View Full Version : Fork Springs-K-tech Linear vs Maxton progs?
DarrenChay
08-09-09, 08:56 PM
Hi All.
I've now received my zx10r shock to upgrade my curvy's rear end, but which fork spring replacement is best for the front?
I'm not looking to swap the front end, just replace springs and oil.
at over 18st i know i need 0.9 springs and possibly 15w oil, but i've heard different views over the Linear versus Progressive springs.
any views/advice always appreciated.
cheers
Daz
i went k-tech as their local.
yorkie_chris
08-09-09, 09:11 PM
I'd go Ktech (or any linear, a spring's a spring). The damping can be better set up with linear.
Depending on how heavy you are I might suggest .95 springs though.
noob-saibot
08-09-09, 09:49 PM
How do you figure out what rate you need for linear?
urbane1
08-09-09, 09:56 PM
I've just fitted Race-Tech linear springs and have found a great improvement over the standard.
If you go onto their website they have a spring calculator. Based on that for street use and 252 lbs they are recommending a .95 spring
rictus01
09-09-09, 01:33 AM
any change will give an improvement unless of course you are a 7 stone little jap guy.
Linear or progressive?
well technically Linear are better and if all roads were track smooth that's the option I'd go for, however "real world" there not, so unless you are setting the bike up for a single purpose my choice would be to fit true Progressives (progressive springs come in a couple of flavours, those that have a tightening whined the whole length and those that have two different sections to them), but it's a personal choice, I've not met anyone who's changed from standard to either and not been pleased with the results.
Cheers Mark.
robh539
09-09-09, 06:37 AM
hi, i have been looking into this, as my forks are knocking. I was looking changing the springs while i was at it. If you set it up for your weight (which i understand), what happens when you have a pillion on, the set up will not be correct anymore?
ta
STRAMASHER
09-09-09, 08:27 AM
My forks are in getting K-Tech linears. Never fancied progressive springs. I want consistancy and fixed up by somebody with a clue.
Let you know in a week.....
.... how pishy and tired my rear shock is.:rolleyes::)
yorkie_chris
09-09-09, 08:52 AM
any change will give an improvement unless of course you are a 7 stone little jap guy.
Linear or progressive?
well technically Linear are better and if all roads were track smooth that's the option I'd go for, however "real world" there not, so unless you are setting the bike up for a single purpose my choice would be to fit true Progressives (progressive springs come in a couple of flavours, those that have a tightening whined the whole length and those that have two different sections to them), but it's a personal choice, I've not met anyone who's changed from standard to either and not been pleased with the results.
Cheers Mark.
Aye, but the duel rate flavour of progressives also give a progressive curve, 2 springs "in series" don't act same as 2 springs in parallel.
Dave20046
09-09-09, 09:18 AM
Aye, but the duel rate flavour of progressives also give a progressive curve, 2 springs "in series" don't act same as 2 springs in parallel.
I've been told/heard they were just an 80s gimmick. Meh miles better than the standard flumps.
yorkie_chris
09-09-09, 09:58 AM
The problem is they make the forks either overdamped at the top, or underdamped at the bottom.
The more you learn about suspension, the more you realise how crap the stock damping is.
I still have to get my .85/.9 springs.
Upgraded the oil to 15w, I currently have progressive springs in from the last owner, I don't rate them at all.
With the previous oil, and the progressives, I could easily bottom the front out buy putting on the front brake and moving forward and backwards, was too soft. Slight improvement with new oil, still not great.
Will be getting linear springs soon.
Dave20046
09-09-09, 01:16 PM
I still have to get my .85/.9 springs.
Upgraded the oil to 15w, I currently have progressive springs in from the last owner, I don't rate them at all.
With the previous oil, and the progressives, I could easily bottom the front out buy putting on the front brake and moving forward and backwards, was too soft. Slight improvement with new oil, still not great.
Will be getting linear springs soon.
Either you have amazing brakes and hide your weight well or the previous owner lied about the springs? (or installed crap ones). My progressives have about 15mm reserve after hard riding/braking etc.
yorkie_chris
09-09-09, 01:45 PM
Sally rides properly, even if he does have a pointy.
Dave20046
09-09-09, 04:17 PM
Sally rides properly, even if he does have a pointy.
I thought braking hard would be the most efficient way of exposing the travel?
yorkie_chris
09-09-09, 04:21 PM
That's what I mean by riding properly lol.
But, under heavy braking some more stiffness can be had by reducing the air gap.
Dave20046
09-09-09, 04:22 PM
That's what I mean by riding properly lol.
But, under heavy braking some more stiffness can be had by reducing the air gap.
An endos an endo lol.
Edit: infact it's probably not (seen some nice nose to tarmac ones)
DarrenChay
09-09-09, 08:01 PM
thanks for the views guys, that'll do nicely.:D
Linear .95's it is then!:smt026
cheers
Daz
yorkie_chris
09-09-09, 08:27 PM
I'm not guaranteeing either way, but maybe the 15w will be too light. I would personally go for one of the higher viscosity 15w oils or make a 17.5w blend if they only do 15 or 20w.
Anyway, it will be a major improvement over stock with 15w in, so if it feels a bit bouncy on rebound afterwards, then you know what to change!
yorkie_chris
09-09-09, 08:28 PM
http://img374.imageshack.us/img374/5305/oildata2ft0.gif
Dangerous Dave
10-09-09, 12:54 PM
Quick and Easy: Progressives and oil to suite your weight.
Expensive yet Perfect: Linear, oil to match your weight, and Race Tech Emulators.
Either way it will be a big improvement over stock.
yorkie_chris
10-09-09, 01:20 PM
Perfect:
No such thing! And emulators are an improvement, but nowhere near.
Sally rides properly, even if he does have a pointy.
........
Thats what I mean by riding properly lol.
But, under heavy braking some more stiffness can be had by reducing the air gap.
How do I reduce the air gap?
I personally, in my experience, don't see much difference with my old pointy(standard springs+oil) or the progressives + standard oil.
There was a noticeable difference between standard oil and the 15W oil.
Oil is matched.
Springs can be ordered.. (will be ordered when I have the cash.
What the hell are emulators?
Bluepete
10-09-09, 01:49 PM
Can I ask a bone question?
Do new springs REALLY make a difference, or it a placebo? ie, "I've spent money on it, therefore it's better"
I know it sounds daft, but I have so little idea about suspension it's almost untrue!
Chris, would I benefit from a set of new linear springs and oil?
yorkie_chris
10-09-09, 01:56 PM
No it does definately make a difference. I know what you are like when you decide to brake and that will almost certainly put the stockers on the bump stops!
Luckypants
10-09-09, 02:08 PM
No it does definately make a difference. I know what you are like when you decide to brake and that will almost certainly put the stockers on the bump stops!
Was just about to post the same thing. If you brake to properly slow down fast, rather than for comfort, then you will definitely benefit from springs to match your (considerable! :smt003 ) weight. When I changed the springs on the SV (and now the VFR) to match my weight, braking was much enhanced due to the reduced dive. Getting the damping right means the forks recover and settle much faster to, so much more confidence inspiring.
I used to run out of spring travel very quickly on the track, having only the bump stops and tyres for suspension under hard braking is not a pleasant experience.
The emulators and heavier oil totally transformed the bike under braking.
yorkie_chris
10-09-09, 02:37 PM
Aye, proper compression damping means you weight the front tyre MUCH faster meaning harder braking, sooner. Ace.
Bluepete
10-09-09, 03:11 PM
match your (considerable! :smt003 ) weight.
:smt098
Dave20046
10-09-09, 03:45 PM
How do I reduce the air gap?
More oil I think?
yorkie_chris
10-09-09, 04:22 PM
More oil I think?
Yes
Bluepete
24-09-09, 07:23 PM
No it does definately make a difference. I know what you are like when you decide to brake and that will almost certainly put the stockers on the bump stops!
I took your advice.
A pair of shiny K-Tech linear springs are now here, 15wt oil too. That's this weekend's fun sorted! Hopefully the new can will arrive too.
Pete
Interesting thread. I need me some better spings and thicker oil.
But, what are Race Tech Emulators and how do they work/what are the effects?
Are word for word brake down for a dumb ass will be much appreciated. :D
Just as an aside, having tried different makes of fork oil in various bikes, and having studied some of the blurb (http://www.peterverdonedesigns.com/lowspeed.htm) and the table as YC showed, I got hold of some Silkolene Pro RSF which has a very high VI (in other words, the viscosity doesn't change as much with temperature as other oils).
The viscosity at 40C of the 10W Motul oil I had been using seemed to match the 7.5W Silkolene RSF, so despite sounding like an unwise move that's what I put in the SVS (linear 0.85 k-tech springs).
Having done more miles now I find it quite a pleasant result, it makes for a very "refined" ride quality with no real evidence of under-damping for my riding style anyway. I definitely noticed the old oil would get more supple as it warmed up, this doesn't give the same impression at all, being much more consistent. Recommended :thumright: , and not as expensive as the Red Line oils.
Unless it deteriorates significantly, I'll probably use the same next time. If you prefer a firmer ride (Matron) then the RSF 10W would probably be better, but note that it sits firmly amongst the "other brand" 15W oils so it definitely one notch up on what it appears to be.
Dave20046
24-09-09, 08:48 PM
Interesting thread. I need me some better spings and thicker oil.
But, what are Race Tech Emulators and how do they work/what are the effects?
Are word for word brake down for a dumb ass will be much appreciated. :D
Sorry for the OT but out of interest binky do you have a completely standard front end?
p.S sorry for being wierd on the phone today, was with my boss and was passing it off as a business call!
Sorry for the OT but out of interest binky do you have a completely standard front end?
p.S sorry for being wierd on the phone today, was with my boss and was passing it off as a business call!
Yes. Still not fitted my new shock yet either, so that's still standard as well. My bike needs a lot of looking after this winter. :(
Forks haven't been serviced in at least 20,000 miles either.
P.S. Didn't notice anything weird on the phone today.
punyXpress
24-09-09, 10:11 PM
.org business is the most important there is!
yorkie_chris
24-09-09, 10:29 PM
Interesting thread. I need me some better spings and thicker oil.
But, what are Race Tech Emulators and how do they work/what are the effects?
Are word for word brake down for a dumb ass will be much appreciated. :D
Emulators add another valve, which gives some control over the compression damping.
It's a bodge, but an effective one. The problem is it does nothing for the rebound circuit.
DavieSV
24-09-09, 10:35 PM
But, what are Race Tech Emulators and how do they work/what are the effects?
:D
I put the emulators in mine with linear springs
Transformed the front end, but I did have to lift the forks through the yokes to notice the mid corner stability
the emulators control the compression damping of the forks that is tunable through the adjustment of a spring (removal of emulator required)
the rebound is now controlled by the thickness of the oil. I have 20 wt in mine.
Fully adjustable suspension in a cheap and nasty fork leg :D
note: damper tubes need to be drilled, so no turning back
yorkie_chris
24-09-09, 10:42 PM
I put the emulators in mine with linear springs
Transformed the front end, but I did have to lift the forks through the yokes to notice the mid corner stability
the emulators control the compression damping of the forks that is tunable through the adjustment of a spring (removal of emulator required)
the rebound is now controlled by the thickness of the oil. I have 20 wt in mine.
Fully adjustable suspension in a cheap and nasty fork leg :D
note: damper tubes need to be drilled, so no turning back
:smt076:smt044
That damping is just the preload on the compression valve, it controls the point where the compression valve pops open, it's not nearly as tuneable as a real shim stack.
As I understand it, the preload on the valve won't have much effect on the HSC side of things.
DavieSV
24-09-09, 10:51 PM
The problem is it does nothing for the rebound circuit.
the rebound is now controlled by the thickness of the oil
It is the damping that I needed to control. That's why I had the emulators.
Under hard braking for a corner, the sv's rebound was so soft, when you let of the brake, the weight transfered to the rear so quick that the front went light just as I was turning in. That's why sv's don't brake into corners IMO
I can now brake hard, turn in and have confidence that the front tyre is still gripping.
Slow down YC you reply before I can type:smt097
DavieSV
24-09-09, 10:57 PM
:smt076:smt044
That damping is just the preload on the compression valve, it controls the point where the compression valve pops open, it's not nearly as tuneable as a real shim stack.
As I understand it, the preload on the valve won't have much effect on the HSC side of things.
As I see it, thicker oil flows slower through an orifice than thinner oil,
The emulators restrict oil flow by spring pressure on a valve (compression)
The emulators do not restrict return flow through a lighter spring pressure on a return valve.
The return flow (rebound) is controlled by the return through this valve by viscositiy
I may be wrong, but the rebound on mine is brill
yorkie_chris
24-09-09, 11:01 PM
I fully agree that the emulators are a huge improvement on stock.
I thought that the rebound was still controlled by the holes in the damper rod though rather than by return valve.
DavieSV
24-09-09, 11:43 PM
more holes are needed to be drilled through the damper rods to allow the oil to flow free though to the emulator.
That is why it is irreversable, unless you buy new damper rods
rather than start a new thread thought i would post here, hope thats ok.
i have a k9 sport and i spoke to my mechanic and he was saying something about putting valve springs on top of the existing fork springs to compress them even more with full preload. he said this would be a cheap method and i shoudl see how i get on with these.
otherwise he said he woudl charge £50 labour for fitting k-tech linears and he would supply the oil, i supply the springs.
does the valve spring idea seem ok (said would be about £20). or should i just get the linears?
any help would be much appreciated
yorkie_chris
25-09-09, 03:52 PM
Hillbilly progressives lol. I do not think they'd be too effective.
does the valve spring idea seem ok (said would be about £20). .....any help would be much appreciated
£20 wasted.
The suggestion hardly justifies comment, but in a word putting any spring in series with another reduces the spring rate (makes it softer). In detail, unless it's a valve spring out of a big diesel or similar, it'll simply go goil-bound and become a "spacer", the weight on the front of a bike will be more than 2 bike-type valve springs would support (even if it was a good idea, which it isn't).
Some people have shortened standard fork springs to increase the stiffness, the main problem is that it reduces the available travel, plus you need to make suitable provision for the cut end (not closed coils so not flat). All in all a rather unsatisfactory compromise.
Just bite the £70 bullet and go with proprietary springs of a suitable design.
Bluepete
26-09-09, 05:08 PM
Done mine, took an hour including a quick trip to get more oil 'cos I didn't get enough!
Thanks Y-C for the advice, I'll ride it tomorrow to check.
Pete ;)
Done mine, took an hour including a quick trip to get more oil 'cos I didn't get enough!
Thanks Y-C for the advice, I'll ride it tomorrow to check.
Pete ;)
What was the verdict Pete?
Think i'm settled on Linears but not sure where to go from there... :( Hagon, K-Tech, Maxton etc ???
What was the verdict Pete?
Think i'm settled on Linears but not sure where to go from there... :( Hagon, K-Tech, Maxton etc ???
I have progressive's, and they are not great.
Just bought a set of K-Teck .85 linear springs for the front from DANINPLYMOUTH, will get back to this thread if I notice a difference.
Before I got the bike, it had 7W oil and progressives, was terrible..
Got 15W oil, improvement but not great, don't like the progressives..
Hopefully 15W oil and .85 springs will do the trick.. :)
yorkie_chris
05-11-09, 05:39 PM
What progressives? Stock ones look progressive.
Mmm I duno, they looked like progressives, I just presumed..
I couldn't see the previous owner needing to change springs, she was lyk 6 stone..
Maybe they were stock, bah...
yorkie_chris
05-11-09, 05:42 PM
Would explain why they weren't nice.
Is there likely to be much difference worth talking about between the main brands?
Also, where can i find out what spring rate i need and oil weight? There's a table or calculator thing somewhere, but i can't seem to find it...
yorkie_chris
05-11-09, 05:55 PM
Between brands of linear no, progressive maybe.
racetech website has calculator
http://old.racetech.com/evalving/menu/searchstreet.asp
I'm not a quick rider by any stretch of the imagination but I do value decent suspension. Back when I had a Honda Bros I swapped the OEM springs for progressives and then tried linear. I found the progressives were better at absorbing small bumps like tar strips but the linears were better for higher speed bumpy stuff. As I really only commute on a bike and dont do track days I sold the linears and kept the progressives as they suited me better.
rory182
25-11-09, 08:26 PM
My curvy has braided hoses fitted so the brakes are pretty solid, I'm a relatively new rider so don't really know what's right or wrong when it comes wrong to motorcycle handling.
I'm 105kg (16.5 stone) the forks have standard springs in them but the previous owner gave me some Progressive springs with the bike, I was intending to fit them along with new fork seals and maybe a heavier oil but have no idea what would be the theoretical best solution.
I try not to brake too heavily, I don't enter corners too fast still gaining confidence but I think the front is too soft for my weight, I'm 6ft 3 so I guess have more weight over the front than smaller people and more weight transfer when braking.
The progressive springs are by a company called Progressive Suspension funnily enough.
-Ralph-
25-11-09, 09:56 PM
I'm doing new springs in a couple of weeks too, once I've had a chance to build my new shed and clear some space in the garage to work on the bike. The questions I'd like to get answers to have already been asked, so I'm only really posting so I see updates in my subscribed threads.
punyXpress
25-11-09, 10:16 PM
My curvy has braided hoses fitted so the brakes are pretty solid, I'm a relatively new rider so don't really know what's right or wrong when it comes wrong to motorcycle handling.
I'm 105kg (16.5 stone) the forks have standard springs in them but the previous owner gave me some Progressive springs with the bike, I was intending to fit them along with new fork seals and maybe a heavier oil but have no idea what would be the theoretical best solution.
I try not to brake too heavily, I don't enter corners too fast still gaining confidence but I think the front is too soft for my weight, I'm 6ft 3 so I guess have more weight over the front than smaller people and more weight transfer when braking.
The progressive springs are by a company called Progressive Suspension funnily enough.
How heavy did the previous owner look?
There may be poundages etched onto the proressive springs - worth a look.
punyXpress
25-11-09, 10:25 PM
This MIGHT help - it's in PS's instruction sheet on their website: ...
Fork Diameter Fork Spring Rate Spring Dia.
35mm 11-1135 18-28 27mm
36mm 11-1136 18-28 29mm
38mm 11-1138 18-28 31mm
40mm (Conventional forks) 11-1140 20-30 33mm
40mm (White Power Upside Down)11-1140UD 18-28 33mm
41/42mm 11-1141 18-28 35mm
43mm 11-1143LT 18-26 36mm
43mm 11-1143MX 19-23 37mm
43mm 11-1143 20-30 36mm
rory182
25-11-09, 10:29 PM
How heavy did the previous owner look?
There may be poundages etched onto the proressive springs - worth a look.
It was the previous previous owner who had the progressive springs fitted and didn't like them, the guy I bought it from said that with me being bigger I'd prob get on better with them than his mate (the previous owner before him) had.
confused yet? :clown:
rory182
25-11-09, 10:30 PM
This MIGHT help - it's in PS's instruction sheet on their website: ...
Fork Diameter Fork Spring Rate Spring Dia.
35mm 11-1135 18-28 27mm
36mm 11-1136 18-28 29mm
38mm 11-1138 18-28 31mm
40mm (Conventional forks) 11-1140 20-30 33mm
40mm (White Power Upside Down)11-1140UD 18-28 33mm
41/42mm 11-1141 18-28 35mm
43mm 11-1143LT 18-26 36mm
43mm 11-1143MX 19-23 37mm
43mm 11-1143 20-30 36mm
Thanks, I have them in the original packaging under my desk at work, will check what they are tomorrow. I presume the spring rate will be useful here in order to compare to a standard naked curvy's fork spring rate?
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