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Long story short my front wheel took a hit and the rim is now slightly bent. Now, since this is a forged aluminium wheel, replacing it costs the best part of 1500EUR. Being on a budget I thought of having it fixed, by bending it back in shape. There are people out there who do these types of jobs regularly.

When I asked around I got controversial replies. Some say it should be fine to bend it back. Other say that the material is now compresssed and that bending it back into shape will leave microscopic gaps of air between the aluminium molecules, i.e. microfissures, causing the rim to bend, crack, break, or explode if stressed.

Is it safe to fix a bent motorbike wheel?

  • 1
    Have you considered checking a junkyard/breaker's yard for a replacement wheel? Maybe ask some of the dealerships, they might keep salvaged/upgraded parts around. – TMN Jun 14 '16 at 15:53
  • @TMN Yup I have. There's some availability online here and there. – JoErNanO Jun 14 '16 at 15:54
  • How bad is slightly bent? Enough to affect tire sealing? Big enough to be able to feel the bad spot once per wheel revolution? – zipzit Jun 14 '16 at 21:32
  • Man, that is a bummer....how did you bend it? Is this on the Duc? – DucatiKiller Jun 15 '16 at 0:29
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Fixing a bent motorcycle wheel is situational.

If you are on a 125 to 200cc motorcycle using it for commuting purpose and will be driving under the speed limit, I would not be worried and its absolutely fine to reuse a bent wheel. provided the bend was minimal , if its extensive then changing would be a wiser option.

If you are on a 600 to 1000cc super sports(anything capable of going more than 100mph) , I would not recommend you fixing it and it will be safer to replace it since you do not know what can happen at high speeds. You might hit another pot hole at the same spot , it can be extremely dangerous.

  • I'm with Anarach on this.. Front wheel on a bigger bike definitely no. Rear wheel is not so risky.. if something goes south there its a problem but not a crazy uncontrollable problem. I'd be comfortable with a repaired rear wheel. – zipzit Jun 14 '16 at 21:31
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IMO, it is not

I'm considering 3 types of rim.

  • Carbon Fiber

  • Billet Forged Aluminum Alloy

  • Cast Aluminum Alloy

All three material types do not lend themselves to flexibility. The brittle nature of the material would crack, perhaps not even visibly.

But, I have to be honest here

I have straightened cast motorcycle wheels using a small jack and a propane torch to heat it up. I also had a truing stand.

The procedure looks like this and that's about how bad my rim was when I did this. I will add, I was VERY young and very broke and didn't consider consequences to actions. That being said. The wheel lasted another two years, when I sold the bike I told the new owner, "get a new rim because this is what I did."

That rim was unpainted and I inspected it with a jewelers loop to look for cracks, did not find any before or after but I have always believed that were microscopic fissures in the rim. I have no proof if that belief is truly a fact.

Procedure

I simply heated up the area around the bend with the propane torch making sure I didn't linger too much in any one area. I was not trying to melt anything or pool up any of the, in my case, cast rim. I was simply making it more pliable.

The rim can soak up a lot of heat and distribute it quickly around the rim as it's aluminium so I set it in the sun for a bit to get up to around 130 degrees F first.

I used the jack to slowly push out the bend and would then put it on my truing stand to check for fault. I did a wash, rinse, repeat of this quite a few times before I got it right. I used blocks of wood to prevent scarring of the rim.

This is what it looked like. I don't recommend this. I never felt good about it. I have had peers validate the solution but at the end of the day, none of us are metallurgists.

enter image description here

Here was my tool list

  • Woah, that's pretty clever. – I have no idea what I'm doing Jun 15 '16 at 7:38
  • Carbon Fiber rims? Which bikes have Carbon Fiber rims? Also, Nice Details.. you DA man – Shobin P Jun 15 '16 at 9:46
  • I'd be surprised if you could bend a carbon fiber rim appreciably without breaking it. Although I imagine they'd flex more before permanently deforming than a metal rim would. – TMN Jun 15 '16 at 15:04
  • Your right, they would just shatter. – DucatiKiller Jun 15 '16 at 16:00
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This probably depends on what type of wheel you have and how badly it is bent.

On bicycle wheels that use spokes, it is possible to repair bent rims, even if the rim is made out of aluminium. This assumes that the damage was not too severe. A fix may require replacement of damaged spokes.

However, I would be very cautious in your case for two reasons:

  • Motorcycles are generally bought to ride at speeds much higher than bicycles. Thus, the cost of wheel suddenly shattering is much higher than in the case of bicycles.
  • Your wheel is not a spoked wheel but a forged wheel. With a spoked wheel, you can change the damaged spokes, but with a forged wheel the load-bearing parts cannot simply be changed to new components, as they are integral to the wheel.

If you nevertheless attempt a fix, do check the wheel for cracks with a bright light. Very often! Metal parts like this don't suddenly fail, they fail by developing cracks that slowly extend. Thus, do short rides first and once you become confident that short rides don't cause a crack to develop, you can take longer rides after which you again inspect for cracks.

Even a single crack, no matter how minor one, means the wheel must be immediately discarded.

Now, if the wheel was made out of carbon fiber, this would be an entirely different story. I would never attempt to repair a carbon fiber wheel. In fact, carbon fiber can be damaged in an invisible manner, so that the damage (that you cannot see) suddenly causes the entire component to shatter.

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