7 speed megarange/megadrive advice please

[bob smythe]

Hello, I have had my specialized crosstrail now for just under 2 years, I recently started having problems. First the gear hanger that holds the derailleur on broke, which I thought was odd. My derailleur was a little twisted but the guy in the shop said it should be ok and fitted a new hanger. After a month I took it to another shop for the gears to be reset because they kept slipping. I thought it best to replace the derailleur with a new one as well, the one that was on before was an altus, the new one being Olivio, I was told the chain had stretched and that it would be better to change it so I had that done as well along with a new rear screw on sprockets.

Ok the problem I have is that I can not go into ratio 3:1 (largest front and back) the chain is too short and it ends up jamming. It does go into that gear but the chain is so tight it doesn't turn. I was told by the guy in the shop that this was normal and that when I was sold the bike I should have been told this, he said with the megarange 34t its very large with the unusually large front crank set.

Is this normal or is something not right. The problem I have is that I do a lot of night riding and tend to forget what ratio I am in, if I go into 3:1 and my chain locks out I could end up breaking it again. I hope this is understandable and that someone can advise.

thank you

 

[Theseus]

You should try to avoid using largest on both front and back at the same time. This puts too much of an angle on the chain. The ratio this produces will be possible using one of the other gear selections. Try the middle ring at the front and somewhere in the middle at the back.

 

[mcshroom]

Although you should avoid using big front and big back, as the chain line is very crooked in this position causing excess wear, the bike should not be set up in such a way as it locks up if you do use that combination. Bike chains should be sized to just fit onto the biggest combination available with one extra link. Otherwise accidentally shifting into that gear in the dark can be a serious hassle when it all locks up DAHIKT

Chain wheel sizes shouldn't be a problem. I have a megarange on a hybrid with a 48t big ring, and many recumbents have far bigger front rings with big rear sprockets.

 

[RecordAceFromNew]

You have been badly served by the shop(s).

The shop which fitted the new chain should have ensured the chain is long enough to allow you to be in both large rings front and back (cross chaining being good, bad or indifferent is NO excuse). Anything else is not acceptable, and can seriously damage your bike and even your health (when the rear mech get bent, sucked into your rear wheel, causing the bike to grind to a halt while you go over the handlebars).

The correct length of the chain can be calculated by this. Find out how many links you need, compare with the existing, and if existing is shorter get yours changed asap.

If you could try to learn setting up gears and changing chains etc. yourself. They are not difficult and if you have any question just ask at the Knowhow forum here.

 

[bob smythe]

Hi thank you for your very prompt replies, so basically even though going into that ratio is a bad idea, there should be no reason why I can't and that the chain is in fact too short, and I should go back to the shop and ask them to solve the problem.

 

[Scilly Suffolk]

Just to second what has been said above:
a) you shouldn't ride in the extreme ratios (large/large or small/small).
b) even so, if the chain locks-up it is too short.

Three options from Park Tool here for checking the length.

As the chain is clearly too short, I'd be going back to the shop that shortened it and asking for a new chain: ask to see the manager. This is pretty basic stuff and any mechanic that can't get it right shouldn't be in business; telling you it is normal is either astonishing ignorance or a downright lie.

Like RAFN says, this sort of thing isn't difficult and it's very satisfying to service and maintain your own bike: lots of resources on the internet including the helpful folk on CC.

 

[RecordAceFromNew]

Hi thank you for your very prompt replies, so basically even though going into that ratio is a bad idea, there should be no reason why I can't and that the chain is in fact too short, and I should go back to the shop and ask them to solve the problem.

Definitely. If the existing chain is as expected shorter than what the calculator suggests, tell them they should do it for free. If they won't, please let us know what reason they gave, and I would be interested which shop it is (so at the very least I won't be going there in the future!).

BTW chain length has to be increased or decreased by increments of multiple of 2 links because consecutive links of a normal chain are different.

 

[PpPete]

^^^^^^
Wot they said.

I once inadvertently set a bike up with a chain too short..... so I know there is no excuse for it. I had no one to complain to though - you do.

Please name and shame that bike shop.

 

[bob smythe]

Thank you for your advice, I went out Sunday on it, its not right at all, I can't use 1st at all it just constantly slips no matter what front gear I am in. I looked at how the dérailleur was set up, it lookes aligned but it sits directly under the sprocket touching underneath, I don't know if this is what the problem is, and the chain is really tight, taking it in today to see what he says