Big Wheels

[Enticer]

I have an 06 RTX stock 121 skid and track. It has the same track scrub on shock problem that everyone has. Has anyone gone to bigger wheels on rear axle? If so is there a problem with tunnel clearance in the back? I would like to go to 7 1/2 inch wheels with a stock axle but this would drop below the slide rail maybe too much. I think with bigger wheels it would help raise the track maybe enough to help stop the rubbing. Any ideas or suggestions? Thanks. Enticer

 

[Beerman]

I'm brand new to Yamaha this year and spent some time looking for a big wheel kit and haven't found anything yet. I'm kinda surprised since there are a bunch out for AC. Maybe the aftermarket will catch up this Fall. I hope so.

 

[yamadoo]

Enticer,

Sorry you have the Shock rub and hope the wheels work. But this is not everybody, many / ? most do not have it.

I keep looking and see no evidence of the slightist contact. Why some mono's have it and most don't is a mystery to me. ? if there was a couple different manufacturing runs with slightlyl different configuration.
Good luck

Yamadoo

 

[Len Todd]

Could it be that the involved suspension components are bent? For example; Could a bent rail move the shock mount?

Could the track tension being too tight casue some track or suspension flexing? Compared to my other sleds, these high torque sleds have thier track set really tight to stop ratcheting. Also, we are hearing a lot about excessive hyfax wear, which stopped on my sleds when I started running the track just shy of ratcheting, which is ~ 1" more than spec.

I suppose if the track was too loose it could hit when letting off on the gas? I know we have a lot of us playing with track tension to get hyfax wear down. Someone could be running with the track excessively loose.

Could the absence of the 4th wheel on the rear axle be allowing excessive track flex, especially with an overly tight track? Who know how tight the tracks are, in some of these posts.

Just some thoughts that I don't recall seeing being discussed much or addressed adequately enough to rule them out.

 

[Beerman]

Even w/o the shock rub issue a big wheel kit would be nice, less rolling resistance, more top speed, better mileage. I'm not aware of any downside to larger axle wheels and not sure why the manufactures don't just do it themselves. Radar guys have known about this for a long time.

 

[kviper]

There was an article in Snowtec mag about big wheel kit's on 121" sled's last fall. They claim with the geometry of a 121 skid and larger wheel's you can not hold a consistant track tension as it goes through it's stroke to the point of the track geting so tight that it will limit travel. I was thinking of a big wheel kit in my GT to but gave up on it after reading the article. IMO the track rub on the shock is coming frome very hard acceleration or track spin and then sudden hook up frome hiting a hole or just hook up after spin on hard pack. This put's a very heavy load over the top of the skid as it is actualy pulling the track frome the rear and due to the upper ideler's being so far apart you get a sag that is multiplied frome the extra load. I don't think track tension will have much to do with the problem but a looser track may help some and bigger rear wheel's may also help as it would flatten out the pull over the upper ideler's. Now you have my .02. Any thought's? kviper

 

[RTX]

enticer
I have asked the same Question as you 2 different times on here and not recieved a straight answer.
to be honest i don't think anyone has swapped these wheels and can tell you the result.
over the summer i am going to machine 2 small wheels out of delrin and mount them on a longer bolt through the top of the shock. these wheels will be just tall enough to keep the track from contacting the shock. the wheels will spin free to help decrease any friction. i am absolutely positive this will work and not cause any inteference issues.
to me it just seems like a better fix.

 

[kviper]

RTX i was looking at the same idea,there is not much room between the internal drive lug's and where the wheel would have to mount aside of the shock mount, it would have to be quite narrow. My shock look's as though it is not wearing any farther so i am not going to concern myself with it for now. Will you just use a bushing in the wheel or a presed in bearing? kviper

 

[Yummy]

Almost 7000 miles and there is not a scratch on the shock. Also I been driving pretty hard in all conditions.

Is it possible that there are 2 models of mono out there? Is the skid build my computer or by hands? Did anyone compare two skids (one that touch and one that don' t) to see if every angles and joints are identicals?

Just my .02 cents!

 

[ReX]

I compared my 05 RX-1's skid (06 pivot arms, shock, etc.) to a friends 06 Apex ER. My shock almost touched the track (less than 1/8" of clearance) while his had about a 1/4" of clearance.

I checked at different suspension loads also and his skid always had more clearance.

There does seem to a good 1/8" or more of manufacturing tolerance.

Having said that, my shock hasn't experience any more wear than his and my sled has a good 600 miles more on it this season (since the new skid). I did install the 4th wheel kit and that might have helped.

Last season my shock wore pretty much all the way through to the bearing but the front pivot arm failed a few times and the track was structurally destroyed with the last pivot arm failure plus the skid got twisted up. This probably explains most of the difference between last season and this one.

All I can say for sure is my shock has lots of life left after almost 6000 miles this season with a skid that never actually broke (minor cracks still) and a 4th wheel kit. Personally with the rate it was wearing at I wasn't worried about shock wear at all (or track wear from rubbing).

 

[bjniceguy]

isn't there a nylon pad that is used on the Attak at the same point on cross shaft. That seams a pretty easy fix??
Doug

 

[craze1cars]

enticer
over the summer i am going to machine 2 small wheels out of delrin and mount them on a longer bolt through the top of the shock. these wheels will be just tall enough to keep the track from contacting the shock. the wheels will spin free to help decrease any friction. i am absolutely positive this will work and not cause any inteference issues.
to me it just seems like a better fix.

I'm not saying your plan won't work, but I would have one serious concern you may not have considered. Those two little wheels are going to be such a small diameter....when your track is spnning at 100 mph I'd love to see what RPM those wheels will be turning! I predict massive heat buildup, possibly wheels cutting deep grooves in the shock bolt, or the hub hole wearing big & sloppy, or whatever mini bearings you put in there siezing. I think they'll just have to spin too fast for this to work....it's hard enough to keep small diameter idler wheel bearings in a snowmobile, and these wheels will be fraction of that diameter.

Then again, if we're just talking about the wheels making very occasional contact with the track, they will NOT be spinning fast regularly, only occasionally in short bursts. Then maybe this will work fine. I'm just not sure...something to consider, though.

I can't remember who, but someone else here once showed a plastic spacer they fabricated for the same location, but they didnt' set it up to spin like a wheel. Just something sort of like a chunk of Hyfax for the track to occasionally rub on to protect the shock against wear. Slightly larger diameter than the head of the shock. IMO this would probably be functional and easier solution than creating spinning wheels.

Just a thought...report back whatever you end up doing...

 

[RTX]

RTX i was looking at the same idea,there is not much room between the internal drive lug's and where the wheel would have to mount aside of the shock mount, it would have to be quite narrow. My shock look's as though it is not wearing any farther so i am not going to concern myself with it for now. Will you just use a bushing in the wheel or a presed in bearing? kviper

Yes you are right it will be a tough fit but it is won't be too tough.
i work as a mechanic but also run a lathe daily so i am pretty competent to machine something to fit in there.
no bushing for my first try at this. just a slip fit over the new shock bolt.

 

[RTX]

enticer
over the summer i am going to machine 2 small wheels out of delrin and mount them on a longer bolt through the top of the shock. these wheels will be just tall enough to keep the track from contacting the shock. the wheels will spin free to help decrease any friction. i am absolutely positive this will work and not cause any inteference issues.
to me it just seems like a better fix.

I'm not saying your plan won't work, but I would have one serious concern you may not have considered. Those two little wheels are going to be such a small diameter....when your track is spnning at 100 mph I'd love to see what RPM those wheels will be turning! I predict massive heat buildup, possibly wheels cutting deep grooves in the shock bolt, or the hub hole wearing big & sloppy, or whatever mini bearings you put in there siezing. I think they'll just have to spin too fast for this to work....it's hard enough to keep small diameter idler wheel bearings in a snowmobile, and these wheels will be fraction of that diameter.

Then again, if we're just talking about the wheels making very occasional contact with the track, they will NOT be spinning fast regularly, only occasionally in short bursts. Then maybe this will work fine. I'm just not sure...something to consider, though.

I can't remember who, but someone else here once showed a plastic spacer they fabricated for the same location, but they didnt' set it up to spin like a wheel. Just something sort of like a chunk of Hyfax for the track to occasionally rub on to protect the shock against wear. Slightly larger diameter than the head of the shock. IMO this would probably be functional and easier solution than creating spinning wheels.

Just a thought...report back whatever you end up doing...

the idea here is not to contact the track all day long but simply to offer a softer/plastic material for the track to hit before it hits the shock.
i intend to make the wheels 1/8 - 3/16 taller then the top of the shock and since the wheels will spin free there should not be alot of issues with friction / rubbing etc etc.

Yes i am aware that a hunk of plastic could be put in there to keep it from rubbing the shock but you still have the track rubbing the plastic which like hyfax will eventually wear and need to be replaced.
I feel that the idea of free spinning wheels will be a much better solution to this problem and this fix will be much more simple than some of you think.
I am curious as to how you will install a piece of plastic on this area of the shock and keep it from ripping off when you are doing 85 mph and the track hits it.

machining the wheels should take me 1/2 hour max. it is only plastic i would be surprised if it took me more that 20 minutes. get a longer shoulder bolt from the local hardware store. install a washer-wheel -washer onto the bolt. remove the nut from the old shock bolt. use the new bolt with washers and wheel installed to drive out the old shock bolt.
install a washer-wheel-washer and loctite the new nut. job complete!!

good luck to everyone and keep us posted on results