Rust on a Ti bike @ bottle cage bolts

[Nooch]

Friend of mine is looking at purchasing a ti bike but is concerned with this apparent rust at that bottle cage bolts.

Would you think it's repairable, would you be concerned, what could have caused it, is there a fear of ultimate failure? Or should he buy the bike, hit it with a wire brush, and get on with his day?

[AngryScientist]

those are the rivnuts that are rusted. pretty typical. rivnuts are a crap solution to bottle cages on ti bikes, but a lot of mfg's did this. welded bosses are vastly superior.

if the price is right, and the rivnuts are in there solidly, i'd have no reservations wirebrushing those clean, clearcoating them so that doesnt happen again, greasing the bolts and going on with life.

[biker72]

Isn't there galvanic action going on between the steel rivnut and ti frame? You can wire brush it and cover it up but the junction between the rivnut and frame is still corroding.

Be nice if it was a titanium rivnut....if there is such a thing.

[Tickdoc]

kinda defeats the whole, err one of the purposes of having a ti bike.

What manufacturers do it this way?

[oldpotatoe]

kinda defeats the whole, err one of the purposes of having a ti bike.

What manufacturers do it this way?

'Was' pretty common, like serotta, litespeed....not sure who does it today but it's way cheaper than welding a boss on there. Hard to tell from pic but I think Lynskey uses rivnuts.

[cribbit]

The rivnut could completely rust through and the only damage to the bike will be that you can't attach a bottle cage.

Are bosses better? Definitely. But this is both cleanable and not a huge issue.

That said, it depends on what the whole bike is. $500 litespeed? Whatever. $1500 serotta? Probably check everything else on the bike a little closer.

[duff_duffy]

Is it just one bolt or all of them? Could always drill out the rivnut and put new one in (easier on seat tube). Local shop did the for $25 for me on a ti bike.

[bigbill]

My Ti Serotta has Rivnuts. The Lynskey has bosses. FWIW, the Serotta rivnuts are aluminum. Wirebrush it and clearcoat.

[oldpotatoe]

Is it just one bolt or all of them? Could always drill out the rivnut and put new one in (easier on seat tube). Local shop did the for $25 for me on a ti bike.

Gotta be careful tho..if the remnants fall into down tube, you 'may' not be able to get them out...ask me how I know...:eek:

[crossjunkee]

I had a ti Vassago (made by Lynskey) that started rusting at the seat tube / BB weld. I would not buy the frame in the picture.

[Pegoready]

kinda defeats the whole, err one of the purposes of having a ti bike.



Welding produces a lot of heat, and one could make the argument that it's a lot better to drill a hole and rivnut it on a lightweight, often-butted tube. This is the kind of thing that can happen around welded bottle bosses that are overheated:

https://www.sheldonbrown.com/rinard/EFBe/tour14db.jpg

I've seen Firefly actually reinforce the area all the way around with what looks like a welded ring in order to use welded bosses. Hats off to them. It's an extreme solution to a simple problem, and most Ti manufacturers aren't going to go through the trouble to do this.

https://i.imgur.com/GECdCk0.jpg

The other argument is if you cross-thread the bottle bolt, it's a lot easier to replace the rivnut than fix the threading on a welded boss.

[FriarQuade]

Welding produces a lot of heat, and one could make the argument that it's a lot better to drill a hole and rivnut it on a lightweight, often-butted tube. This is the kind of thing that can happen around welded bottle bosses that are overheated:

https://www.sheldonbrown.com/rinard/EFBe/tour14db.jpg

I've seen Firefly actually reinforce the area all the way around with what looks like a welded ring in order to use welded bosses. Hats off to them. It's an extreme solution to a simple problem, and most Ti manufacturers aren't going to go through the trouble to do this.

https://i.imgur.com/GECdCk0.jpg

The other argument is if you cross-thread the bottle bolt, it's a lot easier to replace the rivnut than fix the threading on a welded boss.

The top photo failed because there's a massive pin hole in the weld. That's a great place for a crack to propagate.

I believe the Firefly is butted and they just change the butt in that zone for the bottle boss.

[Mark McM]

those are the rivnuts that are rusted. pretty typical. rivnuts are a crap solution to bottle cages on ti bikes, but a lot of mfg's did this. welded bosses are vastly superior.

Whether welded bosses are superior may depend on other factors. As noted, welding may not be possible/practical on very thin tube walls. That's why rivnuts have also been used on very thin walled aluminum and steel frames as well. For example, Keith Bontrager used rivnuts on his ultra-light steel Race Lite MTB frames, because the tube walls at the water bottle holes was too thin to weld.

[happycampyer]

Welding produces a lot of heat, and one could make the argument that it's a lot better to drill a hole and rivnut it on a lightweight, often-butted tube. This is the kind of thing that can happen around welded bottle bosses that are overheated:

https://www.sheldonbrown.com/rinard/EFBe/tour14db.jpg

I've seen Firefly actually reinforce the area all the way around with what looks like a welded ring in order to use welded bosses. Hats off to them. It's an extreme solution to a simple problem, and most Ti manufacturers aren't going to go through the trouble to do this.

https://i.imgur.com/GECdCk0.jpg

The other argument is if you cross-thread the bottle bolt, it's a lot easier to replace the rivnut than fix the threading on a welded boss.Seven uses rivnuts and always has for the reason mentioned above, so for them it isnt a matter of cutting costs. The Firefly is externally butted, and the tube is un-butted where the waterbottle bosses are.

[cribbit]

Seven uses rivnuts and always has for the reason mentioned above, so for them it isnt a matter of cutting costs. The Firefly is externally butted, and the tube is un-butted where the waterbottle bosses are.

I have a Seven without rivnuts :)

[Dino Suegiù]

Can your friend inspect the frame, for this and other possible issues?

At the very least, have your friend ask the seller to remove all 4 bottle cage bolts and photograph all of the rivnuts carefully, if the frame cannot be viewed in person.

I would be less likely to buy a ti frame that looked like that without being able to inspect it myself...unless this is a really special frame, there are so many ti frames for sale now, often in truly mint condition.

[Marin]

Remove the rivnuts completetly and replace, ideally with stainless ones.

[MikeD]

Welding produces a lot of heat, and one could make the argument that it's a lot better to drill a hole and rivnut it on a lightweight, often-butted tube. This is the kind of thing that can happen around welded bottle bosses that are overheated:

https://www.sheldonbrown.com/rinard/EFBe/tour14db.jpg

I've seen Firefly actually reinforce the area all the way around with what looks like a welded ring in order to use welded bosses. Hats off to them. It's an extreme solution to a simple problem, and most Ti manufacturers aren't going to go through the trouble to do this.

https://i.imgur.com/GECdCk0.jpg

The other argument is if you cross-thread the bottle bolt, it's a lot easier to replace the rivnut than fix the threading on a welded boss.


A hole drilled in the frame is a stress riser and rivnuts don't reinforce it very well. I had a Trek aluminum bike where the frame cracked through at a rivnut holding on the front derailleur braze-on. I'd rather have a welded boss.

[Butch]

I was at Moots for ~18,000 frames built with welded in bosses and maybe there were a couple that had issues. Some of those tubes were thin 0.7mm. Just depends how the preparation and welding is done and where they are located IMO.

[FriarQuade]

I was at Moots for ~18,000 frames built with welded in bosses and maybe there were a couple that had issues. Some of those tubes were thin 0.7mm. Just depends how the preparation and welding is done and where they are located IMO.

Bingo. Welding isn't inherently flawed in any way. But it is a process that depends on a certain level of preparation to ensure it's reliable. Same thing goes for rivenuts though.