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Old 19-06-2019, 07:43 PM   #18
chris.p
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Join Date: Mar 2004
Location: lincoln
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Quote:
Originally Posted by Luddite View Post
I still think it's worth checking the static sag in conjunction with dynamic sag. If the static sag is insufficient, you could experience excessive topping-out even if your dynamic sag is within the recommended range.

This is what happened when I first fitted an Öhlins DU737 with a 115N/mm spring to my Evo. The sag figures recommended by Öhlins were minimum 10mm static and 25-40mm dynamic. Out of the box, there was virtually zero or 1-2mm static sag but I didn't adjust it because the dynamic sag with me on board was within the recommended range (about 26mm). The ride was not very smooth and I subsequently backed off the preload to give 10mm of static sag while still staying within the recommended dynamic sag range, which improved the ride considerably. I eventually fitted a softer 105/mm spring but still set the same static sag with slightly more dynamic sag, which now suits me perfectly.

Some (much) more knowledgeable people than me have given the following advice on static sag:

This from Niall Mackenzie in 2003:
https://www.visordown.com/features/g...kes-suspension

"If there's no difference, (between shock fully extended and then with the weight of the bike*), you have no sag and you're in trouble. Your bike will be on its nose braking, the rear end will be hopping and pattering, and if you get back on the gas hard out of a corner it'll probably highside you ."

*my words.

Then, from Tony Foale's bible "Motorcycle handling and chassis design"



That diagram graphically illustrates the "hopping and pattering" that Mackenzie described earlier.

Totally agree you must have the correct static sag.
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