jbphilly

I was working my way up a rocky 4x4 track in the mountains outside Jerusalem yesterday on day 1 of a 3-day outing when my Tubus Vega rack up and falls off the bike. To be precise, the right-side dropout attachment point had failed, as had one of the two points attaching the main rack to the two rods linking it to the seat stays.
Thetouringstore.com has a couple photos showing the parts I'm talking about...

Dropout attachment point: https://thetouringstore.com/TUBUS/VEG...opout%2010.jpg

Other thingy: https://thetouringstore.com/TUBUS/VEG...0Mount%204.jpg

The rack was not (and has actually rarely been) heavily loaded - I just had a stuff sack with maybe 6-8 pounds of stuff lashed onto the top. It's been ridden around on some gnarly dirt roads with similar loads or no load.

The two screws in question were gone - one must have come loose a while earlier, while the other was hopelessly lost amid the gravel on the road. I do have a couple spares that I keep around the bike for just such an occasion, so I was able to get the rack situated again to continue the trip. However, I'd left behind my T20 torx wrench which was needed to tighten the other top mounting point (as seen in the photo) - which had also begun to loosen.

I didn't trust my repair job to hold, given that one screw was still somewhat loose, so the trip ended up being a S24O as they call them. Anyway, I have a few things I want to figure out to prevent this in the future...

-I have heard of screws working their way loose like this, and the recommended solution seems to be Loctite. However, do these screws/bolts generally need to be re-tightened periodically?

-The rack came with a number of spare screws/washers, but only the allen-key kind seen in the dropout attachment point photo, not the Torx kind. Is there any reason why I need to use a Torx-operated screw for that particular attachment point, or can I just go ahead and substitute a regular Allen-key screw?

-Finally, any other experiences like this or relevant advice?

Luckily the trip was quite enjoyable while it lasted. Against my better judgment I took a dirt road down to the bus stop today rather than the paved road and got some great canyon views. Also pretty glad this particular mechanical issue happened on a short outing, rather than several days into a fully-loaded desert sojourn far from civilization...

fietsbob

My most adventurous touring bike, I used an 8.8 tempered steel bolt, (only in hex head, 8 for 5mm bolt)
Loc Tite threadlock , can be painted over to resist rust..

You may not have the hardware tight enough , so flexing in shear fatigued the metal ..

or, being loose, stuff fell out..

get to a bike shop, might be a good time to follow torque specs on the hardware,
thus you need a proper, torque wrench.

jbphilly

Am I right in assuming the source of the problem is the bolts not being adequately tightened? Should I worry about tightening them too much?

jimc101

Sound like user error, the bolt didn't fail, as there would have been some of it left in the frame braze on if it had, sounds like the bolt has undone due to being insufficiently tightened, Loc Tite is a good.

Going by the instructions, you need to torque these down to 4.3Nm https://www.tubus.com/documents/1320934478_Vega.pdf, also it's worth periodically checking them.

jbphilly

Definitely user error. In the absence of a torque wrench, any rules of thumb for knowing how much to tighten the bolts?

Cyclesafe

Tight enough they won't vibrate loose, loose enough you take off the racks when you want too.

During a tour make bolt tightening part of your daily maintenance routine.

indyfabz

+1, especially on the checking periodically. I have had from rack bolts come loose on two occasions. The first time I caught it early. Two years ago, on a rocky road in MT on the 5th day of a trip, I lost one and its spacer and a second one was half way to falling out. The cause was me putting on the rack in haste trying the day before the tour started. I was in a park as rain was moving in. Hurried to get the rack on and get back to camp. Then I did not check tightness after the first day that included a bumpy, unpaved road.

fietsbob

not too hard to break off a mild steel or stainless steel bolt if you have no idea about what you are doing

Hence having a torque wrench and the torque specifications , in
standardized units of measure ... Numbers can be stated,, Nm../ inch/ounces, foot/pounds, etc.

feel of how tight is right is more difficult ,

experience and a few broken or stripped things is a harsh teacher , but effective over time.

Doug64

+2

I check rack bolts about every other day and when I lube the chain. While they have never been "falling out" loose, they have been loose enough to feel it.

LexKing

I was notorious for breaking bolts in my youth. I have found that it is best for me to put things together left handed in the absence of a torque wrench. Enjoy your tour!

MassiveD

A torque wrench should not be required, and I wouldn't trust any torque spec given there are no standardizations in parts. Also, it is difficult to know what a torque spec means when the parts involved are not of high quality. There are interface design specs for bolts in machinery that are much higher than those in... crap. You can't tell what the bearing is is something as crappy as a drop, but poor is the best you can hope for. So if you load the part up you may be overloading it if the bearing is crap. This is why there are custom frames and Paragon Machine Works. So I would use reasonable pressure to secure the nuts and reversible locktite. GE silicone is also pretty awesome at holding junk together.

I tighten most small parts with a wrench between the base of my thumb and my middle finger, without closing my hand. I am feeling the thing shut tight, not trying to be Mongo the Mechanic Clown. It's a feel thing. No big deal if a part shakes loose every now and then. That is how everyone gets from there to here.

Allen bolts are standard on this stuff. When Torxs came out it could function as a security screw because people didn't have them, but the dollar store sells sets today. Also when they were knew the screws and bits tended to appear together, guaranteeing good fits, this is gone for same reason as above, or at least you have to buy quality matched stuff, which works with any of this stuff. Torxs seems to work better in shallow screws, with less spin out. It is also faster to align and works shallower which is better for automated manufacturing. I try to have everything on the bike allen bolts. I will pay way more for a part, or go custom to keep everything in a few allen sizes.

jimc101

Totally lost in your logic for this, in this case.

The OP has a rack from Tubus, which the manufacture gives specific torque setting, they have standardized parts, and a setting in Nm, which is a standard torque spec. For high quality, given that these are high end rack, would take them to be high quality.

For types of bolts, Torx or Hex (Allen is a brand not type) as long as you are carrying the correct tool, it doesn't make much difference on a bike what you have.

Tourist in MSN

When I bought a Tubus Logo EVO, I was dismayed to find Torx bolts. Fortunately, I had some good old fashioned normal M5 bolts that take allen wrenches so I did not have to make a run to the hardware store. I have Torx bolts on one bike, that is enough and I do not want to use any Torx bolts on non-Rohloff hardware.

I always recommend blue loctite on all rack and kickstand bolts. If you are not sure what blue loctite is, do an internet search. There likely would be a similar product in your location in the hardware store. Bolts can be tightened and loosened, but will not vibrate out when blue loctite is used. I also use blue loctite on shoe cleat screws.

I store some extra bolts, one countersunk for shoe cleats, in unused brazons on my bike or occasionally threaded in from the back side on a long brazeon (and locked in place with a nut) so I have spare bolts on my frame at all times.

You are lucky no odd parts got lost in the process.

A friend of mine lost a rack bolt on the GAP trail this past spring, fortunately he found it was missing before anything bad happened. I loaned him one of the spare bolts off of my bike to finish the trip.

The only bolts on my bikes that see a torque wrench are the crank to bottom bracket bolts. I am not saying you should not use a torque wrench, but I have not found a need for them on things like the M5 bolts on racks. And I have never seen a small Torx bolt wrench to torque wrench adapter you would have needed for those bolts.

djb

I too recommend the regular check of rack bolts. I have however over done the tightening once, which makes you feel even more stupid-so I would heed the loctite advice, plus gently check them regularly as all the vibrations tend to loosen up stuff.

This touches on the age old thing of the inherent goodness of being familiar with your bike and giving it a once over regularly. I've said this before, but one real advantage of keeping your drivetrain clean and such is that it gives one the opportunity to be very familiar with your bike, I should say to encourage being familiar with your bike..so to check over stuff like this, which can really avoid pain in the keester situations.

boomhauer

God also invented lock-washers.

MassiveD

I may have missed his situation, I thought that the screw came loose from the bike through the rack. If it was rack to rack, you have a point. I guess one can't go wrong using the manufacturer's specs in that case, it is at least as good as 65 Neuton Mongos. But it certainly isn't a high quality part, being a rack doesn't get you much in that regard. If it was the rack mounting to the drop then all bets are off, I doubt any two of the points are the same, and they will all be horrendous. Break out the glue.

And it would help to have a real torque wrench that cost more than Chicom. Coincidentally I was just buying a torque wrench today for similar sized parts, and it cost 135 dollars, and is a nice cheap one because it only has one setting with the variability being in an adjustible lever arm, which is a cheap way to get precise, compared to what it should cost.

Testing of bolts tightened with even quality wrenches indicates wild variances. So the use of torque wrenches is pretty scattershot anyway. Test of hand tightening is also all over the place even for pros, but I don't know that the variance is worse. I haven't heard it said, but it would make sense if the TW loads at the mean, were closer to some number, but that isn't necessarily progress. Torque wrenches have become more popular since carbon has come out. Often, however, wrenches indicate the TW loads they put on to spec were higher. That's probably a good thing when working with complex systems that should be assembled as closely to spec as possible. But guys who built bikes without a problem for years finding they now have to pinch the bars at a higher load value, when the prior loading always worked, doesn't sound like progress. I can live with having the parts work at the lowest value necessary, rather than some higher Poindexter determined load, particular considering the crap we are working with.

OK reread the OP, sounds like it failed at the drop. I don't think that is in Tubus' brief, all they know is how hard you can crush their stay? They have no idea how their bolt plays with some crap drop?

jbphilly

It was both, actually - I'm not sure which one came loose first, but it took three bolts being loose or one (one rack-to-bike was gone, one rack-to-rack was gone, and one rack-to-rack was loosened but still attached) for the rack to fall off.

The bike in question is a Surly Troll, which has weird dropouts with plenty of places you could install the rack (well, at least two options) but I don't think that's the issue.

Anyway, now that I've been informed that hex bolts are as good as Torx bolts, I should be able to use the spare parts that came with the rack to get things up and running with confidence, and I'll grab some Loctite next chance I get.

digibud

Of course you should be checking them regularly, especially given your usage. That said, blue loctite (often comes in a red tube, strangely enough) will keep the bolt in place very nicely for a very, very long time with no need for you to touch them. Be sure the bolts and nuts/threads are clean. You don't want to apply the loctite over greasy threads and you do want a bit of loctite over all of the threads. I don't knock my bike around as much as you but I have racks that have been on bikes for years. I no longer even check the bolts regularly. That might not hold for you, but blue loctite is the way to go, for sure. Clean male and female threads plus blue loctite on all the threads. Game over.

MichaelW

I have had bolts come loose with lightly loaded racks on aluminium frames but not on heavily loaded steel frames.
My solution was to use anti-rotation star washers.
I also use full length bolts for my water bottle cage to use in case of rack bolt loss or damage.

djb

That's a smart idea, shall stick that in the old noggin for future use.
PS, are you the fellow who did the YouTube video showing how to use toeclip straps to help with Marathon plus mounting?

Tourist in MSN

You want the blue type.

I have bought similar stuff that is made by others with comparable results.

Doug64

There is something to consider if you remove your front rack very often. I remove my front rack 3-4 times a year to ship my bike or switch the rack to a different bike.

Here comes the heresy

I don't use loctite on front rack bolts, I use grease. There is always a chance of cross treading the mounting bolts when trying to allign the rack with the dropout mounting point. This is especially true if you cannot easily start the bolt by hand. In my experience threads and bolts that have loctite residue are more difficult to start by hand. When I say start by hand, I mean engaging several threads of the bolt using my fingers. I want those bolts to be easy to get in and out. When they are tightened up they usually won't loosen, and I've never had one fall out. I also believe that with the same force the bolt is tighter with lubricated threads than non-lubricated threads.

I do use a torque wrench for most other things on the bike, but not for things I need to remove or loosen for shipment, which includes racks, stem, and seat clamp. It is my understanding that torque values are more accurate if the treads are lubricated prior to tightening. However, I have also read that lubricting a bolt prior to torquing it can result in less force required to exert the same gripping force, which could result in over tightening. There is a lot of controversy about whether to lube or not to lube prior to torquing a bolt. Some manufacturers assume clean dry threads, while others will specify differently.

Regardless of what is used on the bolts, regular checks are still an easy safe guard against parts falling off. Heck, it is a bike not an airplane.

Tourist in MSN

I would not call it heresy, grease is a viscous fluid, so it can be better than a dry bolt when it comes to bolt retention in a vibrating bike.

I commented that I recommend blue loctite on rack, kickstand and cleat bolts. But I did not bother to mention that I usually use grease on water bottle cage bolts, fender bolts, stem bolts, brake bolts, etc.

fietsbob

Torque specs are using a standard scale, that number is how tight.

to do the job with accuracy the wrench has the same scale ..


a properly torqued bolt is stretched just slightly, and that tensile force
pulls back just a little and keeps things from unscrewing as easily

greasing threads technically, would have a different Ideal torque , than dry assembled fittings.

Simon Cowbell

I started using Beeswax for accessory (racks, fenders, cages) bolts. It works well enough for the road touring I've been doing, but if I went back to touring 4x4 roads, I'd also go back to using blue Loctite.