Turns out bump steer is good for bumps!

As the front suspension collapses the spindle's camber angle changes which results in a change in the ski's toe alignment. Reducing the amount the camber change through the total suspension travel reduces bump steer. Ski doo added a spacer to separate the upper a-arm from the spindle which reduces the amount of camber change. I experimented with this several years ago and now some of the aftermarket A-arms like Mountaintech's are doing the same.

 
bump steer is also caused by the configuration of the tie rods, their lengths as well as the steering cranks they are hooked to.

You can have a suspension that has 0 camber angle change and still have tons of bump steer.

remember all the srx/sx and vipers we used to brag about the handling???? Huge amounts of bump steer and almost no camber change.

In the age of computer design, it is amazing that any sled would have bump steer at all.
 
Correct, There are other factors that will cause the toe to vary through the suspension travel but if you watch the video I think he was trying to understand what the taller spindle do to reduce bump steer. The Nytro's suffer with both excessive camber change and poor tie rod orientation. I've tested the Mountaintech 43" a-arms on rough trails and found that that the sled holds it's line much better which I'm contributing to the spacer on top of the spindle. If I have time I'll measure how much toe out variation the Nytro has with the 43" wide 2" forward arms installed. I'm wondering if the 2" forward has possibly contributed to a decrease in bump steer.
 
Well in the video he says "increases toe out" thus making it keep its line better in rough conditions. Plus wasn't nytro a rough trail sled in the first place, maybe yamaha engineers are not as so dumb after all?
 
Because the last time I checked drove a skidoo it too was darting, but the harder you push them (nytro and doo) in the rough stuff the better they performed!
 
Darting and bump steer are two different things.

Darting is a function of the ski working against the steering.

Bump steer is a function of the steering working against the ski(which has traction or grip)

Darting is caused by ski rubbers, carbides, and ski design

The more bite the ski has, and or, the more weight on the front, the more bump steer and darting causes a problem
 
BETHEVIPER said:
Darting and bump steer are two different things.

Darting is a function of the ski working against the steering.

Bump steer is a function of the steering working against the ski(which has traction or grip)

Darting is caused by ski rubbers, carbides, and ski design

The more bite the ski has, and or, the more weight on the front, the more bump steer and darting causes a problem
Click to expand...

Thanks for clearing that out I did not know that.
 
I have seen a post on this site where someone placed a spacer on the top of the spindle where the upper a-arm attaches - to increase its height.

Does someone fabricate spacers like that?

This is trying to create similar geometry to the Arctic Cat chasis.

MS
 
I experimented with offset spacers several years ago. If I every go back to stock a-arms I would try something similar to Mountaintech's spacer which would be easy to install under the upper ball joint


 
If you just placed the spacer on the upper ball joint with stock arms, that would help the sled turn much flatter in corners? It would stop it wanting to roll in the corner wouldnt it....What was your experience?

Can the mountainetch spacer fit the stock set up Grizz?

MS
 
Grizz, does the 2" forward design and barcodes 5" forward design have more to do with how flat it will handle through the corners? I have an XTX. Do I really want the sled to be +5" over its stock setup? I want to help eliminate the tippy feeling I've had in the past. A lot of new parts this off season I hope will help that, lower engagement comfort clutch and the taller wrp seat that I think will help me ride it better. However, I also added a backcountry track and have slim Jim's on mtx skis which may not help in the corners. Looking to hear more feedback from those using both the barcode and mountaintech set ups.
 
Adding a spacer on top of the spindles with the OEM arms results in a decrease in the caster angle (I also believe camber would change). The Mountaintech a-arm design accommodates the addition of the spacer and also allows for additional caster/camber adjustment. When I experimented with a few different offset spacers I was trying to do the same thing but with the ability to somewhat correct caster/camber changes. I was trying to keep it simple but decided adding spacers would require a redesigned upper a-arm to get proper caster/camber settings. The idea was abandoned kind of early because at that time I wasn't sure what I was actually trying to accomplish.

I discussed the forward spindle stance with Mountaintech when he was designing his trail version of a-arms. I was concerned with going to far forward. I've been told that moving the spindles forward makes the front feel narrow which is good for off trail riding. I'm not sure if there are other benefits for off trail but I'm fairly certain extending to far forward isn't good for trail riding. I would expect slow/sluggish steering and the possibility of bottoming on rough trails due to the increased distance between track and ski. The +2 forward design is the maximum I'd consider for trail riders.

With the Mountaintech +2 forward trail design the sled feels less twitchy and seems to hold it's line much better (slow/sluggish steering?). It didn't seem to add any additional heavy steering and the sled holds corners well, although entering a corner is tight. When entering tighter turns it's as if it doesn't want to brake the straight line progression and I have to snap the bars to make the initial change in direction. Once that initial change is made it continues through and exits the corner without issue. As far as rough trail, the Mountaintech arms handled very well. I was able to run harder through the bumps and hold my line better than previous setups.

Last season I was running prototype a-arms that had limited caster adjustment which may have contributed to some of the negative handling I experienced. Mountaintech has since made revisions to improve their a-arms and I believe with the new production arms I can now correct the negative handling characteristic.
 
I for one think going further forward is the key to the Nytro, thats why I have the Barcode kit on both my Nytro's. Now I don't trail ride, but use trails, logging roads etc. to get to our riding spots. And for the most part they get pretty beat up by the end of the day. The +5 forward is awesome. Sure its a bit tippy but its 36" wide. But compared to stock, really no comparison. its just plain better. Now reading through Mr. Sleds post on the 42" trail kit in the TY Sled Build section, confirms my experience even more.
 
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