ReX
TY 4 Stroke God
Many of us, myself included, have ranted here at TY4stroke about how poorly the 07 RTX handles rough trails in stock form and there are 100's of posts on workarounds to try to get it to handle them better.
I finally got around to rebuilding my shocks last week and installed Mike Carver's custom valve stacks. The difference is absolutely incredible. The sled now handles bumps better than any sled I've ever ridden.
Before:
- Completely stock it would bottom out at any moderately sized bump and if pushed the sled bounced all over the place (bouncing off the bump stops), making it difficult to control at high speeds on rougher trails.
- To control the terrible bottoming out I installed anti-bottomers and then after that wasn't enough and to try to get 3" of sag I re-arched the torsion springs (I was seeing up to 8" of sag at the rear bumper once 50+ lbs of ice built up with my 240 lbs ready to ride on the seat and about 10 lbs in the trunk). I also tried the optional Yamaha "heavy duty" torsion springs which, while stiffer, actually lowered the ride height.
- With the clicker set to the 2nd from full hard, it would still bottom out fairly regularly but the biggest problem now was the uncontrollable "bounciness" and how the sled wanted to "spring" off every little bump. Off bigger bumps the sled would often launch several feet in the air when it should have only "just" made it off the ground.
I asked Mike Carver to send me a custom valve stack for both the center and main shock. Mike looks after the Yamaha snow cross sleds and the shocks on Yamahs's cross country race sleds. He has been setting up race sled shocks for many years and really knows what he's doing. I asked Mike for a setup for a very aggressive rider weighing 210 lbs or 240 lbs ready to ride who prefers to be able to ride sitting down - even on very rough trails (in other words setting up the shocks to handle all of my weight, not using my knees to reduce the suspension loads). I also asked him to consider 50 lbs of ice built up in the tunnel, 10 lbs of "stuff" in the trunk and another 50 lbs for saddle bags when we go on our saddle bag trips. I also told him I had the anti-bottomers installed (so I needed a little "extra" rebound damping control).
He sent me out a triple stage (4 stages if you include the piston ports) compression valve stack for each shock (stock is just a single stage so no wonder they bottom out easily and at the same time ride so harsh), a new center shock piston, a new custom rebound valve stack for each shock and two shock service kits (o-rings, etc.). He also rebuilds shocks in house if you don't have the tools to rebuild them yourself.
If you want to rebuild them yourself, Yamaha keeps the IFP depths a "secret" (and Mike Carver won't give them out either), but after a little research, advice from others, calculating and testing I decided to use an IFP depth of 124mm for the center and 5mm off the bottom for the remote reservoir on the main shock. These numbers should work well for anyone wanting to rebuild the skid shocks on an 07/08 Apex RTX. They take 300 psi of nitrogen for the final charge. I'm running the clicker pretty much all the way out to allow Mikes multi-stage valving to fully control the ride (the clicker affects mid speed compression damping the most due to the spring and ball design).
After:
I had asked for and was expecting a firm, well controlled ride and that is exactly what I got. Here is a rundown on the performance:
- Now when riding, smallish sized stutter bumps (3-4 inches) at medium speeds (25-40 mph), the ride is similar for harshness as stock with the clicker set on the 3rd from stiffest position. I added this note to give you a feel for how it compares to the stock ride. The ride is much more damped and solid feeling though.
- Smaller stutter bumps in the 1-2" range with a very close pitch (2-3 feet) at 20-60 mph now just totally disappear. The unnecessary harshness for this sort of thing is now gone (Mike’s first compression stage is softer than the stock single stage). Don't get me wrong, the ride is not plush (by far) in all conditions/speeds, but it isn't unnecessarily harsh on little tiny bumps either.
- As the bumps get bigger and the speeds increase, the shocks get stiffer and stiffer in compression. It is now VERY difficult to bottom out. Yesterday riding some rough, high speed trails only once did I bottom it out and that was probably at over 90mph (indicated) off a rise and into a fairly nasty G-out. Without the shock update, the suspension would not only have bottomed out hard, but it would have kicked me high in the air off the exit of the G-out. Instead the suspension soaked up the hit perfectly, just bottoming out, and then perfectly controlled the sled got about 1' off the ground followed by a smooth landing without any "bounce". The front end did bottom out a little, but not too badly either (floats were set at 70psi and have stock valving). To be honest I bottomed out so lightly in the rear at first I wasn’t sure it bottomed out at all. I stopped to have a look at the bump stops to check and found at the rear bump stops that the build up of ice had cracked away (I had been keeping tabs on this because I wanted to get a feel for how much it would take to bottom out). The front skid bump stops never did bottom out but I suspect they must have been very close too.
- Where the sled really shines now is absorbing bumps at high speeds and keeping the sled stable. Some of the trails we were on were high speed mogulled up trails. With the stock valving the sled would have been bouncing absolutely everywhere and very difficult to ride this sort of trail at speed. Now it is simply amazing. Skipping across the top of the moguls or even transitioning from lower speeds all the way through to "skipping" speeds, it is always perfectly controlled.
- One thing I was expecting, but was surprised see how much this changed, is how much harder it is to get the sled off the ground. With the stock valving it would tend to pop the sled high off the ground over almost anything. To give you a feel for this, there is one particular field access laneway in the ditch near my house with about a 1.5 foot rise and a fairly narrow top (maybe 9 feet wide). Even at 30-40 mph it would pop off the rise and get a good 1.5 feet in the air before missing the top of the narrow laneway and landing on the trail on the other side, followed by a couple of cyclic bounces upon landing (that I would absorb with my legs). Now off the same laneway at 30-40, the track hardly gets off the ground at all. Instead to get probably a foot off the ground I have to hit it at about 60 mph, now since I'm travelling faster it covers more distance in the air before a perfectly absorbed landing without any hint of even a single bounce. It is a very cool experience the way this thing lands so smoothly now. Its sort of a single continuous motion, the landing just gets absorbed away and the motion seems to just stop right there without any bounce back at all.
- Another impressive feature with the new valving is how much better braking and accelerating works on rough mogulled up trails. Instead of bouncing all over the place, the track now stays on the ground much more. Braking is further improved because with the stock valving it used to tend to kick the back end up very high off bumps when braking. Now the sled is level and stable when braking.
- With the stock setup I used to have to always be under power to some extend when hitting bigger bumps. If not, the sled wanted to nose dive. Now I can comfortably decelerate or even brake when travelling over the same sort of bumps and the sled stays level.
- One of my most important tests for how well my rear skid rides is how my back feels after riding rough trails. Even though this sled rides very firmly now and does have a much firmer ride compared to stock on high speed, bumpy trails, my back didn't once get jarred. Stock, if I didn't stand up before any bigger bumps I could get that sudden "bang" that would shoot up my back (I spent a lot of time using my knees to make sure that didn't happen). Now I can literally sit down all the time if I want. The ride is firmer, but the maximum loads that my back sees are within what my back can handle.
For a rough trail, aggressive setup I don't think I could ask for anything better. This sled is simply incredible now when pushed hard on rough trails. I probably could have got away with slightly less mid speed compression damping, but now I have the option of turning down the preload on the rear springs and lowering the sled to improve handling while still not likely to bottom out.
What the sled is not though is a luxurious smooth riding sled for when I want to slow down and take it easy (doesn't happen very often though...). I didn't ask for that and I didn't get it. I'll let you guys know if on higher mileage rides if I find it a little too firm (I only did about 500 km yesterday and have about 600 km in total on the revalve).
I finally got around to rebuilding my shocks last week and installed Mike Carver's custom valve stacks. The difference is absolutely incredible. The sled now handles bumps better than any sled I've ever ridden.
Before:
- Completely stock it would bottom out at any moderately sized bump and if pushed the sled bounced all over the place (bouncing off the bump stops), making it difficult to control at high speeds on rougher trails.
- To control the terrible bottoming out I installed anti-bottomers and then after that wasn't enough and to try to get 3" of sag I re-arched the torsion springs (I was seeing up to 8" of sag at the rear bumper once 50+ lbs of ice built up with my 240 lbs ready to ride on the seat and about 10 lbs in the trunk). I also tried the optional Yamaha "heavy duty" torsion springs which, while stiffer, actually lowered the ride height.
- With the clicker set to the 2nd from full hard, it would still bottom out fairly regularly but the biggest problem now was the uncontrollable "bounciness" and how the sled wanted to "spring" off every little bump. Off bigger bumps the sled would often launch several feet in the air when it should have only "just" made it off the ground.
I asked Mike Carver to send me a custom valve stack for both the center and main shock. Mike looks after the Yamaha snow cross sleds and the shocks on Yamahs's cross country race sleds. He has been setting up race sled shocks for many years and really knows what he's doing. I asked Mike for a setup for a very aggressive rider weighing 210 lbs or 240 lbs ready to ride who prefers to be able to ride sitting down - even on very rough trails (in other words setting up the shocks to handle all of my weight, not using my knees to reduce the suspension loads). I also asked him to consider 50 lbs of ice built up in the tunnel, 10 lbs of "stuff" in the trunk and another 50 lbs for saddle bags when we go on our saddle bag trips. I also told him I had the anti-bottomers installed (so I needed a little "extra" rebound damping control).
He sent me out a triple stage (4 stages if you include the piston ports) compression valve stack for each shock (stock is just a single stage so no wonder they bottom out easily and at the same time ride so harsh), a new center shock piston, a new custom rebound valve stack for each shock and two shock service kits (o-rings, etc.). He also rebuilds shocks in house if you don't have the tools to rebuild them yourself.
If you want to rebuild them yourself, Yamaha keeps the IFP depths a "secret" (and Mike Carver won't give them out either), but after a little research, advice from others, calculating and testing I decided to use an IFP depth of 124mm for the center and 5mm off the bottom for the remote reservoir on the main shock. These numbers should work well for anyone wanting to rebuild the skid shocks on an 07/08 Apex RTX. They take 300 psi of nitrogen for the final charge. I'm running the clicker pretty much all the way out to allow Mikes multi-stage valving to fully control the ride (the clicker affects mid speed compression damping the most due to the spring and ball design).
After:
I had asked for and was expecting a firm, well controlled ride and that is exactly what I got. Here is a rundown on the performance:
- Now when riding, smallish sized stutter bumps (3-4 inches) at medium speeds (25-40 mph), the ride is similar for harshness as stock with the clicker set on the 3rd from stiffest position. I added this note to give you a feel for how it compares to the stock ride. The ride is much more damped and solid feeling though.
- Smaller stutter bumps in the 1-2" range with a very close pitch (2-3 feet) at 20-60 mph now just totally disappear. The unnecessary harshness for this sort of thing is now gone (Mike’s first compression stage is softer than the stock single stage). Don't get me wrong, the ride is not plush (by far) in all conditions/speeds, but it isn't unnecessarily harsh on little tiny bumps either.
- As the bumps get bigger and the speeds increase, the shocks get stiffer and stiffer in compression. It is now VERY difficult to bottom out. Yesterday riding some rough, high speed trails only once did I bottom it out and that was probably at over 90mph (indicated) off a rise and into a fairly nasty G-out. Without the shock update, the suspension would not only have bottomed out hard, but it would have kicked me high in the air off the exit of the G-out. Instead the suspension soaked up the hit perfectly, just bottoming out, and then perfectly controlled the sled got about 1' off the ground followed by a smooth landing without any "bounce". The front end did bottom out a little, but not too badly either (floats were set at 70psi and have stock valving). To be honest I bottomed out so lightly in the rear at first I wasn’t sure it bottomed out at all. I stopped to have a look at the bump stops to check and found at the rear bump stops that the build up of ice had cracked away (I had been keeping tabs on this because I wanted to get a feel for how much it would take to bottom out). The front skid bump stops never did bottom out but I suspect they must have been very close too.
- Where the sled really shines now is absorbing bumps at high speeds and keeping the sled stable. Some of the trails we were on were high speed mogulled up trails. With the stock valving the sled would have been bouncing absolutely everywhere and very difficult to ride this sort of trail at speed. Now it is simply amazing. Skipping across the top of the moguls or even transitioning from lower speeds all the way through to "skipping" speeds, it is always perfectly controlled.
- One thing I was expecting, but was surprised see how much this changed, is how much harder it is to get the sled off the ground. With the stock valving it would tend to pop the sled high off the ground over almost anything. To give you a feel for this, there is one particular field access laneway in the ditch near my house with about a 1.5 foot rise and a fairly narrow top (maybe 9 feet wide). Even at 30-40 mph it would pop off the rise and get a good 1.5 feet in the air before missing the top of the narrow laneway and landing on the trail on the other side, followed by a couple of cyclic bounces upon landing (that I would absorb with my legs). Now off the same laneway at 30-40, the track hardly gets off the ground at all. Instead to get probably a foot off the ground I have to hit it at about 60 mph, now since I'm travelling faster it covers more distance in the air before a perfectly absorbed landing without any hint of even a single bounce. It is a very cool experience the way this thing lands so smoothly now. Its sort of a single continuous motion, the landing just gets absorbed away and the motion seems to just stop right there without any bounce back at all.
- Another impressive feature with the new valving is how much better braking and accelerating works on rough mogulled up trails. Instead of bouncing all over the place, the track now stays on the ground much more. Braking is further improved because with the stock valving it used to tend to kick the back end up very high off bumps when braking. Now the sled is level and stable when braking.
- With the stock setup I used to have to always be under power to some extend when hitting bigger bumps. If not, the sled wanted to nose dive. Now I can comfortably decelerate or even brake when travelling over the same sort of bumps and the sled stays level.
- One of my most important tests for how well my rear skid rides is how my back feels after riding rough trails. Even though this sled rides very firmly now and does have a much firmer ride compared to stock on high speed, bumpy trails, my back didn't once get jarred. Stock, if I didn't stand up before any bigger bumps I could get that sudden "bang" that would shoot up my back (I spent a lot of time using my knees to make sure that didn't happen). Now I can literally sit down all the time if I want. The ride is firmer, but the maximum loads that my back sees are within what my back can handle.
For a rough trail, aggressive setup I don't think I could ask for anything better. This sled is simply incredible now when pushed hard on rough trails. I probably could have got away with slightly less mid speed compression damping, but now I have the option of turning down the preload on the rear springs and lowering the sled to improve handling while still not likely to bottom out.
What the sled is not though is a luxurious smooth riding sled for when I want to slow down and take it easy (doesn't happen very often though...). I didn't ask for that and I didn't get it. I'll let you guys know if on higher mileage rides if I find it a little too firm (I only did about 500 km yesterday and have about 600 km in total on the revalve).
