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PostPosted: Sat Dec 14, 2013 3:07 pm 
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friendly kitty

Joined: Sat Oct 19, 2013 9:27 am
Posts: 286
Copy-paste from another forum:

Way back, I mentioned the possibility of modifying Rock Shox' Pure damper so as to lessen the severe spring progression that occurs towards the end of the travel. The issue is that the floating piston that seals the top of the damper oil chamber is spring-loaded. As the fork compresses, this spring compresses as well, and adds even more spring progression than what is already available due to the decreasing volume of the positive air chamber. Essentially, this mod just turns the Pure system into Manitou's TPC.

In essence, both of these systems are virtually identical (hence the patent dispute a while back), but Manitou simply runs a higher oil level that ensures that the compression piston is always immersed in oil, provided the bike isn't inverted.

The mod is simple: remove the Pure compression assembly, then unscrew the top cap from the shaft. Remove the o-ring and washer, then remove the IFP spring and IFP. Slide the IFP back on to the shaft (w/o the spring!!!), then the washer and o-ring, and reinstall the top cap. The oil level is fairly critical; too little and the oil will foam, and too much will create too much pressure in the system during compression, effectively recreating the problem (I think I ran about 75cc of 5wt oil, but I am still playing with it a bit). Once you've checked the oil volume, reinstall the compression damper (with the adjuster rod in place!!!); the IFP is still necessary to seal the top of the Pure tube which is why it's still there.

Provided you've done everything correctly, the compression piston will always be immersed in oil (therefore, the lockout will work as well), there will be no cavitation problems, and the fork's spring rate will be a bit more linear. I tested this setup at Iceman this past weekend and came away pretty happy with it. I don't have hard numbers for you, but my World Cup certainly feels a bit more linear, and I did use more travel than I normally do.

tl;dr: Remove the spring from the Pure compression damper and wallah, you've got a SID with TPC! No more bleeding is a nice plus too!


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PostPosted: Sat Dec 14, 2013 3:45 pm 
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big hucker
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Joined: Wed Jan 16, 2013 7:32 pm
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Location: Dallas, TX
That is very interesting. On what year SID did you perform the mod? As I recall, the Pure Delite had an IFP. But, none of my Pure dampers did. I'll browse through my diagrams later to get a better idea of the process.

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PostPosted: Sun Dec 15, 2013 11:26 am 
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friendly kitty

Joined: Sat Oct 19, 2013 9:27 am
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marpilli wrote:
That is very interesting. On what year SID did you perform the mod? As I recall, the Pure Delite had an IFP. But, none of my Pure dampers did. I'll browse through my diagrams later to get a better idea of the process.

2004 Sid Team on my winter bike.


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PostPosted: Sat Jan 18, 2014 8:04 pm 
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friendly kitty

Joined: Sat Oct 19, 2013 9:27 am
Posts: 286
Can't edit the OP, but here's another mod I got from LeegBier:
Know that spiking feeling with the Pure damper? If you're doing the TPC mod, I suggest flipping the upper piston over, the bigger holes on the lower side will resist spiking quite a bit now.


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