sem fiddy pilot
Poos, where are you?? Some time ago I recall you mentioned something about the merits etc of 25mm cartridges, and I can't be arsed searching way back to find it.
Surely a 25mm diameter piston is going to displace more fluid for any given movement, and with bigger diameter cartridge shims, this will be easier to control? Been thinking about this a bit, and would welcome feedback from KB land
Member, sem fiddy appreciation society
Originally Posted by PrincessBandit
Forum whore
MY thoughts have been...shall we say modernised on my thoughts..
where my theory on the matter was in displacing fluid...a given piston size and rod size...comapared to a larger rod and piston size...in regards to displacing fluid...was that both were displacing fluid...and displacing that fluid is whats required to build damping...what I was not so much as arguing [debating] was that, relitive to capacity within the cartridge...and size of the rod...they were still both displacing a similar amount of fluid at a similar rate...But in actual fact I was incorrect in how it related to the action of building damping...Where infact the smaller diameter cartridge and rod built damping slower..there for letting more stroke occure before it start resisting the action...not good for brake dive control [whick could be corrected with different inernal valving no doubt...but at the expense of loosing other attributes] [and I'm sure robert or JDRacing will be along shortly to correct me if I'm wrong in this case? **prays that I'm not far off the ball park**]
sem fiddy pilot
One of the reasons I ask, is that I now have a set of 25mm cartridges in my bike, and a characteristic I am noticing is a lot less travel being used in general day to day road riding, but not at the expense of harshness. For any given bump the forks are moving less, but the damping is doing it's thing just as if not more effectively than if more travel was being used. I really want to know how/why this is happening, and as mentioned in the first post, would be very receptive to inputs from the rest of KB
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Rest In Peace
From all accounts of road tests on your bike, it is a minter. "...The best handling GSXR I've ever ridden..." I believe was the expression used. You're not worried about its handling are you?
The theory that bigger is better sounds right to me as the 25mm is going to have to work less hard than the 20mm - that just sound right. That's as far as I know because it must get into the Theory of Hydraulics which I bet your 'supplier' could explain pretty well.
sem fiddy pilot
I'm thrilled with the way it handles, Grub. I'm just very interested to get to the bottom of WHY. I'd love to hear for/against ideas on the 25mm concept
Member, sem fiddy appreciation society
Weekend cruiser
The only displacement in a cartridge is that from the damper rod, a K1-K6 GSXR 1000 with a 12.5mm damper rod and 20mm cartridge will displace more fluid than a TL1000 25mm cartridge with a 12mm damper rod, the damper rod is bigger so more fluid is displaced.
The difference is in the swept volume....the amount of fluid the rebound piston passes through.
Pussy your forks have a compression stack on the back of the rebound piston which slows down the speed at which the piston moves through the cartridge thats why you use less travel, the velocity that the forks achieve for a given bump is less.
If Cowpoos did the same to his 20mm cartridges he could achieve the same thing it's just a lot, lot more difficult to pressure balance a 20mm cartridge.
sem fiddy pilot
So, is it generally easier to control 25mm set ups?
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Forum whore
Probally more a evolution of technology and valving spec has as much to do with it as size of the cartridge..and at a guess with more spirited riding you would use more travel as high G-force,bump loadings are applied!!
But I think Jdracing has probally summed it up from a technical aspect in his post quite well.
sem fiddy pilot
Have a ride of it sometime, Poos, and you'll see what I mean. I am running one step DOWN from standard spring weight as well (.95 installed, stock 1.0).
It's showing up how effective the mid-valving is... even giving it a good punt on the rougher stuff, you'll be surprised how little fork travel is used for very effective damping
Yep, JDRacing's explanation is a goodie
Member, sem fiddy appreciation society
Forum whore
I think what he's eluding to is...its easyier to set up/get a good comprimse on the cartridges you have because of the thicker damping rod [14mm ??] and the compression stack your rebound valve has on the back off it...but I dare say there is a lil more to it than that..because the cartridges and any suspension product are only as good as they are setup!!
But on a side note...using less travel may relate to alot of other things aswell...when the cartridges were initually valved and installed..the instal may have had the impression that you were a faster rider than you actualy are...and heavier braker..and they were valved to suit this impression..besides the fact they still work faultlessly in your impression..there still maybe alot more tuned into your setup than you have realised! and credit goes to the technision for make his product usable across a range of abilities and circumstances..sounds like a almost perfect compromise!!
sem fiddy pilot
No secret that Robert set the spec for me... he has been doing suspension stuff for me since 2000, and knows what I like.
What I REALLY want to know is the good oil on 20mm versus 25mm. Where are you, RT? TDC?
C'mon, there's more than one or two of you out there who can enlighten us
Member, sem fiddy appreciation society
Forum whore
I don't think stock spring rate is 1.0...more like .80 I may be wrong...but 1.0 is very heavy for a stock front spring in any sportsbike...and I have ridden stock 750/600...and its a pretty cool bike stock..but seeing as I've been riding on superior suspension for a while I felt its faults easily..front had shit feel..and a odd odd feeling over multiple sharp edge bumps..not sure what sort of feel it was..but I remember it was enough of a odd feeling for me to back off!! other impressions were..bugger all ground clearence..and the rear felt like a typical modern suzuki..out in the dark [because I personally reckon the seats are to dam comfortable!!] with feel..harsh damping..lowly sprung...
And yer..I would love to take her for a spin sometime...I'd preffer on a track though [as I'm not partial to road riding these days]...I have never ridden a bike with the newer ohlins 25mm cartridges installed..and apparently they are good with brake dive control...which is a rea I would dear love some improvment in my front end!! [and feel!! lots more feel!!]
Forum whore
lol...the good oil...that open to debate I suppose...hahaha...Maxima and ohilns oils are well rated in suspension circles...but It probally depends on what your used to working with to a degree!! [i know thats not what your meaning..lol]
sem fiddy pilot
On the 750 the stock spring actually is 1.0, the 600 is .90. I'll lay money that odd feeling you mention was the weak high speed rebound. Robert has taken care of that in the other 750 that lives here.
I don't remember what the stock rear shock felt like, it was only on the bike for a few days after I bought it
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Weekend cruiser
The size of the cartridge is just one of many factors involved in achieving a desirable rate of compression and extension.
Spring rate, air gap, oil viscosity, damper rod size, the size/ number/ position of the ports, the valving on the ports, the bleed size etc all contribute to the overall action of the forks. Taking all of that into account it's possible to have very bad 25mm cartridges as well as very good 20mm cartridges.
The fact that the new Ohlins cartridges provide instant solutions to the action of the previously popular manufacturers product is not solely down to it being 25mm.
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