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So, my front mudguard got a bit hot recently (bike was parked in the full sun w/o wind). It was not happy about this and got very tired, leaning to the lower right below the lamp. Now every little bump results in the mudguard rubbing against the wheel - which is rather annoying.

I thought about using a hair dryer to heat the mudguard again, bending it back to its original position, fixating it and waiting for it to cool off. Has anyone done this? Could it be feasible, or is it to be expected, that the material gets even more tired by bending it back, leading to not enough stability?

Erik
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  • I guess, if you want stability, you use metal mudguards. The plastic ones tend to be a bit - flimsy... If you try heating it to bend it back, try not to cook your light, cables, or other plastic parts in the vicinity. Safest is probably to take the mudguard off your bike, put it into the oven at 50°C for a while, then try to fix it. That way, the worst that can happen is that you destroy the mudguard. – cmaster - reinstate monica Jul 03 '19 at 13:44
  • Thinking again, as mudguards are quite big to put in the oven, maybe it's a better idea to use a warm water bath to warm the plastic. You can easily make a water bath with a defined temperature by mixing known amounts of cold and boiling water. – cmaster - reinstate monica Jul 03 '19 at 13:47
  • Actually the current mudguards are not that flimsy, but rather good quality (Pegasus bike, bought last November), this is why I am a bit surprised they are this susceptible to heat. But yeah, demounting them in order to protect the rest of the bike could be advisible. – Erik Jul 03 '19 at 14:15
  • @cmaster As you say, mudguards are rather big. I wouldn't say it's "easy" to make a large enough water bath by boiling water about a litre at a time. – David Richerby Jul 03 '19 at 15:27
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    Depending on the type of plastic you can easily reshape and form with boiling water. ABS has a melting point around 212°F which is just over boiling water point. Don't submerge the whole guard jist the part that's deformed for about 20 seconds, this should soften the plastic enough to be reformed, once happy dip into room temperature water so the plastic can re-harden. I won't put as an answer because we dont know what plastic we are dealing with but as a general rule most of the common plastics melt around 212°F. A fairly large saucepan should do the trick, only the damaged bit needs warming – Dan K Jul 03 '19 at 16:14
  • Had you considered taking the bike (or fender if it came separately) back to the original vendor - there's a reasonable argument to be made that it's faulty if it can melt enough in the sun to deform that much. – Miff Jul 04 '19 at 09:35
  • @DanK: I did as you suggested, and it worked out quite well. Still have to test it in the long run. Miff: Sun and glasshouse-like conditions. So... I guess about 50°C or more. Last year, with my old bike, a tube burst. Also, taking the bike to the original vendor would cause some trouble timewise, since they are in another town. – Erik Jul 07 '19 at 21:05

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A heat gun is best for shaping plastic, but if it deformed in the sun then a hair dryer will probably work too. Depending on the shape you may want to have a heat-resistant surface on hand to press it against as you heat it; in my experience plastics can become a bit uncooperative and bend in strange ways when heated. Good luck!

Citation: My personal experience from working with reshaping a variety of plastics.

neveroddoreven
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If you have a hot air gun, I think that should be the easiest way to reshape it.

There's a difference between a hot air/heat gun and a hairdryer, the principle of operation is the same, but the maximum temperature they can reach is very different. So in order to achieve what the OP wants the proper temperature needs to be achieved: in the following URL you can find the temperatures to bend (I guess the technical term is thermo-forming ) specific plastics: http://plasticsmag.com/thermoforming.asp?fIssue=Mar/Apr-03

Criggie
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Ricardo de la Cruz
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  • My understanding of Thermoforming is forming from a flat sheet of material not one that has already been formed. – Dan K Jul 04 '19 at 05:19
  • @DanK you are 100% right, but my guess is that if you want to restore the shape of the mud guard, a higher temperature might be needed, hence the heat gun instead of the hairdryer. – Ricardo de la Cruz Jul 08 '19 at 12:44