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Discussion Starter #1
I have just fitted a stiffer set of fork springs and I am happy with the results. What I am wondering is what effect will changing to 15W fork oil have in comparison to the stock 10W oil. At the moment I have left the original oil in.
Any advice greatly appreciated.
 

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15W oil is going to improve your fork a lot, specially since you put stiffer springs.
Putting stiffer springs with standard oil (10W),(you don't mention what kind, are they progressive?) would normally make the bike bounce around in tight bends if you hit a bump.
Thicker oil will provide more damping, and will controll the stiffer springs much better.

Aris
 

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Discussion Starter #4
Thanks for the advice / suggestions guys. The springs I put in are a single rate (linear). The main problems I was having before was that the front would sag far too much and bottom out easily - I an too heavy at 95kg for the stock springs.
The other problem was that a bump mid corner, especially travelling a bit quick, would see the bike do a pretty good immitation of a pogo stick. It would settle down all right but it wasn't exactly confidence inspiring.
I'm kind of feeling my way with trying to improve the suspension and one thing I read somewhere was only to change one thing at a time, hence I changed the springs but not the oil.
I think I'll try increasing the damping setting on the rear and then probably try the compromise route with a 50/50 mix of 10W and 15W in the forks. Another thing I heard was to increase the oil level in the forks a small amount to stop the forks diving too much under hard braking.
I tend not to travel much faster than 110 kph or so because of the number of police enforcing revenue raising, sorry, road safety on our incredibly neglected and over regulated and policed roads
.The main thing I want to achieve is stability and comfort and the ability to push hard when the mood takes me.
Thanks again for your feedback - my phone bill and ISP account is really suffering since I discovered this forum.
 

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Discussion Starter #6
G'day Doug.
The new springs I put in are shorter than stock and I have put in a spacer to bring the effective length to close to the same as stock so I really have much the same pre load as stock although the fork caps were much easier to put back on than I thought they would be. I really haven't had the chance to put enough mileage on the bike since I did the springs to properly evaluate them yet although the comfort aspect feels good.
I don't think I will raise the fork oil level above standard (my manual says 100mm from the top of the tube with no spring and the fork fully compressed, hope this is right) As you said even a small increase can make a huge difference.
I'll definately increase damping and maybe a bit more preload on the rear as you have done.
BTW the spring rate I used is .9 kg/mm. I don't know what the stock spring is but I was told by the suspension guy I got the springs from it would be about 7 or 7.5 kg/mm.
Will post an update when I change the fork oil.
Cheers Glenn.
 

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Discussion Starter #8
Doug
Thanks again for your suggestions, I reduced the preload as you suggested and the sag is about spot on. I also decided to change the fork oil and put in a 12.5w mix. BTW I pulled the forks out to change the oil and the stuff that came out looked really dirty.
I'm really happy with the result as the bike is now well behaved and still comfortable. All in all a good compromise although it probably wouldn't suit a racer.
IMHO its well worth doing particularly if you are like me and on the wrong side of 90kg.
 
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