cupcrazy4

I've got a set of Mavic Aksium wheels that always seem to go out of true. I always stand when going over bumps, try to distribute my weight as best as possible, and avoid crappy roads whenever I can.

Is it just a re-tension I need, or maybe get them rebuilt?

Lawrence08648

How much do you weigh? The Mavic Aksium wheels are not the best wheels for heavier riders but they are fine for lighter riders. The rims are not the strongest and to compound the problem they don't have very many spokes so the existing spokes spokes get stretched. You need to know if all the spokes are correctly tensioned. Sometimes you need to start from scratch. If I had the wheel, I would removed the tire, tube, and rim tape. Then detension the wheel. When the wheel is detensioned, I would check for a twisted rim. I would then even out the spoke length, start tensioning the spokes slowly and in steps to the correct tension checking the spoke tension as I go along and then put some weight on it and check the spoke tension at the end.

urbanknight

How many miles are on them? Any mishaps (crashes, large objects hit, etc.)? Either way, I would check the tension of each spoke and look for major variations on either side.

cupcrazy4

I weigh 170. Problem is I don't have the equipment or expertise to do any of that.

Not that many miles, maybe ~500, I'm not sure. I have crashed a few times though, does that affect the trueness of the rim? I don't think any of my crashes involved hitting anything.

sharkey00

I would start with spoke tension. The result of that will dictate where to look next.

You can do a quick tension check by squeezing pairs of spokes together. If anything is radically off you will be able to feel it.

Otherwise, take it to a shop preferably one with an experienced wheelbuilder.

noglider 

Are you truing the wheels yourself? If so, true it and then retension it, then true it again.

Retensioning involves starting at the valve (so you can keep track) and tighten each spoke a quarter turn. The entire wheel gets tighter, so the last spokes will be a lot tighter than the first ones. If you think you can do another quarter turn, try that.

Also, since the spokes will rotate a bit with the nipples, overtighten and then loosen. This involves turning the nipples HALF a turn and then BACK a quarter turn, with the net effect of turning it a quarter turn.

If you're not truing your wheels, it's time to start. You don't need any equipment. Suspend your bike somehow or turn it upside down. Make sure you're not crimping your brake cables. Take the wheel off and remove the tire. Put it back in. Hook up a pencil or something to your brake to use as a gauge so you can see the rim wobbling in the bike.

Adjust the spokes according to the myriad articles on the subject, available on the web.

rs1101

blunt side impact can affect true, definitely. if the rim is bent, tension will become uneven.. spokes can stretch.. etc

noglider 

I don't think spokes stretch! They only get loose because of a bent rim or because they weren't tight enough to begin with.

shouldberiding

I can't be the only one who was thinking to make a crack about infidelity...

bigfred 

500 miles aren't that many. Have they been to a decent wheelsmith for a retension? If not, do so. If you're not comfortable doing it yourself, find someone who is. They should subsequently be just fine. Aksiums seem to be one of the reduced spoke options prefered by clydesdale weight riders, so they should be just fine for your 170lbs.

urbanknight

If you think about how strange the location of your scrapes and cuts from each crash, it's easy to imagine that the crash could have affected just about any part of the bike as well. Generally, you would have noticed the untrue-ness shortly after the crash, though. Anyway, if the tension is way off on a handful of spokes, chances are the rim is bent and needs to be replaced.

eddy m

I wouldn't retension the wheel unless I had an accurate way to measure tension. I would first check for cracks in the rim around the eyelets, or loose eyelets. After that I would just keep truing it as often as necessary, but I would record EVERY tension adjustment I made, including the amount of adjustment and the exact spoke.
I had once had a wheel that had to be trued almost every day. After a while a spoke broke, and after I replaced that spoke it was perfectly stable for years. If I had paid attention to the adjustments I had been making, I could have identified the problem spoke before it broke, and avoided a long walk home.
OTOH, if those wheels only have 500 miles on them, I'd be looking for warranty help as well. Documenting the adjustments you make will either help your case or void the warranty.

em

eddy m

+1

Lawrence08648

500 miles is not much and 170 lbs is very light for a set of wheels. At your weight, you shouldn't have any problem with any wheel. Since it's going out of true often, you have problem.

If you don't know how to true wheels, you should bring your wheel to a bike shop that has a tensionmeter. Call around. I called 8 bike shops in my area to ask who had a tensionmeter and no one had one and most didn't know what it was. I own one and I'm only a backyard mechanic.

Spokes do stretch, all metal stretches. After stretching, metal then snaps and breaks. It's called metal fatigue. When you sit on the bike, the spokes immediately bend outwards starting from the middle. As you ride and go over undulations in the road and then bumps, the bike moves up and down as the spokes flex in the middle and bend outwards. The worse the bumps, the greater the flexing. The spokes act as shock absorbers. As the spokes flex more and more with either more bumps or a heavier rider, they snap, generally at the J hook. If you don't keep a wheel true or trued correctly, then the spokes even stretch more. The more they flex, the more they stretch, then the more they will stretch in the future and not returning all the way. This is how a wheel goes out of true. If a spoke never stretches, then the wheel will always be trued. You tighten the spokes because the spoke has stretched, it has lengthened, and the tension is now has been lessened so you now have to tighten the tension a little more. A spoke with too little tension or too much tension will flex more and break more often. If a wheel isn't kept true, then the rim develops a slight curve to it and you now have to tighten or loosen spokes more than you should to keep the wheel trued.

Don't get rid of your wheels, they are good wheels for your weight.

noglider 

Lawrence08648, I don't mean any disrespect, but I'm entirely sure that's not true. Tension on the uppermost spokes increases. It decreases on the lowermost spokes. It's this cycling of tension that causes fatigue, which weakens the spokes at the bend. The more tension a wheel has in it, overall, the less this tension changes. So spokes should be as tight as possible, within practicable limits, such as not wanting to break the rims and not being able to turn the nipples from friction. Loosening spokes never lengthens their lives.

cupcrazy4, try retensioning the wheel by turning each nipple a quarter turn tighter. This will make the wheel much tighter overall. Techniques are discussed The Bicycle Wheel, Jobst Brandt's excellent book. The theory is discussed, too, as well as the measurements to determine what I wrote in my previous paragraph. He debunks a lot of folklore like that, with real-world measurements.

DannoXYZ 

I think you want to revisit the physics model of how a wheel works. It's a tension device like a suspension bridge, not a compression like a wagon-wheel. All the spokes have a lot of tension and only the ones on the bottom directly under hub (2-3 of them) lose tension when you add loading to the hub. The amount of tension-loss is directly related to the load. This total tension-loss is then distributed to ALL of the other spokes above the load-zone on the rim. Basically 2-3 spokes loose tension and all the remaining ones increase in tension slightly, but just slightly because there's a lot more of them.

Measure it yourself with calipers. The spokes do not bow out. They lose some of their tension, but unless they lose ALL tension, such as hitting sharp bumps or kerbs, they ones at the bottom will still be under tension and will still be straight. It's actually the rim that's a shock-absorber. It does this by flexing out of its round shape. The flattened spot in contact with the road distributes the load to the spokes above the loaded zone. The harder the impact, the longer the flattened spot and the more tension those spokes lose (because the rim is moving closer to the hub).

Metal-fatigue is also more dynamic and is related to the actual load. Steel has a fatigue limit and if the stress is below that limit, the material will NEVER fail from fatigue, regardless of the number of load-cycles.

To compute stretch-amount, take Young's Modulus for the material. Divide out by the cross-sectional area of the material and multiply by the load. You'll find that the spokes at the bottom will actually decrease in length when load is applied.