Thorn Cycles Forum
Technical => General Technical => Topic started by: gepabu on May 16, 2020, 12:12:57 pm
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Good afternoon,
Does anyone have any advise for dealing with chipped pain that is rusting a little bit and bubbling paint?
At the bottom of my frame the paint has come away from either being chipped or bubbling and eventually falling off. It a little bit rusty. Also there is a patch of bubbling paint, presumably from rust under the paint.
I'd like to be proactive on this to delay further rust.
Any tips would be appreciated
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Hello,
Better scrape off with knife or similar. Then rub the rust off with Emery or similar. Then paint some rust preventer and finally paint over with if possible the same or similar colour that the frame is now.
Best regards,
John
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And the paint? From Thorn?
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Thanks John.
I am a bit apprehensive to start rubbing off the paint to get to the bubbled bit but I suppose I will have to.
The paint in the original from Thorn. I was actually surprised to see rust under the paint as I thought it was meant to be protective.
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Thanks John.
I am a bit apprehensive to start rubbing off the paint to get to the bubbled bit but I suppose I will have to.
The paint in the original from Thorn. I was actually surprised to see rust under the paint as I thought it was meant to be protective.
Either do the job, or get more rust.
I suspect/expect that at some time the frame has been knocked/bumped/dropped or something like this and damaged the paint. It is surprising how water can creep under paint and cause problems. Much much better to have a paint blemish than rust all over the frame.
Which model is the bike? How old? Colour? I actually have one or two little jars of some Thorn colours from previously owned frames/bikes. I might be able to help but cannot promise.
Get stuck in and save your frame!
Best regards,
John
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Yep, kill it or it'll kill the frame. All the loose stuff of, then I'd use a rust converter (I'll find a link to the one I use) then a couple of coats of hammerite, you have a choice of trying to match the paint, or masking off a shape and using something contrasting.
https://www.toolstation.com/rustins-rust-converter-250ml/p97400
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It is very possible that I do a bad job covering it up either by using the wrong stuff, leaving water in or just missing a part which could speed up the rust. It's a tiny patch surrounded by paint so it could be contained?
Thanks John very kind of you. It is a 2013 black audax 858. I will upload a picture of the area later. I am actually not too bothered about finding matching paint. My main concern is I just want to be sure that what I am doing isn't going to effectively exposed a larger part of the frame because of a poor job.
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It is very possible that I do a bad job covering it up either by using the wrong stuff, leaving water in or just missing a part which could speed up the rust. It's a tiny patch surrounded by paint so it could be contained?
Yes you should be able to contain it. You won't know till you remove paint, the bit you're dealing with doesn't need to be shiny new metal, but the edges should be to make sure you have it all.
Once you're rubbed it down to remove anything lose, mask an area off, dry with a hairdryer, rust inhibitor, let it completely dry, two or three coats of hamerite or similar, following the instructions on the tin.
To put this in perspective, some people ride bikes for years with rust and paint bubbling, I sometimes park next to one like that in town, I don't know who's it is or how far they ride, but I first noticed it years ago. You're doing the right thing dealing with it so that it doesn't get worse, and of course it's a shame it's happened, but it isn't a disaster.
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To put this in perspective, some people ride bikes for years with rust and paint bubbling, I sometimes park next to one like that in town, I don't know who's it is or how far they ride, but I first noticed it years ago.
I used to have a bike that I kept intentionally rusty and with cheap but working components, including a very beat-up but still comfortable leather saddle (not Brooks as that might have been stolen anyway).
Parked that bike, secured with a large chain and padlock, at the station in Angers every weekend for 6 months while I was on a training course there.
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Back on topic:
I inspect my bikes every few months for paint damage. When I find some, I rub down with emery cloth, and patch up the damaged area with a paint that goes directly onto metal. I generally apply two coats, sometimes it needs three.
I have 3 colours, red, blue and black.
When the bike starts looking too tatty (except sometimes for the gloss black my colours never match factory paint exactly), I use fine emery cloth to roughen the surface and repaint the entire frame/forks using the old-fashioned paintbrush method.
Not yet had to do this to my Thorn bikes, which are all relatively recent. My 2009 Brompton got the treatment a few years ago (folders take more knocks in my experience) when I decided the mottle effect of gloss black patches on the matt black original paint had gone far enough.
A possible disadvantage of this method is that any decals, stickers, etc. are lost, but I don't really mind if my bikes become anonymous to others, I still know what they are.
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Thanks PH and Martin. When I come to do it I will follow that.
Here are some pictures of it. (The first thing I'll do when I finish exams is give it a clean).
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It is a very vulnerable spot, the good news is it's also one of the thickest tubes and you are dealing with it before it does any real harm.
If it were mine, I'd mask off a couple of cm along each of the joining tubes and after treating the rust paint the whole of the BB area.
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What are your thoughts on using T cut? Does it remove the protection of the paint?
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For new bike owners , would it be possible to put something protective in this area to prevent damage /rust etc?
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...would it be possible to put something protective in this area to prevent damage...
Helicopter tape, Laminex tape or a very long front mudflap (my own choice) can all work well to protect from paint chips caused by thrown stones. Amazon is a good source for the protective tape. My favorite mudflaps are here: https://buddyflaps.com/
Best,
Dan.
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[Helicopter tape, Laminex tape or a very long front mudflap
I'd agree with Dan, though I'd say and rather than or ;)
Unless they're going to be used primarily off road, my bikes have long mudflaps. We sometimes have comical arguments on here about how long they should be, as long as you like, but I don't think there's any such thing as too long. It becomes a compromise between the advantage of interrupting spray and catching on obstacles. If you draw a straight line from the tyre's contact patch and the BB and the flap doesn't intercept this it would do more good if it was longer. My bikes have a coating of Turtle Wax applied last month ready for the winter, it's only in part because I like shiny, it also means the muck washes of easier. Plus when applying I'd have noticed any blemishes that I might not have otherwise seen.
In this OP, I'm not sure what originally caused the damage, but it was neglect that allowed it to get like that. If you ride a lot in the winter, on treated roads, you need to wash that stuff off ASAP, it's highly corrosive. Stone chips on some part of the bike are sooner or later inevitable, they rarely get down to the bare metal, and even if they do a dab of something protective stops the chance of rot.
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Thanks , had a look at those flaps. I’m wondering why these are not standard on all bikes?
Didn’t have a clue what helicopter tape is but now I get it. Again why is this not standard? I would definitely want to do this if I bought a new bike
https://m.pinkbike.com/news/review-7-films-and-tapes-to-keep-your-bike-shiny-and-new.html
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Didn’t have a clue what helicopter tape is but now I get it.../quote]It gets its name because it was originally developed to apply to the leading edge of helicopter blades to protect them from abrasion in dusty or sandy environments (the Gulf War saw a lot of this in use, along with K&N oiled cotton gauze air filters). It remains a little soft so it tends to deform, "puddle", and recover instead of splitting.
For these reasons it can go far toward preventing stone chips on bike frames. "Helicopter tape" has become a sort of generic term and applies equally to a number of similar products, some marketed specifically for "gravel bikes", carbon frames, and suchlike.
Best,
Dan.
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Rusting a "little" bit?? LOL .
Looks like it needs a total sandblast and repaint. Better yet get powder coating.
As for flaps, nothing beats a cut up rubber boot. Standard equip on my bikes.
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Ha 😁I can picture a yellow welly boot hanging off the fender . Nice. And hiviz too.
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Rusting a "little" bit?? LOL .
Looks like it needs a total sandblast and repaint. Better yet get powder coating.
As for flaps, nothing beats a cut up rubber boot. Standard equip on my bikes.
How do you attach the flap to the guard?
Neat idea. Thanks
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Mine have 5 mm bolts cut down and rounded the ends. Heads inside is best for cleaning and safety.
Washers at least 1/2" or a strip of stainless metal all the way between the bolts.
Could need 3, 4 or 5 bolts. One in the middle and the others near both sides. Best is if they are not all in one row. Not necessarily possible on all newer fender materials.
I also have sometimes used a stiff electrical wire wrapped around the outside, half the way down the exposed flap to make a cupped shape. Round shape the wire like the fender and fold the ends around and inside a 1/2", squeezed tight.
My fenders are old, so they are way thicker metal than the half plastic junk sold now.
They shouldn't be less than about 6" from the ground. The flaps are about 4"up. They need to be flexible when riding off squared curbs.
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How do you attach the flap to the guard?
I don't think I've ever attached them the same way twice, it's not a big job, whatever you have lying around. This is the rear one on my Mercury, some thick packing material, a reflective tape, double sided tape to hold it in place and a button head from the inside with a dome nut on the outside. A rear one is really only of benefit to following riders in a group.
Getting the right thickness of material is an art, ideally it won't waft about in the breeze, but will move out the way if in contact with an obstacle. Milk bottles used to be popular (Plastic ones obviously ::)) but I found them too stiff, if you catch one on a speedhump it can damage the guard itself. It used to be a bit of a fashion on Audax to have the cheapest looking flaps on the most expensive bikes, I didn't participate...
(https://live.staticflickr.com/65535/50493837786_bbf766c513_z.jpg) (https://flic.kr/p/2jVY7N7)Merc lights (https://flic.kr/p/2jVY7N7) by Paul (https://www.flickr.com/photos/phbike/), on Flickr
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Getting the right thickness of material is an art, ideally it won't waft about in the breeze, but will move out the way if in contact with an obstacle.
I use 5 litre plastic containers as used for white spirit and many other liquids. These are generally white.
Or, for black mudflaps, 5 litre plastic containers generally used for motor oil. Some oil containers are too thick.
I currently use three 5 mm bolts to fix the mudflap to the mudguard. The round shape of the mudguard gives the mudflap enough stiffness to not bend in the wind, but the material is flexible enough to bend out of the way if I catch it on a curb or rock, although it will usually need to be bent back into shape afterwards.
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Merry Christmas everyone 🌲
What about these ?
https://www.alwaysriding.co.uk/pdw-full-metal-fenders-650-beast-65mm.html
I admit It. I’m a poor man with expensive tastes. Not a good combo 😁
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My red Mercury (2nd page here http://www.sjscycles.com/thornpdf/thorn_mega_brochure.pdf ) has a suitable low-hanging front mudguard with a flap. The specs said that the mudguards were SKS/Thorn Chromoplastic Mudguards -700c/27.5" - P55 but I can't see this currently listed on the SJS website but this is similar https://www.sjscycles.co.uk/mudguards/700-x-35-sks-chromoplastic-mudguard-set-700c-black/ .
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What’s your thoughts on their effectiveness? Would a longer mud flap be better or you happy with the length? Are you noticing and wear and tear appearing under the bottom bracket area?
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I've seen a blogpost by Jan Heine (sorry -- don't have the reference handy) in which he used a 2-ltr Coke bottle (or similar) to make temporary & removeable guards: With scissors, he cut the guard slightly wider that the fenders (front was his main concern, IIRC), and then slipped the guard inside the fender, to be held in place by tension against the rolled inner edges of the fender.
Might serve as a way of testing length/width/coverage before making a more permanent fix with nuts/bolts/washers.
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What’s your thoughts on their effectiveness? Would a longer mud flap be better or you happy with the length? Are you noticing and wear and tear appearing under the bottom bracket area?
I reckon that the mudguard and flap are as low as they can reasonably go (the flap can catch on the threshold of the back door to my garage). I haven't checked the bottom bracket area for damage but my local mud shouldn't be damaging the paint. Inspection for paint damage will have to wait for a thorough bike clean in the spring - any cleaning before then is only an exercise in removing some excess weight. If there is damage then I'll touch up the paint and overlay with some of that helicopter tape.
The tyres (Panaracer Gravelking SKs) are nominally 48mm so 55mm mudguards don't retain much lateral splatter.The mudguards used to be a snug fit on the tyres but I moved them out to provide more space for sticky mud. As I've commented elsewhere, some of my local roads are somewhat filthy at this time of year. Smoother tyres would probably pick up less muck but I want something with some tread to improve likelihood of making contact with the tarmac.
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What are your thoughts on using T cut? Does it remove the protection of the paint?
I've used T-cut on bikes. I've also used it to get coffee rings off a French polished table. It cuts into the outer coating and does remove what is not well baked in. It won't protect your paint but can help restore the look or even out blemishes.
Not sure it would help in this case as it is really just a cosmetic fix
Clean up the area and protect it with something to stop rust setting in again. Even Hammerite might help as a stop gap fix as it primes and rust protects in one.
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I'm even more intrigued by why the derailleur cables appear to cross under the downtube as shown in the OP's first photo...
http://thorncyclesforum.co.uk/index.php?topic=13802.msg102808#msg102808
;)
Best,
Dan.
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I'm even more intrigued by why the derailleur cables appear to cross under the downtube as shown in the OP's first photo...
http://thorncyclesforum.co.uk/index.php?topic=13802.msg102808#msg102808
;)
Best,
Dan.
It isn't that uncommon, depending on certain other factors - bar width, stem length, how close to the stem the cables are taped, where the first attachment/stop is... it can be the lesser of two evils, the slight rubbing and the imperfect angle under the BB, might be less trouble than the sharp angle trying to bring the cable the "right" side of the headtube.