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Discussion Starter #1
Hello!

I'm looking to bump up my 2019 fox 36 from 160mm to 170mm. I heard they tweaked the air spring for the 2021 model. Does anyone know if I can put the 2021 170mm airshaft in my 2019 Fork?

Thanks
 

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The top out hat is longer for 2019, which means the shafts are 10mm longer. You can swap the hats around and it fits, but in your case you will get a 180mm fork instead of 170. The change that actually improves performance for 2021 happens in the stanchion (higher dimple/longer stanchion) so it will still ride like a 2019 fork too
 

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Discussion Starter #3
The top out hat is longer for 2019, which means the shafts are 10mm longer. You can swap the hats around and it fits, but in your case you will get a 180mm fork instead of 170. The change that actually improves performance for 2021 happens in the stanchion (higher dimple/longer stanchion) so it will still ride like a 2019 fork too
Wow thanks for the great reply! I'm thinking the better solution is going to a 170mm 2019 air shaft with a luftkappe mod. Any thoughts on that?


Jon
 

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Discussion Starter #5
That will be quite progressive at 170mm travel.
Huh, I figured going from a 160 to a 170 would increase the positive air chamber volume and therefore help offset the progressivity add of the luftkappe. What's the science behind your comment?

Jon
 

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Huh, I figured going from a 160 to a 170 would increase the positive air chamber volume and therefore help offset the progressivity add of the luftkappe. What's the science behind your comment?

Jon
No the positive air chamber size is the same at top out but at bottom out its smaller. A Luftkappe makes it even smaller.
 

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Huh, I figured going from a 160 to a 170 would increase the positive air chamber volume and therefore help offset the progressivity add of the luftkappe. What's the science behind your comment?

Jon
The size of the positive air chamber does not change when you change out the air shaft, the net effect of the air shaft is to move the lovers further away from the crown. That is why when you lock at the number of volume spacer over the travel range the lower travel options start out with more tokens. So the higher the travel the higher a compression rate the positive chamber have.
 

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Discussion Starter #8
No the positive air chamber size is the same at top out but at bottom out its smaller. A Luftkappe makes it even smaller.
Ahh ok that makes sense. I may give it a shot anyhow. I'm not even sure if a luftkappe will work on a 170mm conversion. I emailed them to find out. Based on what you said I could see there not being enough room in the positive chamber (or it would only let me run 2 tokens instead of 4)
 

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Ahh ok that makes sense. I may give it a shot anyhow. I'm not even sure if a luftkappe will work on a 170mm conversion. I emailed them to find out. Based on what you said I could see there not being enough room in the positive chamber (or it would only let me run 2 tokens instead of 4)
I have the 2019 29er version in 170mm. Run no spacers and fox recommendations +1-2psi

It's hard to bottom it out with no spacers at the fox recommended settings. If you don't ride aggressively you'll never bottom it. But I assume if you want a 170 fork you ride hard.

I have to basically send a 4+ft drop to flat where the 'landing' is big rocks and roots to do it. Most rides I have ~20mm of "oh ****" travel left

I'd ride the stock 2019 170 for a ride or two to make sure you ride hard enough that you'd still be able to bottom a more progressive fork.
 

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Discussion Starter #10
I have the 2019 29er version in 170mm. Run no spacers and fox recommendations +1-2psi

It's hard to bottom it out with no spacers at the fox recommended settings. If you don't ride aggressively you'll never bottom it. But I assume if you want a 170 fork you ride hard.

I have to basically send a 4+ft drop to flat where the 'landing' is big rocks and roots to do it. Most rides I have ~20mm of "oh ****" travel left

I'd ride the stock 2019 170 for a ride or two to make sure you ride hard enough that you'd still be able to bottom a more progressive fork.
Thanks for the reply. I'm mostly going to a 170 because I intend to slacken my La Sal Peak from 65-63.5ish degrees and don't want to stack height to drop. I recently rode a fox 38 and notice the top end suppleness which I attributed to the larger negative air chamber (could be totally wrong!). That's what I was trying to achieve with the luftkappe. I don't think I need a 38 from a stiffness perspective (I like the idea of a lighter fork for my weight (160 lbs).
 
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