Author Topic: 450R Swingarm on Stock 250r Frame - Need some dimensions (Read 11091 times)

troybilt · « **on:** March 03, 2014, 08:12:30 AM »

Can someone measure your frame. Need the vertical and horizontal distances from the pivot to the upper shock mount and lower linkage mount on the frame. I don't have a torn down frame. I scanned the 450r swingarm I can lay this out and see what we we have. Calculate leverage ratios, shock lengths, etc..

rablack21 · « **Reply #1 on:** March 03, 2014, 08:49:31 AM »

Someone get this man what he's asking for!

JoePA · « **Reply #2 on:** March 03, 2014, 09:20:47 AM »

I can get you this when I get home. I'm sure someone has an 86-87 bare frame available.

rk88r · « **Reply #3 on:** March 03, 2014, 11:01:27 AM »

Measurements up to center of holes from flat and level surface the frame is sitting on:

swing arm pivot hole 4"

link hole 1 7/16"

shock hole 12 11/16"

Measurements back from center of swing arm pivot hole to hole centers:

link hole 1 3/8"

shock hole 1 7/8"

Accuracy within a 32nd of inch a 16th for sure.

rk88r · « **Reply #4 on:** March 03, 2014, 11:02:30 AM »

A 88 frame fyi.

sameltoe · « **Reply #5 on:** March 03, 2014, 12:04:36 PM »

Is that a 04/5 swingarm troy?

troybilt · « **Reply #6 on:** March 03, 2014, 12:25:01 PM »

Awesome RK88R that's exactly what I need! I'll update this tonight with a little more info and some calculations...

Sam, yes 04-05, 18.5" long roughly center to center. (I assume that's 04/05 as my 08 is ~19")

rablack21 · « **Reply #7 on:** March 03, 2014, 12:44:15 PM »

Quote from: troybilt;27509

Awesome RK88R that's exactly what I need! I'll update this tonight with a little more info and some calculations...

Sam, yes 04-05, 18.5" long roughly center to center. (I assume that's 04/05 as my 08 is ~19")

Yes, that's a correct assumption Troy. Look forward to further developments. It would just amaze the crap out of me if we were able to come up with a long travel setup using this 450r swinger. Being that the 450rs can add a special linkage to make theirs that way, I don't see why that would be too crazy of a thought.

DOUGLAS · « **Reply #8 on:** March 03, 2014, 04:21:43 PM »

i have this set up on my 87. i used all 06 componets. with the 87 stock front lonkage with the 06 450 linkage reversed it sits in perfect. with the stock 87 shock. for a long travel changing the linkage using an 05 rear linkage with an 89 front linkage should make the bike sit lower offering a longer shock option. in theory.

troybilt · « **Reply #9 on:** March 03, 2014, 07:10:12 PM »

Can someone get me the stock 450r dog bone length and the link length? I have a link but not sure which year it is, I think 08.

troybilt · « **Reply #10 on:** March 03, 2014, 07:31:19 PM »

Nevermind got the measurements... thanks!

OK, here is stock 250r frame with stock 04-05 swingarm with stock 04-05 dogbone and linkage:

On the graph, from left to right bottom axis is full droop to full compression of the shock and the Y axis is the leverage ratio, leverage ratio is a curve not a single number, its the change in wheel travel divided by the change in shock length. I've been setting preload length at half of the travel, good or bad, its just a starting point for now. The orange curve represents stock 08 450r geometry, however, I wasn't 100% sure what parts I had at the time, so take that with a grain of salt for now.

I set the frame at 1" off the ground for full compression, and 13" off the ground for full droop. You'll see right around the 9.5" mark of shock compression the linkage nearly goes over center that is why there is issue with the curve, i.e. bad.

Dashed blue line represents the shock, the red lines represent the swingarm, dogbone, and linkage. This is at the 10" of compression you'll see the dogbone and link are nearly in a straight line so that is causing out problems.

So lets try a few things to correct it.

troybilt · « **Reply #11 on:** March 03, 2014, 07:36:53 PM »

One thing I should point out, this is not what stock travel is, I'm setting it up for the ideal situation for MX.

Also I blew up a portion of the spreadsheet to look at shock lengths, etc... Also the max hang down of the linkage if that is negative means at bottoming out or full compression the linkage hangs below the bottom of the frame, also not good.

troybilt · « **Reply #12 on:** March 03, 2014, 07:41:55 PM »

Here is the stock 250r frame, 04 dogbone, 04 swingarm, 08 link: Looking a little better more like a stock 450r with a little longer shock.

troybilt · « **Reply #13 on:** March 03, 2014, 07:55:25 PM »

Moving in the right direction: (please note this doesn't take into account hitting the silencer or airbox...)

Little less progression, and a 17" long shock.

rablack21 · « **Reply #14 on:** March 04, 2014, 08:44:40 AM »

This is starting to look better. I hope Andy @ Maul Tech is taking notice of this. If we could get roughly 10.5 to 11 inches of wheel travel out of this, that would be awesome. Troy, I'm sure there will be some limitations to what you will be able to safely run this set up on. I'm sure there will be others interested as well, but I know for us mx guys, the longer the shock travel the better. We need every 1/2" that can be spared. Once we get the progression optimized, maybe Andy can create a link that will accommodate this progression.