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DSD Runt or Avalanche Hybrid coil air?

missingLink

Chimp
Apr 14, 2006
39
3
I currently have a Fox 36 160mm for 27.5 with an Avalanche damper. I really like the performance of the fork, but reading about the Runt has me curious. It would be nice to get a little more support/less dive out of the fork while improving small bump compliance. For reference, I live/ride around the PNW/Seattle region. Tiger Mountain/I-90 corridor etc. trails. I like fast tech trails, with small ~5ft drops and jumps. Nothing too extreme.

I like the simplicity of the Runt but wondering if it's going to be too harsh for someone 150lbs? Also, I just found out about the Avalanche hybrid coil/air mod that sounds great too. But I'm not too keen to add that much weight unless it performs considerably better than the Runt. Price is about the same.

DSD Runt: https://diazsuspensiondesign.com/runt
Avalanche Coil/Air: http://www.avalanchedownhillracing.com/Cartridge Kit/Dual coil conversion option.htm

Looking for some feedback with riders who've had experience with one system or both if possible. Speculation welcome too :)
 

StiHacka

Compensating for something
I like the Luftkappe in mine. Simple, lightweight, no need for complicated gadgets.
 

slimshady

¡Mira, una ardilla!
The Runt works the same way Manitou's IRT does. It's a secondary chamber you usually pump to twice the pressure of the primary, and whose volume varies as the fork compresses. It shouldn't be harsh at all from what I know about the IRT. You might have to play with both chambers' pressures at first, but once you have them sorted it will surely improve the fork's support in the midstroke and the initial sensitivity.
 

jonKranked

Press Button, Receive Stupid
Nov 10, 2005
67,691
11,455
media blackout
The Runt works the same way Manitou's IRT does. It's a secondary chamber you usually pump to twice the pressure of the primary, and whose volume varies as the fork compresses. It shouldn't be harsh at all from what I know about the IRT. You might have to play with both chambers' pressures at first, but once you have them sorted it will surely improve the fork's support in the midstroke and the initial sensitivity.
Paging @jonKranked about the IRT in his Mattoc...
i can't comment on the Runt, only the IRT based on my experience with a first gen Mattoc pro.

first, you don't exactly want double the air pressure, but you do need a significant pressure differential between the two chambers otherwise you won't get the intended benefits. manitou's chart for it lists about a 40psi pressure differential across the board, which for the lightest riders may wind up being roughly double. for me it was like a 50% increase or thereabouts.

second, it more or less functions as a dual rate air spring. the main chamber has a lower pressure to provide better sensitivity on the initial stroke through midstroke. as the fork compresses the pressure in the main chamber will approach the pressure in the secondary (IRT) chamber until they are equal. at this point both chambers will compress as the fork continues through its travel. once the pressures are equal, you also have effectively increased the chamber volume, which will make the air spring act a little more linear than normal.
 

mykel

Turbo Monkey
Apr 19, 2013
3,080
1,588
sw ontario canada
I have a RUNT in an Avy'd Lyric/Yari.
It is better than the stock airspring ( I also have an IRT Mattoc ) and yes you need to run a significant pressure differential in both. I'm usually at about 1.7/1.8. You can lessen the main pressure by a couple of pounds to get a bit better small bump, but not lose out in the midstroke because of the secondary chamber. RUNT volume is about the same a single token.

On thing the RUNT did not help with (wasn't expecting it to) but I'm still getting 10mm of the dreaded debonair suckdown. Supposedly fixed with the new airspring assembly, but they said that about the last update - but at this point, I'm still not happy with the way an air spring feels and want to go back to a coil fork.

I was looking at the Avy hybrid spring, but I'm 200lbs and that is the limit for the Lyric/Yari chassis. (Physical limitation of the fork precludes a heavier spring - max for a 150mm Lyric is a 20lb spring. For this spring weight the optimal rider weight is 150-175, so at my weight it would need too much air and I would lose quite a bit of the coil benefit.

Looking at a Vorsprung Smashpot. No worries as my Avy cart does not have the ABS, so just a weight penalty of a pound and a hit to the wallet. Then will put the RUNT up at the pink place and try to recoup a few monopoly monies.

Both the RUNT and the Avy system should give you better small bump and a firmer midstoke. My guess would be that the Avy would be a bit more supple due to the much lower air pressure required and having a spring in each leg which should reduce flex and let things move a bit more freely.
 

missingLink

Chimp
Apr 14, 2006
39
3
Thanks everyone for your insights. At my weight I’m leaning towards the avy coil/air system especially since I already have the damper. The claim of smoother action and an actual coil is enticing.

Been reading reports of the Runt perhaps riding a little too high in the travel which I’m a little wary of. The 1:1.6/7 ratio sounds like the way to go though.
 

missingLink

Chimp
Apr 14, 2006
39
3
Well I ended up getting the Avy coil and long story short, it is amazing. Exactly what I wanted. Super supple of the top and great midstroke support. The Avy damper was already fantastic and the hybrid air/coil system made it even better.

At my weight (145-150lbs) I’m running about half the air pressure now. Backed off the compression and now have it around 4 clicks from full open. Slowed down my rebound by one click.

On a fox 36 160mm I’m now using about 110-120mm where I normally would use about 150mm. Funny thing is it feels about the same amount and perhaps even more bottomless because the progression is just so smooth and composed. It’s given me so much more control.

It sounds like these coils are selling well as it took about 7 weeks to arrive after I ordered. Well worth the wait though.
 

jonKranked

Press Button, Receive Stupid
Nov 10, 2005
67,691
11,455
media blackout
Well I ended up getting the Avy coil and long story short, it is amazing. Exactly what I wanted. Super supple of the top and great midstroke support. The Avy damper was already fantastic and the hybrid air/coil system made it even better.

At my weight (145-150lbs) I’m running about half the air pressure now. Backed off the compression and now have it around 4 clicks from full open. Slowed down my rebound by one click.

On a fox 36 160mm I’m now using about 110-120mm where I normally would use about 150mm. Funny thing is it feels about the same amount and perhaps even more bottomless because the progression is just so smooth and composed. It’s given me so much more control.

It sounds like these coils are selling well as it took about 7 weeks to arrive after I ordered. Well worth the wait though.
good to know. i have a 2015 36 of the 27.5 variety, and have entertained ideas of ways to improve it should i decide to go 275 for my new bike vs 29.
 

missingLink

Chimp
Apr 14, 2006
39
3
good to know. i have a 2015 36 of the 27.5 variety, and have entertained ideas of ways to improve it should i decide to go 275 for my new bike vs 29.
The Avy damper and coil system is a big investment for sure. I was wondering something similar as I’m considering a 29er as my next bike. Craig told me you can swap the cartridge/coil system over to the 29 fork as long as it’s the same travel and model of fork. In my case, Fox 36 160mm. Although I hear great things about the Grip2 damper so I wonder if it will need it.
 

Jm_

sled dog's bollocks
Jan 14, 2002
12,207
4,163
AK
Why would you want to downgrade from a cc to an oc?
I've never had the theoretical advantage of a CC materialize and the ease of maintenance, nothing to bleed, makes it a no-brainer with the OC. Except in the most weight-weenie of applications, the lubrication and reliability of an OC wins every time. Nothing is more frustrating than those CC sucking in oil and air and losing their effectiveness. I know a CC can also have an ABS, but the ABS in the OC is just magic and you also get the oil level tuning possibility. Also, friction, as in the the cartridge slides so effortlessly with no air-tight seals. Again, I know CC can theoretically be better, but year after year all I gotta do is a few oil changes. It's a win-win for me.