Is my derailleur or hanger bent?

Marko1066

Hi Guy's,

New to the forum so go easy on me!

I took the plunge and bought a Bizango 29er from Halfords in December due to good reviews everywhere. I thought I'd swallow my pride and put up with the disapproving looks from the trail blazing elite from my local trails (Swinley).

So far, so good. Very happy with it. Slowly changing bits and pieces saddle, pedals, 1 x 10 conversion, dropper post for no other reason than I enjoy f*cking around with things : ) Anyway, I digress.

The real reason I'm here is because my rear derailleur doesn't appear to be straight and I'm having shifting issues. It seems to be jumping a tooth in the small cog on the cassette and is generally a bit noisy. I noticed the the rear hanger is at a slight angle and has been since it was purchased from Halfords. It went in for its 6 week service and some spotty teenager I mean Halfords cycle technician adjusted things and it was working a little smoother (no jumping). Today it has begun jumping again (admittedly after a little 'tweaking' from me). I'd quite like to get your opinions on the angle of the derailleur as I'd like to get this right before I attempt to adjust things further.

You can see the hanger in the following picture:



If I tighten the grandmother out of the quick release wheel clamp it straightens up the hanger a little. Surely this isn't right though? I left my over tightening pre-torque days in the past years ago when I was 14! Should there be some sort of spacer? Or has someone at Halfords booted it on the way out?



All replies warmly received!

Thanks in advance.

Mark.

LimitedGarry

A bent hanger often doesn't actually seem bent to a naked eye, because it usually gets bent in several different directions. And looking at the picture, it doesn't appear to be bent. There's a special tool for checking that. If you have a suspicion your hanger is bent, the only way to find out is taking your bike to the shop and asking them to check it out. Alternative to that is having that specific tool but it's not a worthwhile investment unless you're setting up your own shop in a big style.

Can you adjust the derailleur yourself (limit screws, b-screw, indexing)? If you're new at doing it, it'll take you a bit to get it right. Check out youtube, there's a bunch of really useful vids about it. It's no rocket surgery, just something you gotta get a few extra experience points for. Once you're good at it, it's a two minute job. That's why you should do it yourself instead of taking the bike to the shop and waiting a day or two.

If the smallest gear is jumping, it's most likely either limit screw set too far in or too much tension on the cable. Bent hanger typically makes you unable to properly index a few specific sprockets. It would have to be bent by David Copperfield himself in order to only affect the very last gear. Not saying it's impossible, just unlikely.

If you were to give your bike to me for maintenance, I'd start by degreasing the bananas out of the whole drivetrain. Then onto the derailleur itself. If you keep riding a chain that dirty, it wion't last you very long.

coulddobetter

Halfords sell hangers for not much cash. As above though if it is just 1 cog affected then minor cable tension tweak or b tension and limit screw adjustments will sort it.Work methodically and turn screws quarter turn max. Often you can get things right in a stand and find you need to tweak things when bikes ridden.

larkim

The angle of the axle to the hangar / frame does look very screwy. You say that you can tighten up the QR to pull things back square, but that you have to do that very hard - it seems unlikely but are you sure that the chainstay triangle hasn't been bent at all in a bit impact? It could just be fore-shortening in the camera image, but the gap to the chain above the axle looks much bigger than below, yet the hanger does seem visually straight. Sorry for an absence of solutions, but that doesn't look right to me. Though I am no expert.

The Rookie

Doing up the QR properly tight will leave a white mark on the palm of your hand, if that's what it takes then it's probably right.

My old hardtail had that exact issue, just did the QR up properly and used it like that for 4 years, Shimano QR's are the best giving more consistent and better loading.

larkim

Just curious at this point - what's the screw that looks a bit like a B-screw which seems to be acting on the hanger at the top? I've not seen an adjustable hanger like that before (though I have limited experience, admittedly!)

FishFish

I think that screw might be for a single cog at the back set up - for tensioning the chain.

Also if you are cycling underwater you can tie a fishing lure to it.

Marko1066

Thank you for all your replies!

Limited Gary - I'm a gas engineer by trade so 'reasonably handy'. I thought I had indexed the gears ok but will have a look at the high/ low limit screws as that seems the most obvious reason for the high gear skipping. Thanks for your input Re: bent hanger. Being somewhat new top the technical world of bikes, I was unsure as to exactly the definition of a bent hanger. To me, at the risk of using a technical term, the whole hanger looks pissed! I was of the understanding that everything should be perfectly parallel to the cassette, and mine isn't! Also, hands up, that chains filthy... *pulls socks up*

Coulddobetter - Thanks, I'll have a go at resetting the limit screws on stand.

Larkim - Music to my ears sir! That's the main reason for me posting. That's not a dodgy camera angle, that's the real deal! That's why I thought maybe a spacer of something was left out as it straightens up slightly when the quick release wheel clamp is overly tightened.

The Rookie - That's a fair shout. I'm just stuck in the ideal world of everything being just beyond finger tight should be fine. I guess maybe my (ultimately budget) bike will never be perfect!

And Larkim, I believe that is a chain tensioner but could be mistaken. I've no idea what the blue paint on it is for!

If truth be told, I reckon once of I've adjusted the limit screws and stopped the chain jumping, I'll stop pissing and moaning about everything else : )

Thanks again for your input.

Mark

The Rookie

Marko1066 wrote:

The Rookie - That's a fair shout. I'm just stuck in the ideal world of everything being just beyond finger tight should be fine. I guess maybe my (ultimately budget) bike will never be perfect!

Every bolt has a correct torque, some being much more than finger tight, torque is merely a convenient (and not brilliantly accurate due to the variability of thread friction) way of setting/measuring clamping load, in the same way the rear QR needs to set to a clamping load to make sure the rear wheel in clamped correctly in place to resist the loads likely to move it, so in the 'ideal world' you would find out what that correct load is and set to it, its certainly more than finger tight and on FS bikes it can often help improve the rear end stiffness for example.

larkim

Ref blue paint - that's thread lock compound, designed to prevent a thread from vibrating loose, but not seal it so tight it can't be adjusted ever again.

Clamping force required to close the QR can be significantly affected by friction within the QR mechanism itself, I believe oiling the cam and cleaning up the cup that the QR handle sits in could help so that whilst force pulling across the axle is very tight, the force to push the QR lever to generate that tightness is reduced from what you are currently experiencing.

And as for what the hanger is, to all intents and purposes on your bike it is the black bit - its a sacrificial part so that if the rear mech takes a wallop the effect is to bend the cheaply replaceable hanger rather than the expensive mech or more expensive frame. I suspect you probably knew that, but just in case...

Marko1066

Ref blue paint - that's thread lock compound, designed to prevent a thread from vibrating loose, but not seal it so tight it can't be adjusted ever again.

Ah, I see. Live and learn!

And as for what the hanger is, to all intents and purposes on your bike it is the black bit - its a sacrificial part so that if the rear mech takes a wallop the effect is to bend the cheaply replaceable hanger rather than the expensive mech or more expensive frame. I suspect you probably knew that, but just in case..

I know what the hanger is, just wasn't so sure if it was bent in the picture!

Every bolt has a correct torque, some being much more than finger tight, torque is merely a convenient (and not brilliantly accurate due to the variability of thread friction) way of setting/measuring clamping load, in the same way the rear QR needs to set to a clamping load to make sure the rear wheel in clamped correctly in place to resist the loads likely to move it, so in the 'ideal world' you would find out what that correct load is and set to it, its certainly more than finger tight and on FS bikes it can often help improve the rear end stiffness for example.

Not literally finger tight. Was more a point in the direction of not having to tighten everything to within an inch of its life!

I've since re-indexed the gears and everything seems to be working fine. I suspect I wasn't fully clicking the shifter back to to its start position before attempting to set up gears (prick.. I know).

Thanks again for all your help.

Mark.