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Red Herring · 24-07-20, 10:32 AM

If you take a 200kg bike and fit it with spring that compresses 1mm for every 10kg, you will get 20mm of sag under just the weight of the bike alone, agreed? (And I know there are two, or even three springs supporting a bike, plus all the issues around rising rate linkages, but for the sake of simplicity lets save that until later....). Now add 100kg of rider and you arrive at your 30mm of desired sag.

Now take a 100k bike. If you want your 20mm of bike sag you need to fit a spring that compresses 2mm for each kg, but if you then add your 100kg rider you will end up with 40mm of sag....... so to get your 30mm of final sag you actually only have a spring that gives you 15mm of sag without a rider.

This is why "figures" don't necessarily work when you try and move them between different bikes with different riders......

It is also why it is far easier to just concentrate on getting the right sag with the bike and rider combined.

24-07-20, 10:32 AM	#50
Red Herring Member Mega Poster Join Date: Dec 2007 Posts: 2,708	Re: 110 miles on MT09SP If you take a 200kg bike and fit it with spring that compresses 1mm for every 10kg, you will get 20mm of sag under just the weight of the bike alone, agreed? (And I know there are two, or even three springs supporting a bike, plus all the issues around rising rate linkages, but for the sake of simplicity lets save that until later....). Now add 100kg of rider and you arrive at your 30mm of desired sag. Now take a 100k bike. If you want your 20mm of bike sag you need to fit a spring that compresses 2mm for each kg, but if you then add your 100kg rider you will end up with 40mm of sag....... so to get your 30mm of final sag you actually only have a spring that gives you 15mm of sag without a rider. This is why "figures" don't necessarily work when you try and move them between different bikes with different riders...... It is also why it is far easier to just concentrate on getting the right sag with the bike and rider combined. Last edited by Red Herring; 24-07-20 at 10:24 PM.