View Full Version : Front fork oil/springs
Morning
I'm looking into the Hyper pro front springs. I appreciate they're a bit more expensive than the Hagons as they're 'proper' progressive rather than two spring rates like the Hagons. My front end doesn't inspire confidence tbh, I'm wondering if you lot reckon I should go for new oil first of all (the previous owner told me it was changed but I think he's fibbing as it dives under braking) before spending more on springs. If just new oil, what's the best rating to go for to stiffen the front end up?
Do the standard springs wear easily over time? The bike's an 05 plate with a shade over 12k on the clock.
Thoughts appreciated :)
John
If it's not too personal a question, what do you weigh, and what sort of riding do you do?
Jambo
Not at all! 13 stone when I'm not training, about 14 when I am. (soon to be back on it given my gluttony over xmas) and I don't ride too hard, I'm certainly no street racer or anything.
The oil could be changed but there are all sorts of reasons why it may dive - oil viscosity, quality, type, air gap etc. Here's what I found with mine.
Bike suspension never set up for me (14.5 stone, bad diving) --> progressive hyperpro & heavier oil (much better but still pogoing) --> New pads and a little later braided lines (IMO better braking feel resulted in more control of front dive) --> Heavier weight oil (20wt - much stiffer initially but not sure air gap right so too harsh on small bumps) --> Rear shock (Ah, much better balance between front and rear) --> Suspension setup (not much different but gave me base settings).
Next is to complete the emulator upgrade with lower wt weight oil and then reset the suspension. All this cost (incl rear shock) about £300+ over time and still not perfect. It may be difficult to shell out £500-£800 for a front end conversion (GSXR etc) but actually if you sit down and work out the figures its not that much more than the gradual modifications when you take into account the proceeds from selling standard front end (which I have heard can be a pita).
I think its more of a question of learning with the bike if you're a newer rider, which I was, or paying for the best solution you can afford if you're a more experienced rider and know what you want the bike to do - which I am now.
Yikes, not intending to spend anywhere near that on it, it's just my commuter which I want to jazz up a tiny bit to make it more my own. Think I'll give the fork oil a change as it's due it according to the Haynes anyway...so will see if that improves things. My friends got 15wt in his with the Hagon springs and it feels infinitely stiffer than mine...might just trial and error it over time. Thanks for the reply :)
yorkie_chris
08-01-13, 02:34 PM
Don't bother with the progressives, get some linears. 0.85/0.9 or so.
stiffer is not necessarily better and can actually be worse. the whole point in suspension is to soak up the irregularity in road surface so the bike chassis stays stable and to keep the tires in contact with the road surface.
yorkie_chris
08-01-13, 02:54 PM
but not sure air gap right so too harsh on small bumps
That's not how the air gap affects things.
Don't bother with the progressives, get some linears. 0.85/0.9 or so.
Mind explaining this to me? I'm a suspension noobie, I've always been led to believe that progressive is better, period. I'm not saying that's the case though, I'd like to hear any different thoughts on it.
stiffer is not necessarily better and can actually be worse. the whole point in suspension is to soak up the irregularity in road surface so the bike chassis stays stable and to keep the tires in contact with the road surface.
Aye of course, would just replace my forks with blocks of wood otherwise haha! If you felt how divey it is though, you'd understand why I'm wanting to change things.
That's not how the air gap affects things.
Also this, done very light reading about this. I assume it's the space left at where the oil tops out in the forks?
yorkie_chris
08-01-13, 03:49 PM
Mind explaining this to me? I'm a suspension noobie, I've always been led to believe that progressive is better, period. I'm not saying that's the case though, I'd like to hear any different thoughts on it.
Every front fork* going is progressive, due to action of spring plus air gap.
Progressive is almost a theory that sounds good. In practice what happens is the effects are additive and work against each other. The soggy crap top end of the spring means you blow through all your travel with the lightest force and then when you need to absorb a bump you are right down in the stroke getting your eyes bounced out because you're in the rock hard part of it where the harder spring plus the air gap acts.
Then because you're forced to set the rebound so soggy so it works in the p*ss weak top half of the travel... in lower half of travel with lots of force i.e trail braking and bumps... it chatters like hell. By extension if you make it work here, then it packs down like hell in the top half. Ugh!!!
Period. Bollox! Nothing is so simple in suspension. Only people saying that are people who are selling progressive springs.
However, progressives are generally better than the biro springs fitted to a lot of stock bikes just because they're a bit stiffer overall, the finer nuances are completely missed in the "oh this isn't trying to kill me quite as much!" elation.
*Telescopic, oil filled, don't be pedantic.
That's not how the air gap affects things.
I confess I don't know but thought this may be the reason. It could just be the oil weight. Can you shed some light on the air gap effect (in one sentence as is your style :))?
yorkie_chris
08-01-13, 04:31 PM
Effects progression of fork towards bottom of travel, little effect at all at the top.
http://www.peterverdone.com/archive/images/content/motorcycle/air%20spring.gif
If it feels harsh on small bumps that can be the fork kicking back at you from weak rebound.
(sorry a bit verbose)
(sorry a bit verbose)
Lol :D
But wait, that didn't seem likely with having used heavier oil? It felt like the front was skipping a bit on imperfect surface at speed because the rebound was slow.
yorkie_chris
08-01-13, 04:37 PM
Lol :D
But wait, that didn't seem likely with having used heavier oil? It felt like the front was skipping a bit on imperfect surface at speed because the rebound was slow.
Well it depends. Stiffness at the point in fork you were using (stiffness, sag, aerodynamics, everything...).
What viscosity oil did you use?
Think is was the Hein Gericke Motul 20wt stuff (heavy duty). Maybe overkill but I wanted to see if there was a difference. General braking stability was better but then the "skipping" and harshness became evident. I thought maybe i had put too much oil in as I used the measure for the standard springs and not the Hyperpro's (can't remember what that was).
wow, headache. Shall I just buy a Gixxer instead?! :D
yorkie_chris
08-01-13, 04:49 PM
Yeah that stuff is thick. Rather slow for acting on the weak end of progressive springs.
yorkie_chris
08-01-13, 04:50 PM
wow, headache. Shall I just buy a Gixxer instead?! :D
You can get as involved or not as you want.
Least brain ache* results from bringing it to me to fit emulators and new springs :)
*Maybe a bit of brain ache, I do make a lot of tea and say c*** a lot.
Looooong way to ride from Weybridge, thanks for the offer though ;)
Gonna give a simple oil change a go, see how adding some slightly thicker stuff goes. I rebuilt the calipers last summer and if the brake fluid and state of the calipers were anything to go by, the fork oil is probably sludge as well by now!
If I were you I'd get some slightly stiffer springs (YC has already made a guess, there's a calculator here (http://racetech.com/ProductSearch/2/Suzuki/SV650%20A,%20S,%20SA/2003-09) that will I'm sure come up with something similar)
The springs will then be something like right for the weight.
And I'd replace the oil. I've tried a few viscosities I found a 10w to be a bit soft on rebound, and a 15w to start getting a little crashy on compression (I do a lot of miles in London, which isn't exactly a smooth surfaced area). So I tend now to mix a bottle of 10w & a bottle of 15w and pour the mix in. It's usually about now that someone points out all oils are different viscosities anyway and links to this site (http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid). Don't get too hung up on it, but do be aware that one manufacturer's 10w and another can be quite different so if you're experimenting for yourself try not to jump brands too often.
There is no "right" setup, regardless of whether you have a GSXR setup or a standard damper rod fork. But by thinking about where it feels good or bad you can tweak it to work quite well for not a lot of money.
My SVs also have a set of cheap knock-off emulators in them too from here (http://www.debrix.com/default.asp). (Thread explaining these is here (http://forums.sv650.org/showthread.php?t=144722))
In short, a bit of thinking and a very moderate outlay can get things working a fair bit better :)
Jambo
My SVs also have a set of cheap knock-off emulators in them too from here (http://www.debrix.com/default.asp).
Btw, anyone have any more of these left (spare to sell)?
Least brain ache* results from bringing it to me to fit emulators and new springs :)
I can testify to this. K-tech linear springs (0.85), debrix emulators inc damper rod spacer and mods, and some fresh silkolene pro rsf 10w oil all fitted by YC for a very reasonable price.
I would have done it myself but my inconsiderate wife decided to drop baby number two right about the time I was gonna do it :)
Looooong way to ride from Weybridge, thanks for the offer though ;)
Do it by post, I did. Whip the forks off, remove springs & drain out the old oil. Box up and send (cost me about £15 I think). I had mine received back and fitted to the bike within a week! Top service :)
These mods made a helluva difference btw, especially when combined with the zx rear shock and sag etc set right.
Many thanks Jambo, brilliant info :)
Spanner Man
10-01-13, 07:45 AM
Good morning all.
Could this be the first progressive v linear 'debate' of 2013? :D
If you want an excellent upgrade to the standard springs, which suit all round riding. A set of Hagon's will be the best £90 odd pounds you'll ever spend. (I doubt that out of the many hundreds of sets I've fitted, the customers can all be wrong.)
If you want a more specific improvement, for say, fast road, or track days. Go down the linear/emulator route.
Don't forget that suspension settings are to a degree 'personal'. Some like it soft for comfort, & some like it harder, for performance.
If you want a bike that handles like a race rep, go & buy one. :grin:
Cheers.
muzikill
10-01-13, 08:26 AM
stiffer is not necessarily better and can actually be worse. the whole point in suspension is to soak up the irregularity in road surface so the bike chassis stays stable and to keep the tires in contact with the road surface.
This. How many boy racers do you see with lowered cars. You think it makes it more comfy? Overspending to make it worse. Im sure there are the same reasons for bikes as well.
yorkie_chris
10-01-13, 08:59 AM
(YC has already made a guess, there's a calculator here (http://racetech.com/ProductSearch/2/Suzuki/SV650%20A,%20S,%20SA/2003-09) that will I'm sure come up with something similar)
My guess is probably better than the calculator ;)
Calculator just looks it up on a graph, it's not massively scientific.
yorkie_chris
10-01-13, 09:03 AM
Good morning all.
Could this be the first progressive v linear 'debate' of 2013? :D
If you want an excellent upgrade to the standard springs, which suit all round riding. A set of Hagon's will be the best £90 odd pounds you'll ever spend. (I doubt that out of the many hundreds of sets I've fitted, the customers can all be wrong.)
They're not wrong, hagons/progressives are a definite improvment over the stock biro springs.
They're not as good as linears of the correct rate though. And the linears are cheaper to boot!
We are not talking strictly "making it harder" here. The hagons at the bottom of their travel with the recommended air gap are ridiculously stiff. You never see the bottom half of the travel!
So where's a good place to get linears from? I'm happy spending less for an improvement over stock believe it or not :D!
yorkie_chris
10-01-13, 11:06 AM
Ktech £85.01
Wicked, will pick some of those and the seals up from that site :)
Just to add, I'm 12st (before christmas), fitted 0.85 K-tech linear springs in my curvey with std internals.
I use Silkolene PRO RSF oil, reckon it's one of the best oils for viscosity stability over the usual temperature range. I use the 7.5W (compares closely to many 10W oils, 35cSt at 40C) which is at the comfortable end of damping, many would probably prefer the 10W but it suits my style.
Overall a good value package, dramatically better than the std springs. Best bang for buck mod you can do. If you want to spend a bit more then go the next steps.
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