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How I remove flat spots

PB Forum :: Mechanics' Lounge
How I remove flat spots
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Posted: Nov 6, 2010 at 23:40 Quote
So I spent $$$ on new wheels then soon after smashed the rear and got a flat spot. It was bad enough for me to notice while riding so something had to be done. I didn't want to cash out on a new wheel so instead I thought hard on how to repair it. I ended up spending ~$20 on some tools and manage to do so.

Basically the idea is to insert a bottle jack in between the hub and the rim where the flat spot is. Then operate the jack to press the flat spot out.

It worked for me, first try. I wouldn't consider it "good as new" but I'm definitely satisfied with the outcome.

Before going off and trying this, please consider the following:
-don't expect this to fix any severity of flat spot. Mine was minor so it worked. Yours might be major so.... maybe it'll work, I don't know.
-contents under pressure! Ya, so protect yourself when doing this.
-your bike is different from mine so be sure that you make adjustments to protect the parts on you bike.

Ok, here we go:

1. You will need the smallest bottle jack you can find. I got a 2-ton jack from Princess Auto for $16. Also from there I grabbed a $4 rubber boat bumper. You also might need some wooden spacers and piece of rubber to protect your rim from scratches.
photo

2. I don't have a truing stand so I clamped on a piece of metal to use as a reference when finding the flat spot. A zap strap works as well.
photo

3. Mark where the flat spot starts and finishes as well as the center (most flatted spot)
photo

4. With a ruler, ON A GOOD PART OF THE RIM, measure and note the distance between the hub and the edge of the rim. Compare it to the flatted side of the rim. This will tell you how much you need to press out. I required ~5mm.
photo

5. Remove the spokes within the flatted area.
photo

6. Install the bottle jack under the center point of the flat spot. I placed the boat bumper over my hub, then the spacer, then the jack and piece of rubber.
photo

7. Double check everything is lined up and give it a couple pumps. Keep an eye on your spokes, cog, hub, etc. ensuring nothing is getting bent. Be careful not to over do it. You might wreck something like bust a spoke or crack your rim. After some tension has been applied remove the jack and measure your progress against the measurement you made of the good side. Reinstall the jack and repeat as necessary.

8. Reassemble your wheel and have a pro true it. The end.

Posted: Nov 7, 2010 at 0:16 Quote
That's a pretty nifty McGuyver way of fixing what would be a dead rim.

O+
Posted: Nov 8, 2010 at 7:58 Quote
Its a very smart Idea, make sure to include "DO AT YOUR OWN RISK"

only downside to this is that you already damaged your rim causing the flat spot, pushing it back to normal will only do more damage as your are flexing and bending the metal back. Does make it weaker. This comes from personal experience.
I did a fix similar (minus bottle jack) few years ago and blew up the rim later.

Its like taking a pcs of metal and bending it, now bend it back to normal. It will be weaker.

So for all who does this, do at your own risk. You are taking your bike/life into your own hands.

Posted: Nov 8, 2010 at 19:30 Quote
knobzy wrote:
Its a very smart Idea, make sure to include "DO AT YOUR OWN RISK"

only downside to this is that you already damaged your rim causing the flat spot, pushing it back to normal will only do more damage as your are flexing and bending the metal back. Does make it weaker. This comes from personal experience.
I did a fix similar (minus bottle jack) few years ago and blew up the rim later.

Its like taking a pcs of metal and bending it, now bend it back to normal. It will be weaker.

So for all who does this, do at your own risk. You are taking your bike/life into your own hands.
Yes, all true. But in my case it was a small flat spot so there's reason to sweat it.

Posted: Dec 26, 2010 at 7:15 Quote
i'd just pay $30 for a complete true at the bike shop.

Posted: Apr 19, 2011 at 18:11 Quote
Interesting method, and looks like it could work. I was wonder about another method. Taking a two blocks of wood, one shapped for the inside of the hoop and one shaped for the tube side of the hoop, and some kind of hydralic press. The reason I ask about this method vs. the posted above, my rim isn't laced ATM. I'll have to think about the different methods possible

Posted: Apr 20, 2011 at 3:39 Quote
NorthEasternDH wrote:
i'd just pay $30 for a complete true at the bike shop.
if the rim is truly flat-spotted, they won't be able to do anything better.

Posted: Apr 20, 2011 at 4:40 Quote
Buddy, where I'm at, I'd be lucky to find a bike shop lmao. I'll have t see what's available

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