Viper suspension adjustment

[mbarryracing]

Looking at the attached picture I see the adjustment cam set the the “smallest” position which means this is the least stiff position. Confirm both cams are in the same position. At 190lbs you should be seeing more drop when you measure the rear height with nothing on the machine and then when you sit on it.

Another question, when you kneel on the back of the machine and deflect it downward, then take your weight off the machine how fast does the machine bounce back? I typically like to see about 1.5 seconds from fully compressed to the sled returning to the rest position. Sorry for all the ??s.

Hi Joe, no thankyou for asking. Yes when I kneel on the back bumper it rebounds right back up within 0.5 to 1.0 second.

Mbarryracing, did you buy the sled new or used? If used was the person you purchased the machine from a big guy, say 300+lbs or did you buy from a dealer and no idea about the previous owner? I was just thinking that maybe the recoil spring and or the shock springs are aftermarket? It is just a thought?

When I put Elka 2Stage shocks on my Viper they requested my weight to valve them correctly and to but the right springs on the shocks. If say a 150lb person was to ride my sled those shocks would be way to stiff. Cannondale27 may be on to something in his posts suggesting a revalue/servicing the rear shock. From the picture all looks normal including the rubber stop blocks.

I bought this sled brand new, left over still in a crate in November 2017. It did have all the factory suspension parts. It has always ridden what I call a harsh / little hard on the small bumps that my Apex would roll right over, I think the seat foam absorbs more of the impact from small bumps than the suspension but this Viper rarely bottoms out and is great on the rough trails which it was probably more calibrated for being a RTX. As I'm getting older I am becoming less of a hard whoop and bump banger and becoming more of a sit down groomed trail kind of rider. I'm sure there is a better suited suspension calibration on a different model Viper, but this one was the right price and worth tuning the suspension for my style. I'm no suspension guru, more of an engine tuning guy, so I'm asking the more experienced for help.

What I did just notice while doing this exercise is that when I kneel on the rear bumper and compress the rear suspension the machine is rocking on the center shock / front of the skid as the front of the machine rises up a little like a teeter totter. In my quest to try to get the sled to be more plush in small bumps I do NOT have the front shock preload jacked up NOR the limiter strap sucked up. When I sit on the machine the front and rear sag about the same distance.



The center shock this season in a quest to try to get it more plush I replaced the factory spring with a HyGear Twisted Spring Dual Rate center shock spring set for my weight. It has the minimum pre-load on the collar to keep it in place. It's not the spring that is causing this because it rode more harsh before I replaced it.
When I lift the track off the ground and set it back down, the front and back of the track touch the shop floor at the same time.

Cannondale will definitely get your shocks were they need to be it will feel like a completely different machine when he's done. You might want to ask him about changing out your rear springs they were very stiff in the 2014/15 models.

I had the feeling that I probably needed to change both the mousetrap springs and re-valve the shocks to retune this rear suspension to be more plush. First I wanted a sense check that either (1) what I have now is normal /to be expected for a 15 RTX-DX calibration and nothing was "wrong" , and (2) it could be more plush because other models are not like what I am experiencing. Can I replace shocks and springs for a different 129" model's?

cannondale, do you consider the rear shock to be the 1.5" so is it better to toss it and go with a different 2" rear shock that can be tuned better?

 

[srvfan]

I have a 2016 RTX , in my group are a mix of Cats and vipers . The RTX 129 with qs3 is by far the stiffest one . We have two 137” in group with same shocks and they are much softer . Push down on the bumper and they compress and rebound much better . The other 129 with base shocks is marginally better than mine but still stiffer than the 137 qs3 skids one of which is a 2020 Cat RS 6000 performance cross country model with the 2.0 kashima ones . My point is that I think the 129 skid geometry is different than the 137 and I don’t know if it’s really fixable . Cannondale did my shocks and that made them a bit better I have the BOP relocate kit and that made it better but I took it off to do a long fast ride with saddlebags I think I’m gonna put it back on I weigh 200 suited up. I don’t believe a few extra inches of track on the ground is the difference that’s more about the geometry or something because the 137 skids are much softer Just pushing down on them

 

[srvfan]

I don’t know if the base 129 has different springs I have the shock on 1 i’ve tried it on to and three on three I think you could jump a house and it wouldn’t bottom . With everything on one I have only ever bottomed on a few very hard nasty hits at high-speed. I think you would have to soften the shocks by 50% to be able to actually get it soft enough to use the adjustment knob for different conditions. Had a buddy ride it who was over 100 pounds heavier than me and he thought it rodr decent with the settings still on 1 he would have to go to two for a really rough trail when you consider he’s 50% heavier than me that shows how far off I think it is for the average person

 

[mbarryracing]

My stock shocks have no adjusters on them.
I saw that BOP relocation kit for the rear spring block adjusters and was wondering how that attached. I might go that route if I can't determine if there are softer springs to use.
Can you post a pic of that BOP block adjuster kit installed for me when you put it back on?

 

[titanrcr]

My stock shocks have no adjusters on them.
I saw that BOP relocation kit for the rear spring block adjusters and was wondering how that attached. I might go that route if I can't determine if there are softer springs to use.
Can you post a pic of that BOP block adjuster kit installed for me when you put it back on?

A softer torsion spring that a few of us use are the Cat 1704-354 and 1704-355 springs (left and right). I have both a 129 and 137 LTX with these springs and stock re-valved shocks. This setup works very well.

 

[mbarryracing]

titanrcr,
thank you that is a real world recommendation that I was looking for. Found a Cat spring chart on ArcticChat.
1704-354/355

Wire Diameter (A),Angle (B), Coils, Coil Width (C), Length (D). Length (E), Spring Type
.375 75° 8.75 4.32 18.50 5.5 Square

I think what I have in my RTX is the 1704-576/577
.405 94° 6.75 3.65 18.50 5.5 Square.

Was hoping to get this sorted out before my Old Forge trip...

 

[titanrcr]

titanrcr,
thank you that is a real world recommendation that I was looking for. Found a Cat spring chart on ArcticChat.
1704-354/355

Wire Diameter (A),Angle (B), Coils, Coil Width (C), Length (D). Length (E), Spring Type
.375 75° 8.75 4.32 18.50 5.5 Square

I think what I have in my RTX is the 1704-576/577
.405 94° 6.75 3.65 18.50 5.5 Square.

Was hoping to get this sorted out before my Old Forge trip...

You will need to get the shocks re-valved as well but these are the springs you want, Good luck...

 

[titanrcr]

While you have the skid out I highly recommend installing both the "center shock cross shaft" and "upper cross shaft saver" from Barn of Parts. In my opinion these are both a "must do" improvement on these sleds. If you do this you will find that the center shock lower bushing will need replacement at the same time.

 

[mbarryracing]

That has already been done, along with the BOP front tunnel saver plates. Also did the BOP driveshaft saver wedge when I serviced the driveshaft bearing this season, which I think is also a must-do...

 

[titanrcr]

That has already been done, along with the BOP front tunnel saver plates. Also did the BOP driveshaft saver wedge when I serviced the driveshaft bearing this season, which I think is also a must-do...

Completely agree, Both of my vipers and my Winder have the wedge installed. Last must do on my list would be 4 wheels across the back which I have also done. I guess the fuse box relocate on the Vipers should be done as well, just did one yesterday although I did my own fix for that.

 

[srvfan]

You will need to get the shocks re-valved as well but these are the springs you want, Good luck...

That’s great info on the springs . I wonder if this is a better solution then the BOP relocate kit . With the kit your taking the tension off the springs to make them softer but it’s still the same spring rate

 

[titanrcr]

That’s great info on the springs . I wonder if this is a better solution then the BOP relocate kit . With the kit your taking the tension off the springs to make them softer but it’s still the same spring rate

I'm not familiar with the BOP kit and it may or may not work as well as these different torsion springs but I can tell you these springs with the proper shock revalve work very well. Changing the torsion springs is a bit more work than relocating the spring block but I know it works.

 

[Mike P]

The 129" and 137" were not designed for a plush ride. The chassis is built and designed to be driven hard, take larger hits requiring a stiffer suspension which may have an uncomfortable feeling for some especially when driven at lower or higher speeds while seated. If you soften up the suspension and the ride height the performance will be changed. There is no doubt about how ruff a sled might feel and the impact this will have on ones enjoyment of the ride especially at the end of a long day as trail conditions change. Pulling corners at speed with a soft and overly compliant setup could have you digging out your sled or worst. As you make changes to your sled that effect its ability to handle safely at higher speeds it is extremely important to understand the pros and cons of the changes made. Good luck, be safe and enjoy the ride.

 

[cannondale27]

The 129" and 137" were not designed for a plush ride. The chassis is built and designed to be driven hard, take larger hits requiring a stiffer suspension which may have an uncomfortable feeling for some especially when driven at lower or higher speeds while seated. If you soften up the suspension and the ride height the performance will be changed. There is no doubt about how ruff a sled might feel and the impact this will have on ones enjoyment of the ride especially at the end of a long day as trail conditions change. Pulling corners at speed with a soft and overly compliant setup could have you digging out your sled or worst. As you make changes to your sled that effect its ability to handle safely at higher speeds it is extremely important to understand the pros and cons of the changes made. Good luck, be safe and enjoy the ride.

Actually the DX was designed to be plush. The lighter torsions will help. Switching to the 2” rear will help also. Get from 2016 ltx. Better Valving ALMOST as good as my Valving. If those springs still don’t do it the SRX springs will. As matter of fact I would just do that right away. Can always make them stiffer. Also where is your transfer blocks set?

 

[Mike P]

Actually the DX was designed to be plush. The lighter torsions will help. Switching to the 2” rear will help also. Get from 2016 ltx. Better Valving ALMOST as good as my Valving. If those springs still don’t do it the SRX springs will. As matter of fact I would just do that right away. Can always make them stiffer. Also where is your transfer blocks set?

I agree with your assessment of the DX model design leaning in the plush direction. With the stock factory DX suspension package the ride will be smother and at low speeds more comfortable. My suspension references were to his current set-up, " I have the RTX-DX model.............129" track.". More importantly the effects of softening up a suspension has on the overall handling on the ProCross chassis. Ultimately a persons riding style will dictate what is required under there seat. Have fun, enjoy the ride.