Spring weight for bike weight.
 

Keeping it quick and simple... If you have springs that are at the lighter end of the options (for rider weight) in the forks, at some point will going too light will be too soft for the bike?
I've fitted 8.5n/mm K Tech springs in the stock SV650s K8 fork and to get static sag to anywhere near 10mm I've got the preload wound in to just one ring showing, so nearly all the way in. Luckily it's working out ok for rider sag too, but should I be concerned having that much preload? Or does it even matter where it is as long as it's right?



* Disclaimer.. still setting up and not actually ridden it yet, so know I should get out and ride and see.
* When I bought it a few years back I had no idea what preload was until someone pointed out it was all the way in and I hadn't noticed... which shows how blissfully unaware I can be : )

Re: Spring weight for bike weight.
 

The risk is that under full compression the springs will not have enough 'travel' and could bind up. However I think this is pretty unlikely as, hopefully, the designer has not permitted enough preload movement to allow this to happen, when set up with the correct sag of course....

Re: Spring weight for bike weight.
 

lets try and get you to understand what the springs actually do. springs come in a weight, the correct weight is determined by the rider and the bike weight. too light a spring and the bike will easily bottom out on its suspension. too heavy a spring and the bike suspension will move less resulting in a harsh ride.

with .85 front springs you are looking at a rider weight of 10-12st (12st being a tad too soft)

preload does not change the weight of the springs. preload only raises and lowers the height of the bike.

"bike" sag settings are the ONLY measurement that matter. you set the bike sag settings and leave it there.

"rider" sag settings are to CHECK the measurements to tell you if the springs are correct for the weight of the bike and rider.

front and rear both have different "bike" sag settings. for road use i would recommand that the rear is set to 10-15mm and the front set to 20-25mm. add another 20-25mm both front and rear for rider sag. when you sit on the bike with your feet up and in your usual riding position in full gear the bike should move closely the same front and back.

set bike sag and leave it.
check rider sag.

there is a whole host of things that are spouted on the net about setting rider sag only.. these people are muppets. i could go into a long list is why its not done that way but the main one is "topping and bottoming" out.

when the "bike" sag settings are done then you need to put a cable tie round the front stanchion as an indicator. after about a week or so longer if you can keep reducing/raising the front preload till you have about 5-7mm of travel left on the front forks.

thats pretty much the basics of setting the sag.

after a few weeks or months you can start to check things like tyre wear to determine how your suspension is copping and what can be altered.

Re: Spring weight for bike weight.
 

I'm spot on in the middle of that. I used the Racetech online form and it gave me a recommendation of 8.3n/mm or as near as I could get. This is for general road use.




So me setting front static sag for 10mm is too much preload for the bike alone?


Yep, noted.. I've seen some of the most confusing clips on Youtube explaining it all wrong. Some by people who are obviously good at setting things up but have no talent for conveying ideas or teaching in a simple coherent way. Others that simply focus on setting rider sag and totally ignore bike sag!



I've got the cable tie in place already. No one has ever mentioned this aspect of adjustment over time. Good to know, cheers.

Re: Spring weight for bike weight.
 

Good test ride today.

Bibio.. your figures are way more plush than a lot of recommendations online. Most don't mention that they're for track setups though. I've got it all set up more in line with your recommendations and it's feeling great. I still need to work on it over time and the forks are still showing up their crudeness, but it's all so much better than it was with everything stock and old oil etc.


I decided I can't afford a rear shock at the moment but did manage to grab a bargain ZX10r shock that I'm hoping will get me by for a while. It's actually really good! The back of the bike is about 1cm higher but that feels good too. I've got the static sag set at approx 15mm and a friend helped me check rider sag today and it's 38mm, so all in the right area but I'm going to tweak it slightly and see how it feels. Also did a few repeated sections of roads today to play with compression and see how it feels. I started with compression and rebound 2/3rds out, then compression full in, then full out, then half way, then dialed it out untl it felt good and confident again. Compression full off was very comfortable, but the back didn't feel planted. The bike didn't feel as balanced front to back either and was seesawing a bit under braking and accelerating. I ended up back with it where I started and it feels great. Again I'll tweak it as I ride to get more of a feel of what it's doing. Rebound seems ok. I need to try more variety of roads and speeds to get more of a feel for it though.


Forks are set with 25mm static sag and I've not checked rider sag yet as I was keeping the cable tie in place for a couple of rides to see how much travel I use. I've not done anything extreme to test it yet (not sure I ever will on purpose!) but at the moment it looks like the cable tie has moved about 80mm up.


Something about the forks still doesn't feel right though. I am trying to hit drains and road imperfections to check the suspension reactions, but the back handling it all really well seems to be showing up what the fork is lacking. I'm still being a bit slammed about and wobbled on the front on bits of road that the back is coping well with. I'm guessing the only way to improve that its to fit some emulators. Maybe when budget permits.


All in all though, definitely a huge step in the right direction. I tried a setup with the stock shock before swapping over and the best I could get was 7mm of static sag with no preload on. Something wasn't right with it. Definitely felt like having a block of wood in there.

Re: Spring weight for bike weight.
 

springs by and large dont affect harshness/plushness of ride as thats the job of the dampening system.

the "clickers" on suspension have nothing to do with "hard/soft" or bump apart from fast comp clickers. the clickers are for slow chassis movement e.g. breaking and cornering (slow compression and rebound).

dont worry too much about comp and instead concentrate on rebound.

you will never get the front rebound slow enough without mixing the oil correctly, welding up the rebound holes and setting the correct oil height. when the front rebound is set correctly you will notice that after braking on the front and you let go of the brakes the front will rise back up and stay there. simple test is the "bounce test". the front should go down then come back up with no or about 1-2mm of overshoot then settle with no other "bounce".

Re: Spring weight for bike weight.
 

The rebound definitely has more noticeable changes with adjustment. Compression seems to be a bit more subtle.


This is what I'm finding. It's not that the forks aren't reacting to bumps etc, just that it really unsettles the balance of the bike the way they react. The speed they react seems all wrong and mismatched to the (now smoothly controlled feeling) back. Would emulators change this? (with the welding up the rebound holes and drilling dampers)

Re: Spring weight for bike weight.
 

unless you know how good suspension should feel you will chase your tail.

define "unsettles the balance of the bike"..

emulators by and large only control the "dive" of forks and if not set correctly can make matters worse. with emulators (well all suspension really) its a balancing act between dive and bump. the more vicious you make the valve the less it can react to bumps but you get less front end dive. this is great for track day heroes and racers but not so good for road use. there is plenty information on the net about how to set up for race but very very little for road. this is because its easy to set suspension for race but much more difficult to get it right for road.

its all trial and error until it suddenly falls into place at which point it will put a fekin huge smile on your face.

your tyre wear will tell you everything but that takes time. in the meantime you can only set rebound and compression by doing bounce tests and riding.

Re: Spring weight for bike weight.
 

Harsh bumps cause the classic pogo effect on the front still. It dives a lot less with the K Tech springs (8.5n/mm compared to what I believe were the stock 6.7n/mm) and new oil (10w) and feels a lot firmer and controlled in use cornering etc, but as you say it's bouncing back up and unsettling getting off the brakes or over bumps, going about a cm or two too far up, back down and back up and then down again before it settles into place. This is causing the bike to feel like it's seesawing for a second or so.


So emulators don't help slow rebound at all?

Re: Spring weight for bike weight.
 

yup lack of rebound on the front.

emulators will slow down the rebound but not by much.

have you welded up the top rebound holes in the damper rods?

what brand of fork oil did you use?

how much oil did you put in each fork leg and was the springs in or out when you measured the oil height?