Bad Diagnosis from Decathlon

Lozz360

Über Member
Location
Oxfordshire
Had a problem with the B'Twin Ultra whereby the bottle cage bosses on the down-tube had both come loose. So despite the bolts being tight, the water bottle would wobble about which is annoying.

I took the bike into the local Decathlon (Oxford), same branch the bike was purchased from in March 2017. I was asked by one of the mechanics if I had tightened the bolts. Well yes, I replied. He then said that the only way to repair this was to replace the frame! Somewhat surprised that a pair of loose bottle cage bolts would mean that the aluminium frame was now junk, I said "OK but there is a lifetime guarantee on the frame". His response was that not in this case as it was obvious I had over-tightened the bolts! This remarkable feat of forensic science was achieved without even attempting to remove the bottle cage to inspect the bolts or the bosses. Mechanic then looked on the computer and said that there were just three frames left in the large size that mine is (discontinued model). The cost would be £259 and to help me out they would transfer all components to the new frame free of charge. I said I would think about it.

On returning home, I went on YouTube and did a search on "bottle cage boss repair" or similar and there was an American chap who showed how to easily tighten these bosses without any special tools. It is literally less than a five minute job. Incidentally, the proper name for the bosses is riv-nuts as they are a cross between a rivet and a nut. I am somewhat annoyed to think that the mechanic must of known it was a simple repair. I know he is not new to the job as he was the same chap that sold me the bike over two years ago.
 

biggs682

Smile a mile bike provider
Location
Northamptonshire
I thought Decathlon bikes frames had a lifetime warranty ?
Perhaps he had not heard of riv-nuts
 

Globalti

Legendary Member
Come on now, surely you don't expect a Decathlon mechanic to know how a riv-nut works? Unfortunately by their design they are prone to work loose in the frame, either by vibration or under the effects of salt water oxidation.
 
The bolts are very temperamental. I’ve knackered one pair of bolts on of my Ultra frames, by over tightening them in the past. If you do manage it ( easily done ) just epoxy the bolts in. It means you won’t get the cages off again, without breaking the bond, but that’s easy to live with. The frame isn’t “junk” or a warranty replacement case, because the bolts have been over tightened, Decathlon were right about that. It’s not ideal, but it’s fairly common. The bolts really only take a couple of Newton meters torque, or they break the threads.
 

Phaeton

Guru
Location
Oop North (ish)
There is a tool you can use to tighten them up, you can also make one that will work, you need a flat plate with a 6mm clearance hole in it, 2 washers, 6mm nut & a longish 6mm bolt. put the nut onto the bolt, then the 2 washers, then the plate, screw this into the Riv-nut make sure it's all the way in, then holding the bolt so it can't turn screw the nut down, this will effectively re-squash the riv-nut. Alternatively as long as they haven't used the harden steel rev-nuts just drill them out & replace.
 
Location
Loch side.
Just buy a rivnut tool. They're pretty handy around the workshop if you do sheet metal work. It costs no more than a pop riveter. You'll also need a Dremel with a diamond grinding bit to gnaw off the flange on the old rivnut. That will then drop into the downtube, which you remove through the BB shell next time you operate on your BB.

Every bike shop should have a rivnut tool, I don't understand why not. It is easy money because so many of them fail.
 
OP
Lozz360

Lozz360

Über Member
Location
Oxfordshire
I thought Decathlon bikes frames had a lifetime warranty ?
Perhaps he had not heard of riv-nuts
Yes a lifetime warranty for their aluminium frames. But in this case I had apparently over tightened them. The mechanic decided this was the case without even looking at the bolts or the fastenings. Are riv-nuts not used on many bikes? I believe they are so a mechanic should have heard of them.

Edited to correct the auto correction of "riv-nut" which came out as "rob-nut". Although "rob-nut" probably describes the Decathlon staff member concerned!
 
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I tend to makes sure the riv-nuts are squished in properly with the tool before I start attaching bits to them. I’ve had loads that I suspect weren’t, probably on a ‘safer to not go in hard enough, than too hard’ basis, from wherever the bike was built up.
 
Yes a lifetime warranty for their aluminium frames. But in this case I had apparently over tightened them. The mechanic decided this was the case without even looking at the bolts or the fastenings. Are rob-nuts not used on many bikes. I believe they are so a mechanic should have heard of them.
He’s probably ( definitely ) seen this before, and was working to a ‘standard procedure’.
 
OP
Lozz360

Lozz360

Über Member
Location
Oxfordshire
The frame isn’t “junk” or a warranty replacement case, because the bolts have been over tightened, Decathlon were right about that.
The Decathlon mechanic stated exactly that. The frame needed replacing because the bolts had apparently been over-tightened. They had not, as I have since managed to tighten the riv-nuts and the bottle cage is now completely secure.
 
OP
Lozz360

Lozz360

Über Member
Location
Oxfordshire
There is a tool you can use to tighten them up, you can also make one that will work, you need a flat plate with a 6mm clearance hole in it, 2 washers, 6mm nut & a longish 6mm bolt. put the nut onto the bolt, then the 2 washers, then the plate, screw this into the Riv-nut make sure it's all the way in, then holding the bolt so it can't turn screw the nut down, this will effectively re-squash the riv-nut. Alternatively as long as they haven't used the harden steel rev-nuts just drill them out & replace.
Thanks to Youtube, I used an oversized nut, a washer, the bolt for the bottle cage, 5mm allen key and an adjustable spanner. The repair took less than a minute. My point is, was Decathlon trying to scam me into replacing the frame or are their experienced mechanics just not aware of how a bottle cage is fitted to the frame?
 

Milzy

Guru
I hate riv nuts. My oven door catch is on one that’s come out. It needs welding on.
One tool I don’t have is a rivet gun or rivet popping device.
 
OP
Lozz360

Lozz360

Über Member
Location
Oxfordshire
Perhaps he has just transferred from Halfords
He's been there at least since March 2017 as he was discussing the bike with me when I purchased it new. I wanted to make sure I could make all the adjustments necessary to fit as this bike was a size smaller than the other bike I had, a Triban. His assistant helpfully informed me that it was possible to adjust the seat height on these bikes! What will they think of next?
 
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