Loctite Blue 242 vs Red 271: Which Threadlocker?
By Nate Sawyer, Editor · Updated July 2026
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Loctite Threadlocker Blue 242
The default threadlocker for anything you'll service again: valve covers, brackets, bike and equipment bolts. It stops vibration loosening but still breaks free with a wrench, which is exactly why it's the most-reached-for bottle in the shop.
| Type | Medium-strength anaerobic threadlocker |
|---|---|
| Set time | Fixture ~1 hr on steel |
| Full cure | 24 hr |
| Bonds | Metal threaded fasteners up to 3/4 in (M20) |
| Strength | Medium; ~115 in-lb breakaway on 3/8-16, removable with hand tools |
| Temp range | Up to 300F (149C) |
Loctite Threadlocker Red 271
The permanent threadlocker for bolts that must never back out. It roughly doubles the holding torque of blue, so it belongs on structural and safety-critical fasteners, with the tradeoff that you'll need a torch to ever take them apart.
| Type | High-strength anaerobic threadlocker |
|---|---|
| Set time | Fixture ~1 hr on steel |
| Full cure | 24 hr |
| Bonds | Metal threaded fasteners up to 1 in (M25) |
| Strength | High; ~230 in-lb breakaway on 3/8-16, needs heat (~500F) to remove |
| Temp range | Up to 300F (149C) |
Our verdict
The rule is simple: blue for bolts you'll service again, red for bolts that must never move. Blue 242 is medium strength (~115 in-lb breakaway on a 3/8-16 fastener) and comes apart with ordinary hand tools, making it right for valve covers, brackets, bike and equipment bolts. Red 271 is high strength (~230 in-lb, roughly double) and needs about 500F of heat plus heavy torque to remove, so it belongs on structural and safety-critical joints like suspension and frames. When in doubt, choose blue - you can always re-apply, but red on the wrong bolt means a torch later. Both need bare metal-to-metal contact to cure.
Frequently Asked Questions
- What is the difference between Loctite 242 and 271?
- Strength, and therefore whether you can ever take the bolt apart again. Blue 242 is medium strength at roughly 115 in-lb breakaway on a 3/8-16 fastener and comes off with ordinary hand tools. Red 271 is high strength at roughly 230 in-lb - about double - and needs around 500F of localized heat plus heavy torque to remove.
- When should you use red threadlocker instead of blue?
- On bolts that must never move: suspension components, frames, machinery and other safety-critical or high-vibration fasteners. Anywhere you will service the bolt again - valve covers, brackets, bike and equipment bolts - red is overkill and will make future you miserable.
- Is red threadlocker permanent?
- Effectively permanent for hand-tool purposes, but not literally. It comes apart with about 500F of heat and heavy torque, which is a real workshop operation rather than a roadside one. Plan for that before using it on anything you might need to disassemble in the field.
- Do both work the same way?
- Yes. Both are anaerobic, meaning they cure in the absence of air and require bare metal-to-metal contact, so neither will set on plastic threads. Both fixture in about an hour on steel, reach full cure at 24 hours, seal threads against leaks and corrosion, and are rated to 300F. Blue covers fasteners up to 3/4 in (M20); red goes to 1 in (M25).