Why epoxy in frame tubing “weep holes”?

You know those little holes at the top and bottom of chainstay and seatstay tubing? I’ve heard they are referred to as “weep holes”, and that the reason they are there to begin with is to release hot gasses during the welding process, and the reason that some holes are near the bottom of the tubing is so that any water or condensation that may have entered the finished frame (at any time in its life) can drain and allow the frame to dry out.

I was cleaning up a couple of large Alpinestars Cro-Mega frames, and I noticed epoxy had been used to plug the bottom weep holes on the drive-side seatstay on both bikes, although I acquired these bikes from different sellers, so I’m wondering if epoxy is applied at the factory for some reason. No other holes have been epoxied on either frame. In addition, I have other Cro-Mega frames that don’t have any of the weep holes plugged, although they are smaller frames.

I also have a Nishiki cromoly frame that has ALL weep holes sealed with epoxy, and seller said he knew nothing about it, and I have identical Nishiki frames that don't have any holes epoxied.

Sealing holes that are there for drainage and aeration purposes seems outright wrong to me, but perhaps there is a reason for this? :?

Sorry in advance for my ignorance on this matter, and thanks in advance for the insight and sage advice from the RB collective.

A couple of pics, here:

Just thinking as a layman, presumably if you bought it new and were happy there was no moisture inside the tubes (or you used some sort of treatment) it might make sense to stop future corrosion.

If a frame is built up I would assume that not too much water would get through the seattube/headtube/BB/bottle cage mounts (unless you fully immersed it !), so it would keep everything dry. Seems like a lot of effort tho.

Frank - I used to seal the holes back in the day for the reasons mentioned above by madjez.

From experience, the stays would usually begin to bubble around the holes due to the great UK weather letting water in to the tubes at these locations.

They had served their purpose during welding to exhaust the gases, and they weren't intended as 'weep holes' in my eyes...

I didn't use epoxy however, it was lapped layers of waterproof tape which I would cut off and renew every few weeks.


Cheers,
BB.

4 of my older bikes have all the vent holes brazed closed, my Marin Team Issue (TET), 91 Yeti FRO, 89 Wicked Chance, and Rossin SLX (road bike).

I've always considered this a bonus and sign of build quality, obviously it is an extra step most mass produced frames cannot justify.

That being said i've never seen vent holes sealed in that manner. Maybe the original owner or manufacturer used a frame sealer product or wax buildup? Not sure.

lack of knowledge by me might see this opinion wrong

I always thought the weep holes were to allow excess bonding agent/vapours to exit and air in until fully cured. Once that job has been done then fill the holes to stop crap getting in?

MADJEZ":19phe57r said:

Just thinking as a layman, presumably if you bought it new and were happy there was no moisture inside the tubes (or you used some sort of treatment) it might make sense to stop future corrosion.

If a frame is built up I would assume that not too much water would get through the seattube/headtube/BB/bottle cage mounts (unless you fully immersed it !), so it would keep everything dry. Seems like a lot of effort tho.

Click to expand...

MADJEZ,
I had assumed that someone had purposely sealed the holes to prevent moisture entering the tubes without considering that moisture could get in through other areas of the frame, but perhaps they considered it and decided it wasn't an issue unless, like you say, the bike was fully immersed.

I was curious why it was only the one location on both bikes that had been sealed, but perhaps all the other locations were blown out while I was cleaning the frame, as I had applied degreaser inside the bottom bracket and the head tube, and then inserted a garden hose at full pressure to rinse it and to blow out any loose rust or other debris. For those concerned that I was actually introducing water into a frame, please keep in mind that moisture is not a problem where I live; it's so hot, dry, and sunny in the mountains of SoCal that the frame was bone dry in a matter of minutes after rinsing.

BoyBurning":19phe57r said:

Frank - I used to seal the holes back in the day for the reasons mentioned above by madjez.

From experience, the stays would usually begin to bubble around the holes due to the great UK weather letting water in to the tubes at these locations.

They had served their purpose during welding to exhaust the gases, and they weren't intended as 'weep holes' in my eyes...

I didn't use epoxy however, it was lapped layers of waterproof tape which I would cut off and renew every few weeks.


Cheers,
BB.

Click to expand...

Tom,
If an experienced RBer like yourself is doing it, it must be a good idea. I realize that the insides of the tubes are typically bare metal as they don't receive any coating from the manufacturer, so keeping moisture away at all costs makes sense, especially in an area prone to moisture.

It's a shame manufacturer's don't do more to protect frames from rust by coating the insides of tubes, whether by dipping or by pressure. Maybe they don't consider it to be a big issue, so, like Mr.Toad indicated, perhaps they feel they can't justify the extra cost in time, money, and resources involved. Certainly the added weight of the extra paint can't be that much of an issue.

I always use Weigle's FrameSaver on all frames that I keep, even though moisture is not a big issue where I live, and although it's an added expense and a time-consuming messy, smelly job, I feel it's the best I can do to ensure a bike's longevity.

Mr.Toad":19phe57r said:

4 of my older bikes have all the vent holes brazed closed, my Marin Team Issue (TET), 91 Yeti FRO, 89 Wicked Chance, and Rossin SLX (road bike).

I've always considered this a bonus and sign of build quality, obviously it is an extra step most mass produced frames cannot justify.

That being said i've never seen vent holes sealed in that manner. Maybe the original owner or manufacturer used a frame sealer product or wax buildup? Not sure.

Click to expand...

Mr.Toad,
I didn't realize that some manufacturers closed up those holes. It's definitely some kind of epoxy on these frames of mine, because it's very hard (not wax), but perhaps you're right about it being some sort of epoxy-based frame sealer, and it has me wondering if what I see is just the excess that drained out as it was curing.

sylus":19phe57r said:

lack of knowledge by me might see this opinion wrong

I always thought the weep holes were to allow excess bonding agent/vapours to exit and air in until fully cured. Once that job has been done then fill the holes to stop crap getting in?

Click to expand...

sylus,
That makes perfect sense to me, but like Mr.Toad points out, perhaps it's an extra step that most manufacturers can't justify, even if the frames they make are high quality in every other aspect.

Thanks to all once again for all your insight.

As an aside Pace f8s have little black plastic plugs in their vent holes

The holes also allow internal condensation to dry after a cold frame is returned to the house after a winter ride. I treat my steel frames with Frame Saver or Boeshield during major overhauls.
Cheers

Re:

Sorry to dredge this up, but it appeared in a search and I can easily set the record straight on this particular matter. In 1992 I was with Alpinestars when we began to see '92 Cro-Mega frame failures at the drive side stay above the dropout. The stress riser inherent in the design applied directly to the relatively large heat-affected zone allowed the tube to buckle, usually on the forward face in response to applied driveline torque.

This was discovered very early in the model year as I recall. and there were large numbers of bikes(relatively speaking) still sitting in distributor stocks, undelivered to dealers. In an effort to prevent a total recall of the Cro-Megas, we brainstormed the concept of reinforcing the stay with a high tensile 2 part epoxy. Trials were conducted, a protocol extablished, and materials were purchased and sent to distributors. We sent a crew to Europe I know, not sure what happened in Japan. Our guys unboxed every single Cro-Mega in those unheated warehouses and had to commandeer heaters to get the epoxy warm enough to inject. Glad I wasn't along for that! I know I ordered all the materials, and had a hand in the trials. I suspect that the injection idea may have started with me as well, but I wouldn't want to claim it as original thought!

Re: Re:

BudsBikeBuilder":2qzf7iij said:

Sorry to dredge this up, but it appeared in a search and I can easily set the record straight on this particular matter. In 1992 I was with Alpinestars when we began to see '92 Cro-Mega frame failures at the drive side stay above the dropout. The stress riser inherent in the design applied directly to the relatively large heat-affected zone allowed the tube to buckle, usually on the forward face in response to applied driveline torque.

This was discovered very early in the model year as I recall. and there were large numbers of bikes(relatively speaking) still sitting in distributor stocks, undelivered to dealers. In an effort to prevent a total recall of the Cro-Megas, we brainstormed the concept of reinforcing the stay with a high tensile 2 part epoxy. Trials were conducted, a protocol extablished, and materials were purchased and sent to distributors. We sent a crew to Europe I know, not sure what happened in Japan. Our guys unboxed every single Cro-Mega in those unheated warehouses and had to commandeer heaters to get the epoxy warm enough to inject. Glad I wasn't along for that! I know I ordered all the materials, and had a hand in the trials. I suspect that the injection idea may have started with me as well, but I wouldn't want to claim it as original thought!

Click to expand...

So there you go then all you early Cro-Mega owners

Interesting story, must have sat there and quietly done its job otherwise it would have been more widely known as a glorious failure.

Thanks for joining just to share your knowledge.