Dialing in suspension
 

I have a 1999 CBR600F4 that is completely stock and used only on the street. I am new to street riding, but have been riding and racing dirt bikes for 22 years. I would say I am a competent street rider, but not yet completely comfortable on the street (meaning I am not used to 100 horsepower and traction all the time).

I understand dirt bike suspension and how to properly set up the machine for an individual rider (utilizing the proper springs and static sag and what the preload, compression, and rebound clickers do). The most important step is making sure the fork springs and shock spring are matched to my weight (140lbs).

I have to say the CBR suspension feels pretty good. I’ve set the rear preload to the stock setting and softened the compression damping and increased the rebound damping. The fork preload and compression has been increased and the rebound slowed (slightly). Haven’t measured the static or rider sag on the bike yet.

From the RaceTech website (which I have used many, many times over the years and trust to be an accurate assessment), it recommends stiffening the fork springs (from .75/kg to .81/kg) and softening the rear spring (from 14.2/kg to 13.5/kg).

Talking to a local suspension shop that specializes in street bike suspension, they feel Racetech is way off and recommended going to .95/kg fork springs (which I know is a HUGE increase), and getting a Penske shock (which is serviceable and easier to change springs on).

My question is, what rate fork springs and shock spring would be best for my weight? Is there another place that accurately calculates spring rates?

Anyone? If this post needs to be in a different forum please let me know.

the calculator
 

yes the web site is wrong for sure. cbr 600s are set up for a 165 pound rider from factory. i weigh in at 200 and i use a .95 spring in the front of my f3 so deff. that would be way to stiff for your weight.

Update-

I installed .85 fork springs and factory Honda SS-8 oil (stock oil height) on the bike and have put 1000 miles on it.

They work awesome. They are stiffer than the factory .75s, but it's very subtle. I backed off the preload, and set the comp and rebound clickers back to stock settings (previously set stiffer with the stock springs installed).

.95 is way to stiff for your weight,even in race conditions,unless you are REALLY fast!!

yeah the bike was meant to race right from the get go for a 160-170 lbs rider. just change the fuild to freshin the forks and rear shock up. the springs you have now front and rear are perfect for your weight you dont have to run hardly any preload. .95 kg is way to much. i have 90 lbs on you and i have 1.0 and they are perfect. and by the way no company in the world makes a spring for the f4 and f4i rear shock because i checked and had the ppl who do most of the racecars in the midwest (including irl cars)check 2. one lady at one shop here in indy checked 8 companies and said a japanesse can make whatever starting at 800 and 3 months build time. the spring is tappered. i put a 99 r6 shock and hypertech spring on my f4.