Spring Rate and free sag

I have an '05 YZ250 (2 stroke) :naughty: and I weigh 213 lbs. I put a 5.2 rear spring on it as per Race Techs spring calculator and when I set my race sag to 95mm I only have about 6mm of free sag. First of all do I really need to go to a stiffer spring to get the free sag better? Also, how do I know what Spring to buy next in order to get it in the proper range? Would 5.4 be sufficient or do I need to go stiffer? IF the calculator said go to 5.2 and that didn't work it's only a guess to know where to go next. At $109.00 a pop, you would think that the spring rate calculator would be a little better.

Anyway, I don't want to guess at it so if ant body could help I should would appreciate it.

I have the same bike and weigh 200. I use a 5.1 rated spring, but it tested at 5.0 (the stock 4.9 tested at 4.8) I set my sag at 100-105mm and have 20-25mm free sag, thats right on the money. I also raise my forks in the clamps 5-12mm depending on the track for better turning and to work with the rear sag numbers. I got the rear sag and fork tube numbers from a friend that works for team Yamaha. This is the same set-up Reed and DV have on their practice bikes and both do use stiffer forks springs.

Give these numbers a try, that might make your new spring work for you. If not, it is possible that the spring you think is a 5.2 may really rate as a 5.0?, you need to get it tested to be sure.

Your race or rider sag should be 30 to 35% of the total rear wheel travel. I would guess your rider sag should be 105mm to 110mm. Then check your static sag. It should be at least 25mm to 30mm.


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