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I’ve recommended these super lightweight bicycle cassettes from AliExpress many times, but it looks like they could have an issue…
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These lightweight SLR Gen3 cassettes from a brand called ZTTO on AliExpress, are pretty incredible for the price. They are MUCH lighter than the equivalent cassettes from Shimano or SRAM, and you can find them for around £60-£70. They use some very intricate and frankly, quite good looking CNC work, and come in a bunch of colours and sizes.
The largest 3 gears are machined from a single block of 7075 aluminium, while the rest are made from a single block of steel, however it’s the aluminium gears that could be a problem.
A viewer sent me some pictures of his cassette where the top two aluminium sprockets had completely sheared or snapped off the back of the cassette. After taking a more detailed look at the design, it’s quite easy to see how this could have happened.
I have run these cassettes on my road bikes for over a year at this point, with no real issues, but it looks like it might be a good idea to proceed with caution when it comes to the 11-36 version of this cassette…
AliExpress affiliate links below ↓
FYI, It wont cost you any extra, but I get a little kickback from AliExpress, which helps!
Ztto SLR Gen3 cassettes:
https://s.click.aliexpress.com/e/_c4VLune7
https://s.click.aliexpress.com/e/_c3OHmkWX
Ztto SLR Gen2 cassettes:
https://s.click.aliexpress.com/e/_c4BZaFMr
Ztto ULT full steel cassettes:
https://s.click.aliexpress.com/e/_c3yroFwB
SROAD/SPEDAO cassettes (also a good option):
https://s.click.aliexpress.com/e/_c4ExXdhd
Timestamps:
00:00 – Intro
00:33 – ZTTO SLR Gen3 cassette failure
01:24 – Cassette design
02:34 – Why haven't mine broken?
03:58 – Does use-case matter?
05:05 – Should I be worried?
07:10 – Alternative cassettes
08:21 – Bonus clip
Intro roll:
Created by Dev Joshi - http://www.go2dev.co.uk
Instagram:
https://www.instagram.com/tracevelo/
Email:
tracevelouk@gmail.com
Please note:
I am not a professionally trained bike mechanic. There can be risks associated with using products that are unbranded, untested, or come from sources where the provenance is unknown. Please talk to a qualified bike mechanic if you are in any doubt.
In essence, be careful, do your research, and cycle safe!!!
Keywords: AliExpress cassette review,ZTTO cassette,ZTTO SLR Gen3 cassette,Aluminium cassette,Lightweight cassette,budget cassette,ZTTO bike parts,mono-block cassette,best lightweight cassette,AliExpress lightweight cassettes,CNC aluminium cassette,cassette failure,Chinese bike parts,ZTTO cassette review,aluminium cassette durability,monoblock steel cassette
Bike part mentions in this video
ZTTO SLR Gen3 11speed Road Bike Cassette 11 Speed 11-30 11-32 11-34 11-36 11-28T 112g K7 11s Spokets HGR universal
Ultralight SPEDAO SLR2 Road Cassette 11 Speed 11-25/28/32/34T Bicycle Freewheel CNC K7 11V HG Sprocket For R9100 Bike Parts
ZTTO Ultimate 11/12 Speed Road Bike Cassette Ultralight 11s 12s 11-28/30/32/34/36T Gravel Cassette 11V 12V Black Freewheel HG K7
ZTTO Ultraight 11 12 Speed Road Bike Cassette 11s 12s 11-28/30/32/34/36T ULT Sprocket 11s 34T Gold Flywheel 11V 12V Gravel K7 HG
ZTTO ULT2 12 Speed 11-30T 34T 36T Road Bike Cassette 11 steel with 1 AL Gravel Ultralight 12S Bicycle Freewheel 12V Sprocket
CassetteZTTO SLR Gen3 11speed Road Bike Cassette 11 Speed 11-30 11-32 11-34 11-36 11-28T 112g K7 11s Spokets HGR universal
Created: March 12, 2025The reviewer analyzes the ZTTO SLR Gen3 11-speed cassette, focusing on a specific failure where the top two sprockets sheared off. They note the cassette is lightweight, visually appealing, and affordable. The design involves the top three sprockets milled from a single aluminum block with the rest being steel. The reviewer has used smaller versions (11-28T) for years without issue, but identifies a design flaw in larger sizes (11-30T and up) where the top two sprockets are connected by a thin ring of supports, creating a potential cantilever beam effect and stress risers. They attribute the specific failure to use on a rough cyclocross course with spiky power delivery. The reviewer concludes that these cassettes prioritize weight savings over durability and safety margin, advising caution with larger sizes.
AI-Summary
Pros
- Great looking
- Incredibly lightweight (e.g., 117g for 11-28T vs. 260g for Shimano 105)
- Affordable (about 60 quid)
- Shifting performance is 'really decent', about 90-95% as good as Shimano/SRAM
Cons
- Design flaw in larger sizes (11-30T, 11-32T, 11-34T, 11-36T) where top two sprockets are connected by a thin ring of supports, creating a weak point
- Risk of sprockets shearing off, especially under high, spiky loads (e.g., climbing out of saddle on rough terrain)
- Questionable safety margin due to extreme material milling
- Noisier than official Shimano cassettes during running
- Aluminum teeth on upper sprockets can snap if shifting under load, as aluminum is softer than steel chain
- Prioritizes minimal mass and competitive weight claims over long-term durability and high-cycle fatigue life
Key Points
- Brand: ZTTO
- Model: SLR Gen3
- Construction: Top three sprockets milled from a single block of aluminum, the rest is monolock steel
- Weight: 117g for 11-28T size
- Failure observed on an 11-36T cassette after ~150km while climbing
- Design varies by size: only the 11-28T version does not have the 'double stack' layout for the top two gears; larger sizes do, increasing risk
- Larger sprockets are more flexible/compliant, increasing failure risk
- Recommended for users who accept trading safety factor for weight savings
- Suggested alternatives: ZTTO cassettes milled from a single steel block with aluminum spider, or the older SLR Gen2 where only the largest sprocket is aluminum
Ultralight SPEDAO SLR2 Road Cassette 11 Speed 11-25/28/32/34T Bicycle Freewheel CNC K7 11V HG Sprocket For R9100 Bike Parts
Created: June 23, 2025The reviewer does not mention the 'Ultralight SPEDAO SLR2 Road Cassette' at any point in the video. The entire transcript is dedicated to analyzing lightweight cassettes from the brand ZTTO, specifically their 'SLR Gen 3' model and other generations. The reviewer discusses a specific failure of a ZTTO cassette, analyzes its design, compares different sizes, and discusses alternatives like the ZTTO SLR Gen 2 and steel cassettes from ZTTO. The brand SPEDAO is not referenced.
AI-Summary
ZTTO Ultimate 11/12 Speed Road Bike Cassette Ultralight 11s 12s 11-28/30/32/34/36T Gravel Cassette 11V 12V Black Freewheel HG K7
Created: December 01, 2024The reviewer analyzes the ZTTO SLR Gen 3 ultralight cassette, focusing on a specific failure case where the top two sprockets sheared off. They describe the cassette's construction: the top three sprockets are milled from a single aluminum block, with the rest being monolock steel, resulting in significant weight savings (117g vs. 260g for Shimano 105). The reviewer has personally used smaller versions (11-28T) for thousands of miles without issue but identifies a critical design flaw in larger sizes (11-30T and above). In these larger cassettes, the top two sprockets are connected to the third by a thin ring of supports, creating a potential cantilever beam effect and stress risers at sharp internal corners. This design, combined with spiky power delivery (e.g., in cyclocross) and the increased flexibility of larger sprockets, increases the risk of failure. The reviewer concludes that these cassettes prioritize minimal weight and low cost over structural safety margin and long-term durability. They advise caution, particularly for the 11-36T and 11-34T versions, and suggest stronger alternatives like ZTTO's all-steel or Gen 2 cassettes. They also note the shifting performance is decent but not as good as OEM, the cassettes are noisier, and aluminum teeth can snap if shifting under load.
AI-Summary
Pros
- Incredibly lightweight (e.g., 117g for 11-28T vs. 260g for Shimano 105)
- Great looking and available in funky colors
- Low cost (about 60 quid)
- The reviewer has run smaller versions (11-28T) for thousands of miles/years without problems
- Shifting performance is described as 'really decent', about 90-95% as good as Shimano/SRAM
Cons
- Design flaw in larger sizes (11-30T, 11-32T, 11-34T, 11-36T): top two sprockets connected by thin supports, creating a weak point
- Risk of sprockets shearing off, as evidenced by a viewer's cassette failing after ~150km
- Sharp internal edges (90° corners) act as stress risers
- Prioritizes weight saving over safety margin and long-term durability
- Built to a low price point, which compromises robustness
- Larger sprockets are more flexible, increasing failure risk
- Noisier than official Shimano cassettes during normal running
- Aluminum teeth on the upper sprockets can snap if shifting under load, as aluminum is softer than steel chain
- Not suitable for abuse like shifting under heavy load
- The reviewer questions how much safety margin, if any, is built in
Key Points
- Brand: ZTTO, model referenced is SLR Gen 3
- Construction: Top three sprockets milled from single aluminum block, rest is monolock steel
- Weight: 117g for 11-28T size
- Price: About 60 quid
- Failure case: Top two sprockets sheared off as one piece on an 11-36T cassette after ~150km while climbing
- Design analysis: Thin support arms create a cantilever beam effect; sharp internal corners are stress concentrators
- Size matters: Only the 11-28T version has a different, safer web structure where only the largest sprocket uses thin supports. All larger sizes have the risky 'double stack' layout for the top two sprockets.
- Use case matters: Spiky power delivery (e.g., cyclocross, out-of-saddle climbing) increases stress
- Alternatives suggested: ZTTO cassettes milled from a single block of steel with a chunky aluminum spider, or ZTTO SLR Gen 2 cassettes where only the largest sprocket is aluminum.
- Shifting: 90-95% as good as Shimano/SRAM, but noisier
ZTTO Ultraight 11 12 Speed Road Bike Cassette 11s 12s 11-28/30/32/34/36T ULT Sprocket 11s 34T Gold Flywheel 11V 12V Gravel K7 HG
Created: February 21, 2026The reviewer analyzes the ZTTO Ultraight cassette, focusing on a structural failure in the 11-36T version. They explain the design flaw, compare it to the more robust 11-28T version they use, and discuss how use case and sprocket size affect failure risk. They conclude these cassettes prioritize weight over durability.
AI-Summary
Pros
- Lightweight (prioritizes minimal mass)
- Visually appealing with colors
- Good value (built to a price point)
- Shifting performance is decent (90-95% of major brands)
Cons
- Potential structural failure in larger sizes (11-34T, 11-36T) due to design
- Sharp internal edges and 90° corners act as stress risers
- Thin support arms create a cantilever beam effect on top sprockets
- Larger sprockets are more flexible, increasing failure risk
- Noisier than official Shimano/SRAM cassettes
- Aluminium teeth can snap if shifting under load
- Questionable safety margin due to extreme material removal
Key Points
- Failure observed on an 11-36T version used in cyclocross.
- Design differs by size: only the 11-28T version has a safer design where only the largest sprocket uses thin support arms.
- Larger sprockets act as longer lever arms, increasing peel-off forces.
- Use case matters: spiky power delivery on rough terrain stresses the cassette more.
- Cassettes are CNC-machined from aluminium, pushing material limits.
- Recommends steering clear of the 11-36T and 11-34T versions.
ZTTO ULT2 12 Speed 11-30T 34T 36T Road Bike Cassette 11 steel with 1 AL Gravel Ultralight 12S Bicycle Freewheel 12V Sprocket
Created: February 21, 2026The 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.