Rear Gear Alignment

[Yellow Saddle]

You've answered your own question. You'll see this only happens when you back pedal AND the chain is on the biggest sprocket. In that position the chain's angle from the top of that sprocket to the chainring in front is at an angle big enough to make the chain want to "correct" it when backpedalling. This doesn't happen when you pedal forward because then the chain enters the sprockets from below and the derailer cage is designed to correct the chainline before it goes onto the cassette. When backpedalling, the chain enters the cassette without the benefit of pre-correction by a derailer.

 

[Cyclist33]

thanks, that does go some way to explaining it although it happens on several of the bigger cogs!

 

[Yellow Saddle]

thanks, that does go some way to explaining it although it happens on several of the bigger cogs!

Yes, it will happen on a few of them. Try it tonight from a variety of sprockets on the back and let us know tomorrow morning what you found. It is much worse on bikes with short chainstays than ones with long chainstays because of the accentuated angle in the former.

 

[lpretro1]

You may well find the freehub is getting gummed up - spin the pedals forward and then let go - they should stop and the wheel should keep rotatong freely. If you find the pedals get pushed round as well then this is an indication of the freehub not being free enough. if the latter then you then try back pedalling you will find that chain comes off

 

[uclown2002]

Holy Thread Hijack!

 

[uclown2002]

Update:-
I tried a brand new, unused AND true wheel but the results were the same; 15 mm out at 12 o'clock. I didn't notice any movement at the hanger and hanger mount when closing the skewer. Given it's my No 3 road bike that's as far as I got with it. Used the hanger alignment tool to bend the new hanger and consequently the shifting is improved.

Thanks for all the advice.

 

[Yellow Saddle]

That's a good result then.

 

[bpsmith]

Took a while after being suggested in first reply.

 

[bpsmith]

I took my bike to bits earlier to check out my rear alignment, as could see and hear it was out when riding.

Put the Park DAG-2 on and, just from the weight of the tool, could see that it was actually cracked. A brief check showed that it was way out of alignment too, but there were no signs of it having touched anything and I have no idea when this could have happened.

Any ideas guys? Can a hanger crack from just usage?

Could there have been a weakness that became a problem from riding it hard or must some event have happened?

It doesn't sound likely that it could happen from usage, but I cant explain it otherwise.

 

[sittingbull]

A friend of mine had a Giant MTB on which the hanger broke clean through whilst out riding. He swore nothing had happened to it, then or previously. He had owned the bike from new.

 

[bpsmith]

Same scenario as me. Mine is 8 months old and only I have ridden it and nobody generally goes in my garage unless I am there.

 

[Yellow Saddle]

Let's see those cracks. Photos please.

 

[bpsmith]

It's academic now. Threw the thing in temper yesterday and now in 2 pieces.

 

[Yellow Saddle]

It's academic now. Threw the thing in temper yesterday and now in 2 pieces.

Academics is fun. Unthrow it. Take a photo of the cracks and we can discuss what happened.

 

[sittingbull]

Having read this thread with interest and having had a recent drive-side altercation with the tarmac resulting in an obviously bent hanger, I decided to get a Park hanger alignment tool.

It seems straightforward to use, basically it's trial and error until getting a satisfactory result.

First thing I noticed though is that this tool is heavy, and that weight has been extended further out from the hanger (compared to the previous tool) to allow the tool to rotate past a pannier rack etc

Update:-
I tried a brand new, unused AND true wheel but the results were the same; 15 mm out at 12 o'clock........

In fact I'm not surprised that new hangers would appear out at 12 o'clock due to this weight flexing the hanger towards the wheel.

I'm sure Park will have considered this in the tool design and presumably tool weight has a negligible effect, plus countless users seem happy with the results, but I'm still wondering whether the tool itself could distort the results?

Am I missing something?