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Suspension sag and Spring Nm

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I have finally come to the conclusion that I need different springs for my kxf 450. I weigh 83kg in full riding gear and when the standard spring is set too 35mm static sag (just sat on the ground) I get a reading of 90mm rider sag (with me sat on the bike). As far as I am aware the spring is 5.5kg as standard? and was wondering if anyone else has changed their springs (who is very similar weight to me) and what strengths did you go for. I just don't want to be buying a shit load of rear springs until I get the right numbers (35mm and 105mm). Any help is much appreciated.

 

Andy

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basically the sag reading is done vice versa. set the rider sag to 105mm, then read the static sag.

if it's not more than 40mm, it's within the range

 

you are close to the average weight for the stock spring, so the only spring that will also fit your weight

would be a 5.7kg/mm edit 5.3kg/mm

Edited by kawamaha

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damn, you're right. my fault 

You can search for a older stock KX450 spring, until 2009 they had a 5.3 stock.

 

Nevertheless I’m wondering why you get those sag numbers. I am the same weight as you

and the stock spring fits perfectly.

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Strange :/ i will have another measure when i get home tonight. The bike has only been ridden a handful of times since brand new so maybe this could affect it? I will have a look at the older years and see whats available.

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as far as I remember, I have a 5.3 at home, I can search for it if you are interested, shipping

would be about 14 british Pounds, so overall much cheaper than a new one...

 

but measure your sag numbers once again...

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I measured them again today. Same as before :/ I even managed to coax one of my heavier mates onto it to see what sort of measurements im getting with him on it. hes 13.5 stone and sat neutral on the bike its 35mm static and 98/100mm rider sag! Im only just over 11.5 stone. I either start eating a lot of pies or get a new spring. But im now unsure that going down .2kg will give me the right amount needed?

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Brand new bike. stripped the whole thing and greased up every bearing myself to make sure that it was ok. So as far as i can see it is fine and feels fine with the shock removed.

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then you have to try...

i measured the stock 5.3 as 5.2kg/mm, but can't tell you, if the stock 5.5 has maybe only 5.4

 

I guess the static sag will be near 40mm with the 5.3 and near 30mm with the 5.1 spring.

you may also try another post in the Suspension Forum, some knowledgable guys there...

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As already mentioned, stock 5.5 or else the older stock 5.4 should be right for you. 90mm sag would be unrideable for most people. Horrible oversteer and many other front /rear balance issues ruining traction and stability.

If the rear is that high and it kinda works, then I'd guess the front of your bike is setup way too firm and high for how you ride. In which case lower/soften both ends.

Also be sure to measure sag with you sitting or standing in the same position as you normally ride in. Maybe your a weight aft type of rider.

Edited by numroe

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num, im around a lower class intermedate so like you say it has the characteristics that you described above. it oversteers to death and is unstable when hitting bumps fast as it starts to headshake and also tries kicking me up the arse over braking bumps

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Try lowering the rear at the track, and find what works best.

 

If it does those things when riding, then you're riding a stink-bug. 

 

You could be measuring something wrong, or else something wrong with the rear suspension.  90mm rider, 35mm static, 5.5 spring and 83kg rider, doesn't make sense.

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