ride height, fork rake, strut rod???

[cbc76am]

I just built my first timbersled. I had an 06 KTM 525 in the garage with 10 hours on it so why not?

Test run 1 was good, climbed up to 8k feet and got into some fresh and deep, its fun in the powder but on groomed or packed its a struggle on the arms to keep this thing tracking or even fun. Initially I raised the strut rod until the track was sitting evenly and the rake looked similar to a wheeled bike... not so good.

I obviously had too much ski pressure so I dropped the strut rod to the bottom and raised the forks to the limit. That did help... but one thing concerns me. the track is lifted off the ground on the back as a result of the geometry. The limiter strap is 3rd hole... so longer side of things and shocks are at stock 70psi. I also moved the limiters in on the convex front arm for now as the body roll was a bit of an additional question mark to the sketchy ride on hard pack.

Any thoughts on the geometry of the track to ground? Please don't try to dumb things down or anything in replies.. as an engineer and an ex professional motocross and snowcross racer... I know the mechanics of the skid, ski pressure, and the bike geometry and head tube slack angles. I'm just new to combining the two.

a photo of the track lift is attached

Thanks in advance for any feedback.

 

[AZ800]

I'm less of an expert than you on bikes and suspension and my snow bike was already setup when I bought it used, but a big part of the struggle on trails may just be that you're not use to riding it yet.
Seemed natural in the powder but my first couple rides I was hanging onto the bars on the trails like my life depended on it. Arm pump, hands cramped up, sore muscles just from a trail ride.
I'm certain it was more me getting used to the bike than the bike setup.
Think I was correcting for every little twitch of the ski and was all over the trail which I apparently now don't do.
Unless the trail is ultra hard or down to bare ground, I've not had any of that sensation since getting used to the bike.

Fwiw, that picture just looks wrong in my limited experience. Bet it wheelies like a mofo though. My track and every bike I've seen, the track is flat on the ground.

 

[wwillf01]

When you say raised the fork does that mean the triple clamps are as high as they can go? Making the closest shock to your bike softer will increase ski pressure. Then finally if your from forks are too soft will will make it erratic handling wise. On my kit the rear of the track comes off the ground a bit on my Lt but not that much.

Sent from my Pixel XL using Tapatalk

 

[eric82930]

Its a common mistake, you need to slide the forks UP which will lower the front of the bike and get rid of ski pressure. Then adjust the strut so the back of the track is just barely touching and run less psi in the rear shock.

 

[cbc76am]

understood

I did lower the forks which would increase the ski pressure... it was because I was trying to get the track sitting more level with that move. it just doesn't look right like that...

Fork springs at 5.8N/m I run 4.6 on the trails at 180lbs - so I think I got that right. the valving is soft but spring rates should be about right for the leverage that the track creates.

Good call on getting used to it. As the day progressed I certainly became more used to the wondering on the road that was hard packed from a snowcat plowing.

 

[cbc76am]

If I lowered the forks a few mm and adjusted the strut until the track was about level it would be way out on the strut threads. Most posts I've read say people were cutting them down or running them buried. Would you also decrease the length of the limiter strap to allow the track to flatten out... regardless of the increased pressure?

Thanks for the help.

 

[eric82930]

I never noticed much gain sucking up the limiter on a bike. It helps tame a 160 hp sled on super steep climbs but bikes just don't have that problem. Yours is so out of balance you would have to take 2 inches out of the limiter which would only leave you with 4 inches of front track travel before it bottoms out. If your strut is out of threads you may be able to drill a closer hole in the shock link. I drilled 3 holes on my sx kit because I didn't have an adjustable strut. New adjustable struts are $150 so that would be my last choice.

Also you might want to just ride it that way and see what happens. When I first started this sport I purposely set mine up that way to lower it and get rid of ski pressure but after I got used to riding the hacked up roads, I gradually tuned it back to a more even pressure setup and I don't seem to mind anymore.

 

[CATSLEDMAN1]

seat time

the wondering front end.........as mentioned has a lot to do with seat time, don't worry be happy.

however if you would like to get it dialed , a lot of good trail manners has to do with your front ski mouunt strut and how far back the trail on your ski bolt is located. TS does not allow much if any adjustment there. But you want it right, you will need to try moving the mount to find the sweet spot. Stock TS no room to rotate back, got to make a plate and experiment. After building a good number of these front mounts from scratch I learned to leave plenty of room to rotate the ski to find a good setting. WR, YZ absolutely won't be the same, SX and EXC absolutely can't be the same,the more fork rake out on the bike , the further you need to pull the ski mount back.

When you want your bike to climb and glide through the powder, your stut setting for the track will be right at track level on the ground and no weigh bias to the front of the track.............front weight bias makes better trail handling and poor climbing manners.

 

[cbc76am]

Thank you, good advise. I was looking at the limiter strap and front shock and thinking about how it's under the rider on a sled, the TS kit it's behind the rider and leveraged in a way that makes it almost not a functional component. I've got plenty of room on the strut to level the track. I was just trying to fix the front end like a noob. I've readjusted the strut to allow the rear to just be off the ground. Also fixing the chain tensioner from hitting the subframe when the 3rd shock compressed and the pipe from hitting the SX frame on bottom out. So obviously I was headed the wrong direction.

I reead a good deal about shimming the ski, changing the rubber limiter direction and such. I'll look at the position and see what I can play with on that. Thanks for the good info guys.

 

[cbc76am]

updated photos with strut adjusted for level

Here I've readjusted the strut to level the track. I'll try to live with the trail manners and play with the ski position. I'm guessing I will need to fabricate the U bracket that the ski mounts to the pivot with in order to add front to rear movement points.

 

[Excalibur]

What size tank is that and do you run it full? Something to consider where the weight is. They just are not great on the trail. The harder the pack and amount of ice it gets worse. The more you ride and relax a bit the more confidence you will have. Set it up for the off trail fun stuff.

 

[cbc76am]

it's a 2.9 gallon. I've been running it at 80%. Good thoughts on the weight positioning though.

 

[Excalibur]

That is not bad at 2.9 gallons. It is nice to have the capacity. Weight including rider position to the rear helps a bit. They just are not great on certain trail conditions. Unfortunately some trail is usually needed to get to the good stuff. I just went on two family trail rides, one bike with six snowmobiles. Trail skills gets better, always looking for an escape through the trees!

 

[cbc76am]

I'm going to move the bars back a step or two once I get my new twisted engineering flex bars in a week or so. re-rig the cockpit to let me sit back 3 inches further without stretching out too much

 

[chumbilly1]

Here I've readjusted the strut to level the track. I'll try to live with the trail manners and play with the ski position. I'm guessing I will need to fabricate the U bracket that the ski mounts to the pivot with in order to add front to rear movement points.

How did you get the sx strutrod to work on a pds frame? Doesn't it hit the side of the linkage on the kit? There is fore and aft adjustment built into the ski.

 

[cbc76am]

This is the 2015 SX model... only 50 of them made. It was re-designed to make it fit. It's super tight and only clears when it's adjusted out a bit. They reworked that linkage a bit, added the tilting front arm and some other minor mods on this kit.

 

[cbc76am]

I didn't realize there was a way to adjust the ski... I'll have to google that a bit. Having no manual as I bought the kit 2nd had leaves me guessing on a lot of things... and asking for help here. Thanks chum