Using the correct Spring Rate is extremely important.
The goal for any Spring Rate choice, whether you have an Air or Coil shock or fork, is achieving the correct Sag Rate. “Sag” is the distance the shock or fork compresses when you’re on the bike. It's usually measured in millimeters.
Your Sag Rate is the base for all suspension tuning and it's different for each rider since we all weigh differently. Without correct Sag, no amount of tuning will allow your fork or shock to ride at the optimal level. We recommend 25%-35% of the shock’s Stroke Length, aka “stroke”, for the optimal Sag Rate depending on the shock size and riding style. For HELM forks we recommend 10%-25% of stroke for the Sag Rate depending on riding style.
To learn more about how to set your Sag Rate, consult your fork or shock manual. They can be found on our website HERE.
At this point you may be saying “I get Sag, but what is the shock or fork’s Stroke Length?” Glad you asked...
Stroke, often called “travel” on suspension forks, is the maximum distance the shock or fork can compress. You will need to determine your shock’s stroke in millimeters to find your optimal Spring Rate. This is often found on the bicycle manufacturers website, on the shocks packaging, or you can measure the “eye to eye” difference between the shock fully extended and fully compressed. Example… a 210x50mm shock will be 50mm shorter if measuring the eye to eye of the shock fully extended, to fully compressed.
Make sure to remove the spring on Coil shocks and/or release the air pressure from Air shocks before doing this so the shock can compress fully to bottom out..
Suspension fork stroke is the same as “travel” and is also listed on the bicycle manufacturer’s website. Or you can measure, in millimeters, the distance between the wiper seal and where the stanchion tube meets the fork’s crown. This distance should be in 10mm increments. 100mm, 140mm, 170mm, etc.
So now that you’re a Sag and Stroke expert, how do you find your ideal Spring Rate?
If you have an Air shock or fork, simply add air until the Sag Rate is approximately 25%-35% of the shocks stroke, or 10%-25% of the fork’s stroke, depending on riding style and preference, and you are done.
Make sure to follow our Tune Guide HERE and go Ride!
If you have a Coil shock, continue to the next steps below..
First step is rider weight. How much do you weigh with your riding gear on? Helmet, shoes, hydration pack, etc.
Second step is finding the fork or shock’s Stroke.
Third we need to know the bikes Rear Wheel Travel. This can also be found on the bicycle manufacturers website and is usually listed in millimeters.
Finally we enter all of this data into one of many Spring Rate calculators available online. TF Tuned is one of the UK’s premier suspension service centers and they have a great calculator HERE. Make sure to choose the correct unit of measurement (mms/inches etc.)
After entering your data and calculating the Spring Rate, most riders find themselves within 50lbs of their ideal rate. Our linear VALT springs are available in 50lb rate increments so if you find yourself in between rates, you can typically go to the next rate up or down in 50lb increments. For example, if you find that you need a 436lb spring, you can often use a 450lb spring. If you are on the lighter side at say 413lbs you may want to choose a 400lb spring.
The final step after installing the spring on the shock and on the bike is adjusting the preload. Preload is used to adjust Sag Rate on Coil shocks to allow for the optimal amount of Sag. Using the preload ring on the shock, you can add preload (tighten) or reduce preload (loosen) on the spring to dial in your Sag Rate.
You should use no more than 6 turns and no less than 1 turn of preload. If you need more than 6 turns to achieve Sag, you need to go up 50lbs in Spring Rate. If you need less than 1 turn, you need to go down 50lbs in Spring Rate. Using less than 1 turn can also cause the spring to be loose on the shock body and may cause damage.
For Helm Coil forks, the stock Spring Rate is 55lbs. To set sag, you will add preload using the preload adjuster on the fork’s crown until you achieve 10%-25% sag. If you find you have maxed out preload and have too much sag, go to a heavier rated fork spring. If you cannot achieve sag with the stock spring and no turns of preload, you may need a lighter rate fork spring. We offer Helm springs in 10lb increments from 35lb to 65lb.
35lb spring - AAG0421 RED - (90-120lbs rider)
45lb spring - AAG0422 BLACK - (120-160lbs rider)
55lb spring - AAG0424 GREEN - (160-200lbs rider) ** Stock Spring in Helm Coil
65lb spring - AAG0426 BLUE - (200-240lbs rider)
Even with this information Spring Rate can be subjective to your riding style and preference. Factors such as leverage rate can also affect and alter the ideal Spring Rate you need. You may find you need a heavier or lighter spring than recommended to achieve sag. The important thing to remember is to use whatever Spring Rate is necessary to achieve approximately 25%-35% of the shock’s stroke, or 10%-25% of the fork’s stroke.