Marks on Seat Tube- cause for concern?

[EasyPeez]

I noticed these marks at the top of the seat tube when cleaning my bike at the weekend. I'm not sure how long they have been there but it can't have been that long as I clean it regularly and haven't noticed them before. There's also one small one at the top of one of the seat stays (second pic).

I'm hoping it's just blemishes where a bit of weather has got under the paint but am worried it might be the beginning of a deeper crack in the frame.

I've taken out the seatpost and run my fingers around the inside and can't feel/see anything untoward, but am a bit concerned that there seems to be a small crack linking the two circular/crescent shaped blemishes on the right hand side (hopefully just visible in the top picture).

Bike is a Boardman CX.

I would appreciate any input from those more experienced than me on here. Thanks for any advice/insights.

Andy

 

[EasyPeez]

Sorry, thread title says seat post but clearly I meant seat tube.

 

[Smokin Joe]

I can't see anything that would worry me in either picture. The marks atop the tube are from the clamp.

 

[EasyPeez]

I can't see anything that would worry me in either picture. The marks atop the tube are from the clamp.

Thanks. Just to clarify, when you say they're from the clamp, does that mean I've overtightened it? I'm not sure how the marks half an inch below the clamp would be caused by it? Likewise the one on the bridge/seat stay. They're all 'of a type' - dark circular slightly raised blotches, with the ones half an inch below the clamp being linked by a small crack.
Not doubting your knowledge, and obv pleased at the assessment that they're nothing serious, just trying to work out how they have been caused.

Cheers.

 

[Pale Rider]

Is the bike finished in dark grey and silver?

I wonder if the frame is painted all dark grey with silver over those parts that are, er, silver.

Thus what you can see is some of the dark grey paint underneath.

Assuming the bike is ally, it won't rust in the accepted sense of the word - oxidation will give the appearance of light powder coat.

The crack sound a bit more worrying, unless that is no more than cracked paint.

Even if it is a small fissure, it's unlikely to go very far with the seat post clamp nearby.

I know your bikes get regular use, so I reckon it's reasonable to put this down to fair wear and tear.

 

[EasyPeez]

Is the bike finished in dark grey and silver?

I wonder if the frame is painted all dark grey with silver over those parts that are, er, silver.

Thus what you can see is some of the dark grey paint underneath.

Assuming the bike is ally, it won't rust in the accepted sense of the word - oxidation will give the appearance of light powder coat.

The crack sound a bit more worrying, unless that is no more than cracked paint.

Even if it is a small fissure, it's unlikely to go very far with the seat post clamp nearby.

I know your bikes get regular use, so I reckon it's reasonable to put this down to fair wear and tear.

The bike is silver all over, no dark grey areas. The marks, being raised up, seem more like the result of pressure from below, rather than paint being chipped off. It is aluminium and there are no signs of oxidisation - I'm pretty anal with my cleaning regime.

I'm sorry the photos aren't better; I couldn't get the camera to focus if bringing the lens any closer to the bike.

The bike's from Halfords but I suspect even if it was a crack in the frame they'd explain it away as something else. Maybe I'm doing them a disservice but my experience of the mechanic abilities in my local branch has not been good.

I'll see if I can get a couple of LBSs to offer their thoughts. Hopefully it's just superficial as you suggest.

Thanks for the help.

Andy

 

[Smokin Joe]

The marks made by the clamp are just from the friction caused when you tighten it. I can't see any cracks myself.

 

[Globalti]

Is it a steel frame or alloy? Painted sliver or simply lacquered?

If lacquered steel those dark crescent blemishes took to me like areas where flexing of the frame has caused the lacquer to lift, allowing water to get underneath and oxidise the metal. I notice that your clamp is causing what I would say is excessive deformation to the top of the seat tube; the areas of stress are exactly around the round part of the "keyhole" and would indicate stresses radiating out around the circular cutout. At the top of the seat tube similar areas of oxidation would be happening where the clamp has damaged the finish or the finish doesn't protect the cut off end of the tube.

Or I might be wrong and they may just be blemishes caused by something settling and drying on the paint, in which case a rub with a polishing compound ought to remove them. I can't see signs of blistering of the lacquer where there is discolouration.

 

[burndust]

That particular model of boardman was known to have issues with the finish

 

[alecstilleyedye]

Sorry, thread title says seat post but clearly I meant seat tube.

ftfy

 

[EasyPeez]

Is it a steel frame or alloy? Painted sliver or simply lacquered?

If lacquered steel those dark crescent blemishes took to me like areas where flexing of the frame has caused the lacquer to lift, allowing water to get underneath and oxidise the metal. I notice that your clamp is causing what I would say is excessive deformation to the top of the seat tube; the areas of stress are exactly around the round part of the "keyhole" and would indicate stresses radiating out around the circular cutout. At the top of the seat tube similar areas of oxidation would be happening where the clamp has damaged the finish or the finish doesn't protect the cut off end of the tube.

Or I might be wrong and they may just be blemishes caused by something settling and drying on the paint, in which case a rub with a polishing compound ought to remove them. I can't see signs of blistering of the lacquer where there is discolouration.

Aluminium frame - Boardman CX Team 2015. I'm not sure how you tell if it's painted or lacquered but it's a very shiny finish so my guess would be the latter. Your explanation of moisture getting under the lacquer following the stress on the seat tube cracking the lacquer sounds about right

That particular model of boardman was known to have issues with the finish

Thanks for the heads-up. I've had a Google about that model and see that the 2014 version seems to have had issues as you say, but the stuff I can see, such as on this thread, looks completely different to the marks on mine, and in a slightly different place. These pics look more like a witness crack?

http://singletrackworld.com/forum/topic/2014-boardman-cxs/page/2

As per @Globalti 's explanation in this thread

https://www.cyclechat.net/threads/boardman-cx-comp-paint-crack-issue.146690/

The marks on mine seem very different?

 

[FishFright]

To me it looks like the seat post is a tiny bit too small and its distorting the seat tube. The circles appear to be delamination of the finish , if there is one.
For a more informed diagnosis pop on to the CTC* forum and ask either 531Colin or Brucey

*yes i know its changed name but grrrrr

 

[Globalti]

Yes, the lifting of the lacquer is a sign of stress in the area of the slot keyhole so I would worry more about that and about eventual cracking; I would try shimming the post with a soft drinks can, which may be boringly low-tech but soft aluminium makes an ideal shim material. If it fits it will prevent that seat tube from deforming so worryingly at the top and provide a more even grip of the seat post. However take care to smear everything with grease to prevent it all sticking together with aluminium oxide. Bend over a lip on the top of the shim to prevent it from dropping down the tube and have the cut at the front.