nishiki12

Hey Y'all

Back in March, I joined this forum and my first post was about my ****ty decision to drill 2 1/4" holes in my seatstays to mount a rack. I took 'em out at the end of February, and then I read an article on Material Physics and realised how bad big ass holes in cylindrical aluminum can be. You gave me mixed answers (i.e. "ur a dumbass, ur gonna have ur bike fall out from under you and you'll break your tailbone")

Well, I did smash my tailbone, but that was during a basketball game. What didn't happen was that my bike, with its holy stays, broke in half. I did crash it several times doing fast downhill trails at a local park, and every time I checked it for cracks, and every time there were none. I even made a fiber optic light from an old lamp and peeked inside the stays to look for cracks inside, and found none.

Now, during the summer I took the rack + ammo can panniers off, since trail riding with loud rattling behind you is not ideal. But now, it's winter again, and Mother Nature has decided to nuke my city with snow for a couple of weeks, so the rack and panniers are going on again.

This time, I'm mounting them with proper p clamps on the seatstays and chainstays, so no stress will be directly on the holes. My question is, do you guys think that my bike'll be fine through this winter and into next summer + fall (I'm getting a new bike sometime around this time next year)?

Just in case these come in handy:

Bike: Nishiki Anasazi Hardtail
Wheels: 27 in, 700c
Frame Size: 16
Frame Material: Aluminium
Holes: Clean through both sides of the seatstays, 1/4 - 1/3" diameter

Thanks in advance
Mounting points: 6 (2 factory-drilled holes, 2 p clamps on seatstays and 2 on chainstays)
Rack + Pannier Weight: Max 10 lbs, Normally around 7 lbs
Riding Area: Suburban Neighborhoods + maybe gravel roads

fietsbob

Riv nuts go in larger holes, then reinforce them as they expand..

plan B) fill with epoxy putty


and worry..







..

Kapusta

Gresp15C

Nobody can give an authoritative answer but a mechanical engineer, and they're not going to. Anything else is a guess.

Maelochs

it was a bad idea, but the result is not guaranteed ... your seat stays might or might not fail at any time. Since you have been willing to gamble this far .... whatever.

jj1091

I clicked on it just wanting to see how you'd drill 2 1/4" holes in anything on a bike. Well, maybe the seat.

nishiki12

Lol no, I meant that there was one 1/4" hole per seatstay. 2 was the amount of holes.

Mark Manner

If it fails going down hill or in traffic, you might die. Other places maybe just broken bones. To me it wouldn't be worth the risk, and I would save up and buy a new frame and hang that one on the wall. Frames make cool looking art anyway, and it is always fun to get a new one.
Good luck!
Mark

cyccommute 

No, nishiki12 won't "die" if the frame fails under most any circumstances. Frame failures aren't of the "bike shatters into a million pieces" variety...even self-inflicted frame failures. Both seat stays are unlikely to fail at the same time and even if they did, the bike wouldn't do anything more than hit the tire against the seat tube. It might be an exciting ride but it wouldn't result in "death!"

Was it something dumb to do, yes. But it isn't deadly.

While I stand by what I said above, your frame is probably going to fail at some point as you know from the article you read. The more you pound it, the more sooner the failure will occur. When it does, I would suggest a less destructive method of attaching a rack to your new frame. A p-clamp will do the job nicely. A much better, but more expensive, clamp is available from Tubus . I've had great success using that mount even for the lower mount on bikes without rack mounts.

Mark Manner

Hi, I agree it's not more likely than not to result in death. However, I never said or thought that the frame was going to explode upon failure. I do think that if one seat stay breaks going downhill at 40mph and the seat tube hits the tire, it very likely could result in a crash. At that speed, its serious.

wingless

Gresp15C

search Amazon "vinyl coated clamp." Use innertube rubber as a shim if needed.

Flip Flop Rider

can you hear the noise from the holes?

unterhausen

I forget if I answered the other thread. I am a mechanical engineer, and I did my Ph.D. thesis on monitoring fatigue cracks in aluminum. The answer is that it may take a long time to break or it might never break. The one thing to consider is that if it does start to crack and the cracks become visible, the growth will start to accelerate exponentially. The loading on stays may be such that you will not get any cracking, it's hard to know without doing more analysis.

I do think it's better at this point to use p-clamps. The top of the rack doesn't need much stabilization. The holes are much more likely to crack if the load is applied there with a bolt. I found a paper about that once, but I failed to save the reference.

TiHabanero

Why not reinforce the holes with something like a bolt bonded in place? Back in the 90's steel bikes with holes in the top tubes for internal cable routing sometimes failed at the holes if they did not have a reinforcing collar around the hole brazed in place. Perhaps bonding something into the hole will have the same affect as a reinforcing collar.

Maelochs

Ride it until it breaks and kills you ... then come here and post about it.

Wileyrat

The only thing I can add is good luck. Oh, and keep your medical insurance up to date.

Kedosto

unterhausen

I forgot to mention that you should look at those holes fairly frequently.

Hoopdriver

Seat stays are probably the least stressed of all frame members. It's doubtful that there will be a dramatic failure; especially with rim brakes, which would resist any wheel misalignment. Disk brakes create their own stresses on a seat stay but not at the point of your experimental modification. I wouldn't worry too much but you probably want to keep your eye on them.

Reynolds 

OP, you weren't the first to do this.

mtbikerinpa

Such overtightening on those.... ouch.

In my experience a seat stay on a rim brake bike takes more deflective force than a disc would. The compliance outward is often higher than it is on vertical(what disc would do). Can of worms maybe, but my steel frames especially were prone to bowing outward (as much as 1/8") with v-brakes or cantilevers and haven't had a single problem with flex since adding discs(which was adding the tabs). As was stated, the failure mode is not instantaneous in either case, so if you monitor your frame when you clean it there shouldn't be any sudden surprises. If the holes were fairly cleanly drilled and centered the tensile force would be carried around the eyelets in a decent manner. All aluminum frames fatigue at some point its just a matter of when and what point of the frame goes first.

NickDandy

Find someone with a TIG welder that does Aluminum. Maybe a place that repairs Mag Rims for cars.
Just have to keep it cold while welding.

Shawn