RD-M4000 Alivio; suprisingly tough?

[Brucey]

hanger stiffness is basically an irrelevance except in a few instances; during shifting the load on the gear cable (and therefore the approximate lateral force on the RD) is rarely in excess of 10-15lbs.

Buying a new adaptor/hanger is not a disaster but

a) you are still walking home

b) if there was no breakage then there would be no need for a replacement part

c) you are assuming that a replacement hanger/adaptor is readily available. This is very often not the case; there are at least 70 'common' types and that does not include the many that allow for 'direct mounting'. There are man-years of time wasted trying to source these ruddy things and I would estimate that world-wide, at any given time, there are several thousand bikes off the road either temporarily or permanently because the correct thing cannot easily be had.

Just to be crystal clear, in case it wasn't obvious the previous three times I said it, I expect you to be able to easily straighten the top part of RD-M4000 should it get bent in any way. This is pretty much the point of this entire thread.

I would expect you to be able to straighten a bent RD-M4000 well enough to ride home with minimal tools; a small adjustable spanner would be plenty. You are not buying spare obscure/expensive parts and you are not walking home. There are plenty of other RDs that just break and/or break the rest of the bike when they get bent. This model appears to do neither thing at all readily, (although other models made to a similar design still might, because they are made using different materials.)

cheers

[The utility cyclist]

A few years back I got run into by a teenager who sprinted out from the side of the high street after he'd looked at me or should I say through me, totally wiped me out and fractured left elbow and right scaphoid . Turned out the Ultegra rear mech was bent, I managed to bend it back into shape and it's been used ever since (some 5 years later). It's not always lower end kit that can be surprisingly tough.

[Sweep]

Interesting thread and thanks for starting brucey.

Useful for my plan to build up stocks of components for 8 and 9 speed.

But remain a tad puzzled by Shimano's M and T prefixes.

M= Mountain?
T = Trecking?

What's the difference? I kind of had the idea that what was thought of as "trecking" owed more to MTB stuff that "racing", ie: availability of lower gears, stress on taking it easy rather than killing yourself and pushing against big rings in an attempt to power-sneer your way away from the puny competition.

So what is "trecking"? Something mysterious between MTB and racing?

[thelawnet]

Interesting thread and thanks for starting brucey.

Useful for my plan to build up stocks of components for 8 and 9 speed.

But remain a tad puzzled by Shimano's M and T prefixes.

M= Mountain?
T = Trecking?

T is trekking.

https://bike.shimano.com/en-EU/components/trekking.html

It seems to have slightly different meaning at different price points, at the top-end 'touring', at the lower end just 'hybrid'.

Previously there was MC - Mountain Comfort.

T also overlaps with 'C' - city.

[Sweep]

thanks for that link lawnet, but it's just unenlightening marketing waffle.

And semi literate to boot.

(not suggesting you are)

[Brucey]

T series parts appear to be mostly (ex) Mountain bike type parts that have been repurposed and/or refinished. Current MTBs have largely departed from standard QR hubs and rim brakes etc so they have basically repurposed the kinds of parts that you might have fitted on an XC MTB a few years ago, for touring, trekking etc. Trekking is touring with flat bars, 700C wheels and maybe tackling the odd unsurfaced path. It is all good stuff but the implicit assumption appears to be that

a) you want to use a Mountain bike chainline (and therefore you are happy with a large Q value) and
b) that you want to use flat bars

Thus it is rare that you see a full set of T type parts on a touring bike built in/for the UK, with dropped handlebars. If you look at (say) Spa's touring bikes they use T series parts where they can but this is mostly hubs, V brakes and RDs.

cheers

[Sweep]

Thanks brucey.

My reading from your far far greater knowledge is that there isn't a great deal of difference between mountain and trekking.

My 2016 Ridgeback Expedition has T4000 hubs front and rear and a T4000 front mech.

Will replace hubs in time, together with rims/wheels, but may way replace front mech when/if it goes with a laid up spare of same.

The rear mech on that bike is Deore.

I also take it from your post/s that T4000 stuff is generally decent/pretty tough stuff?

[Brucey]

I also take it from your post/s that T4000 stuff is generally decent/pretty tough stuff?

well it is decently made shimano equipment, mainly based on designs that were branded 'deore' a few years ago, but with variations. If you look after it OK it will mostly work alright.

No big surprises there apart from the experience with the RD-M4000, which seems unusually difficult to damage in such a way as it cannot be repaired.

cheers

[thelawnet]

Thanks brucey.

My reading from your far far greater knowledge is that there isn't a great deal of difference between mountain and trekking.

My 2016 Ridgeback Expedition has T4000 hubs front and rear and a T4000 front mech.

T4000 is 'Alivio', and the T4000 hub is a previous-generation Alivio M430 hub simply rebranded as T. The M range now being mostly disc hubs, where as the T stuff still has more rim brake options. I don't think the T series is high priority for pointless gimmicks, sorry 'innovation', so they may use older parts with a new name. Hence also the use of 10-speed rather than 11-speed on XT.

The T4000 front derailleur should be the same basic componentry as the M4000, however it is designed for bigger chainrings and a 12t top-mid jump rather than a MTB 40/30/22.

[hamster]

hanger stiffness is basically an irrelevance except in a few instances; during shifting the load on the gear cable (and therefore the approximate lateral force on the RD) is rarely in excess of 10-15lbs.

Buying a new adaptor/hanger is not a disaster but

a) you are still walking home

b) if there was no breakage then there would be no need for a replacement part

c) you are assuming that a replacement hanger/adaptor is readily available. This is very often not the case; there are at least 70 'common' types and that does not include the many that allow for 'direct mounting'. There are man-years of time wasted trying to source these ruddy things and I would estimate that world-wide, at any given time, there are several thousand bikes off the road either temporarily or permanently because the correct thing cannot easily be had.

Just to be crystal clear, in case it wasn't obvious the previous three times I said it, I expect you to be able to easily straighten the top part of RD-M4000 should it get bent in any way. This is pretty much the point of this entire thread.

I would expect you to be able to straighten a bent RD-M4000 well enough to ride home with minimal tools; a small adjustable spanner would be plenty. You are not buying spare obscure/expensive parts and you are not walking home. There are plenty of other RDs that just break and/or break the rest of the bike when they get bent. This model appears to do neither thing at all readily, (although other models made to a similar design still might, because they are made using different materials.)

cheers

Quite - my local shop mechanic told me that it's all so tetchy now that any damage causes them to swap the frame hanger as standard. It's their experience that even minute misalignments are a source of ongoing trouble. It is made worse by modern Shimano designs demanding that the gears at the most extreme chainlines are now essential as opposed to merely convenient as on a 3x system.

[Brucey]

I just checked the material in the adaptor from RD-M786 (shadow plus dyna-sys 10s) and it was aluminium, not steel. I have corrected slight bends in these mechs, but I don't doubt that the adaptor is nowhere near as ductile as the steel one used on less posh models.

It is worth noting that when it comes to making a bent mech work again, the shadow/shadow plus arrangement is more likely to yield a satisfactory result. The reason for this is that there is only one pivot axis to get at the correct angle, and the adaptor can always be moved to some extent in order to get this right.

In mechs with a sprung b-pivot, there are two pivots that must remain parallel to one another if the pulley cage is always to move in a single plane; often enough a bent mech will no longer have these pivot axes parallel and furthermore this kind of deformation isn't always easy to either spot or correct.

IME shimano mechs with two sprung pivots break wholesale (usually by the parallelogram pins tearing out of a knuckle or just shearing off) about half the time should they take the 'death plunge' into the spokes. Quite a few shimano mechs in recent years have had plastic lower knuckles, yet these mechs often fail at the top knuckle, not the lower knuckle, presumably because the leverage is greater at the top knuckle.

Because there is no 'weak link' in many cases, the forces can get very high; if a knuckle does not fail it is also possible for the inner side plate from the parallelogram to yield in compression. This usually results in an unrepairable mech since the buckling of the inner side plate is very difficult to correct.

In a busy LBS it is not unusual to have several RDs/hangers that need replacing every week because the mech has gone in the spokes. It isn't always clear exactly why this happens; there are several possibilities.

1) that the stop screws were never properly adjusted and it was only a matter of time before the mech got shifted into the spokes

2) that something happened in the rear wheel (eg a slack spoke) that snagged the mech, or likewise a screw has come loose in the RD (eg the one securing the guide pulley)

3) that the stop screws were correctly adjusted at one time, but the screw setting has moved or the stop screw seat has worn, thus throwing the adjustment off

4) that the mech gets slightly bent (eg in a daft parking knock, or by the bike falling over) and is moved far enough that it will tangle with the spokes the next time bottom gear is engaged.

When viewing the remains of a mech it is impossible to tell what happened for sure. However stop screws do wear, and mechs get knocked often enough to push them out of line; a little tlc would prevent many of these incidents, for sure.

cheers

[pwa]

Is it common for mechs to end up in the wheel? I had it happen once, around 1970ish, and not since.

[Brucey]

Is it common for mechs to end up in the wheel? I had it happen once, around 1970ish, and not since.

ah, you probably look after your bike... not your average cyclist then.?...

cheers

[NATURAL ANKLING]

Hi,
I have no idea well not much as I live isolated in the sticks
One death dive in all my 50 years of cycling.
But I am not your average LBS punter also.
Despite touring off road over 95% of dartmoors off road rideable tracks / paths / open land, I had no problem with 90's alivio mech and alivio drive train, it was bottom end then but worked very well.

Maybe bend's better than break, well it is, and glad to see you are so mean green after all.....sush just don't tell your LBS they might sack you

[pwa]

In my "make it up as you go along" fashion I have always taken action if a rear mech taps a spoke. Not something to leave. Sometimes it means truing a wheel. Or (horror!) if all else seems properly adjusted I have even applied a bit of controlled pressure to bend the mech arm out a few mm. But I never continue to ride knowing that a mech is getting too close to the spokes.