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Maintenance - aluminium v carbon

Old 05-16-23, 01:42 PM
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Gosh
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Maintenance - aluminium v carbon

Just bought my first full carbon bike. I do most of the general maintenance on my aluminium frame/forks/wheels bike so just wondering if there is any difference, good practice, doís /donít for the carbon bike. Thanks
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Old 05-16-23, 03:01 PM
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I wouldn't think a lot would be different. However, be careful with over tightening fasteners on the carbon bike. Possibly use a torque wrench if in doubt.

Carbon and Aluminum will mix some, but I'd avoid an aluminum seat post or stem.
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Old 05-16-23, 03:11 PM
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Agreed that the basics are pretty much the same with the torque control being the big concern. I suggest either assembly paste or anti seize for the fixed but removeable bits like stems and posts.

What some don't know is that carbon will react with metals and seized stems, posts and corrosion can still happen. Just like other bikes this corrosion is generally in the hidden places that are not viewable with out some disassembly. If the bike sees much water (humidity, rain, washings) I suggest pulling the parts out of the carbon frame at least annually, more often if the conditions are worse or the rider is a high mileage one. Andy
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Old 05-16-23, 03:53 PM
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Originally Posted by CliffordK
Carbon and Aluminum will mix some, but I'd avoid an aluminum seat post or stem.
What is the issue with an aluminum stem? Almost every CF bike I have looked at in my price range since early 2017 has an aluminum stem.
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Old 05-16-23, 04:16 PM
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For an external stem as most CF bikes have, it may not be too bad.

I have one CF frame that I still have to dig the seatpost out of. I got it with the seatpost cut short. 3 layers. CF frame, aluminum spacer, and CF seatpost. All stuck together tight. It isn't something that looks pretty.

At least if your aluminum stem reacts with a CF steer tube, it should be easy enough to cut it off, or pry the clamp open.
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Old 05-16-23, 05:02 PM
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Originally Posted by CliffordK
I have one CF frame that I still have to dig the seatpost out of. I got it with the seatpost cut short. 3 layers. CF frame, aluminum spacer, and CF seatpost. All stuck together tight. It isn't something that looks pretty.
That's probably a unique situation where you have a thin aluminum shim between two carbon fiber objects. You have a large carbon sink connected to a tiny aluminum piece, and hence the aluminum corrodes easily. A regular aluminum seatpost would most likely be fine in that same bike.
In any event seatpost shims suck and are to be avoided.
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Old 05-16-23, 05:08 PM
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Originally Posted by icemilkcoffee
In any event seatpost shims suck and are to be avoided.
On my CAAD4 build, I am using an Al seat post shim to shim the 1" Al steerer to 1-1/8" so I can use readily available Al stems; is this going to cause a problem long term?
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Old 05-16-23, 05:15 PM
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Originally Posted by SoSmellyAir
On my CAAD4 build, I am using an Al seat post shim to shim the 1" Al steerer to 1-1/8" so I can use readily available Al stems; is this going to cause a problem long term?
The stem, shim and steerer are all aluminum, so there should be no corrosion issues.
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Old 05-16-23, 09:07 PM
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Originally Posted by icemilkcoffee
The stem, shim and steerer are all aluminum, so there should be no corrosion issues.
Yes, but they may be different grades of aluminum. The steerer is unknown (because the frame is old), the shim is 6061, and the stem is also 6061, but I may have to get a different stem if it does not put the handlebar at the right position.
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Old 05-16-23, 09:23 PM
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Any form of anodizing, and the thicker the better, will greatly reduce/prevent corrosion between carbon and aluminum. I suspect that more modern materials have also helped to mitigate this since I've dealt with plenty of carbon posts sitting in aluminum frames and have witnessed virtually none of the corrosion that was evident in the early carbon/aluminum bikes of the early 90s.
As to how to treat the bike, just the same but use that torque wrench.
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Old 05-17-23, 04:50 AM
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Originally Posted by CliffordK
I wouldn't think a lot would be different. However, be careful with over tightening fasteners on the carbon bike. Possibly use a torque wrench if in doubt.

Carbon and Aluminum will mix some, but I'd avoid an aluminum seat post or stem.

Thanks for advice
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Old 05-17-23, 04:53 AM
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Originally Posted by Andrew R Stewart
Agreed that the basics are pretty much the same with the torque control being the big concern. I suggest either assembly paste or anti seize for the fixed but removeable bits like stems and posts.

What some don't know is that carbon will react with metals and seized stems, posts and corrosion can still happen. Just like other bikes this corrosion is generally in the hidden places that are not viewable with out some disassembly. If the bike sees much water (humidity, rain, washings) I suggest pulling the parts out of the carbon frame at least annually, more often if the conditions are worse or the rider is a high mileage one. Andy
Thanks for advice. I think I read some considerable time ago about a possible issue using grease for a bottom bracket in a carbon shell. Is this a concern or was I imagining it.
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Old 05-17-23, 07:04 AM
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Originally Posted by SoSmellyAir
Yes, but they may be different grades of aluminum. The steerer is unknown (because the frame is old), the shim is 6061, and the stem is also 6061, but I may have to get a different stem if it does not put the handlebar at the right position.
Huh? What does the grade of aluminum have to do with anything????


Posts get stuck because they weren't lubed correctly in the first place and weren't removed now and then to replace it. The best lube when carbon is being clamped on or in is carbon paste, which has little beads of plastic that add traction and help isolate the two parts.
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Old 05-17-23, 07:46 AM
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Originally Posted by Gosh
Thanks for advice. I think I read some considerable time ago about a possible issue using grease for a bottom bracket in a carbon shell. Is this a concern or was I imagining it.

Early on in the carbon age many were concerned about resin breakdown from chemicals. This is pretty much a non issue though as the vast majority of consumer available solvents and lubes won't attack the cured resin or the base fiber. This is what Craig Calfee stated in his presentation at a NHABS years ago and mimics my far less experience too. Before we became aware of assembly paste the standard shop bench grease (Park, or other) was used with no problems for many years. But grease does have a limited ability and life. Reread Kontact's post about periodic refreshing of this stuff. Andy
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Old 05-17-23, 09:51 AM
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Originally Posted by Andrew R Stewart
Early on in the carbon age many were concerned about resin breakdown from chemicals. This is pretty much a non issue though as the vast majority of consumer available solvents and lubes won't attack the cured resin or the base fiber. This is what Craig Calfee stated in his presentation at a NHABS years ago and mimics my far less experience too. Before we became aware of assembly paste the standard shop bench grease (Park, or other) was used with no problems for many years. But grease does have a limited ability and life. Reread Kontact's post about periodic refreshing of this stuff. Andy
All noted, thanks again for response
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Old 05-17-23, 10:48 AM
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Originally Posted by Kontact
Huh? What does the grade of aluminum have to do with anything????

...
I'd have to look but it wouldn't surprise me if different aluminum alloys were located in different places along the galvanic scale. That is very much the case with stainless steels. The two common types are located far apart. One does just fine in marine use around aluminum and the other forms basically a battery.
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Old 05-17-23, 11:36 AM
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Originally Posted by Kontact
Huh? What does the grade of aluminum have to do with anything????
Maybe "grades" was not the best word. Different aluminum alloys (e.g., 6061 vs 7075) may have different galvanic resistance, although (like Russ Roth said) anodization pretty much makes that a non-issue. But in my example, the steerer is not anodized.
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Old 05-17-23, 08:05 PM
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Originally Posted by 79pmooney
I'd have to look but it wouldn't surprise me if different aluminum alloys were located in different places along the galvanic scale. That is very much the case with stainless steels. The two common types are located far apart. One does just fine in marine use around aluminum and the other forms basically a battery.
I wouldn't say 0.3 is a big range for either stainless or aluminum alloys. The galvanic corrosion that is common in bikes is 0.9 to 1.2 - carbon or Ti to aluminum. Aluminum to steel isn't even a problem.

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Old 05-17-23, 11:42 PM
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Originally Posted by SoSmellyAir
What is the issue with an aluminum stem? Almost every CF bike I have looked at in my any price range since early 2017 has an aluminum stem.
Fixed it. I don't think very many people have full CF stems on CF steer tubes. Some, yes, but a small portion. I've never had a full CF stem in our garage among the various CF forks. CF seat posts are much more common, but again, certainly not essential.
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Old 05-17-23, 11:44 PM
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Originally Posted by 79pmooney
I'd have to look but it wouldn't surprise me if different aluminum alloys were located in different places along the galvanic scale. That is very much the case with stainless steels. The two common types are located far apart. One does just fine in marine use around aluminum and the other forms basically a battery.
That may be true, but is it relevant? I bet not.
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Old 05-18-23, 06:27 AM
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Originally Posted by Gosh
Thanks for advice. I think I read some considerable time ago about a possible issue using grease for a bottom bracket in a carbon shell. Is this a concern or was I imagining it.
For some bottom bracket formats, for example Trek's BB90/95, you are supposed to put grease in the bearing seat before installation to prevent creaking and wear. I used a PTFE (Teflon(R) actually) based grease on my Domane.

In some cases I've seen people suggest bearing retaining compound. I don't think I'd use this in a CF frame, unless the frame mfr or bearing provider suggests this. For most bearing installations in metal frames I think grease is recommended between the bearing seat and the OD of the bearing, and between the spindle and the ID of the bearing.
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