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Calculating the proper Spring Rate for your weight - KTM

9558 Views 1 Reply 2 Participants Last post by  Kamikuza
How to calculate the spring rate needed for a particular rider weight?
Lets put our brains together and build a proper thread with correct information.
Just like in math class you must prove your answer by showing all your calculations.

I found the following list online
"this list of springs is for all LC4: Enduro, Adventure, Super Competition, SuperMoto !

spring rate: use for:
50/260 for lite and short rider
56/260 STD on LC4 up to 1993
60/260 STD on Competition 1994
63/260 STD on SXC 625 2006
66/260 STD on Enduro 640 2006, STD on SXC 625 2007 or rider up to 75Kg
70/260 STD on SuperMoto 2006, Adventure 640 1997-2006
75/260 STD Rally Dakar, and STD on SuperMoto 2004
80/260 for big rider and or "lots" of baggage

Here is an online metric calculator for the metric conversions;
Metric Converter

Now lets work on the following bike;
2005 KTM 625 SMC
Factory settings:
Spring Rate= 4.4N/mm
Spring preload= 28mm (1.10 inches)

Spring Rate= 70/260 (154.3 lbs / 10.25 inches) Does this mean that this 70kg spring is what is needed for a person weighing +-150 lbs?

Lets hope that we can learn the proper way to calculate the spring rate needed for our bikes and our constantly changing body+gear weight.

Thanks in advance for your time and knowledge.

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Again, I dunno about SM but you should have enough range in preload adjustment to account for riding naked and fully geared up - and within reason, for a passenger. (Personally, I don't allow passengers except in emergencies - like the guy who hit a monkey in the mountains and we all couldn't get cell coverage so I dubbed him to a pay phone in the town.)

Set the sag, then how close you are to the limits will let you know if you need to change springs. Unless you're well outside the 'norms' of weight or riding it at the limit, I doubt most people need to worry ...
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