Rear Suspension Geometry and Shock Choice

[Gionnirocket]

I'm contemplating changing my base 650lb spring shock with an air adjustable one. My current eye to eye measures in at 170mm. The shock that I'm looking at comes in two close enough flavors at 165mm/40mm travel and 190mm/ 50mm travel.
The 165 looks like it would go in no problem and it would drop the rear angle of the frame and height of the seat minimally
The 195 looks as it would have enough frame clearance and raise the rear frame angle and seat height less than an inch which seem acceptable. I'll also have to lengthen the rear brake and shift cable.
I lean towards the 190 for greater travel but then the 165 will be an easier install and probably not affect geometry at all.
Anyone have experience experimenting with such endeavors? Am I failing to consider some other factors?
Any input would be most appreciated.

 

[Gionnirocket]

I'll put this out there for anyone who might be considering to do the same.
I ended up going with the 190mm after some thought as I figured they would be more versatile as I can adjust the initial sag with air pressure.
To help me be sure it wasn't a total mistake I temp'd up a 190mm spacer out of some 3/4" angle iron and took it for a few mile ride.
I've had the shock for a few days now and it's definitely a noticeable improvement with no real change in the feel of the bike's geometry.
I'm probably spending more than what a new bike would cost on this ol' tank... but I'm really enjoying working on it and it's keep another bike out of the landfill while I keep myself out of trouble.... I think I see air forks in my future

 

[Ravi Kempaiah]

I would be wary of investing in air suspension for that particular frame.
Your bike looks like a very clean DIY job. What concerns me is the frame quality and the pivots used on that frame for the rear suspension.
I had the exact same bike back in 2011 and once I upgraded to a better E-bike with RockShox suspension, I started noticing several things (frame flex, suspension response, geometry limitations, etc.)
I have no doubt that better brakes, slightly better suspension would render that bike very useful for another couple of years. Have you considered a triangle battery like this instead of the rear rack battery?

EM3ev 52V (14S6P) Hard-Case Triangle Ebike Battery Pack With Bag | EM3ev

EM3ev 50V (AKA 52V, 14S6P) Small Triangle Ebike Battery Pack, uses top quality official Samsung and LG Chem cells safety features not to be found elsewhere.

em3ev.com

This will fit in the front triangle, provide a HUGE range (52V, 21Ah), and enable the rear suspension to work slightly better.

 

[Gionnirocket]

I would be wary of investing in air suspension for that particular frame.
Your bike looks like a very clean DIY job. What concerns me is the frame quality and the pivots used on that frame for the rear suspension.
I had the exact same bike back in 2011 and once I upgraded to a better E-bike with RockShox suspension, I started noticing several things (frame flex, suspension response, geometry limitations, etc.)
I have no doubt that better brakes, slightly better suspension would render that bike very useful for another couple of years. Have you considered a triangle battery like this instead of the rear rack battery?

EM3ev 52V (14S6P) Hard-Case Triangle Ebike Battery Pack With Bag | EM3ev

EM3ev 50V (AKA 52V, 14S6P) Small Triangle Ebike Battery Pack, uses top quality official Samsung and LG Chem cells safety features not to be found elsewhere.

em3ev.com

This will fit in the front triangle, provide a HUGE range (52V, 21Ah), and enable the rear suspension to work slightly better.

Thanks Ravi.
I did look into triangle batteries as well as the one that you suggested but could not find one that would fit without being a very custom build. Not being sure how this was all going to work out I didn't want to incur the added cost of a custom battery at the time. As for the bike I'm not worried about the frame as I mainly ride for exercise on paved surfaces or hard packed earth trails and I'm way past my dare devil days. The suspension upgrades are purely old man comfort add ons at this point and that's why I didn't even consider a product such as Rockshox as it's designed for applications far beyond how I intend to ride. I have the rear rack/battery floating on springs as well so it moves pretty freely with the rear suspension though I'm well aware the added weight and location are far from ideal. For how I ride now I'm still happy with how it handles changes in directions and the overall feel. I knew well the limitations of the bike at the start and I have no delusions that I can upgrade this into a Yamaha YDX

 

[FlatSix911]

I'll put this out there for anyone who might be considering to do the same.
I ended up going with the 190mm after some thought as I figured they would be more versatile as I can adjust the initial sag with air pressure.
To help me be sure it wasn't a total mistake I temp'd up a 190mm spacer out of some 3/4" angle iron and took it for a few mile ride.
I've had the shock for a few days now and it's definitely a noticeable improvement with no real change in the feel of the bike's geometry.
I'm probably spending more than what a new bike would cost on this ol' tank... but I'm really enjoying working on it and it's keep another bike out of the landfill while I keep myself out of trouble.... I think I see air forks in my future

Nice work on the new air shock... well done!