You cannot insure just the frame because the policy covers the entire bike and insuring for less than the bike’s value would be considered “under insuring”, and it has an inherent downside.

• Example: Complete bike build $7,000 that includes the frame cost of $3600. Client insured the bike for $3600 with a $100 deductible.
• Scenario: Bicycle involved in a crash and the frame is broken beyond repair. No other damage to the bike, just the frame. Cost to replace the frame is $3600 which would be considered a total loss by the insurance company that would pay the full value of the insurance ($3600) less the deductible ($100). Claim paid $3500, and because this is a total loss the insurance company retains possession of the entire bicycle, not just the frame. 
• Outcome: Client ships the entire bike off to the insurance company and is left with $3500 to replace a $7000 bicycle.
• Advice: Insure the bicycle for as close to MSRP as affordable.