Bike safety after accident

LiDavies

Bought my 14 year old son a Halfords 21" Carrera Vengeance mountain bike at the beginning of June for £330, built instore. 3 weeks later, after probably less than 10 rides out, the chain slipped when at speed and he fell off onto concrete breaking his arm. Not the best start to the school holidays!

The bike is back in Halfords to have a look at, but there is extensive damage to it. I don't know about bikes so only see the cosmetic damage, big gouge of the seat, top covers of gear leavers broken off, lots of deep scrapes on metal parts. What concerns me is the mechanical damage and the future safety of the bike now. Would I be best to call it quits with this bike or try to repair?

I am also in two minds whether the chain slippage is one of these things that happen and its just unfortunate (he has never had chains coming off on any of his previous bikes - Python, Dawes, Ridgeback bought at cycle shops), or if there was a fault with the bike or it was incorrectly built. What are your thoughts on this?

fenix

Oh the poor kid. Bad timing indeed.

I'd think the bike should be fine - it's a sturdy bike - if the gears are fixed - and the saddle replaced - I'm sure it'll ride just fine.

Was it definitely the chain slipping ? Not his foot slipping off ? It's almost impossible to really say what happened.

LiDavies

Fenix wrote:

Was it definitely the chain slipping ? Not his foot slipping off ? It's almost impossible to really say what happened.

He says he was standing on the pedals cycling at the time, going downhill on steep back road and he remembers the chain coming off and the pedals jerking away from him, he says he wasn't changing gears at the time. But obviously I only have his story for what happened.

Safety is my number one priority, and I am more concerned he gets a bike back that is safe. I don't know what kind of damage has been done to all the moving parts and my lack of bike knowledge means I now have broken confidence with either the bike, the initial setup or ability to fix. As it has now had a bit of a battering is there more risk this could happen again? It doesn't help that I met a friends mum who tells me her sons Halfords Apollo bike chain has slipped off regularly since new despite taking back to the shop twice.

Halford have said £45 for new gears as covers only can be replaced, £20 for new seat, and that's before they looked closely at it. For a £330 is it worth just buying a new one?

Maybe I should just wrap him up in cotton wool for the rest of his teens!

steve_sordy

Unfortunately Halfords do not have the best reputation amongst the bike fraternity for their bike set up and maintenance skills.

If it was poor set up that caused the chain to slip, and the same person sets it up again, then the same thing may happen.

Based upon what you said in your post, a likely cause is as follows:

The chain is too long and when crossing rough ground at speed, the lower strand whips up and down and can strike the chain stay. It may also develop a standing wave, like you can do with a skipping rope. You can see this whipping up and down on many photos of bikes descending. A change of speed or frequency of hits to the bike can cause the wave to move forward and the chain comes off. This is why many riders invest in (or used to) what are collectively called "chain devices". These keep the chain on in a variety of ways. With advent of single ring gearing, narrow/wide chain rings and clutches on the rear mech have pretty much stopped chain whip and chain loss, so you don't tend to see so many chain devices these days (or at least I don't), outside the down hill bike parks any way.

So, make sure that the chain is not too long. Put the chain in the biggest front gear and the biggest rear gear. Adjust the chain length so that the rear mech lower arm points forward at 45 degrees. There is another step for certain types of full suspension bike, but for a hardtail that is all you need to do.

If you want to go for a chain device, in my mind the best (and cheapest) for a bike with more than one front ring is the dangler type. They also work well on bikes with one front ring (not narrow-wide) and maybe no clutch mech.

Read this review, to see how the dangler type works:
https://www.bikeradar.com/mtb/gear/cate ... -12-46125/

Then buy one of these instead: Same exact idea, but about one third the price (they last just as long as well).
https://www.tredz.co.uk/.RSP-Chain-Dire ... IX2fD_BwE#

cougie

Also maybe sprinting out of the saddle downhill might not be the safest option...

LiDavies

cougie wrote:

Also maybe sprinting out of the saddle downhill might not be the safest option...

I think he's learned that lesson the hard way

02gf74

Chain can come off if it is too long over a bump.

Without seeing the frame it is difficult to make an assessment, marks may be cosmetic or there may be frame damage, are there any cracks visible and any tubes dented or bent.

FishFish

Well at least he was a boy and not a girl.