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AER 48 TC250 I like these changes - used Restackor

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I recently picked up a 2017 TC250.  I've not been real happy with the handling, but for the first 3 hours or so of riding I liked the forks.  While plush on the soft stuff after a while I started to notice it spiked pretty hard and in fact I sprained my wrist just being on the shy side of a double and having a hard landing (not a crash).  I'm by no means a suspension guru but I tried modeling the check plate design in Restackor for a baseline but I'm not real confident in the results because the center relieved check plate properties are relatively unknown to me.  I put the 250 SXF shim stack in Restackor but based on the way I modeled it, they would have a pretty severe cavitation issue.

cavitation.jpg.32e259e53976e4fc14c770b2fa9eed45.jpg

Also if I understand correctly some float (and bleed) on the mid-valve bring the low speed damping rate curve closer to the asymptote so I wanted some conventional float.

1153048641_FloatandBleed.jpg.5cc952f9010d084caef9ad80bba1f33d.jpg

I had some shims from previous revalves so I dug all my 8mm ID 0.11 KYB shims and came up with a mid-valve stack along with a stiffer basevalve, made a cup and spacer for the float and added a spring (just something from the hardware store, 0.21" dia wire).  The rebound is the same as the SXF.  Here is where I ended up:

Combined.jpg.a41d30db4995c5e09f088e7c995fc600.jpg

You can see the affect of the bleed on the Damping Coefficient.  The cavitation is gone as well.  On the force curve the top line is the 250 SXF as a baseline.

Base.jpg.bad7b8a80c23a9de568738081f0924d3.jpg

Rebound.jpg.28fc6c75df9b42f33f8ee79e6ce16f74.jpg

Mid.jpg.283bd2cb9399113affaf7b8947dcc936.jpg

For the mid float I made up these pieces and put them in.  Dimensions are nominal, I had to do some hand fitting to get it just right.  I also added a 2 mm bleed.

Cup.jpg.06b83bdd830f2cbc1ed0e3d38027a48e.jpg

Spacer.jpg.953941e4d92d8b164fbd3eba4ed4bfcb.jpg

Mid-Valve.thumb.jpg.60585a05e09ccbaf2826c77097fd1ef0.jpg

The forks are slightly better now as far as the spike, but what amazed me is how much different the entire bike feels.  It tracks better, the front end seems to stay in contact with the ground better or something.  I feel way more confident, it is night and day better.  It's difficult to articulate what changed but the entire bike just feels balanced and ..... conventional?  It's gone from a bike I haven't really been enjoying to something I had a blast on yesterday.  I may try replacing some of the 0.11 shims with 0.10 and get the overall damping force down a tad as it's on the high side but it's very acceptable as is.  

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Your mid shims have no limit on how far they can bend ? I think that's why you notice they feel nice , but will the shims last ?

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This is really interesting and I will be eager to see what else you do with this. The AERs on my ‘18 250XC have okay plushness on low speed rocks and chop but seem to blow through the mid stroke and have extreme ramp up (harshness) in the end stroke. I’m getting to the point where I want to do some tweaking.

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1 hour ago, mog said:

Your mid shims have no limit on how far they can bend ? I think that's why you notice they feel nice , but will the shims last ?

Yeah I'm concerned about that too, and is 2 face shims enough?  They might flutter too much.  I didn't have enough room to add more to the stack.  I think I can make my cup have an integrated stop though, It just didn't occur to me until after I had it done.

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2 face shims isnt much , and with no limit shim you might only get a few rides from it ,I don't know as I have never pushed a mid that far , but it will give you low speed and a good amount of blow off of high speed

It's a good experiment if nothing else

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3 hours ago, mog said:

2 face shims isnt much , and with no limit shim you might only get a few rides from it ,I don't know as I have never pushed a mid that far , but it will give you low speed and a good amount of blow off of high speed

It's a good experiment if nothing else

How many face shims is enough?  I can go down to 0.1 and get 4 without much change.  How much lift is too much?  I can easily integrate a limit in the cup, but they aren't deflecting enough to hit it unless I start at the top and go down 2mm.  So how much good is that stop doing when it will only come in to play at the highest speeds?  These are all the questions I really have no answers to.

I did try a 14mm clamp on the basevalve based on a suggestion by n2dirt, it lowers the overall rate down to where I think I'd like it better and without cavitation.

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Look at the sxf mid ,what's it limit ? Ktm will have done enough testing to get it reliable

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On 9/27/2019 at 11:49 PM, mog said:

Look at the sxf mid ,what's it limit ? Ktm will have done enough testing to get it reliable

I looked through a bunch of WP stacks and they usually use a 0.3 mm clamp.  In reading through the forum, I see references for all the way up to 4x clamps at 0.3 mm or 1.2 mm clamp before the stop.  How does this look for the midvalve for face shim qty and lift:

4x30    0.10
28    0.10
26    0.11
25    0.11
23    0.11
22    0.11
21    0.11
2x20    0.11
2x19    0.11
2x18    0.11
17    0.11
14    0.25
12    0.80
25    1.50

And for the base valve:

6x30    0.10
4x28    0.15
26    0.15
24    0.15
2x22    0.15
2x20    0.15
2x18    0.15
14    0.3
25    1.50

 

This lightens things up a bit, keeps me from cavitating, and provides what I think is a reasonable stop without changing things drastically.

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I looked through a bunch of WP stacks and they usually use a 0.3 mm clamp.  In reading through the forum, I see references for all the way up to 4x clamps at 0.3 mm or 1.2 mm clamp before the stop.  How does this look for the midvalve for face shim qty and lift:
4x30    0.10
28    0.10
26    0.11
25    0.11
23    0.11
22    0.11
21    0.11
2x20    0.11
2x19    0.11
2x18    0.11
17    0.11
14    0.25
12    0.80
25    1.50
And for the base valve:
6x30    0.10
4x28    0.15
26    0.15
24    0.15
2x22    0.15
2x20    0.15
2x18    0.15
14    0.3
25    1.50
 
This lightens things up a bit, keeps me from cavitating, and provides what I think is a reasonable stop without changing things drastically.
Looks good to me

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You're missing a few parameters in your restackor - namely float.  I have a conventional mid stack on my 300XC - set up for rocky trail - and it works well.  No limit plate and the shims survive well.  I'm running the MXT midvalve, which has larger ports, but that mid stack looks SOFT!  It will be softer once you model in float.  BTW, big cartridge, big float.  I'm at 1mm and feel I should go more...

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1 hour ago, bikedude987 said:

You're missing a few parameters in your restackor - namely float.  I have a conventional mid stack on my 300XC - set up for rocky trail - and it works well.  No limit plate and the shims survive well.  I'm running the MXT midvalve, which has larger ports, but that mid stack looks SOFT!  It will be softer once you model in float.  BTW, big cartridge, big float.  I'm at 1mm and feel I should go more...

I have 0.3mm float modeled in the mid valve compression stack.

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Good luck on your quest with the handling of the bike.  I test rode a 17 250TC & 17 250SX in that yr. & didn't like the handling characteristics of the Euro bikes.  I was looking to upgrade an 03 CR250 & ended up keeping it as I felt the newer Euro 250 2t's weren't an upgrade.  

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On 10/4/2019 at 10:42 AM, mxaniac said:

I have 0.3mm float modeled in the mid valve compression stack.

oh, yeah, you listed your pages out of order and I didn't read the titles...

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Thought I should post an update.  These stacks were too soft, it felt very harsh and I thought it was too stiff until I was able to watch someone else ride the bike and realized it was blowing through the stroke.  I also integrated a shim stop into the cup I'd made for float.  I had to tweak some thicknesses to get the nut fully threaded on the shaft after adding shims.  It feels really good now, still plush on the stutter bumps but soaks up the bigger hits better now.

10 clicks on compression, 9 on rebound, and 200mL of oil.

Base Valve Stack (6mm ID)

12x30    0.10
4x28    0.15
26    0.15
24    0.15
2x22    0.15
2x20    0.15
2x18    0.15
2x14    0.15
25    1.50

Mid Valve Stack (8m ID)

4x30    0.10
2x30    0.15
28.00    0.10
2x26    0.11
25.00    0.11
23.00    0.11
22.00    0.11
21.00    0.11
2x20    0.11
2x19    0.11
2x18    0.11
17.00    0.11
15.00    0.25
12.00    0.80
25.00    1.50

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