121 vs 136

Skinner

Skinner

SUPER SPONSOR
I'm sure this will sound stupid,,however,,What does it take to put a 136 inch skid in a 121 inch chassis? Are the mounting holes the same, or does the rear have to be moved back? Can't help but think the difference would be in the rail length, location of the idler wheels, and a tunnel extension.
Sorry if I sound dumb, has anybody ever done this??
 
Last edited:

Hey Skinner....I use the same mounting holes. Just add an extension to the rails. I used 1/4" x 3" alum. plate. Take off the track adjustments.Bolt the extensions to the rails using the existing track adjuster holes.Cut slot in extensions for the adjustment and bolt adjuster on.It's actually quite easy!!. Also depending on how much rail extension you add you might have to put on a tunnel extension.It's easy to break one of those up also. It works great,done a few of them. Cheers!
 
136 install

I sure do appreciate the input guys. Heres the deal. I would like to take a complete stock 136 suspention and bolt it into a 121 inch chassis.I'm a little worried about lengthening the existing rails because this is going into a high perf dragsled. Would feel better if the rails were one piece. So that leaves me with,,,,,are the location holes in the 121 chassis different than the 136 MM. If so, what is the difference, is it the rear location, the front location or both if at all. Thanks again for all your help.
HONTRI: that sled of yours needs to be in a museum!!!!!!!!!!:rockon:
 
Dave, I am putting that 136mm (proaction) In my sled and it has rail extentions to make it a 144. I have not drilled any holes yet. (waiting for Aluminum) But I am going to Use wildmaxs install to referance. I am thinking the front will bolt in the same as the 121. I am going to drop it 1/4"(+\-) to gain a little clearance by the drivers to stuff a rip saw in it. then, I am figuring that 121-136=15 Inches, divide that by 2 (for track wrap) gives me 7.5 inches farther back for the center and rear mounts....Now this is only beer can engineering. I haven't done anything but look it over yet. Thats what I was thinking anyway......Would love to hear others thoughts on this before I start punch'n holes. Just thinking.....I bet your not talking about a proaction for racing. eitherway though, I was thinking that the only real difference would be rail lenth.......But I could be wrong.
 
Last edited:
Rail length

Jeremey, thanks for the input. We are thinking on the same lines, I hope you are correct in your assumptions. Would make an easy change in case I wanted to switch between a 121 and a 136. It would be nice to compare numbers with the two different skids in 660 feet

Thanks bud
 
Wheelies

Tony, thats exactly what I'm after, a 257 inch skid. (No wheelies LOL) This imp motor is pretty stout, don't want Brutus getting hurt. Will sacrifice a weight disadvantage to keep it safe. We both know the effects of major hook-up at the starting line, its hard on the
"Fruits of the Loom"
 
Last edited:
Skinner, pics of Samueljacksons XT project



he made those extension by himself. PM him for details.







Ike
 
I've used rail extensions on one of my SRXs - I think from Tracks USA store. It has held up good for over 3000 miles.

I read on the last couple of topics that some fellows are still referencing my diagram on changing the rear skid. Keep in mind that the dimensions are only showing where the holes were located on a stock '97 VX800 with a Pro Action. Most 121" Pro Actions will fit (including RX-1 skids). There is a limit of 1 1/8" on the track lugs and many folks will simply lower the rear and idler shaft mounting holes to get the clearance for the taller lugs. Keep in mind that this can increase the front ski down pressure resulting in heavier steering and loss of performance because of increased drag. The other thing that can come into play with lowering the holes is the structural integrity of the tunnel. Even though an inch or so does not seem like much, it increases the overall moment arm by maybe 25% on lateral movement - every hard turn or slide. Probably nothing will happen in the lifespan of the average sled but stress cracks at the tunnel side/top corner wouldn't surprise me.

If I ever customize another one for off trail, I have considered moving the coolers to the bottom of the running boards - however, I like the stock location for cooling efficiency. Actually, for a longer skid on a modest budget, I think I would install the complete MM rear half onto the VX800. That way a lot of the custom fab is done and the benefits of the larger fuel tank and seat are there too.

I haven't been on the site for awhile - maybe this has already been discussed.
 
Skid

Good stuff guys.
Wildmax: These are my same concerns. Theres wind of guys moving the 121 back and using a 136 track. My concerns are the same as yours, the structural integrity of the chassis. that moves the mounting holes into the tunnel. Even if you rivet plates in the side, it still has nowheres near the strenght of the bulkhead. If I am understanding you right, you change out the rear swingarm assembly and obviously the rails on the 121 skid. If that is correct, does that allow you to use the stock mounting holes (front and rear) in the standard 121 inch chassis???? Again, with the same concerns you have, I don't want to change any hole locations. If I had to do that, I would probably start looking for a MM chassis.

Thanks again for all your input
 
Last edited by a moderator:
Dave
When I put the 97 Mountain Max skid in my 95st, I used my 97 Vmax 600 with a 121 for a reference guide. The 136 Mountain Max skid was the same for the 2 front holes but the rear mounting holes were 7 1/2" farther back for the 136 compared to the 121. I would assume this is the same for any st skid that came from the factory. It supports the rail at the back better but if you're just gonna be drag racing with it, you'll probably get away with some stout rail extensions.

Ian
 
136

IAN, long time bud, how are ya? Thanks for the info, thats what I was after. Had Tom Hartman (Mountain Performance) out in Idaho machine me some billet rail extensions with the right offset. Allows us to use a 136" track with a 121 skid. Still 121 hyfax vs 136, a little less resistance. Were not bangin around in the mountains, just wanted a bigger foot print so this should work good without the extra weight. His machinging is a thing of beauty and Tom is just a super guy to work with. You guys with the mountain sleds give him a call when you need things, you won't be dissapointed. Thanks again Ian, take care
 
You must log in or register to reply here.


Back
Top