Cycling UK Forum

Sorry to jump in with a problem for my first post on this board, but I am totally flummoxed and don't really know what to do next. There seems to be plenty of good advice from knowledgable people here, so I am hoping somebody might be able to help me.

I bought a new Pashley Parabike a few years ago. From the start it has given me problems with the SA 5 speed hub. Despite lots of searching online, I haven't really found any complaints about this hub, so assume it is usually fairly reliable.

It will skip and crunch in pretty much all gears and 5th is so bad it may as well not be there. On first investigation, the hub had been set up with the settings for rear facing/vertical dropouts rather than the forward facing dropouts fitted to the bike. I set it up correctly and changed the gear cable which seemed to be sticking. Whilst slightly better, it didn't really cure the problem and the bike was put away and didn't really get used for a couple of years.

I recently took a deep breath and opened the hub. I immediately found two loose bearings from the ball ring bearing. I went through each part examining, cleaning and regreasing. Nothing appeared to be worn/damaged, except the pawls on the gear ring which had a couple of minor chips. (I think this would be caused by the skipping, and not be the cause of the problem?)

Needing the bike, I reasssembled the hub, thinking the problems may have been caused by the loose bearings. When reassembling, I did the RH cone up finger tight and backed it off just enough so the hub span freely without play and then adjusted the hub using the LH cone. I still have the same problems. and just wondered if anybody could shed some light on them please?

you say RX-RD5 but if it was 'a few years ago' then are you sure that it wasn't X-RD5(W) model? They are quite different, and RX-RD5 has only been fitted for a couple of years or so.


RX-RD5 with rotary shifting


X-RD5(W) which uses toggle chain shifting.

There are also XL variants which use 90mm brakes instead of 70mm ones.

FWIW any chipping on the high gear drive pawls (in either model of hub) is 100% symptomatic of bad adjustment of the gear. Even with the correct settings this happens accidentally with bad shifters/bad cables; the shifter overshifts on downshifts and then sticks in the overshift position. Instead of being in (say) 3rd gear, you are half-way into second gear and the high gear pawls are half-retracted. Needless to say they slip and are then damaged. Once damaged the pawls won't drive properly in gears 3,4,5. Bad adjustment can also kybosh the sun locking in either type of hub.

Slippage in gear 5 can realistically only arise from a few sources. The most likely (barring chain/sprocket/cable problems) are;

1) slippage of the sliding clutch vs the planet cage (in which case it would normally also affect gear 4)
2) sun pinion not locked properly (although the same sun pinion is used in gear 1 it is not necessarily locked in the same way)
3) slippage of high gear drive pawls (also affects gears 3,4 as well as 5)

It is not unusual for balls to be dislodged from the acetal ring bearing retainer during assembly/disassembly; probably they fell out as the hub was being taken apart. If the retainer is worn or the driver pawls are extended as the driver is withdrawn, balls can easily be dislodged. They are best kept well-greased during reassembly if the retainer is a bit worn. If balls had been floating around loose in the hub in service it would have smashed itself to bits.

I suspect that the problem -unless it is not exactly as described- presently lies in the sun locking. However it has probably been caused by the shifter/cable. If so, fixing the hub without doing anything about the shifter/cable is not going to provide a good solution.

FWIW the sun locking in (W) hubs is described in more detail in my 'slightly crazy world' post. In RX hubs the suns are locked by four pawls which are actuated in the same way as in the SA 8s hubs. I have seen the pawl locking controls damaged in 8s hubs so I would assume that the same thing can happen in the RX series 5s hubs too.

cheers

Many thanks for replying Brucey. Definitely RX-RD5 with rotary shifting/70mm brakes. I have another bike with X-RD5(W) hub. I think the bike is about 4 years old, but I haven't got the greatest memory for these things so could be slightly younger.

As I mentioned, the hub hasn't really worked properly since I got it, so the high gear pawls being damaged by bad adjustment doesn't surprise me. The adjustment process that SA describe in their literature resulted in different results each time, with the markings aligning in different places despite sometimes not adjusting the cable tension. The cable was replaced and seemed to rectify a lot of that. I was starting to wonder about the shifter, so I will investigate that. The gear change on it does seem a bit wishy washy sometimes, especially on 1 and 5. Can shifters be overhauled, or would you suggest replacement? I imagine the latter.

I will investigate the three possibilities for gear 5 slippage you describe. Very useful info. I think the sun locking sounds like a possible cause combined with the possible shifter problem.

I'll update this once I have tried a few things.

Thank you so much.
Ian

I think the very first bike which were shipped with the RX hubs are about three years old now. You don't say which shifter you have but the Pashleys I have seen with this hub use the SL-C50T shifter



This has identical internals to the earlier SL-S50 shifter



and as a consequence has exactly the same problems, being mainly

1) stickiness (so that it overshifts on downshifts) and
2) backlash between the lever/drum and the index mechanism.

You can strip the lever and correct 1) but it is not really a one-time DIY proposition; you need a very unusual size of circlip pliers to get into the lever at all and then you need to have almost infinite patience (plus a load of specially made shims) to adjust the preload on the index mechanism, and to be able to modify other parts as needed. Ideally you need some means of measuring the force required to overcome the index detents so that you get the least stickiness without ghost shifting.

Even if you overcome 1) you are still left with 2); the backlash increases quite quickly with wear and there is basically nothing much you can do about it; the interface between the lever/drum and the index mechanism is so small and soft it is bound to wear (but it wears much less quickly once 1) is corrected). Because the cable is attached to the lever/drum (rather than the index mechanism) a worn lever won't latch in first gear position unless it is pulled much further than normal. This strains the cable and is liable to throw the adjustment out. I have seen levers which wouldn't latch until they were moved +30 degrees more than normal....

The interface between the bracket and the static parts of the index mechanism also wears, but this is never the main source of problems in this lever design.

If you want to use a standard (i.e. faulty) lever you can do; just keep the adjustment spot on and make sure that you pull the lever back to the detent position after every downshift.

In point of fact a normal lever problem isn't going to cause gear 5 to fail in an RX hub; however a bad cable might, causing the gear 5 pawl not to be fully lifted when gear 5 is engaged. Once the gear slips then the gear 5 pawl itself may chip. The other thing that may happen is that there is a load passed back through the pawl arm such that it may be damaged. I have seen both types of damage in 8s hubs and the 5s parts are designed in the same way, i.e. the pawls have sharp edges and shallow engagement (cf Shimano Nexus/Alfine sun locking pawls which have deep engagement and rounded profiles; they are much less easily damaged).

You can see the sun locking pawls here

http://www.sturmey-archer.com/files/catalog/files/39/PART%20LIST%20-%20RX-RF5.pdf

for some reason the RX-RD5 parts listing (which I think ought to use the same pawls)

http://www.sturmey-archer.com/files/catalog/files/38/PART%20LIST%20-%20RX-RD5.pdf

doesn't break down the axle assy (which has a different part number anyway)

If the RF sun locking pawl parts fit the RD hub then it may be possible to repair your hub using #15 (HSA911) but

a) I have no means of knowing if they definitely fit and
b) I have never seen these parts for sale; SA may want you to buy a new axle assy or a new internal.

The high gear drive pawls (HSA923) are likewise not for sale anywhere that I can find but if damage isn't too bad they can be dressed; just make sure the dog ring matches the new pawl shape and that the pawls are an identical length to one another. HSA927 (C50 driver) is available and comes with new pawls.

If you are faced with having to buy a new internal, often you can buy a complete hub for the same money (if you shop around) which then rather begs the question 'why bother to carry on with this b. hub anyway?'

For many years the selling points of SA hubs (with more than 3 gears) have been (in no particular order);

- low weight
- simplicity
- really reliable drum brakes
- nicely polished aluminium shells
- good spare parts availability
- low cost spare parts
- some compatibility between disparate SA hubs

in a nutshell you might be prepared to put up with an increased chance of problems because the hub was nicer to use when it was working and it could be fixed fairly easily/cheaply.

In the RX-RD5 I see only two of the above remaining. I have an X-RD5(W) on my carrier bike and I think it is far from perfect; however I think when it breaks I can fix it; I can buy spare parts for it. I also have both a spare 5s internal and I know I can make up a 3s internal to fit that hubshell too. With an RX series hub I'd arguably be in a worse state, even if the hub was ostensibly 'better' in some respects.

cheers

Just mentioning, neither the written sheet of instructions & diagrams for setting the shift cable length that came with my RX-RF5 nor the pdf instructions available from Sturmey-Archer's website bore any resemblance to the actual, in-the-metal physical realization of my hub. However, after I empirically determined the correct length (aligning the yellow marks on the hub when the shifter is in 2nd gear) the hub has been smooth and quiet with positive if relatively slow shifting.

it has been awhile so I might not remember this rightly but there is no fixed cable length on SA hubs with rotary shifting; the reason for this is that the reaction arm for the shifter cable is (unlike in shimano hubs) not fixed, but can be installed in more than one position. This allows you to install the hub in any frame without having so many different possible NTWs (cf shimano) but does mean that the cable length varies with the exact installation. Fortunately it is not difficult to get the cable length within the range of the barrel adjuster.

cheers

The current RX-RF5 reaction arm has marked orientation settings for 'R' (fork ends, or 'reversed'), 'V' (vertical) and 'S' (semi-horizontal, or 'standard') dropout types. Seems like the instructions should (but don't) suggest three corresponding starting measurements for 'cable-anchorage unit' distance with, as you say, fine tuning at the barrel adjuster.

http://www.sturmey-archer.com/files/catalog/files/38/MANUAL%20-%205%20SPEED%20ROTARY%20HUBS.pdf

in section 3.9 it lists two different cable settings but I think (like you say) there ought to be three, since (in 3.2) there are three different settings for the shift cable reaction arm.

cheers

From reading all the related sa 5 speed posts it would appear that the sa gear shifters are poor in design and responsible for most hub failures.
What's the alternative?
After market shifter?
Friction? (Brucey has covered this before)

It can be OK to use a pair of friction shifters with a twin-toggle 5s hub but I wouldn't recommend running a single cable SA 5s hub with a friction shifter.

Currently the most commonly seen shifter type for bikes with 5s hubs is the thumbshifter, SL-S50 etc. However there are also twist shifter and trigger shifter options. My limited experience of those is a bit underwhelming too; the twist shifters don't seem very durable and it is debatable if the cable pulls are perfectly matched to the hubs.

The trigger shifters appear to be based on the same architecture as Microshift shifters which are sold in various guises for various applications. These shifters are basically intended to pull ~3mm per click. They revise the spacing of the ratchet and the radius of the quadrant inside the shifter to make it suitable for other applications. The version I have seen most of is the microshift trigger shifter meant for use with Nexus 7 hubs; this pulls about 5mm per click and has a larger than normal quadrant inside. The result of these changes is that the cable invariably frays and breaks inside the shifter, well before it should and well before the shifter wears out. The cable frays and breaks for two reasons; 1) the cable passes out of the shifter body at an angle (because the quadrant is larger than normal), so that the cable chafes on the back of the barrel adjuster and 2) the quadrant isn't constant radius inside the shifter which results in excessive flexing of the cable, fraying and then breakage. I don't know if these features are carried over into the SA 5s branded versions of this shifter, but since the cable pulls are similarly large, it seems quite likely.


microshift Nexus 7 type shifter


sturmey DL-S50 shifter


sturmey DL-S30 shifter

Trigger shifters for S40 C50 and S80 hubs are of a different pattern



and are more of an unknown quantity

cheers

Thanks for all the replies. So pleased with the responses to my problem.

It sounds like my bike may have been one of the early versions with the rotary hub, and from what Brucey said the SLC50-T shifter is highly suspect. Is the DLC50 trigger shifter a suitable alternative? I will probably change it just to see if there is any improvement, but if the thumbshifters are all the same it seems a bit pointless to stick with it. Overhaul sounds like the proverbial pain in the posterior.

I did gently dress the pawls before putting them back in - I agree the spare parts situation for these hubs is not as good as for their predecessors. Having searched part numbers, not much shows up as available. I will soldier on for a while, but as you say why carry on with a hub that might never work properly.

I had the wheel out yesterday to fix a broken spoke. While it was out I took a look at the changing mechanism. The fulcrum arm on my version only has two markings. One for standard dropouts and one for rearward facing/vertical dropouts. It was originally set up on the second of those options - how I don't know as nothing seems to line up when putting the wheel back in. Perhaps it was a Friday afternoon bike!

I agree with Sid that there are differences between the instruction sheet and the physical hub, but the measurement for the pinch bolt seemed quite straightforward and I haven't had any problems with getting the yellow marks aligned once I changed the gear cable and put the fulcrum arm in the correect position. It seems quite a good system to me.

they went through three different iterations with the thumbshifter for the (W) 5s hubs and they didn't really fix the thing.

By all means try a DL-C50 shifter; it is that, a rotary shifter or pulling the thumbshifter back to the detent position; not much of a choice really. I have rebuilt a few SL-C50 type thumbshifters and they appear to have worked OK, but I have no idea how they worked out in the long term.

cheers

Thanks Brucey. I will give it a go and report back.

out of interest what date marks do you have on your RX-RD5 hub? There should be two marks; one on the brake plate and one on the hubshell.

BTW if you want your extant shifter rebuilt I can do it. However with the RX series hubs the return spring pressure can be varied (by the way the hub is set up) so there are a few more checks and balances when installing the thing. Get this or the cable wrong and the sun locking in top gear might be the first thing to fail.

cheers

some photos inside a microshift shifter for a Nexus 7s hub





In the second photo you can also see the remains of an old cable. The flexing in the high gears usually ruins the cable first.

You basically have no chance to change a cable unless you take the shifter half to bits. In at least one LBS they simply bin this shifter when a bike comes in with one and it needs a new cable; this works out a lot cheaper for the customer in the long run. The SA DL-S50 and DL-S30 shifters are built on this design and may well have similar problems.

cheers