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I have recently joined the cycling world after committing to losing weight. I am a heavy rider at about 28st (390 lbs) and have after some advice gone for a GT Avalanche. I have had the bike less than a month and only have around 15 miles on the bike.

I use the bike to travel to work which varies from light off road to road.

I was riding back from work and realised that the wheel had started to buckle. Upon getting home I have noticed that some of the spokes were loose. Is this normal and if not is it due to the weight the bike is being asked to carry? Will a home fix be enough to mend the issue?

Update:

I have contacted the seller who has advised me to get booked for their free 6 week service where they can service the bike and they can also true the wheels.

The question I have now is until I am able to get the bike serviced am I able as a temporary measure able to fix this at home and use it as I use the bike for getting to and from work?

Unfortunately, most bikes are only rated to 300lbs or less. However, if this is a new bike, you should take it back to the shop and get them to fix it. They can't claim they didn't know you were a heavy rider when they sold you the bike.

You might need to get more substantial wheels with more spokes. Wheels designed for touring bikes might be more appropriate. Also, when riding, you need to be careful to avoid potholes and other bumps in the road and don't go up and down kerbs. If you can't avoid a bump, lift your weight off the saddle so your legs and arms are acting as suspension – this applies to riders of any weight and it's more comfortable for you as well as the bike!

Spokes getting loose is not a laughing matter. The more spokes get loose or break, the more uneven the load is distributed to the spokes, and the more likely other spokes are to get loose or break. Accumulate enough failed spokes, and your wheel fails. And failed spokes after only 24km means that something is very wrong with the wheel's built.

As such, your wheel definitely needs to be rebuilt immediately.

When the wheel is rebuilt, it needs to be rebuilt such that no spoke can ever loose tension when you use it. Most importantly, that means that the spokes must have even tension, but also that their tension must be high enough. I'd recommend giving the wheel to a professional builder, and to tell them that the wheel is supposed to carry you. Hopefully, they'll be able to produce a built of high enough quality to avoid repetition of the failure.

What you can do to reduce the likelihood of failure, is to avoid accelerating too hard: The force you can put on the chain is much higher than the force a 70kg person can put on the chain. And that force on the chain is directly proportional to the torque that your spokes need to deliver to the rim. If you put your bike in first gear and then stand on your pedal to accelerate, you'll pretty much kill any rear wheel. Just try to take acceleration a bit more slowly until you have lost weight.

It is possible to re-tension loose spokes at home, using a spoke key and the frame of the bicycle as a truing stand. In your case I would not do so.

If the wheel started to fail so quickly from new, I think it would fail again even faster with a home repair. In the worse case the wheel could fail catastrophically injuring you and damaging the bike. In the best case you get stranded.

When you take the bike in for service, the repair shop will hopefully be able to re-build the wheel. They may be able to build it to a higher strength than it was originally by increasing the spoke tension, but it may fail again of course. If the wheel can't be re-built or fails again, you can consider getting a stronger replacement wheel with a higher spoke count and heavier gauge spokes.

Loose spokes and buckling wheels on a new bike are definitely not normal.

That could be incorrect assembly but may also be a result of the weight of the rider and not getting the right advice:

The design specifications in the GT tech manual book list "330 lbs / 150 kg" as the maximum weight limit for that model. Although not explicitly mentioned for the Avalanche I assume that is the limit for the combined weight of the rider and all gear.

For your weight, you either need to find reliable wheel builder who will make wheels for you, or you need to become one. Possibly both in that order.

Wheel will be most important part of your bicycle and you should strive to put best components in it, and be sure it is built with your weight in mind.

Unwinding of spokes is almost certainly result of not enough of tension on them for your weight. To be able to put enough tension, you need as many spokes as you can, and very strong rim. It should have no less than 36 spokes, heavy duty rim like rigida sputnik or andre, and double butted spokes.