Loctite Blue 242 vs Red 271: Which Threadlocker?
By The DIYPicks Team · 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.