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I am trying to understand if the problem I've got falls into a common problem for freewheel hubs. After googling and reading, I am still not sure if there is only this factor to what has happened.

I've done less than 200km on the "hybrid" bike I've got less than two months ago. I can't say I've abused it. I don't feel like it :) Mostly on asphalt occasionally a unpaved road but nothing dramatic like jumping curbs or riding over tree roots. A few days back we went to have a 30ish km ride and I've started to hear this clicking/clunking noise with vibration and sometimes with that feeling of the rear wheel moving sideways. From the 80-90s, when I was a kid and bikes were built differently, this usually meant you have a mess in the hub's bearings. Rightly so, when I came back home and removed the wheel, I've discovered the axle is bent

This is a Shimano MF-TZ21-CP 7 gears set that appears to be a very cheap one. I wish I knew earlier I have to check this too. I think the hub is equally cheap.

Now, I have no idea if this is a "very bent" or "slightly bent" much less I know of what is the cause of what, bent axle munches on bearings or munched bearings bend the axles?

I am reading a lot of people saying the core problem is the "leverage" a freewheel hub creates on the axle and that a heavier weighted rider should expect it to bend or break sooner. I weight 100kgs (220lbs), is it that much for less than 200km "leisure" rides? I mean, am I supposed to buy a box of axle kits to change every 100km?

Update after visiting the shop at May 8th:

So I went to the seller's shop, and left the bike there. As expected, they "didn't have time" to check the damage and quote the work while I was there. Though they told me right away that I "got into a pothole" which I am sure I didn't. At least not a pothole I would consider any danger for any type of bicycle.

So I've told them I didn't and left. Next day the shop owner calls me and says to come and pick up the bike. I ask her if and how much I'll have to pay to which she answers "come here, we'll explain". My favorite. They claim it is impossible to get into a defective axle, and it is impossible it was bent without being "hit". I keep insisting I've treated it properly and didn't ever jump a curb or got into a pothole. They give up with that look of offended honesty to which I say that I am not going to rob them over it and I am not going broke by paying an hour of work and a 150mm steel rod. She says that she is going to be fine too without me paying. I try to explain that it is not a question of paying, but of the service they offer, and that I need to understand if I have to sell the bike right now to avoid repairing it all the time, or it is just a matter of bad luck. And she doesn't take it well either, saying that she only sells good bikes and not department store junk and nobody ever came back with this bike and blah. So I take the bike and go home. Seems like going back there with any other problem is not the best option now.

TL;DR: Got the axle replaced "on warranty" with some good Shimano 9mm (as they said). Seller wasn't happy about it and I am not convinced it is not going to happen again.

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Generally, bikes which ship with freewheels now a days are pretty low quality. That being said, even at 220 lbs, it probably shouldn't have broke anyway. You can replace the axle again, and if it still causes problems, buy a better rear wheel. –  Batman May 3 at 23:05
    
I (who weigh about 235) have never had this problem, in 40 years and thousands of miles of (on-road) riding with freewheel bikes, nor have I heard of others having the problem. But I don't talk much with off-road riders, and it is true that an advertised advantage of the freehub design is that the axle assembly is less apt to bend. –  Daniel R Hicks May 4 at 0:20
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@DanielRHicks As I understood, you're using bikes of other quality, so you don't have this problem, but as Batman mentioned, today's bikes comes at pretty low quality. 100kg is enough to bend an axle. There are better axles and wheels thou. If you riding with a backpack, I would recommend you to upgrade the rear wheel to a freehub and a cassette, but it's pricy (about 100-150$ for non shimano cassette). –  Alexander May 4 at 6:25
    
@Alexander Thanks! Do you think I can get away with upgrading only the wheel/hub to the same number of sprockets cassette or it means changing derailer and shifters too? the bike costs €350-€400 ($450-$550) so itr doesn't make much sense to do costly upgrades. –  Michael Tabolsky May 4 at 7:33
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If you upgrade you should probably buy an entire new wheel -- likely cheaper than buying the hub and getting the wheel rebuilt. And if you do that you can presumably get a freehub wheel (with new cluster) and keep your current derailers and shifters. But try simply changing out the axle first. –  Daniel R Hicks May 4 at 13:53

1 Answer 1

I don't think 100kg should bend a decent axle. I have 7.000 km since I replaced my axle with a Point $5 one and it's still ok, on a freewheel 7-speed hub like yours. Definitely they should replace it on warranty. If not, you can replace only the axle with a better one.

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I doubt its something that would be replaced under warranty, unless you can prove a manufacturing defect (which is difficult / will be more time/money than just getting the new axle). Its just most likely bad luck - kinda like how you won't get a free new tire if your sidewall gives out for your car under warranty. –  Batman May 22 at 0:15
    
I thought the shop must prove that it was not a manufacturing defect. Anyway, it's a $15 part: wiggle.com/shimano-rear-universal-qr-146mm-axle –  Marius May 22 at 0:23
    
@Batman it wasn't easy or pleasant but I didn't pay them to replace it. They seemed to take it as an offence and insisted that I "got into a pothole" which I insisted I didn't. Then I said I won't become a broke if I pay them for this and they said that they are not going broke because of me not paying either. So.... I think if something more warranty worth happens, I am at my own :) –  Michael Tabolsky May 22 at 8:56
    
@Marius It's not only the price of the part, it is also the time. Either mine to search, understand, order, install, check, uninstall, do it again but properly. Or of a bike mechanic. –  Michael Tabolsky May 22 at 8:59

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