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jay_88

Spring/valving question

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Why do bikes these days run stiffer springs for example the yz450f

2009 

4.7kg fork springs 

5.5kg rear and weight 238lb

2018

5.1kg fork

5.7kg shock 

245lb

now there’s not a bit different on weight..

did they used to use soft springs/firm valving? I much prefer how the 09 feels sag wise just by sitting on it 

 

 

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The fork needs to be stiffer as the new chassis weights the front more ,and it can do that if the rear is stiffer

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46 minutes ago, mog said:

The fork needs to be stiffer as the new chassis weights the front more ,and it can do that if the rear is stiffer

That statement doesn't seem to go quite far enough. Maybe add "and it can do that if the rear is stiffer "Also"", as increasing shock spring rate too prevents weight transfer from the stiffer front end to the rear, had they left the shock spring the same.

If the new chassis weights the front end more, requiring stiffer fork springs to compensate, a stiffer shock spring would be prudent just to keep the suspension balanced front to rear. Putting in stiffer forks springs to support the weight of the new chassis, but leaving the rear as is makes the front end unbalanced with the rear, causing a weight shift transfer from front to rear.

 

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They have gone stiffer on the valving also. Alot of the manufacturers test riders are fast former pros and in the shootouts they always have fast guys including current pros, so I think they are trying to satisfy the fast guys who need that stiffer suspension.

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The suspension I’ve ridden and prefer have had more rear sag with the forks flush or close to it but 60-65mm fork race sag which gives excellent front feel which I’m guessing is a soft spring which keeps handling awesome

im wondering how all this is achieved with no wallowing or harsh bottoming 

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 it was more common to use more preload on the fork springs maybe? At least WP used to run 8-10mm preload and they are closer to 0 today.

 

 

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9 hours ago, AEES said:

 it was more common to use more preload on the fork springs maybe? At least WP used to run 8-10mm preload and they are closer to 0 today.

 

 

Manual on the 09 250sxf still says total installed spring length 492mm same as my 14 sxf which I was under the impression  gives 4mm preload?

orginally the 09 had 4.6 which were good but a touch on soft side dived in braking bumps, higher oil was a bandaid fix which obviously gave mid stroke harshness so I recently swapped with 4.8kg 

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