# Drilling a hole in the seat tube. Risky?



## titaniumgearsolid (Mar 13, 2008)

Planning on getting a Rockshox Reverb Stealth soon. And yes, my frame doesn't have internal routing for the Stealth's hose. I figured I could just drill a hole in the seat tube for the hose to pass through. And if my speculations are correct, the seat tube is the least stressed part of the frame so a single hole will not compromise its strength or integrity. By the way, frame material is aluminum.

I'm curious to hear your thoughts on this.


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## aBicycle (Jun 13, 2012)

Sounds crazy and dangerous.


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## patrick2cents (Apr 30, 2010)

I wouldn't.... Even if it isn't as stressed as the other tubes, a hole in a tube creates a serious weak spot. You might be right and it wouldn't matter, but there's a good chance it could cause premature failure.


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## mtbzarg (Oct 6, 2011)

I have to agree with the replies given so far. To great of a risk in my opinion.


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## CharacterZero (May 19, 2004)

titaniumgearsolid said:


> Planning on getting a Rockshox Reverb Stealth soon. And yes, my frame doesn't have internal routing for the Stealth's hose. I figured I could just drill a hole in the seat tube for the hose to pass through. And if my speculations are correct, the seat tube is the least stressed part of the frame so a single hole will not compromise its strength or integrity. By the way, frame material is aluminum.
> 
> I'm curious to hear your thoughts on this.


Do you have water bottle mount holes? I'd just widen one of those a bit and wear a camelback...


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## b-kul (Sep 20, 2009)

CharacterZero said:


> Do you have water bottle mount holes? I'd just widen one of those a bit and wear a camelback...


this or i know cam mccaul drills a hole in his bb on his trek slope bike and he goes a lot bigger than any of us so...


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## h2ored (Oct 3, 2008)

b-kul said:


> this or i know cam mccaul drills a hole in his bb on his trek slope bike and he goes a lot bigger than any of us so...


hole in BB is much better idea. Hole in seat tube or anywhere else for that matter would not only weaken but cause stress concentration...bad


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## Sheepo5669 (May 14, 2010)

I dont think you would have any problems with a small hole in the seat tube.


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## Caffeine Powered (Mar 31, 2005)

Do it, just not at a joint of the tubes. Frame tubes have plenty of holes for escaping gasses when welding so having a random hole shouldn't hurt if it's well placed.

Unless it's carbon fiber.


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## dead_dog_canyon (Sep 8, 2010)

Stress concentration is not my area but I did do some real failure tests of plates with holes in college - this gave me a 'gut feel' for it&#8230;.

I agree with Caffeine about go for it and stay away from the joint.

Keep the hole as small as possible. 
As you can see from this chart the stress is some kind of exponential function. The smaller the better.


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## jeffscott (May 10, 2006)

titaniumgearsolid said:


> Planning on getting a Rockshox Reverb Stealth soon. And yes, my frame doesn't have internal routing for the Stealth's hose. I figured I could just drill a hole in the seat tube for the hose to pass through. And if my speculations are correct, the seat tube is the least stressed part of the frame so a single hole will not compromise its strength or integrity. By the way, frame material is aluminum.
> 
> I'm curious to hear your thoughts on this.


You certainly can....lots of bottle holders mount there...

But you need to insert the proper sleeve akin to the bottle holder inserts, that support the edges of the hole to reduce the stress riser.


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## PretendGentleman (May 24, 2011)

jeffscott said:


> You certainly can....lots of bottle holders mount there...
> 
> But you need to insert the proper sleeve akin to the bottle holder inserts, that support the edges of the hole to reduce the stress riser.


even this is probably overkill. just make sure the hole is nice and round to avoid stress risers. I'd not only avoid a joint, but I'd stay a couple of inches away from any joint (i.e., weld for most bikes).

I've drilled plenty of holes, even in carbon frames and never heard of any cracking. Roadies will often ride only in sunshine and leave corrosive sweat residue on their frames. The cable guides will corrode so much that we'll knock em off, drill out the hole, and rivet a new one on. works 100% of the time, and these are wimpy road frames, often with pro riders pedaling them and the holes are in downtubes and toptubes.


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## jeffscott (May 10, 2006)

PretendGentleman said:


> even this is probably overkill. just make sure the hole is nice and round to avoid stress risers. I'd not only avoid a joint, but I'd stay a couple of inches away from any joint (i.e., weld for most bikes).
> 
> I've drilled plenty of holes, even in carbon frames and never heard of any cracking.LOts of threads on here about frames cracking Roadies will often ride only in sunshine and leave corrosive sweat residue on their frames. The cable guides will corrode so much that we'll knock em off, drill out the hole, and rivet a new one on. works 100% of the time, and these are wimpy road frames, often with pro riders pedaling them and the holes are in downtubes and toptubes.


Yup so put in the cable guides like I said...

What are you going to do leave an edge to wear away at the cable or housing as the case maybe.


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## PretendGentleman (May 24, 2011)

jeffscott said:


> Yup so put in the cable guides like I said...
> 
> What are you going to do leave an edge to wear away at the cable or housing as the case maybe.


I definitely wouldn't advise against what you are suggesting, but I wouldn't hold off on the project because I was lacking a guide to press into the hole. It matters to a greater extent if the housing will move a lot.

I'm curious if the cracked frame threads you are referring to are frames that have cracked because of a hole drilled through the frame.

I suspect that I should have said,


PretendGentleman said:


> even this is probably overkill. just make sure the hole is nice and round to avoid stress risers. I'd not only avoid a joint, but I'd stay a couple of inches away from any joint (i.e., weld for most bikes).
> 
> I've drilled plenty of holes, even in carbon frames and never heard of any cracking. Lots of stories about frames cracking, but very rareley does the crack occur more than an inch or two from a weld or joint Roadies will often ride only in sunshine and leave corrosive sweat residue on their frames. The cable guides will corrode so much that we'll knock em off, drill out the hole, and rivet a new one on. works 100% of the time, and these are wimpy road frames, often with pro riders pedaling them and the holes are in downtubes and toptubes.


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## harpo-the-biker (Aug 21, 2010)

Don't.


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## ou2mame (Apr 23, 2010)

if you want to chance it, go for it. but it may lead to a frame failure. its up to you if thats a risk that you're willing to take. there is no definitive answer. is it 100% safe? nothing is.. frames break and there's no holes drilled into them. i would imagine that a frame with a hole probably has a slightly higher chance of breaking, but it would obviously be determined by circumstance. is it worth the risk? thats the only real question you have to ask.


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## tillman40 (Mar 10, 2012)

*Lightening parts*

I came from an auto racing background. We drilled holes in almost everything to drop weight. And we were doing 160 +. As long as the joints are not compromised you should be fine. Most non-carbon bikes are over engineered anyways..


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## dead_dog_canyon (Sep 8, 2010)

Have you thought about all the stresses the bike goes thru when you are riding it? Maybe I'm a geek / nerd but I do sometimes on long climbs to get my mind off pedaling.

The pedals put side to side and torsional forces of the bottom bracket and frame. Your weight puts vertical forces on frame. Hitting bumps puts fore and aft forces on the frame and all forces are fed thru the wheels. The tires flex. The rims flex and have torsional forces about the axles. All this is happening at once&#8230;..

Scroll down for some pics Bicycle Frame Efficiency | Bike Think

Here is a link to a guy that has done some very simple FEA stress analysis on some bike parts. These models are over constrained but you can get an idea of what is going on.
Jeffery McGehee - YouTube

I have sat thru some 'dog and pony show' presentations (design reviews) where the stress guys have spent 6 months modeling this stuff. Very very cool to see the animation in color&#8230;..


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## 006_007 (Jan 12, 2004)

b-kul said:


> this or i know cam mccaul drills a hole in his bb on his trek slope bike and he goes a lot bigger than any of us so...


I bet its been a while since Cam has paid for a frame as well.......


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## titaniumgearsolid (Mar 13, 2008)

Yeah, seems like the seat tube has more stress than I thought.


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## titaniumgearsolid (Mar 13, 2008)

The Intense Tracer 275 has such a hole.. It could have been engineered (reinforcement/butting/etc. that could strengthen the stress area in the seat tube). Or it could be just that - a hole.


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## Trial11 (Oct 5, 2011)

titaniumgearsolid said:


> The Intense Tracer 275 has such a hole.. It could have been engineered (reinforcement/butting/etc. that could strengthen the stress area in the seat tube). Or it could be just that - a hole.


You would think Intense would have some idea of where the high and low stress points exist. Hopefully they didn't just jump on a forum and ask if they should drill a hole randomly in their seat post


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## BShow (Jun 15, 2006)

I would think that as long as it's well placed, you'll be fine. 

I would ask in the framebuilders forum or over on velocipede salon. Not many of us clowns over here will know definitively one way or another. 

Rest assured, drilling a hole will void your warranty.


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## titaniumgearsolid (Mar 13, 2008)

Reviving this thread with pics showing someone already did it...


























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