The drill is whining!
A customer brought in a GT gravel bike.
On the left and right blades of the front fork, there are three M5 downtube holes on each side,
and on both the left and right, the rivnuts in the middle and lower positions have come loose
and are stripped, so they asked if I could fix them.
This was a case that came up on the phone a while back—
I said "I can probably fix it," but
I never expected them to actually come here by train from S Prefecture in the Kanto region.
Apparently all the shops in their area refused to do it.
↑Right middle
↑Right lower
First I considered just re-riveting the original rivnuts,
but they were deformed so badly that was out of the question,
so I decided to replace them with new ones and re-rivet.
To do that, I either pinch the flange of the rivnut with pliers or,
if the rivet has some hold, grind away the flange with a drill,
but the rest of the rivet falls into the fork blade.
First I removed the pressure anchor in the headtube
and checked whether the fork blade, fork crown, and fork tube
were connected, and whether there was enough cavity for the rivnut fragments to pass through.
I inserted a shift cable for probing through the rivnut hole,
and while there was a slight catch on the crown,
I was able to pull the cable out through the fork tube hole.
They are connected.
But since there was a possibility the rivnut fragments wouldn't pass through,
I got the customer's approval with the caveat "worst case, some might stay in the fork blade,"
and started the work.
As it turned out, I was able to recover all of them.
↑Left middle
↑Left lower
The lower left one looks like the carbon might be cracked, but
it's only the paint and the surface layer, so no problem.
The frameset had a lot of scuff marks,
but the customer has already done overseas bike touring with a sleeping bag,
so it's not that they handle it roughly—
the usage conditions are just harsh.
I asked about the countries and routes for the next planned trip,
but they'll be passing through politically unstable areas,
which made me wonder if that's really okay.
I ground away the flange with a drill.
Rivnuts that are loose enough to spin with the drill can be pulled out slightly,
so I can crush the flange part with pliers or similar tools
and drop the rest inside.
↑Honestly, this one wasn't riveted much at all.
↑Right middle and lower
↑Left middle and lower
I re-riveted those, but when I looked closely at the upper two on both sides,
the flanges of the rivnuts were lifting, so
I ended up re-riveting all six holes.
The customer said they only use the middle and lower ones as carrier bosses.
↑Replaced parts
↑Ground or crushed rivnut flanges
↑Remaining parts of the rivnut
Hardly riveted at all.
It wouldn't be wrong to say that for GT gravel bikes,
the fork downtube holes are treated like fashion,
and the manufacturer never intended for hard use—
it's slipshod work like that.
There's a messy, sticky epoxy adhesive applied,
but when I tried to break it away, it was so hard that my fingers couldn't budge it at all.
I also applied two-part epoxy adhesive as insurance to the newly installed rivnuts,
but it seems it was held in place by that insurance alone initially.
By the way, the other five came out relatively easily with the bike inverted on a workstand holding the seatpost,
but the last one required removing the front fork from the frame to retrieve it,
which was a lot of extra work.
I even considered giving up on recovering the sixth one.
↑Stuff like this also came out of the fork.
The work started with the two on the right—middle and lower—
and I recovered the rivnut fragments,
but since they'd already fallen into the fork,
most of them came out when I recovered those two.
What these are:
↑I'm not sure if this was the exact combination,
they used a small metal seal to cap the rivnut threads before applying the adhesive,
so the adhesive wouldn't seep in.
The customer said they hardly use the upper downtube holes, but
when I shone a light into the right upper hole,
I could see this seal blocking the back.
I can't tell about the left upper, but for the other four holes,
a long bolt must have poked it, and the seal peeled off.
The front fork had two selectable positions for the hub axle.
Currently the rear position is selected,
but I suggested to the customer that logically the front would be better,
and they said that if they switch to the front,
the disc rotor they have now won't fit.
It's 140mm, and they've already bought a 160mm rotor,
so they'll switch the hub position when they swap rotors.
That aside, the brake pads were worn down to the point of failure (not metaphorically),
so I replaced them.
The rear brake pads were also fairly worn, so I replaced those too.
↑Replaced brake pads
Top is from the front,
bottom is what was on the rear brake.
The rear brake pads are still usable, but
the front pads are worn down to the bone.
They were flush with the return spring thickness.
But anyway (← well, it's not "anyway" really),
with the front fork set to the rear position and a 140mm rotor,
the brake pads aren't designed to contact the disc rotor properly.
On the complete bike, depending on the year and spec
(this model's name is "spec" so it's confusing, but I mean component spec),
the disc rotors are either 160mm front and rear or 160/140mm,
so even with the hub set to the rear position, there's a chance the 140mm rotor won't fit.
I checked, and on the flatmount adapter—when the marking says 160mm,
the rotor is 180mm compatible, and when it says 140mm, the rotor is 160mm compatible—
so indeed the 140mm rotor wasn't compatible.
I've seen the same spec on Cannondale Topstones, though I don't know if they still do it.
This is a separate issue, but there are frames where
putting an aluminum spacer between the rear brake caliper and frame
like a cushion makes it compatible with 160mm rotors, and without the spacer it's 140mm compatible—
whereas other frames have the chain stay seat post height on the left side
already at the height of "with spacer,"
so direct caliper mounting works with 160mm, and 140mm is not compatible.
A friend of mine rides a Focus frame with a 140mm rotor on the front and 160mm on the rear,
which is an unusual choice. When I asked why,
the rear can't be 140mm so it has to be 160mm,
and the front is 140mm because the early Shimano road disc rotors
rub and squeal like crazy at 160mm, which was annoying,
so they chose 140mm, and specifically an MTB rotor with a smaller cooling fin than road rotors.
We've had customers who bought a Merida cyclocross frame and only later found out
the rear brake wasn't compatible with 140mm,
and honestly, framesets and complete bikes should list
compatible rotor sizes much more clearly.
Some catalogs list complete bikes as 160/160mm front and rear but don't clearly state whether the rear can do 140mm,
or they list a bike as 160/140mm but don't clearly mark whether the front can also do 140mm.
The Specialized Aethos has brake mounting holes on the fork that are wider than the spacing
adapters from component makers provide, so you need a fork-specific adapter,
but that one doesn't support 140mm.
Given that this is a lightweight frame, a lot of people want 140mm up front,
but the manufacturer has other priorities that prevent that from being an option.
I have my own strong opinions about requiring a proprietary adapter—comparable to the pointlessness of Roval wheels—
but the real problem is that it's not clearly communicated that
aside from modifications it's impossible to install a 140mm front rotor.
In fact, there are people who found that out only after buying an Aethos.
A customer brought in a GT gravel bike.
On the left and right blades of the front fork, there are three M5 downtube holes on each side,
and on both the left and right, the rivnuts in the middle and lower positions have come loose
and are stripped, so they asked if I could fix them.
This was a case that came up on the phone a while back—
I said "I can probably fix it," but
I never expected them to actually come here by train from S Prefecture in the Kanto region.
Apparently all the shops in their area refused to do it.
↑Right middle
↑Right lower
First I considered just re-riveting the original rivnuts,
but they were deformed so badly that was out of the question,
so I decided to replace them with new ones and re-rivet.
To do that, I either pinch the flange of the rivnut with pliers or,
if the rivet has some hold, grind away the flange with a drill,
but the rest of the rivet falls into the fork blade.
First I removed the pressure anchor in the headtube
and checked whether the fork blade, fork crown, and fork tube
were connected, and whether there was enough cavity for the rivnut fragments to pass through.
I inserted a shift cable for probing through the rivnut hole,
and while there was a slight catch on the crown,
I was able to pull the cable out through the fork tube hole.
They are connected.
But since there was a possibility the rivnut fragments wouldn't pass through,
I got the customer's approval with the caveat "worst case, some might stay in the fork blade,"
and started the work.
As it turned out, I was able to recover all of them.
↑Left middle
↑Left lower
The lower left one looks like the carbon might be cracked, but
it's only the paint and the surface layer, so no problem.
The frameset had a lot of scuff marks,
but the customer has already done overseas bike touring with a sleeping bag,
so it's not that they handle it roughly—
the usage conditions are just harsh.
I asked about the countries and routes for the next planned trip,
but they'll be passing through politically unstable areas,
which made me wonder if that's really okay.
I ground away the flange with a drill.
Rivnuts that are loose enough to spin with the drill can be pulled out slightly,
so I can crush the flange part with pliers or similar tools
and drop the rest inside.
↑Honestly, this one wasn't riveted much at all.
↑Right middle and lower
↑Left middle and lower
I re-riveted those, but when I looked closely at the upper two on both sides,
the flanges of the rivnuts were lifting, so
I ended up re-riveting all six holes.
The customer said they only use the middle and lower ones as carrier bosses.
↑Replaced parts
↑Ground or crushed rivnut flanges
↑Remaining parts of the rivnut
Hardly riveted at all.
It wouldn't be wrong to say that for GT gravel bikes,
the fork downtube holes are treated like fashion,
and the manufacturer never intended for hard use—
it's slipshod work like that.
There's a messy, sticky epoxy adhesive applied,
but when I tried to break it away, it was so hard that my fingers couldn't budge it at all.
I also applied two-part epoxy adhesive as insurance to the newly installed rivnuts,
but it seems it was held in place by that insurance alone initially.
By the way, the other five came out relatively easily with the bike inverted on a workstand holding the seatpost,
but the last one required removing the front fork from the frame to retrieve it,
which was a lot of extra work.
I even considered giving up on recovering the sixth one.
↑Stuff like this also came out of the fork.
The work started with the two on the right—middle and lower—
and I recovered the rivnut fragments,
but since they'd already fallen into the fork,
most of them came out when I recovered those two.
What these are:
↑I'm not sure if this was the exact combination,
they used a small metal seal to cap the rivnut threads before applying the adhesive,
so the adhesive wouldn't seep in.
The customer said they hardly use the upper downtube holes, but
when I shone a light into the right upper hole,
I could see this seal blocking the back.
I can't tell about the left upper, but for the other four holes,
a long bolt must have poked it, and the seal peeled off.
The front fork had two selectable positions for the hub axle.
Currently the rear position is selected,
but I suggested to the customer that logically the front would be better,
and they said that if they switch to the front,
the disc rotor they have now won't fit.
It's 140mm, and they've already bought a 160mm rotor,
so they'll switch the hub position when they swap rotors.
That aside, the brake pads were worn down to the point of failure (not metaphorically),
so I replaced them.
The rear brake pads were also fairly worn, so I replaced those too.
↑Replaced brake pads
Top is from the front,
bottom is what was on the rear brake.
The rear brake pads are still usable, but
the front pads are worn down to the bone.
They were flush with the return spring thickness.
But anyway (← well, it's not "anyway" really),
with the front fork set to the rear position and a 140mm rotor,
the brake pads aren't designed to contact the disc rotor properly.
On the complete bike, depending on the year and spec
(this model's name is "spec" so it's confusing, but I mean component spec),
the disc rotors are either 160mm front and rear or 160/140mm,
so even with the hub set to the rear position, there's a chance the 140mm rotor won't fit.
I checked, and on the flatmount adapter—when the marking says 160mm,
the rotor is 180mm compatible, and when it says 140mm, the rotor is 160mm compatible—
so indeed the 140mm rotor wasn't compatible.
I've seen the same spec on Cannondale Topstones, though I don't know if they still do it.
This is a separate issue, but there are frames where
putting an aluminum spacer between the rear brake caliper and frame
like a cushion makes it compatible with 160mm rotors, and without the spacer it's 140mm compatible—
whereas other frames have the chain stay seat post height on the left side
already at the height of "with spacer,"
so direct caliper mounting works with 160mm, and 140mm is not compatible.
A friend of mine rides a Focus frame with a 140mm rotor on the front and 160mm on the rear,
which is an unusual choice. When I asked why,
the rear can't be 140mm so it has to be 160mm,
and the front is 140mm because the early Shimano road disc rotors
rub and squeal like crazy at 160mm, which was annoying,
so they chose 140mm, and specifically an MTB rotor with a smaller cooling fin than road rotors.
We've had customers who bought a Merida cyclocross frame and only later found out
the rear brake wasn't compatible with 140mm,
and honestly, framesets and complete bikes should list
compatible rotor sizes much more clearly.
Some catalogs list complete bikes as 160/160mm front and rear but don't clearly state whether the rear can do 140mm,
or they list a bike as 160/140mm but don't clearly mark whether the front can also do 140mm.
The Specialized Aethos has brake mounting holes on the fork that are wider than the spacing
adapters from component makers provide, so you need a fork-specific adapter,
but that one doesn't support 140mm.
Given that this is a lightweight frame, a lot of people want 140mm up front,
but the manufacturer has other priorities that prevent that from being an option.
I have my own strong opinions about requiring a proprietary adapter—comparable to the pointlessness of Roval wheels—
but the real problem is that it's not clearly communicated that
In fact, there are people who found that out only after buying an Aethos.