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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?

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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 3, 2019 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 3, 2019 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 3, 2019 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 3, 2019 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 3, 2019 at 16:14

2 Answers 2

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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.

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    You mean a mandril or a form - some kind of backing to support the floppy plastic while it sets. Gloves would also be a good idea - hot plastic is hot.
    – Criggie ♦
    Jul 3, 2019 at 20:29
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    @Criggie Indeed it is! Gloves are always an excellent choice.
    – neveroddoreven
    Jul 3, 2019 at 20:42
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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

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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 4, 2019 at 5:19
  • @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 8, 2019 at 12:44

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