RC46 front right brake caliper - bolts snapping!

Hi all

The stretch bolts on my RC46 1999 fi x right side front brake caliper keep snapping, even though they are new bolts. They will not tighten to the specified torque of 31nm. Instead the torque reduces and the bolt snaps. I've inspected the threads on the caliper and they look ok, also there is no metal in the bolt threads.

The weirdest thing I've ever experienced doing mechanics!! I've ordered another caliper (used) but has anyone got any ideas why this happens?

yours flummoxed,

Nidgy

 

Yeah I doubted my torque wrench so borrowed a really expensive one and it still snapped bolts at 26nm

 

That makes no sense. I have had the front end apart on all my VFRs multiple times and never an issue with bolts snapping. Are you using genuine bolts?

 

1. Is it #29 that you're snapping?

2. sure you're looking at NM scale on torque-wrench and not lb*ft?

3. are these brand-new never used bolts from plastic bag bought from Honda dealer ?

4. Post photos of broken bolt pieces. Zoom in on 2 sides of break. How deformed is break? Can you re-assemble cleanly or is there lots of distortion?

5. Test fit any other clean bolt by hand (no threadlocker), are you able to spin it all way in by hand?

 

usually, finger-tight + 1/4 -1/2 turn works right----we hope no cheap chinese bolts

 

Yes genuine new honda bolts p/n 90107mt3003

 

1. Yes i think so (21 on my pic)
2. Yes nm on sealey digital torque wrench
3. yes p/n90107mt3003
4. wildo
5.will try this too
6. thx!

 

You're welcome!

I'm thinking there may be something inside bracket threads which may be damaging bolts?

5. Since these bolts come with dry-threadlocker compound, it may be possible there's some build-up or some contaminants such as sand or metal fragments may have gotten trapped inside? Test is to verify you can screw in normal bolt by hand all way in without requiring too much force.

7. Also good idea to verify calibration of torque-wrench. I test them every couple of years just to be sure.

 

Have you run a tap down to clear the threads?

 

Should really confirm there's something messed-up in threads of bracket before running tap through. Better to use thread-chaser in this case.