How is the water getting in.

[phopwood]

All,

I don't post very often, but I always hanging around.

I built up my Sherpa a year ago using parts from an old mountain bike, the bottom bracket (Square Taper cheapo and over 10 years old) was coming to the end of its life over the last few weeks.  So yesterday I put a new one in, but there were a few drops of water in the bottom bracket shell, the bottom bracket was quite rusty where the water had been sitting.

I did grease the seat post up when I put it together last year, but it is possible that I did not grease it up enough.  So the question is, is the water getting in between the seat post and frame by capillary action or some other way.  It is also possible that it got in, in between the BB locking ring and the BB as this is just a friction fit.

All the best.

Peter

[jags]

I'll go with seatpost if your 100% happy with the saddle height then  put some silicone  around the post to completely seal it.

[rualexander]

You'll never get an airtight seal to your frame and some of the air that gets in will contain moisture in the form of humidity which will condense inside the frame and end up as droplets around the bottom bracket.

[Danneaux]

Hi Peter!

Always good to see a post from you.

The Sherpa is remarkably well-sealed against water entry, with the frame's vent holes well-hidden up underneath the crown shoulders on the fork and well down the seat tube for the seatstays ( photo of the ones on my late Sherpa here: http://www.thorncycles.co.uk/forums/index.php?action=dlattach;topic=3896.0;attach=1251 ). The chainstays vent into the BB shell.

Still, it can happen, and water entry through the seat lug kerf is the most likely point of entry.

If you park the bike by laying it down on its side or by leaning it heavily, then small amounts of rain can enter through the BB Shell in that manner as well. The entry point is via the notches in the sealed BB lockring, the ones that lock the shell in place.

Using mudguards and a long mudflap have pretty much eliminated most eater entry for me, combines with a generous greasing of the seatpost. I generally park my bike with a longish saddle cover that also covers the seat lug, so that helps as well.

Hope this helps.

Best,

Dan.

[phopwood]

Thanks for your replies,  I had a close look at the old bottom bracket and the plastic shell they are far from a perfect fit,  so my money at the moment is water was getting in there.  I will take the new one apart again and put some good old fashioned grease on all the likely culprits.
Like any bike in the UK it spends a lot of its time in the rain, I am not worried about a bit of water was just wondering where may have got in.

All the best.

Peter

[mickeg]

On my Sherpa, I do not recall if the downtube and headtube are open to both the seattube and headtube or not.  I was surprised when I recently built up a Nomad MkII that there was a piece of tape covering the toptube and downtube holes inside the headtube.  I concluded that the tape was installed by Thorn to keep water out of those tubes if water got past the upper headset bearing.  My Nomad has S&S couplings, so water can't get down to the bottom bracket from this route of water entry, but if those tubes are open on both ends, that could be a route of water ingress to the Sherpa bottom bracket.

I have no clue how water got into my Sherpa on a tour I took in May were it rained for several days.  But when I pulled the seatpost when I got home, I could see a bit of water down the seattube.  I left the seatpost out of the bike to aid evaporation.

I honestly do not know how much damage water ingress into the frame will cause, assuming it is not salt water.  A couple years ago I bought a used Bridgestone MB-6 that was built in the 1990s, it had been stored outside in the rain and snow for over a decade.  A two inch diameter tree was growing up through the frame and had to be cut down so I could get the bike.  Getting the bottom bracket out was a real chore and there was a lot of rust accumulated inside the tubing, but I gave it a thorough treatment of JP Weigle Frame Saver and regularly ride that bike for nearby errands.  I also store it outside.

Before I built up the Nomad, I also gave it a good Frame Saver treatment, but I put new tape over those holes after I was done treating it.