bampilot06

Just want to know what my options are. Long story short: Brand new bike, week old, got taken out in a group ride. Along with chipped paint and some bent parts the rear seat stay got dented. I will know soon if a new frame is even possible but if not can I continue to ride it like this? What should I look for l?
and if it fails will it be catastrophic or slow?

mpetry912 

I would say that is cosmetic only.

Touch up the paint and stay out of groups who ride like they have something to prove.

/markp

bampilot06

Guy was from out of town. Hopefully, I never see him again.

Kontact 

Totally safe. With good touch up paint, filler and patience you can make it go away.

bampilot06

If I put filler, I wouldn’t know if it cracks right?

veganbikes

It is not cosmetic only sorry but keep a close eye on it and maybe reach out to the OEM and see if they have a crash replacement or warranty on it.

Kontact 

If it cracks, it won't be down in the dent where the filler is.

And it won't really matter. You aren't going to crash because one stay cracked.

Kai Winters

Leave it as it is as a constant reminder to be aware of those around you at all times and the unpredictability and chaos that can ensue...

Paul_P

What about insurance, either their's or yours ?

Kontact 

Sure. Wear torn bike shorts as well.

FBinNY 

It's a seat stay, and the dent doesn't seem too catastrophic (sharp crease or crack) so odds are it'll last until something else kills off the bike.

Use body filler and a bandaid. Or use some trim, and do the same on the other side and forget about it.

maddog34

Matching and Blending Clear coated Metallic Paint is NOT easy.

Leave it be... ride it.

bampilot06

A jerk from out of town joined our group ride. I am assuming he decided to go for a KOM during the ride. I was number 3 in the pace line. Number 1 peeled off, Number 2 had to slightly go around him, I followed number 2. This guy decided to go between the number 1 guy who was rotating to the back and the number 4 guy. He hits number 1 tire, doesn’t go down but loses control and catapults into number 4 and they both get thrown into me all at 28-30 mph.

So aware of my surroundings? Not really much I could do to avoid this. Completely unnecessary.







Took this right before the crash.


Along with the dent. It bent a chain ring, bent the hanger, broke the barrel adjuster off the RD. bent the rear wheel, slight wobble in the front wheel, and cracked my helmet.


Havnt looked to see if my home insurance policy would cover it, but that would just cause my rates to go up.

Pop N Wood

Man, tough crowd.

Sucks your new bike got wacked. On the bright side you now no longer have to worry about that first scratch.

choddo

bent a chain ring! Nasty.

Nice bike. Is that an alu Emonda?

bampilot06

Yes the 2023 ALR.

Harold74

FWIW: I'm a structural engineer. Which, of course, does not make me a professional bicycle designer.

I have some level of concern for seat stays because:

1) I believe that they support the bulk of the rider's weight and are among the most -- if not the most -- heavily taxed compression members of a bike frame.

2) Seat stays tend to be slender, as yours are.

In my work, I routinely deal with industrial building columns that get dented by forklifts. If the dent is very near the bottom of the column, I don't usually fix it. If the dent is near the middle of the column, I absolutely do as the dent will promote premature, catastrophic buckling without warning.

I like that your dent is kind of near the end of the member. I would like it if it were closer to the end of the member.

Does your frame have a brake bridge above the rear tire (disk brake obviously)? That would add to my comfort level a bit as the connection to the adjacent stay would tend to brace the damaged stay.

If this were my own bike, I would be a bit concerned.

To a degree, this might be something that you could load test, ideally simulating dynamic effects somehow. Maybe have a big guy stand on the pedals and jump up and down at the least.

As for fixing, I'd like to see the dent pulled out. I doubt that would be possible without damaging the paint however.

Harold74

Looks like no brake bar.

choddo

Interestingly, not according to this simulated analysis of a 75kg rider - in fact the body of the seat stays don't even feature in the high stress areas for any of the load cases they assessed (front & rear wheel bump, climbing out of saddle, climbing in the saddle). The upper area of the join of seat stay to seat tube did show up as a stress point for rear wheel bump and climbing in the saddle but with stresses quite a bit lower than other areas. Outside of the chain stays took the brunt of it, moreso on the drive side, especially when climbing out of the saddle.
https://pdf.sciencedirectassets.com/...07160/main.pdf

bampilot06

I just went back to the shop to look at the bike again. I concerned the seat stay had buckled where the dent was, and also the seat stay was bent towards the chain stay.

Happy to report no sign of buckle nor did the seat stay bend towards the chain stay. Looks like it’s just the dent.

I am still waiting to see whether or not I can get a new frame.

I sold two bikes to build this so, if I a new frame isn’t an option, then I will have to just ride it as it.

Harold74

Can you repost the link? I didn't take me to the paper which I'd love to check out.

I'll reserve final judgment until I see the paper but the stress analysis may not be relevant here. OP's problem isn't material stress, it's member capacity. And those two things can be quite different. Members that experience mostly tension or flexure will tend to achieve stresses close to their yield stress. Same goes for joints. A slender compression member like a seat stay, however, is likely to buckle long before it reaches it's yield stress.

However much of a rider's weight is assumed to rest on the rear wheel, the seat stays will wind up resisting a compression load larger than that. It's just truss math. And dynamic factors will only increase that load.

Harold74

Another potential issue with this is fatigue. Aluminum is very prone to fatigue issues. Hence the sacrificial derailleur hanging thing. To an extent, the dent will act as a stress riser for the compression stresses passing through it. And that ought to lower it's fatigue resistance.

Harold74

That's great, I was going to ask about that.

If it's any consolation, were I to bet money on the outcome here with no regard for your safety, I would absolutely bet that you will not have problems with the stay. I'd take maybe... 8:1 odds on that.

Trakhak

From this page (where results of FEA testing are presented), a brief explanation of why seatstays are usually very slender:

The patterns in which the total energy is distributed among the frame tubes are also interesting. For example, the seatstays absorb most of the vertical impact loads, but they do not play a major role in the other cases. Since vertical impact is not a significant factor in overall performance, the seatstays thus become prime candidates for shedding excess material (subject to strength constraints).

Harold74

Thanks for sharing that (quote from Sheldon's site). This is basically what I've been getting at. Seat stays are one of the few members on a bike frame that don't have to deal with significant bending moments. As such, they've been made slender to shed weight. But that very slenderness tends to make them fragile with respect to things like damagage.

Another plus for OP is that, with disk brakes, I'd have to imagine that much less braking induced bending stress would wind up up in the seat stays relative to rim brake setups. And that which would remain for disk brake setups would wind up in the non-drive side which is undamaged.