thorn xtc seatpost bolt

[mikey3]

hi folks first post ,while tightening my seatpost bolt up today ,it snapped and the threaded end is stuck fast ,any ideas how to get it out,i think it will have to be drilled out ,but if that damages the thread where do i go from there! and if i do manage to get it out any idea where i would get a replacement,i can,t use the bike until this is done  ,thanks

[Toby.]

I assume that your bike is quite corroded and the bolt has not been moved for many years.

Start with penetrating oil such as WD40, lie the bike on its side and apply a little every so often and allow it to soak down the thread, this may take 24hrs or more.

If there is enough of a stub sticking out then you could hacksaw a screwdriver slot to v.carefully apply some torque, but if not you may need a small stud extractor. This s a tool with a tapered and coarse self-tapping left hand thread that you would screw into a pilot hole carefully drilled up the centre of the bolt, allowing you to apply a little torque.

Stud extractors are available from motor accessory shops.

The key is to be really gentle with the torque and to persevere with the WD40!

You could do a temporary repair with a jubilee clip as a seat clamp! if you do destroy the thread in your frame then you could use a longer bolt and a dome nut to secure the seat clamp.

[pdamm]

I had a similar problem and drilled a small pilot hole then used a wood screw as a stub extractor (because I didn't have a real one and I'm cheap)

Peter

[stutho]

Hi  mikey3,

I don't own a XTC, but if it is the same arrangement as an RT & RST then there might be a simple way to remove the bolt.  This process relies on the fact that you can access the thread end of the bolt as well as the head end.

If the head has COMPLETELY sheared from the thread then there is no longer any holding torque on the thread, this is a big advantage.  If the head isn't completely sheared the it is worth removing what remains of the head with a large drill bit.

Once the head is destroyed  uses a small (0.5mm) standard drill bit in middle of the bolt but on the thread end. The idea here is to drill a pilot hole for next bit, however some times drilling this hole will start to unscrew the damaged bolt. The pilot hole only needs to be a few mm deep.  If you can control the speed of the drill then you want a slow speed

The final step is then to switch to a medium bit (2mm).  The object this time is not to drill through the bolt but to turn the bolt.  Again we are drilling from the thread end of the damaged bolt. (Again, use a slow speed).


This method will normally works and should not damage the threads but if you are unsure at any point then stop and get a second opinion.   

[mikey3]

hoorah  managed to drill offending bolt out and find another that fits just right,chipped a bit of the paint work though with is a bit annoying ,and no the bike isnt old and rusted ,the bolt was just very weak indeed,hope none of the others are as poor quality

[ians]

funnily enough (or not ...) I've just done the same thing on my RST.  Undoing the bolt to fit a new seat post and it sheared off.  Luckliy there was about 5mm of the threaded end and I unscrewed it with Mole Grips.  Could have been a disaster away from home.

This is a 8 month old bike - no corrosion - carbon seat post still slides smoothly in.  Have always been a little concerned about this aspect of the frame design - a collar is so much easier.

ian

[Toby.]

Sorry to make negative asumptions regarding the age and condition of your Thorn; this is why: My 2 year Raven Tour and 3 year old Explorer were both fitted with good quality A2 stainless binder bolts as standard, these should last a good while before there is any chance of a problem. However; when giving my wife's brand new RT a careful look over a couple of days ago I noticed that the binder bolt was a very inferior ungraded and chrome plated bolt, I have changed it now!

One key element of Thorn bikes in my view is the attention to detail that they usually apply to such areas as these, a binder bolt failing is a small problem in a bike shop or well equiped garden shed; but a real pain on tour!