Extended Length Rear Shocks? (1 Viewer)

[TeCKis300]

This might be a stretch. Wondering if anyone has pictures or measurements of extended length, extended travel shocks for the rear? Would like to get more downtravel.

In the middle of modifying the stock rear AHC shocks and wonder how much more length I should try. I'm leaning towards 1" longer at the moment. Understanding there's a balance of min length to make sure the shocks don't become the compression limiter. I can lower the rear bump stops to manage that a bit, but ideally I can get more overall stroke.

 

[TN LX570]

Are you extending the AHC shock? I’ve been toying with the idea of raising the bottom shock mounts in the rear.

 

[TeCKis300]

5511

Are you extending the AHC shock? I’ve been toying with the idea of raising the bottom shock mounts in the rear.

Yes.

Going at it a different way. Instead of modifying the shock mount on the axle, figure it was easier and less permanent to modify the shock. Going to cut the lower bushing eyelet and weld an extension.

Picture for inspiration. Right old, left new.

 

[bloc]

I remember measuring out my kings compared to stock and posting those numbers on here somewhere. I’d have to assume they extended them about as much as is safe without worrying about running out of travel.

Can dig up those numbers if it would help.

 

[TeCKis300]

I remember measuring out my kings compared to stock and posting those numbers on here somewhere. I’d have to assume they extended them about as much as is safe without worrying about running out of travel.

Can dig up those numbers if it would help.

That would be awesome if you can dig it up. I found a 100-series reference and they're pretty similar in rear suspension architecture, but would be great to have a 200-series database.

 

[turbo8]

Fox list their dimensions

FACTORY RACE SERIES 2.5 RESERVOIR SHOCK (PAIR) - ADJUSTABLE | Truck Shocks | FOX

FOX redefines ride dynamics for ATVs, mountain bikes, motocross, off-road vehicles, snowmobiles, trucks, and UTVs.

www.ridefox.com

 

[TeCKis300]

^ Thanks @turbo8

That makes the beginnings of a rear shock database!

I'm measuring from the shaft ledge where the first washer sits, without any bumpers or shims, to the lower eyelet center

Rear Shock	Extended Length (max)	Compressed Length (min)	Stroke (max-min)	Shaft Diameter	Shock Body Diameter
OEM AHC	25.5"	16.75"	8.75"	1.28" (30mm)	2.14" (54.3mm)
Fox 2.5 Reservoir	23.97"	15.2"	8.77"	7/8"	2.5"

Would be awesome if other have measurements to contribute.

Interestingly, I've found some data on the 100-series from this thread, and lengths seem to vary dramatically. From the 2 data samples of this thread, the 200-series rear shock length is in the upper ballpark.
Bilstein Rear BE5-2740 21.71"
Fox Rear 985-24-067 22.95"
OME Rear n101 24.02"
OME Rear 60002 24.1"
King Rear 25.11"
Icon Rear 56510: 25.67”
Fox Rear 985-24-009 26.15"
Icon Rear 57802 26.3”
Icon Rear 57802C 26.3”
OME Rear 60071L 26.50"

 

[bloc]

That would be awesome if you can dig it up. I found a 100-series reference and they're pretty similar in rear suspension architecture, but would be great to have a 200-series database.

3/4” longer than stock. Post here:

Suspension Travel Comparison

I got lazy as I knew I had enough clearance with AHC high for that particular trail so I left the hitch on. This was definitely not pegging the suspension out and was on AHC high. Even on a little rock, there's plenty of flex to go around.

forum.ih8mud.com

 

[TeCKis300]

Good stuff. Based on the inputs, I'm leaning towards a 1" or 3/4" extension.

Looking at my old shocks and the dirt witness mark on the shaft, there's about 1/2" travel that's never engaged (it was more obvious than this pic but I've manually compressed it to test). On a jump, there's possibility this section of the shaft does get engaged. The shock does also have additional travel and protection from bump stops on its shaft.

I'm thinking to extend the shock 1", and lower the frame bump stop 1/4". So extend droop by 1", and expand the stroke by 3/4". There's a chance that the shock body is too long in a max compression situation, but between AHC and coil airbags that I've installed, the spring rate is progressive which should take most of the shock out of a really hard landing for example. Might be safer to do a 3/4" extension.

Here's how I think I'm doing the extension. Cut existing bushing eyelet at marks so they now serve as a standoff bracket. Then weld donor eyelet from old shock to the newly created legs. May weld in some additional supporting metal. Trying to avoid welding nearer the shock body in case there's anything there that's heat sensitive.

 

[bloc]

My gut tells me you should strongly consider some extra bracing between the original eyelet and shock bottom, especially with AHC putting a significant amount of the vehicle's weight on that eyelet as opposed to a standard shock which would only see the damping forces.

Whereas stock there would be very little tendency for the shock to "bend" off the eyelet because it attaches right at the circumference, now with an additional inch of distance between the post and the bottom of the shock body I'm imagining those bending forces getting multiplied dramatically...

Can you cut the bottom of your old shock open to see what's down there and determine how much impact some welding would have? It seems reasonable that bottom cap that is welded on is heavier gauge steel than what is used on the sides.. you could most likely avoid burning through there, as long as you avoid an sensitive internals like you mention.

 

[TeCKis300]

My gut tells me you should strongly consider some extra bracing between the original eyelet and shock bottom, especially with AHC putting a significant amount of the vehicle's weight on that eyelet as opposed to a standard shock which would only see the damping forces.

Whereas stock there would be very little tendency for the shock to "bend" off the eyelet because it attaches right at the circumference, now with an additional inch of distance between the post and the bottom of the shock body I'm imagining those bending forces getting multiplied dramatically...

Can you cut the bottom of your old shock open to see what's down there and determine how much impact some welding would have? It seems reasonable that bottom cap that is welded on is heavier gauge steel than what is used on the sides.. you could most likely avoid burning through there, as long as you avoid an sensitive internals like you mention.

Thanks for that input and I've been debating the same over those factors.

The eyelet metal is pretty dang heavy and wide. I was debating to whack it off completely and put in a new standoff as it would be aesthetically better. But can't imagine it would be stronger, especially if I put in a filler plate. Something like what's in blue to support the legs

 

[bloc]

I’m attaching an image of what I’m thinking. My concern would be any sideways force now has much greater opportunity to bend the welded interface sideways. Before it was simply resting on the bushing and retained there. Now the shock end is effectively retained to the end of a post the diameter of that existing weld… any sideways force (like even the whole assembly being very slightly off center) is multiplied.

Additional bracing to keep it from “rolling” off that post would help, at least in my head.

 

[TeCKis300]

I’m attaching an image of what I’m thinking. My concern would be any sideways force now has much greater opportunity to bend the welded interface sideways. Before it was simply resting on the bushing and retained there. Now the shock end is effectively retained to the end of a post the diameter of that existing weld… any sideways force (like even the whole assembly being very slightly off center) is multiplied.

Additional bracing to keep it from “rolling” off that post would help, at least in my head.

View attachment 3023484

Having cut the eyelet off, the interface there is quite robust.

 

[bloc]

Having cut the eyelet off, the interface there is quite robust.

View attachment 3023493

I don't doubt that, but it is designed for the forces seen by the shock sitting on the eyelet. You will be altering those forces quite a bit.

Also I'm not suggesting completely filling those areas, simply adding a triangle shaped vertical brace to help resist sideways deflection.

May all be overkill, but I've always felt that is a good path when making changes like this.. ones that could result in not being able to get off the trail if something goes wrong.

 

[TeCKis300]

I don't doubt that, but it is designed for the forces seen by the shock sitting on the eyelet. You will be altering those forces quite a bit.

Also I'm not suggesting completely filling those areas, simply adding a triangle shaped vertical brace to help resist sideways deflection.

May all be overkill, but I've always felt that is a good path when making changes like this.. ones that could result in not being able to get off the trail if something goes wrong.

Good points but I'll likely leave this part alone as it's robust enough in my mind. I imagine other areas will fail first before this interface will.