Yet Another Cycling Forum
General Category => The Knowledge => Topic started by: jsabine on 07 July, 2016, 12:18:56 am
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Following an incident on the Wild Atlantic Way audax, my derailleur hanger is somewhat bent ... Steel frame, so roadside attention with a pair of pliers got it straight enough that I had most gears - but it needs fettling. Happily, I'd been meaning to acquire an alignment tool anyway, so this just accelerates the process.
Clearly I'm not about to spend $185 on the work of art from Abbey Bike Tools (http://www.abbeybiketools.com/collections/best-sellers/products/hag) or £180 on Shimano (https://www.cyclestore.co.uk/shimano_tlrd11_rear_derailleur_hanger_alignment_tool-ID_58659)'s offering, but is it worthwhile spending £55 on the Park Tool (http://brilliantbikes.co.uk/frame-and-fork-tools/69-park-tool-usa-derailleur-hanger-alignment-gauge-dag-1.html) version rather than Wiggle (http://www.wiggle.co.uk/lifeline-derailleur-hanger-alignment-tool/)'s Lifeline variant at £25 - or, seeing as that's currently out of stock, £32 on the one Chain Reaction (http://www.chainreactioncycles.com/x-tools-pro-gear-hanger-alignment-tool/rp-prod122319) sells? Is there another one I should look at? (The Unior (https://www.amazon.co.uk/dp/B004XVQH8G/) looks solid, but no saving over the Park. Merlin (https://www.merlincycles.com/cyclus-gear-hanger-alignment-tool-92156.html) has a Cyclus one for £28.)
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I've got the Cyclus one. It works, as I expect do all the others.
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you don't need a tool if you have a spare wheel with a 10x1 threaded axle.
Just;
a) fit the usual (non-disc) wheel in the frame the other way round (this makes room for the other 'tool' wheel to be fitted).
b) fit the spare wheel to the right-hand side of the gear hanger by screwing the 10x1 threaded axle through the hanger.
c) If the bend is bad, fit the track nut on the inside of the hanger.
d) tweak away
What you are aiming for is a hanger with 0 to 1 degree 'toe out' and 0 to 1 degree 'negative camber' (NB the latter is the opposite to what happens when the bike falls over).
You can get close enough by eye (probably more easily than with 'the proper tool' in fact), but if you want to be super accurate, on a 700C wheel 1 degree is a difference of ~11mm between the gap on one side and the gap on the other.
hth
cheers
[edited to change 'toe in' to 'toe out'...d'oh! ]
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Wot 'e sed...
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I know about the wheel trick - this is probably at least partly an excuse to buy something New! Shiny! (and a hanger tool is a damn sight cheaper than a lot of other things I could be eyeing up).
Thanks for the guidance on technique and the accuracy needed - I'll try to contain my natural tendency to aim for +/- 1mm difference ...
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BTW with a steel frame, depending on the dropout design, there is a chance of the dropout bending (where you don't want it to) when the hanger is being tweaked.
To mitigate against this possibility, it is usually a good idea to brace everything by fitting a solid axle hub into the dropouts when you are tweaking the hanger. Needless to say, the stronger the axle in the bracing hub is, the more good it can do.
cheers
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I have the wiggle tool and it's OK but I find there is a little bit of slop in the fittings, so you need to keep them loaded/ tensioned to ensure a consistent measure.
I've used it a good few times since I bought it over a year ago now.
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Mostly it's bent hangers on Carreras and other 'cheaper' bikes I fix. Usually soft cast alloy rather than CNC machined.
Couldn't see it pointed out above so I'll stress that you mustn't try to straighten a hanger on the bike without the wheel (or a hub) firmly fitted in the rear dropout and if you see any signs of stress or cracking on the hanger then don't mess about, just replace it. When they crack they have done their job...
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Mostly it's bent hangers on Carreras and other 'cheaper' bikes I fix. Usually soft cast alloy rather than CNC machined.
Couldn't see it pointed out above so I'll stress that you mustn't try to straighten a hanger on the bike without the wheel (or a hub) firmly fitted in the rear dropout and if you see any signs of stress or cracking on the hanger then don't mess about, just replace it. When they crack they have done their job...
Yep, mines on a steel frame, but I honestly couldn't see doing a straightening without the wheel being in place as you use that (rim) as the point of reference ???
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The cyclus one has always worked well for me - got it from Rosebikes
You need to have the wheel in to use these things so isn't the above a bit of a moot point? [edit - i.e. what Torslanda said)
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Yep, mines on a steel frame, but I honestly couldn't see doing a straightening without the wheel being in place as you use that (rim) as the point of reference ???
Ah, to explain. I use the same method as outlined so eloquently by Brucey upthread. Using the hub as the datum, a Shimano axle screwed into the hanger and a handlebar over the axle for leverage. A long lever allows quite precise adjustment in small increments.
I also keep a small number of new hangers - the most common - for those that have been BTF.
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Today I bought the Park Tools DAG 2.2 (2.2 fits more frame types).
It's a tool that will last a lifetime and has already got one derailleur changing more slickly.
If you're going to go to the trouble of adjusting gears on your's, and family members', bikes then this gets you off to a perfect start.
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I have a long-standing policy that whenever I need a tool, I buy the Park one. It's cheaper in the long run.
I've never felt the need to buy a hanger alignment tool though - I think I've had two bent hangers in the last 25 years, and I've just taken it to a shop. Although if you follow Doctor D on facebook, you'll see that most frames would benefit from a tweak, even new ones straight from the factory.
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While I'm largely a believer in the notion that there's nothing so expensive as cheap tools, I do quite like to know what the extra money is paying for. Given that most alignment tools seem to be a bit of box section, a pointer, and an M10 screw, with any minor slop easy enough to compensate for during occasional home use, I hadn't really managed to convince myself that the Park was worth going for above some of the cheaper options.
That makes it even more of a mystery how I seem to have ended up with the Campag alignment tool. It's actually almost elegant.
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Thread necromancy.
I've just bought a cyclus alignment tool to sort out our TSO, it has a bash guard fitted in a stable door manner1. If I'm understanding Brucey's directions above I want on a 26" wheel:
Zero gap behind the pointer at the top of the wheel and 10mm between pointer & rim at the bottom.
Zero gap behind the pointer at the front of the rim and 10mm between pointer & rim at the rear.
Is that correct?
1Carefully protecting alignment gaps of about 40mm in the vertical plane & 17mm horizontal, both the wrong way.
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I just realised I said 'toe in' when I meant to say 'toe out' (I've edited my original post accordingly). In any event the dimensions quoted are the maximum allowable rather than a target.
There is a better description here (SI instructions for RD-7400)
https://si.shimano.com/pdfs/si/SI-N-81A-000-00-ENG_GER_FRA_DUT_ITA_JPN.pdf (https://si.shimano.com/pdfs/si/SI-N-81A-000-00-ENG_GER_FRA_DUT_ITA_JPN.pdf)
which appear to permit ~0.5 degree 'toe in' to ~1 degree 'toe out', and recommends a small amount of 'toe out'. Interestingly it doesn't mention camber angle of the hanger, but other SI techdocs do, IIRC.
cheers
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Just go for the hanger bolt parallel with hub axle in both directions. Easy to understand and achieve.
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further to the above this is the park tool diagram (with which I do not entirely agree)
(https://image.slidesharecdn.com/dag-2instructionsandpartsdiagram-131204104702-phpapp02/95/dag-2-instructions-and-parts-diagram-1-638.jpg?cb=1386154056)
to meet the shimano specs I suggest that you set the pointer at C then check at A. The clearance at A should be ~5mm greater than at C.
Similarly set the pointer at D then check at B. The clearance at B should be ~5mm greater than at D.
I have used the park tool and the pointer is annoying because it gets in the way if you have a tyre on the rim. Another annoyance is that the tool is usually a slack fit on the post so can flap about. You need to allow for any backlash when using the tool.
NB the wheel in the bike needs to be true else this alignment procedure won't work. Similarly if you are using a spare wheel as a tool (in the hanger) to check/set the hanger alignment, it too needs to be true. You can overcome either or both issues by turning the wheel(s) so that you are always measuring at the same point on the rim.
BTW I think it is worth the effort to set a little 'toe out' as recommended; shifting is often noticeably improved vs a perfectly 'square on' hanger.
cheers
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https://www.wiggle.co.uk/park-tool-derailleur-hanger-alignment-gauge-22
I have one of these. It’s absolutely superb.
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Regarding using an untrue wheel in ther bike inconjunction with a Park , or similar approved, tool, is a valid work around to rotate the wheel to positions A, B, C and D with the pointer of the tool? I did this the other day, using the valve as a handy marker.
Assuming the untrueness of the wheel is a wobble in the rim and not a more serious failing, I can't see why this won't work.
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Regarding using an untrue wheel in ther bike inconjunction with a Park , or similar approved, tool, is a valid work around to rotate the wheel to positions A, B, C and D with the pointer of the tool? I did this the other day, using the valve as a handy marker.
Assuming the untrueness of the wheel is a wobble in the rim and not a more serious failing, I can't see why this won't work.
yes, hence
……. You can overcome either or both issues by turning the wheel(s) so that you are always measuring at the same point on the rim.
cheers
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Regarding using an untrue wheel in ther bike inconjunction with a Park , or similar approved, tool, is a valid work around to rotate the wheel to positions A, B, C and D with the pointer of the tool? I did this the other day, using the valve as a handy marker.
Assuming the untrueness of the wheel is a wobble in the rim and not a more serious failing, I can't see why this won't work.
yes, hence
……. You can overcome either or both issues by turning the wheel(s) so that you are always measuring at the same point on the rim.
cheers
Ah. Memo to self: Read the whole thing first. Idiot (me).
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I’ve got one of the cheap ones and it works. I’d rather not have to use it often mind. I sorted the hanger on the big yellow truck a few weeks ago, only after buying a couple of spares (it’s alloy) from China. The bike has been blown over and I was quite surprised the SLX mech and road link seems to survive bu the hanger not.
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That is the intent. The replaceable hanger is the weak link that saves everything else from damage.
Shimano’s misaligned tolerances regarding hanger alignment for recent mechs are a bit of a shit solution. Campag engineered its triple mechs to hang skew-wiff from a correctly aligned hanger for better chain management.
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….Shimano’s misaligned tolerances regarding hanger alignment for recent mechs are a bit of a shit solution....
only since 1984...?
FWIW several manufacturers (esp SRAM) use imperfect parallelograms such that the toe angle of the mech varies through the stroke, apparently to better match the chain entry angle at the bottom of the mech. To me this seems a little in conflict with the observation that the tolerances specified by shimano appear to be set so that positive camber and 'toe-in' are avoided. Certainly if these become excessive indexed gear systems can work a lot less well, and with a perfectly square-on hanger you are still 'in tolerance' but by the time you strap a mech on these errors are just a bit more likely to happen.
BTW I modified my Park Tool hanger aligner so that I could adjust the slack out it; no more annoying wobbling about. I also made it so that the part that screws in the hanger is
a) able to be 'bolted through' (i.e. the hanger is clamped from both sides securely instead of relying on the screw threads) and
b) can more easily be replaced should the need arise.
I normally use it with a set of Vernier calipers to measure the setting. If I ever reinstate the original pointer, I shall modify it so that it is on a hinge, so that it can be moved out the way (without losing the setting) when the tool is being swung between positions.
cheers
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I prefer my 1st edition Shimano hanger tool, complete with little ruler. It was much nicer than the previous Campag tool and the others I’ve tried recently.
http://velobase.com/ViewTool.aspx?ID=200131aa-6578-40ad-bbaa-ea3f3f559cf3 but doesn’t show the supplied SS ruler and the chromed centring tool designed to screw onto a bare freewheel hub (in place of checking against a wheel).
Part of the reason I like 8sp is the greater tolerance of misalignment and wear. I’ve seen too many folk having shifting problems from trivial causes partway through a 1200.
If 0.5 degree is the difference between working and not, you are asking for trouble. Should I realign the gear hanger when swapping between Shimano and Campag mechs? Don’t be silly.
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If 0.5 degrees is the difference between working and not, you are asking for trouble. Should I realign the gear hanger when swapping between Shimano and Campag mechs? Don’t be silly.
good
better
best
IME campag mechs usually work well at the shimano settings too, i.e. the range of settings that is OK certainly overlaps. However plenty of bikes have gear hangers that are imperfectly aligned, and/or flex more than half a degree (differently) every time the QR is done up. But then again plenty of bikes have gears that don't work quite as well as they should do, too.
In reality you should probably realign the hanger so that the mech works as well as it can do; in the case of many used mechs (and some new ones) this means adjusting it to suit, which may be outside any manufacturer's specifications.
cheers
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If 0.5 degrees is the difference between working and not, you are asking for trouble. Should I realign the gear hanger when swapping between Shimano and Campag mechs? Don’t be silly.
good
better
best
IME campag mechs usually work well at the shimano settings too, i.e. the range of settings that is OK certainly overlaps. However plenty of bikes have gear hangers that are imperfectly aligned, and/or flex more than half a degree (differently) every time the QR is done up. But then again plenty of bikes have gears that don't work quite as well as they should do, too.
In reality you should probably realign the hanger so that the mech works as well as it can do; in the case of many used mechs (and some new ones) this means adjusting it to suit, which may be outside any manufacturer's specifications.
cheers
And this is probably and iterative process;)
lW&B - yes, positive that the hanger twisted rather than the mech. I was more surprised that the road link stayed straight. However, a moments thought illustrates that the moment results in more force at the hanger than anywhere else in the chain.
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Given that plasticly deforming aluminium takes away from its fatigue life, repeatedly realigning a replaceable aluminium hanger to compensate for derailleur wear is not a good idea. Work hardening is a real thing. When I was a bike mechanic, the rule of thumb was that realigning a crashed aluminium hanger once would probably be fine but doing it more often risked failure down the road.
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Thanks Brucey :thumbsup:
The cyclus tool works well, precision is easily achieved. Hardest part is getting the wheel absolutely straight in the frame this being a nutted axle. Flipping thing wanders as the nuts are tightened.
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Are the dropouts parallel and undamaged? The wheel wandering when tightening axle nuts is usually the result of uneven contact between axle nuts and dropouts.
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Given that plasticly deforming aluminium takes away from its fatigue life, repeatedly realigning a replaceable aluminium hanger to compensate for derailleur wear is not a good idea. Work hardening is a real thing. When I was a bike mechanic, the rule of thumb was that realigning a crashed aluminium hanger once would probably be fine but doing it more often risked failure down the road.
this is a very sensible precaution. However I note that in the last couple of decades, the range and quality of ductile aluminium casting alloys has improved somewhat. I therefore fancy my chances of straightening a bent replaceable hanger a bit more these days.
In general terms a ductile material will plastically deform (and it may work-harden) up to a point and then you are on 'a slippery slope' to failure.
(https://www.admet.com/wp-content/uploads/2017/07/ductile-specimen-shape-during-testing.png)
The curve above is from tensile testing but something similar may be seen in bending too.
So when you are straightening something, if the force required to move it is still increasing, you probably have a way to go yet. However if it isn't or it is actually starting to decrease, then you are in the poop and the part is well on the way to failure.
A really ductile material will withstand several tens of percent elongation to failure; this might correspond with straightening a bent hanger a couple of times (depending on how bad the bend was and how ductile the alloy is) or resetting a gear hanger (by a much smaller amount) about a dozen times or so.
cheers
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All true Brucey but the residual fatigue life of aluminium is what I am talking about. To cold-set an item means taking it past the yield stress. That significantly drops the number of additional low stress cycles the item can sustain in future. High stresses mean few cycles before fracture. Tensile tests explain the response to a single stress event. Fatigue tests explain the response to repeated stress cycles.
There are lots of instances of derailleur hangers broken while riding (that destructively drags the derailleur over the cassette) after an unremarkable gear change. Possibly a complicated combination of overstress, crack initiation and propagation, fatigue and corrosion but minimising potential factors (e.g. repeatedly cold-setting aluminium) seems like a good idea.
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one way of representing the likelihood of fatigue failure is on a diagram like this one;
(https://www.efunda.com/designstandards/springs/images/soderberg.gif)
The mean stresses in the part are low (mostly residual stresses after straightening) and the applied cyclic stresses are also low. In practice this means that for a hanger to break in use, it (more or less) has to be cracked when it is put back into service. So as if it needs to be said, if you have straightened a hanger, you should check it for cracks before using it again.
Like spokes, once there is a crack, nothing will save the part from eventual failure. Without there being cracks present, normal service stresses are unlikely to cause the part to fail; were it otherwise, you would see failures in undamaged gear hangers more often than you do.
cheers
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Apologies if I’ve missed someone mentioning this further up and I’ve missed it.
It is, in my experience, vital to fit a wheel as tightly as you would to ride the bike before checking/adjusting the hanger. When you put a wheel in and tighten the quick release you’ll often see the angle of the hanger change a little.
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You could always make your own like this:
https://www.youtube.com/watch?v=KIzd0xdkowM (https://www.youtube.com/watch?v=KIzd0xdkowM)
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I did a very bent one on my Cinder Cone with a long steel rule, some calipers and a lot of eyeballing. It was skewed (you can check this relative to the RH BB shell face) as well as bent inwards. Those old steel built-in hangers take a fair bit of welly to realign.