Are you running larger tires, or gear reduction? It’s important to know what change from stock your gear ratio is so you can properly clutch your CVT transmission.
Step 1: If you are running larger tires, figure out your gearing change in percent with this formula:
Current Tire Size – Stock Tire Size / Stock Tire Size x 100 = Tire Size Change
Example: Stock tire is a 29″, went to 32″. 32-29 = 3 / 29 = .1034 x 100 = 10.34% Change
Step 2: If you changed gearing you will need to figure out what % you reduced your gearing. The gear or portal manufacturer should have this information. After you know the ratio simply subtract it from your larger tire % calculation from the gearing % calculation.
Example: We have 35″ tires and the stock tire size was 29″. This is a 20.6% increase in gearing(using the step 1 calculation). Our aftermarket gear reduction decreased our gear ratio by 30%. That would mean overall we are 10% lower than the factory gear ratio. This means you can actually run more clutch weight than what we call for.
Lower Gear Ratio = More Clutch Weight (might need a steeper helix depending) add 1 clutch magnet per arm for every 7-8% decrease in overall gearing.
Higher Gear Ratio = Less Clutch Weight (might need a shallower helix depending) remove 1 clutch magnet per arm for every 7-10% increase
Keep in mind tire weight also plays a big part in how you should clutch for larger tires, but this will get you very close. Always make sure you test peak RPM after setting up your clutch. With portals or gearing/tires setups that have a lower gear ratio than OEM, you should check peak RPM at a lower point. We normally suggest 55-60mph, but if you are 15% under geared, you’d want to check at roughly 45-50mph.
See this article on how to check peak RPM: https://aftermarketassassins.com/tech-blog/f/clutch-testingverification#