00-NUKE
Expert
This is what I've come up with so far. The sweet spot for my 2011 with the 14mm mod was 8.25mm (.3250 in) Lower. Seems like such a minimal change, but I am now sitting bump steer free! 
AK, I'll keep up to date with ya this winter to find out how those ski-doo spindles work out.
AK, I'll keep up to date with ya this winter to find out how those ski-doo spindles work out.
Attachments
00-NUKE
Expert
AKrider said:
I actually still have about a 2mm toe. This setting of 8.25mm lower on the tie rod sets it at 1mm toe inside of the scrub curve at fully extended and 1mm toe outside of the scrub curve at full compression. I think this is due to the upper a-arm and lower a-arm not being the same length and the slight change in camber. Anyway, that is closer than I figured I would ever get. I'm happy with that!
It's too much to grind. Perhaps, if you bent the stock tabs down and ground down the base of the ball? But then you are looking at constant measurements to ensure that you find the right height. I think this was the easiest road. This mod made no change to the previous scrub, caster, or camber. The trails will only tell, but I would think that basically eliminating the bump steer could only improve the handling.
I think you've got it. Two millimeters of toe change is not much at all and with the normal slop in the steering components, it is probably the best we will ever get.
When you measured from the fully extended position, did you take into account the shock length? I noticed the a-arms will drop out a few inches lower than they would with the shock installed. I rested the spindle on some blocks of wood so I'd know where the fully extended point was with the shock. I noticed the ski experienced more toe change at the very bottom and top of the stroke with the shock removed. I'm wondering if your toe change might decrease if you had measured outside of the shock's stroke limits?
When you measured from the fully extended position, did you take into account the shock length? I noticed the a-arms will drop out a few inches lower than they would with the shock installed. I rested the spindle on some blocks of wood so I'd know where the fully extended point was with the shock. I noticed the ski experienced more toe change at the very bottom and top of the stroke with the shock removed. I'm wondering if your toe change might decrease if you had measured outside of the shock's stroke limits?
00-NUKE
Expert
AKrider said:
I have almost exactly 5" of shock and 8-1/2" of stroke. All of that was taken into consideration. The 14mm bushing mod on the top of the spindle helped maintain center as well. I think with completely stock settings, the outcome would not be as forgiving.
I may shim the upper ball joint back a little. When I shaved it 5.08mm to gain some outward camber, I may have gone a bit much. We'll see. When the weight shifts to the outside, so does the upper a-arm, putting the spindle into a negative camber with a stock setup. I went to the extreme on the upper ball joint to make sure this doesn't happen. This would be my only other concern at this point.
That's interesting, I didn't realize you did the upper ball joint mod. When you say 5.08 mm, is that the total for both upper ball joints or for a single ball joint? I did the upper ball joint mod but only had 2.5 mm removed from each ball joint. I actually found I could reduce the toe change by going back to the stock ball joint, which puts the spindle at 0 degrees camber, fully extended, at the bottom of the shock travel.
Since you've got an '11, Yamaha already incorporated the 2.5 mm upper ball mod using shorter upper a-arms. I'm pretty sure you could reduce your toe change even more if you shimmed your upper ball joints back to stock since you'd reduce the amount of camber change. I'm thinking your sled probably has around 4 degrees negative camber when the spindle is fully extended.
I wasn't sold on the 2.5 mm upper ball joint mod when I tested it last spring. It made my sled push more in the corners. In theory it should have cornered better. I don't think the spindle ever goes into positive camber (leaning outwards from the sled) when cornering, even in the stock set up, at least on the '08. It should never happen with the '09 and newer geometry since they are already starting off with negative camber.
Your results have pretty much convinced me that '09 spindles would be a worthy upgrade to my '08. Your upper ball joint spacer mod is a good idea as well since it is going to reduce the amount of camber change on the spindle.
Since you've got an '11, Yamaha already incorporated the 2.5 mm upper ball mod using shorter upper a-arms. I'm pretty sure you could reduce your toe change even more if you shimmed your upper ball joints back to stock since you'd reduce the amount of camber change. I'm thinking your sled probably has around 4 degrees negative camber when the spindle is fully extended.
I wasn't sold on the 2.5 mm upper ball joint mod when I tested it last spring. It made my sled push more in the corners. In theory it should have cornered better. I don't think the spindle ever goes into positive camber (leaning outwards from the sled) when cornering, even in the stock set up, at least on the '08. It should never happen with the '09 and newer geometry since they are already starting off with negative camber.
Your results have pretty much convinced me that '09 spindles would be a worthy upgrade to my '08. Your upper ball joint spacer mod is a good idea as well since it is going to reduce the amount of camber change on the spindle.
00-NUKE
Expert
AKrider said:
I shaved them 5.08mm each. The reason for the added ball joint mod was due to the the upper a-arm mod. The upper a-arm gets pushed up. When moving it upward, it forces the ball joint further outward at the same time due to its arc. The ball joint mod is required to keep the 2011 stock spindle camber when the 14mm mod was added. I went further by shaving each one as far as I could (5.08mm) before having to add more threads to the ball joint shaft, purely for testing. Unfortunately I ran out of time last year, but overall was still an improvement over stock settings. Now with this bump steer discovery, I am excited to see what it does!
Thanks for the explanation. I now see why you did that. It will be very interesting to see your how set up performs on the trail!
00-NUKE
Expert
AKrider said:
I'll keep you posted. Got a Looooooooong time til winter.
multi sled
Extreme
ak rider sorry it has took me so long to respond,i didn't say i didn't like the zbros,it's just that with their setup there are some trade offs, first it lowers the front end and changes the geometry,it virtualy gets ride of bump steer and makes the sled much more trailable ,that lowered frontend also exposes the engine to more trail junk,good thing i put the aluminum skid plate on,like i said it would hold the trail alot better,but in soft snow had a hard time getting it to come around,have team fast air shocks on the frontend,so spent alot of time playing with air and suspension settings.the more air made it more responsive,but it made the steering hard.i was trying to got it handle like my boys switchback,you just lean on it and seems to go where you want.also had some issues with keeping the nuts tight on the joints,had to cotter pin them all,locktight wouldn't hold.all said it made it alot more predictable and enjoyable.
I'd be really interested in learning what exact changes Zbros did. I think I know but it would be nice if they listed what they did on their website. The Skins front end lists all the changes they made.
ruffryder
TY 4 Stroke Junkie
So now who is going to make a custom spindle??
