Paint coming off by internal brake cable stops - should I be worried?

Back by popular demand, the general all-things Road forum!

Moderator: robbosmans

Nickldn
Posts: 2008
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

I have recently noticed a chuck of paint has come off by the rear internal rim brake cable stop in the top tube of my beloved Propel frame. It looks like the paint is lifting in that area and also seems to be not right by the other brake cable stop at the front of the top tube.
1000024389.jpg
That area is under tension due to the brake cable, so I guess it could fail if there was a fault in the layup.

Should I be worried about a fault in the brake cable stop area causing the paint to lift?
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB Zipp SL70 bars 6.5kg

S-Works SL8 Dune White SRAM Red AXS Craft CS5060 wheels Roval Rapide bars 6.6kg

bobones
Posts: 1334
Joined: Mon Aug 12, 2013 11:19 am

by bobones

I had the same thing on my old Scott CR1, and all I did was apply nail varnish and forget about it. Nothing bad happened after years like this.

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



User avatar
Mr.Gib
Posts: 5683
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

It would be nice to see a few better pictures of the area with the actual damage in clear focus. Paint coming of like that should not be ignored - that is not normal.

Doesn't Giant have a lifetime warranty? If you are the original purchaser, Giant should take care of you. Second owners get some protection as well.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

Nickldn
Posts: 2008
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

Here are more photos of the defects at the back brake cable stop, a chunk of paint has come off and there is a load more paint bubbling around the cable stop area:
1000024407.jpg
1000024406.jpg
There is some paint bubbling around the area where the brake cable enters the top tube, but none had come off yet, quite hard to see in a photo:
1000024422.jpg
No idea why this has happened but worried about some kind of issue with the top tube causing the paint to move and bubble.
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB Zipp SL70 bars 6.5kg

S-Works SL8 Dune White SRAM Red AXS Craft CS5060 wheels Roval Rapide bars 6.6kg

User avatar
bedampft
Posts: 259
Joined: Wed Jul 18, 2018 8:04 pm

by bedampft

The paint is only coming off the metal insert, looks like corrosion. Do you sweat a lot? Or use the bike on a trainer? Sweat would drop on the toptube and than run down the side, collecting on the underside where the insert/ cable stop is.

Nickldn
Posts: 2008
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

Corrosion...that sounds bad. Maybe I need to take a peek inside the top tube to check.

No the bike is not used on a trainer, nor do I sweat that much. But thinking about it I can't visualise sweat running through a horizontal top tube to affect both cable stops, which are both at the bottom of the tube.

The bike is stored inside, so not much chance of corrosion from wet air. Not ridden in the rain either and water doesn't collect in the top tube.
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB Zipp SL70 bars 6.5kg

S-Works SL8 Dune White SRAM Red AXS Craft CS5060 wheels Roval Rapide bars 6.6kg

Nickldn
Posts: 2008
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

Nope, can't see any sign of corrosion inside.
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB Zipp SL70 bars 6.5kg

S-Works SL8 Dune White SRAM Red AXS Craft CS5060 wheels Roval Rapide bars 6.6kg

User avatar
Mr.Gib
Posts: 5683
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

IMO 100% warranty situation. I've seen 15 year old Giants (and countless other frames without so much as a blemish is the paintwork).

Perhaps the area wasn't properly primed or prepared for painting, or some other error in the process. The bubbling is a clear sign of failure from underneath - not a wear and tear issue.

Please report back on how Giant deals with this. I had a TCR replaced due to a single paint crack.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

Nickldn
Posts: 2008
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

So today I finally went to see my local Giant dealer. Sure enough this issue is down to galvanic corrosion. The aluminium brake cable stop inserts are corroding due to contact with the carbon fibre in the top tube.

Good news is the bike is safe to ride, but the corrosion is likely to get worse over time. Seems the aluminium inserts weren't sufficently protected against contact with the carbon. Shame.

I really like my Propel,it's great to ride and I beleive Giant Advanced SL frames being some of the best in the industry in terms of low weight and great ride feel. Let's see if Giant can fix the issue.
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB Zipp SL70 bars 6.5kg

S-Works SL8 Dune White SRAM Red AXS Craft CS5060 wheels Roval Rapide bars 6.6kg

User avatar
Mr.Gib
Posts: 5683
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

Nickldn wrote:
Thu Jun 13, 2024 9:01 pm
Seems the aluminium inserts weren't sufficently protected against contact with the carbon.
Aluminum touching carbon is bad? Have had many carbon cranks with alu chainrings - no issues over decade+. Many alu hubs against carbon dropouts - also no issues for many years. Same with alu stem on carbon steerers, seatposts, etc. etc.

Something seems amiss.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

Nickldn
Posts: 2008
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

Mr.Gib wrote:
Thu Jun 13, 2024 10:10 pm
Nickldn wrote:
Thu Jun 13, 2024 9:01 pm
Seems the aluminium inserts weren't sufficently protected against contact with the carbon.
Aluminum touching carbon is bad? Have had many carbon cranks with alu chainrings - no issues over decade+. Many alu hubs against carbon dropouts - also no issues for many years. Same with alu stem on carbon steerers, seatposts, etc. etc.

Something seems amiss.
That's the official verdict. Backed up by many sources, like:

https://compositeenvisions.com/document ... -aluminum/

I think careful protection (paint?) is needed to make it work.
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB Zipp SL70 bars 6.5kg

S-Works SL8 Dune White SRAM Red AXS Craft CS5060 wheels Roval Rapide bars 6.6kg

bobones
Posts: 1334
Joined: Mon Aug 12, 2013 11:19 am

by bobones

Mr.Gib wrote:
Thu Jun 13, 2024 10:10 pm
Nickldn wrote:
Thu Jun 13, 2024 9:01 pm
Seems the aluminium inserts weren't sufficently protected against contact with the carbon.
Aluminum touching carbon is bad? Have had many carbon cranks with alu chainrings - no issues over decade+. Many alu hubs against carbon dropouts - also no issues for many years. Same with alu stem on carbon steerers, seatposts, etc. etc.

Something seems amiss.
Aluminium nipples in carbon rims are also susceptible to galvanic corrosion. Nipple heads eventually just give way under the tension of the spoke. Pays to check for telltale white deposits around nipple heads by peering into spoke holes and replacing them all before they start failing. You can sometimes shake a tremendous amount of white gunk out of a badly affected wheel.

User avatar
wheelbuilder
Posts: 1315
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

Mr.Gib wrote:
Nickldn wrote:
Thu Jun 13, 2024 9:01 pm
Seems the aluminium inserts weren't sufficently protected against contact with the carbon.
Aluminum touching carbon is bad? Have had many carbon cranks with alu chainrings - no issues over decade+. Many alu hubs against carbon dropouts - also no issues for many years. Same with alu stem on carbon steerers, seatposts, etc. etc.

Something seems amiss.
Nothing amiss. It's when the carbon plies are "wrapped" around an aluminum insert like a dropout. They are supposed to be insulated with a layer of fiberglass. You see it all the time on frames with bonded aluminum dropouts.
Never cheer before you know who is winning

Nickldn
Posts: 2008
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

wheelbuilder wrote:
Fri Jun 14, 2024 8:35 am
Mr.Gib wrote:
Nickldn wrote:
Thu Jun 13, 2024 9:01 pm
Seems the aluminium inserts weren't sufficently protected against contact with the carbon.
Aluminum touching carbon is bad? Have had many carbon cranks with alu chainrings - no issues over decade+. Many alu hubs against carbon dropouts - also no issues for many years. Same with alu stem on carbon steerers, seatposts, etc. etc.

Something seems amiss.
Nothing amiss. It's when the carbon plies are "wrapped" around an aluminum insert like a dropout. They are supposed to be insulated with a layer of fiberglass. You see it all the time on frames with bonded aluminum dropouts.
Indeed. It seems these aluminium inserts were not insulated on the Propel Advanced SL leading to galvanic corrosion. Shame, as it's causing so much hassle.

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



User avatar
Mr.Gib
Posts: 5683
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

Well that's a big fail for Giant. And general credit to the industry (that I regularely savage for their incompetence) for doing a decent job of dealing with the risk of carbon/alu interface - never seen anything like this in a recent bike. I do recall however on older Colnago carbon frames (C40, EP, etc.), that the paint would often bubble around the external mounted cable stops. Same thing I guess. As per the science, an electrolyte like sweat must be a big accelerator.

I assume the process, if it occurs at all, is normally so slow that it is not an issue. But is does bring to mind a local frame builder who does raw carbon threads in their T47BB shells. Maybe a little anti-sieze is all it takes to stop the galvanic corrosion.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

Post Reply