The ZTTO ULT2 cassette is extremely lightweight and offers decent shifting, but larger sizes (≥30T) have a design flaw in the top aluminum sprockets that can cause failure under load, making them a safety concern.
Pros
- Extremely lightweight
- Visually appealing with nice colors
- Good value for the price
- Shifting performance is decent (90-95% of major brands)
Cons
- Potential structural failure in top two sprockets of larger sizes (30T, 32T, 34T, 36T)
- Design creates cantilever beam effect and stress risers
- Less safety margin due to aggressive material removal
- Noisier than official Shimano cassettes
Key Facts
- Weight is extremely low, used on sub-6kg climbing bikes
- 11-28T version has stronger web structure; larger versions (30T-36T) use a double stack layout with thin support arms
- Larger sprockets act as longer lever arms, increasing stress and risk of failure
Reviews & Ratings
The reviewer uses a ZTTO ULT2 12-speed cassette on their lightweight climbing bike, noting it is extremely light and a good compromise between weight and durability, but they need more miles to fully evaluate it.
AI Summary
Pros
- Extremely light weight
- Good compromise between weight and durability
Cons
- Durability not yet confirmed; reviewer needs more miles to be sure
Key Points
- ZTTO ULT2 12-speed cassette
- Used on a sub-6kg climbing bike
- Part of weight-saving modifications for hill climb racing
The reviewer analyzes a failure of the ZTTO ULT2 cassette, specifically the 11-36T version, focusing on a design weakness in the top two aluminum sprockets. They explain the structural and use-case factors that likely led to the failure and compare the design across different cassette sizes.
AI Summary
Pros
- Lightweight (ultralight, prioritizes minimal mass)
- Visually appealing with nice colors
- Good value (built to a price point)
- Shifting performance is 'really decent' (90-95% of major brands)
Cons
- Potential structural failure point in the top two sprockets of larger sizes (30T, 32T, 34T, 36T)
- Design creates a cantilever beam effect and stress risers
- Less safety margin due to aggressive material removal
- Noisier than official Shimano cassettes
- Aluminum teeth can snap if shifting under load
- Prioritizes weight saving over durability and safety factor
Key Points
- The 11-28T version has a different, stronger web structure where only the largest sprocket uses thin support arms.
- Larger versions (11-30T, 32T, 34T, 36T) have a 'double stack layout' for the top two sprockets connected by a thin ring of supports, increasing failure risk.
- Larger sprockets are more flexible and act as longer lever arms, increasing stress.
- Use case matters: spiky power delivery (e.g., cyclocross racing) puts massive stress on the cassette.
- The cassettes are CNC-milled from aluminum, pushing the material's limits.
- The reviewer suggests steering clear of the 11-36T and 11-34T versions.
Where to Buy
Questions about ZTTO ULT2 12 Speed 11-30T 34T 36T Road Bike Cassette 11 steel with 1 AL Gravel Ultralight 12S Bicycle Freewheel 12V Sprocket
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