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Shortening eye-to-eye on a RP23

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thad

Monkey
Sep 28, 2004
388
21
I am thinking about an AM bike that comes with a 7.5X2.0 RP23. I would like to shorten the eye-to-eye a 1/4" to slack the HT and dump the BB.

Is there an easy way to do this? I don't think you could add a spacer to reduce eye-to-eye, only stroke. Is the only option shortening the shaft?
edit- I guess the easiest option is offset shock hardware, but I'd rather do it cleaner than that.
 
T

thad

Monkey
Sep 28, 2004
388
21
They do not make a RP23 with the eye to eye I desire.

5.5 x 1.0, 6.0 x 1.25, 6.5 x 1.5, 7.5 x 2.0,
7.875 x 2.0, 7.875 x 2.25, 8.5 x 2.5
 
HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
Yeah, you just need to space out the top out bumper. Problem is that the air spring curve will get a little weird.
 
P

Pslide

Turbo Monkey
Jan 14, 2002
1,373
0
Feet on the ground, head in the clouds.
I am speaking with no experience here, but...

From the cut away, it looks to me like if you disassembled the shock completely, including unthreading the main external shaft (exposed lower sleeve) from the central bushing housing, you could grind a few mm off the end of it near the threads, and then reassemble. Not going to get you 1/4" though.

I would think HAB's idea would work too in theory.
 
W

WBC

Monkey
Aug 8, 2003
578
1
PNW
I've done it before where I used the shims and oil seals from replaced seal kits as a spacer between the piston and the bottom of the air can. I rode the shock like that all last summer on my xc bike without issue.

That said, it was on a 4" frame so lesser performance wouldn't be noticed as much, and when you do that, the piston doesn't pass by the air equalization dimple the same way. That might cause durability issues and could make the shock harsher off the top because it wouldn't allow for the negative air to counter the initial stiction.

I wouldn't do it on a customer's bike, and the difference is so small that it seems like you could get the same effect on your dynamic geo by running your suspension stiffer up front, softer out back. Or riding a smaller tire in the back.
 
leprechaun

leprechaun

Turbo Monkey
Apr 17, 2004
1,009
0
SLC,Ut
If you shorten it then the hydraulic topout won't work properly.

The answer is way too easy! I discovered sort of by accident that you can overfill the negative air chamber with Float Fluid and it can't stand up all the way. I have an X Fusion air shock that's 1/8" shorter now. haven't tried to shorten it more than that. It's trial and error in terms of using the fluid. Grease works better since oil tries to drip out while assembling the air sleeve.
 
HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
leprechaun said:
If you shorten it then the hydraulic topout won't work properly.

The answer is way too easy! I discovered sort of by accident that you can overfill the negative air chamber with Float Fluid and it can't stand up all the way. I have an X Fusion air shock that's 1/8" shorter now. haven't tried to shorten it more than that. It's trial and error in terms of using the fluid. Grease works better since oil tries to drip out while assembling the air sleeve.
Click to expand...
Brilliant. I forgot about how the top out mechanism in those works. That makes a lot of sense though.
 
al-irl

al-irl

Turbo Monkey
Dec 9, 2004
1,086
0
A, A
NoUseForAName said:
Wasn't there an Irish (?) guy who posted on here saying he made offsetshock eyelet reducers?

There you go:

http://www.irishdh.com/forum2/viewtopic.php?f=2&t=13080
Click to expand...
yeah kev makes the offset bushings the biggest amount of offset is 6mm but it doesnt affect the stroke of the shock so u might end up with issues at bottom out. I have one in my bike at the moment and they do exactly what it says on the tin. A cheap and easy way to update the geo on ur bike. Not sure if it will work on this particular application
 
C

contactjt

Monkey
Apr 4, 2007
167
0
A nice halting site, Switzerland
If you will have no issues with frame contact get offset reducers.
As pointed out earlier, you can't reduce the i2i without messing with the properties of the air spring at top-out.
Adding float fluid will potentially cause issues with the seals and the equalisation port.
For the best solution find a shock in the custom length on ebay (as suggested) or get a custom length shock from a fox service center, they have access to all the parts the OEs have.
What I did when I needed a custom length RP23 shock is get my original OE Float R and use the custom length parts to make a custom length RP23 and use the standard length parts left over from the RP23 to build up the Float R to a standard length for selling.

Best of luck,


JT
 
H

herbman

Monkey
Feb 16, 2011
104
8
North West Tasmania
hi, long time read first time poster.

had been looking at shorting up my rear shock on my force for the last few months, so last night i removed the air can and added 10ish ml of oil to the negative air chamber.
this reduced the stroke by 10mm, there is no topout and the shock seems to be working as its ment to or be it with a shorter stroke.
now i will trash it till it blows up and then look at finding a shorter stroke shock, as the force with a slacker HA and lower BB seems alot funner to ride.
 
T

thad

Monkey
Sep 28, 2004
388
21
Thanks for the input, very informative. Good to know they do make a 7.25X1.75

The grease trick sounds easy, so does the spacer. Though I don't want to mess up the negative travel... or lose travel really.

I think I am just going to drill another lower shock mounting hole. Retain the full 130mm travel. I measured the frame without shock, and at 5.25" between shock mount holes the shockstay brace clears the seattube by a red irish c-hair. It's just a flat brace, so I may grind it for some extra clearance.

Shortening the shock a 1/4" should slacken the HT about 1deg, and lower the bb about 1/2", correct? I guess I should probably throw wheels and a fork on it, and measure...
 
al-irl

al-irl

Turbo Monkey
Dec 9, 2004
1,086
0
A, A
do the oem shocks for the giant trances not have an oversize eyelit on one of the ends of the shock. Which i would have thought rendered them pretty useless to all but a giant trance.
 
E

eatmyshorts

Monkey
Jun 18, 2010
110
0
South OZ
Careful with the too much grease solution - can cause the shock to get lock down - pressure build up on the negative side of the air can, due to a semi blocked air port, forcing the shock to stay in the fully compressed position.. Sorting out a shock with lock down can mean drilling into the air can to release the pressure - explody shock if not careful too.. Heard of the air can punching through an iron roof after it was relieved..

To effectively change the travel using the air spring you really need to change the port position between the positive and neg chambers..
 
Uncle Cliffy

Uncle Cliffy

Turbo Monkey
Jan 28, 2008
4,490
42
Southern Oregon
al-irl said:
do the oem shocks for the giant trances not have an oversize eyelit on one of the ends of the shock. Which i would have thought rendered them pretty useless to all but a giant trance.
Click to expand...
Nope. Standard size eyelit. The co-pivot on the lower rocker doesn't use spacers or a DU. The pivot bolt is aluminum and just slides through the shock...
 
mtg

mtg

Green with Envy
Sep 21, 2009
1,862
1,604
Denver, CO
My Covert has a 7.5x2.0 shock, and I bought a Monarch as a second shock to shorten for 4x, slalom, etc. Shortening it 3/8" works pretty well geometry wise, but of course as mentioned, the negative spring is a challenge. The Monarch uses an elastomer negative spring, so I've been experimenting with spacers to engage the negative spring deeper in the travel.
One option is to buy one of the new Push Monarch RTs, as they are offered in 7.25x1.75.
 
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H

herbman

Monkey
Feb 16, 2011
104
8
North West Tasmania
it sounds like what i did with my force. but i keeped the forks at 140mm as i like the 66 HA:)

with it short shocked and way slacker the force as become my go to bike and im now thinking my selling my sanction


if you just want to try it out with a shorter shock, just throw some oil in the negative spring of the air can. i have done this and it has been going strong for over a year now.
 
T

TWeerts

Monkey
Jan 7, 2007
471
0
The Area Bay
......OR....... try this:

http://www.ebay.com/itm/Offset-Shock-bushings-Mounting-Hardware-Mount-kit-All-frames-Proshox-/300611150162?pt=Cycling_Parts_Accessories&hash=item45fdd22152

you could forget about shortening your i2i all together, and simply move the bolt centers on either end of the shock. can get up to 6mm shock offset or up to a 1.5 degree headset change and brop the bb by .5.

edit: irealize you have aknowledged this option, but imho, its the cleanest way to go about it as opposed to air can spacers, what not
 
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H

herbman

Monkey
Feb 16, 2011
104
8
North West Tasmania
don't know if you would get away with off set mounts as there is a brigde on the rear stays that will contact with the seat tube?

i reduced the stroke on stock RP2 by 7mm. which reduced the travel to 130mm and gave the bike a 13.5 bb with 2.25 ardents on it.
it is a super fun bike to ride now, have just thrown the sanctions drop outs and 12mm axle on it to see how it handles with the stiffer rear end on it.


forion.jpg
 
H

herbman

Monkey
Feb 16, 2011
104
8
North West Tasmania
only oil. there is 7-8ml of 80/90 final drive oil. have heard of others using grease.

it was only ment as a test but it has worked well and the shock is holding up fine so far and it been over a year now.
 
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