[mgmannin]

I purchased a used Gary Fisher Ferrous frame on eBay. Its made of ox platinum steel tubing and has an eccentric bottom bracket. I brought the frame to a shop to be media blasted and powder coated. The results after the media blasting were disappointing. There are several small holes in the seat tube because of rust/rot. Is the bike safe to ride? Biggest hole is 4mm.

Besides welding in a new seat tube is there anything I can do. One guy at the bike shop recommended sawing off the end of a seat post and jamming it down to the bottom bracket for added strength. Others have told me it is ok to ride because its high strength steel.

Opinions/suggestions?

 

[Rody]

Mg,

The best solution would be to cut out the lower half of the seat tube, just above the water bottle bolts. A new piece can be fashioned to fit in, an internal sleeve pressed inside to bridge the joint, secured in place by circumferentially welding the joint and bullet welding the superior/inferior aspects. Once completed, it should produce an invisible repair, prolonging the life of the frame.

The fact that your frame is already stripped and blasted will expedite the process. A ball park price for such work should be around 180 dollars.

cheers,

rody

 

[TrailMaker]

Hey;

I would VERY carefully inspect the inside of the seat tube visually. If you had a boroscope or video inspection probe, that would be helpful. Rusting from the inside out means you have at least 50% more corrosion on the inside as is visible outside, with other spots likely ready to bust through at any moment. Make sure any sectioning of the tube takes that into consideration. You obviously want to remove all the rot with this procedure, and you might want to consider some sort of remediation of any surface rust elsewhere inside this tube.

Frankly, I'd be a bit concerned with the rest of the tubes. I'm not sure an old frame is worth all that effort, frankly... unless it was had some sort of provenance.

 

[mgmannin]

Thanks for the replies

Frame is a 2008 and was only $150. I can't justify spending another $200 to replace the tube. Might be forced to buy a bike directs aluminum special.


Do you think jamming a modified carbon seatpost covered in some type of adhesive would strenghten the tube?

 

[mickuk]

We discovered the same type of pepperpot corrosion holes on my wife's ancient Rockhopper when it got blasted. It was in both the chainstays and the seat tube. We didn't do anything with the bare frame for years, then eventually I built it into something else, and so far it hasn't got worse, cracked or killed anyone!

I chopped off the back end and used the front triangle (including the holy seat tube) for a full suspension kiddy carrying bike. Cutting open the unused chainstays, I found the internal corrosion actually wasn't too extensive (just along the bottom edge where water could pool).

If you keep an eye on it for cracks starting from the holes, I can't see any kind of seat tube fracture being rapid or catastrophic.

The cheap minimum option is to get it powder coated at a place that has an iron or zinc phosphate dip. This should help stop any internal corrosion getting worse (in the UK the phosphate and a basic industrial powder coat costs me about £35). Maybe cheaper if you just let them do it in whatever colour is going down the powder line that day . Maybe also drill a hole in the bottom of the bb shell before coating to make sure any moisture that gets in the tube through the holes can drain out easily.

Regarding shoving in a bit of seatpost - if it needs to go in a long way, be aware that the seat tube won't be reamed all the way down (so it might not go in far enough). Also the bottle bosses might get in the way, and if it is internally butted tubing (meaning the middle of the tube is a larger diameter bore), then you might end up loosing the seatpost in there and having it rattle about.....

 

[TrailMaker]

Here's a thought;

You could fairly easily choose a tube that is close to but perhaps slightly larger than the seat tube, cut a piece that is long enough to take care of the rot, cut that tube in half lengthwise, form and fit the halves to the seat tube area in question, and bond them on using automotive steel panel bonding adhesive. This could be done quite neatly by a DIY'er, and would be extremely strong if done well.

Perhaps not the artisan's choice, no doubt, but relative to pitching the frame and your $150 with it, solutions like this make some sense.

 

[eurospek]

Frame is a 2008 and was only $150. I can't justify spending another $200 to replace the tube. Might be forced to buy a bike directs aluminum special.


Do you think jamming a modified carbon seatpost covered in some type of adhesive would strenghten the tube?

Or just buy a 2011 On-One Inbred, they are currently 25% off, which off their $300 or so MSRP is a screaming deal ATM.