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Do you really need independent HSC/LSC?

rigidhack

Turbo Monkey
Aug 16, 2004
1,206
1
In a Van(couver) down by the river
Wasn't LSC really taking care of you when you land a jump or drop? It's a big hit but fairly a fast one.
Sorry, but no. LSC is "low speed compression" right? This means that the input into the damper is a low speed input. Think brake dive, pedal bobbing and small bumps. HSC is for the big, quick hits. On a drop, you go from no load to big load in an instant. I find that most people tend to think the two have more to do with the speed the bike is traveling, rather than the speed the damper is asked to respond.

I do agree that getting on a hardtail now and then is a great thing. It forces you to pick lines and be smooth, rather than just riding like you are driving a snowplow. I am seriously considering trying Goats Gully on the HT this season, just to say I did it.

And yes, you can go big (and fast) with no (rear) suspension at all.

 
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P.T.W

Monkey
May 6, 2007
599
0
christchurch nz
Junior-T (with HSCV), Float, 888, Judy, and E150

That's it. I don't make enough money to buy a new one every year so those are the ones that came with my bikes, except the 888.
Hmmm what model Float 32 or 36? RL?, RLC?, RC2? or just plain old R??? :think:
 
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norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,346
1,587
Warsaw :/
Sorry, but no. LSC is "low speed compression" right? This means that the input into the damper is a low speed input. Think brake dive, pedal bobbing and small bumps. HSC is for the big, quick hits. On a drop, you go from no load to big load in an instant. I find that most people tend to think the two have more to do with the speed the bike is traveling, rather than the speed the damper is asked to respond.
I know what LSC typicaly does, same for HSC and I know it has nothing to do with speed you ride. I wasn't simply sure about landing jumps. I had a hazy memory of reading something from a respecable source that LSC had something to damping but I can't recall so I may've been drunk when I've read that ;)
edit:
OK reminded myself what it was exactly - smooth landings are still lsc, unless you have a harsh landing hsc shouldn't be taken into consideration. (can give links but I think it's obvious ;) )


Junior-T (with HSCV)
You put it there yourself? Because I'm sure as hell not junior model had hscv.

So you have never actually owned a fork with both HSC and LSC adjustments?
Actualy I don't see him mentioning which 888 he had - some of them had hsc and lsc
 
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P.T.W

Monkey
May 6, 2007
599
0
christchurch nz
You put it there yourself? Because I'm sure as hell not junior model had hscv.



Actualy I don't see him mentioning which 888 he had - some of them had hsc and lsc
Im guessing the 888 is the 888RC3 ATA he mentions in the first post in this thread.

All im pointing out is that Mr Troll is commenting on a subject he has zero or at best very little personal experience off.
 
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norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,346
1,587
Warsaw :/
Im guessing the 888 is the 888RC3 ATA hes mentions in the first post in this thread.

All im pointing out is that Mr Troll is commenting on a subject he has zero or at best very little personal experience off.
Right. My bad.
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,855
9,559
AK
Actualy I don't see him mentioning which 888 he had - some of them had hsc and lsc
No, they didn't. Even forks with the "X" cartridge didn't have low-speed compression, just the "end-stroke" and an overall adjustment. The valving was too simple to give HSC and LSC control (I know, I have two of these).
 

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,346
1,587
Warsaw :/
No, they didn't. Even forks with the "X" cartridge didn't have low-speed compression, just the "end-stroke" and an overall adjustment. The valving was too simple to give HSC and LSC control (I know, I have two of these).
Well marz claimed they had lsc and hsc. I've heard before it wasnt really it but there were 2 compression knobs so one can be mistaken ;)
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,855
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AK
Well marz claimed they had lsc and hsc. I've heard before it wasnt really it but there were 2 compression knobs so one can be mistaken ;)
I know, or how they claimed that the adjuster on the RC3 was high/low compression, kind of a non-direct way to say it's an overall adjustment that simply makes it harsher rather than does anything usefull.
 

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,437
1,017
My own world inside my head
You put it there yourself? Because I'm sure as hell not junior model had hscv.



Actualy I don't see him mentioning which 888 he had - some of them had hsc and lsc
The JT had what Marz called the HSCV. It was technically a hi speed circuit, but a weird funky circuit, that didnt really do what it was supposed to from the factory, with the moderate 5 weight oil, it really didnt ramp in a usable way.... Most people just called it a bottom out valve. Its not a shim stack, its a valve on a spring, the faster the fork moved/accelerated, the more it could compress the control spring/valve. its on the bottom of the leg when you have the lowers off. I played with the spring on my 66 a bit, and oil weights finally came up with something that works well for me. Alot of people found it to be a system that spiked when it became active, alot of people didnt like it, but I think thats because alot of people dont understand exactly what it is or how its supposed to work.
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,855
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AK
The JT had what Marz called the HSCV. It was technically a hi speed circuit, but a weird funky circuit, that didnt really do what it was supposed to from the factory, with the moderate 5 weight oil, it really didnt ramp in a usable way.... Most people just called it a bottom out valve. Its not a shim stack, its a valve on a spring, the faster the fork moved/accelerated, the more it could compress the control spring/valve. its on the bottom of the leg when you have the lowers off. I played with the spring on my 66 a bit, and oil weights finally came up with something that works well for me. Alot of people found it to be a system that spiked when it became active, alot of people didnt like it, but I think thats because alot of people dont understand exactly what it is or how its supposed to work.
HSCV was a cartridge damper. The Jr T had "SSV" or "SSVF" depending on the year. What you are describing is SSV/SSVF, not HSCV. HSCV used a "base-valve" similer (but much more crude) to what motorcycle cartridge dampers used, this had a piston with compression shims (2) on one side and rebound shims(2) on the other side. I have a picture of it because I sawed one of the HSCV cartridges in half to see what was inside. The low-speed rebound is controled by a piston on a damper-rod connected to the top cap, again with the HSCV cart.

And yeah, I had a Jr T too, it sucked.
 

bikesair

Chimp
Jun 30, 2009
67
0
San Luis Obispo CA
This thread kind of went crazy haha.

No I have never had a fork that had independent HSC and LSC adjustments. Kind of the whole reason for the thread I guess (do I need one?).

Not one 888 had independent HSC and LSC adjustments. To my understanding the compression adjustment on RC3 and RC2X simply changed the port size of the compression piston (closed em up or opened up). Jayem over on MTBR knows the most out of anyone I have talked to about the workings of RC3. With that said it really is a HSC and LSC adjustment (even though its all the same circuit). It will affect how your fork works on LS events and HS events. I wish someone could give a clear answer though on exactly what is going on with what the compression adjustment is doing :think:

Now if what is said above is true, you are always compromising between LSC and HSC. Do you want more LSC? Well then you get more HSC as well. You want little HSC? Well then you get little LSC (the dive issue). The big mistake I see a lot of people making is trying to control bottom out with compression. They ramp up the compression to keep the fork from bottoming out but you do NOT need to make that sacrifice (to your lsc). Use VA...or PAR to do that. From my experience in riding my 888 VA produces a much more progressive feel than PAR. VA starts progressing through the last 20-30% of your travel whereas PAR starts progressing through the last 10% of your stroke. PAR acts more like a bypass imo.

HSCV got described already and yes I did the mod myself. Super-T's came stock with HSCV but the Junior-T's received SSV or SSVF as previously stated.
 

miuan

Monkey
Jan 12, 2007
395
0
Bratislava, Slovakia
This thread kind of went crazy haha.
No I have never had a fork that had independent HSC and LSC adjustments. Kind of the whole reason for the thread I guess (do I need one?).
Unless you have very good understanding of compression damping and know how to use its benefits in real world cycling experience, it's a better idea to keep riding your rc3 fork. I have one and it's a solid, well performing fork.

Not one 888 had independent HSC and LSC adjustments. To my understanding the compression adjustment on RC3 and RC2X simply changed the port size of the compression piston (closed em up or opened up). Jayem over on MTBR knows the most out of anyone I have talked to about the workings of RC3. With that said it really is a HSC and LSC adjustment (even though its all the same circuit). It will affect how your fork works on LS events and HS events. I wish someone could give a clear answer though on exactly what is going on with what the compression adjustment is doing :think:
Bypassing the HSCV with a variable orifice is not really adjusting the HSC. It's actually a LSC setting. Adjusting HSC would involve changing shim preload or oil viscosity.

Now if what is said above is true, you are always compromising between LSC and HSC. Do you want more LSC? Well then you get more HSC as well. You want little HSC? Well then you get little LSC (the dive issue).
Depends on damper layout. Anyway, it's not like an increase in HSC from 1 to 2 will initiate equal increase in LSC. Thus with dual adjusters you are still able to maintain the desired ratio between LSC and HSC. We may even start to consider a layout with 3 stage pistons, but frankly, for an average Joe, adjusting 2 dials correctly is still more than a challenge.

The big mistake I see a lot of people making is trying to control bottom out with compression. They ramp up the compression to keep the fork from bottoming out but you do NOT need to make that sacrifice (to your lsc). Use VA...or PAR to do that. From my experience in riding my 888 VA produces a much more progressive feel than PAR. VA starts progressing through the last 20-30% of your travel whereas PAR starts progressing through the last 10% of your stroke. PAR acts more like a bypass imo.
No. Whether you use VA or PAR, it's a positive-sensitive thing. Whereas HSC damping will work in any part of the travel. Upon high speed square edge impacts, your spring can't provide enough force to counteract the impact, making your fork pack up. Depending on how much force your wrists and arms can withstand, you may use HSC to transfer this bump force to you, keeping your fork from packing. For many amateur riders including me, this is not much of an issue, and they actually don't need to use much HSC simply because they don't ride aggressively enough.

The RC3 has preset HSC damping which you can crank down to some degree with the adjuster if you don't actually need it. The issue is, you lose a lot of desirable LSC in this process. You are better off with a pair of adjusters.

Lastly, PAR is not a bypass. It is a secondary positive air spring that lets you tune the spring curve progressiveness higher than with a traditional Solo Air / Float 2-chamber air spring system.
 
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bikesair

Chimp
Jun 30, 2009
67
0
San Luis Obispo CA
I know what PAR is and I guess now that I think about it can't really be compared to a bypass because it doesn't affect the damping, only your preload. It's more like a bump stop than a bypass (in the auto world).

Position sensitive is exactly what I said about VA and PAR. It has nothing to do with your damping. I understand that. Again, it is more like a bump stop that behaves differently depending on where you are in your stroke. VA being a lot sooner in your stroke than PAR. Of coarse it all depends on how you have the thing set up, so...most of this is subjective.

BUT, thank you miuan for your input.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,031
5,921
borcester rhymes
Sorry to resurrect a trainwreck of a thread, but I'm thinking about sending my DHS back for a retune as the rebound is too slow for my liking and I hate the way bikes ride with slow rebound damping. I'm currently debating whether I should add the Hi/lo adjuster for another $150. I've been extremely pleased with my two avalanche shocks in the past, particularly the one with Hi/lo, but I'm trying stay true to the low-budget intentions of my project. The cost is $125 for a revalve and the adjuster is $150. It'll cost another $85 to add it further down the road if I decide, but if I can do it now and be done, I'll save money in the long run.

I know I said earlier that if you're happy, then who cares, but I had the hi/lo chubbie tuned for great low-speed ground feel but it opened right up when you started smashing rocks. There was also some discussion of crossover between the two adjustments in the past, and I wasn't sure if that meant the upgrade itself was truly necessary or not.
 
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Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
From what I remember of the original build thread it was fairly budget conscious, in that case I think the money will be better put towards other areas of the project. If you are already getting a re-valve specific to your frame, it should be quite good without the additional fine tuning. No doubt the extra adjustment will be better, but is the rest of the bike really at a level where that small loss will be the limiting performance factor? My goal would be to improve the bike as evenly as possible.

A good idea might be to tell Craig your preferences when it gets re-valved, so that those characteristics can be lightly incorporated into the tune without requiring you to spend the extra money for external adjustment.
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,855
9,559
AK
For fun, I sawed open that very damping cartridge, the RC3. It's extremely crude, it's a spring against a washer over the orifice holes, and the rebound is a check valve with no high speed blow off.
 
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djjohnr

Turbo Monkey
Apr 21, 2002
3,001
1,693
Northern California
When I was GM of Bikesmart years ago, we had a pallet of Marzocchi forks. It's so long ago that I don't remember the model, but they were supposed to have either SSV or SSVF damping and were OEMs from a certain manufacturer. About a week after we sold the first one, a buyer called in and said there was no damper in the legs. I pulled one open and sure enough, all that was in there was a "piston" a couple of millimeters thick. That was it. No rebound or compression assemblies. No shims. No check valves. Just a paper thin piston. We call Marzocchi and they sent us a bunch of assemblies, but I feel bad for anyone that bought a bike with those on em.