensions
FRAME
Specification Desc./Quantity
Type High strength steel tube
Steering rake 25.7°
Trail 128.3 mm (5.05 in)
SUSPENSIONS
Specification Desc./Quantity
Front hydraulic telescopic fork diam. 41 mm (1.61 in)
Stroke 168 mm (6.61 in)
Rear Swingarm in die-cast light alloy with 1 shock absorber with adjustable spring pre-load and rebound damping.
Stroke 102 mm (4.02 in)

This is from the on line shop book. I think it's wrong! I set mine at 2" but it took 7-10000 miles to get that much.

That's correct information Vagrant. The shock stroke is 102mm but because it's at an angle, the wheel travel is 170mm, so the sag needs to be 50 - 60mm.