Rear Wheel Lock-up Mystery

[Maharg]

Last week, while cycling up a steep hill to get home, my bike experienced a fault which no-one (including the mechanics at our local bike shop) can properly explain. What happened was that the bike came to a dead halt in the road. I got off, had a look, couldn't find anything obviously wrong, got back on the bike and carried on cycling, only to have the experience repeated again. . . again. . . and again. Deciding I needed a new chain and cogset, I took the bike into the shop to have the work done, and in addition ended up having a new back wheel, plus a replacement middle ring on the bike's triple chainset. Fine, except the fault continued. So back to the shop whose friendly staff suggested that the problem could be due to the rear wheel's skewer shifting under pressure, causing the tyre to rub against one of the frame's rear stays. At any rate, they replaced the (temp) QR skewer with a nutted one, and there has been a mild improvement.

Nevertheless, the problem still persists; that's to say the bike 'locks up' when I'm cycling uphill in bottom (20") gear. In fact the problem becomes exponentially worse if I attempt to get up the hill in any higher gear. Also, there's this: I've had tyre rub before on other bikes (in the distant past), so I know what that feels like. This is different in that I'm talking about a sudden dead halt, and I real do mean sudden. . . like it feels mechanical not frictional, which strongly suggests that it's something to do with the transmission. A tyre rub would give me fractional warning time, all the more so since I'm only doing 4 ~ 5 mph whenever it happens. So what can be the cause of the fault? I've checked the 26T innermost chainring and it looks fine. Could it be something to do with the rear deraileur, the jockey wheels perhaps? Can't be due to the new chain and cogset, not if they're replicating the fault during the bike's previous transmission setup. So what the hell is going on? In short I'm completely foxed! Any ideas therefore will be greatly appreciated.

Apologies in advance about the length of this post. . .

 

[Ajax Bay]

My 'best' guess would be chain suck: ie the crank suddenly was 'stopped' "the bike came to a dead halt"
Why was the middle ring replaced? I would change the small ring, which is presumably the ring you were in when this happened.
See this 'chain suck' thread https://www.cyclechat.net/threads/p...-when-in-the-small-gears.269738/#post-6228182

If the rear axle was shifting (being pulled forward on the right hand side by the immense torque you're exerting up that hill) pulling the tyre onto the left chainstay then you wouldn't be able to just "[get] off, had a look, couldn't find anything obviously wrong, get back on the bike and carry on cycling".
If the tyre was stuck against the chainstay it would be immediately obvious when you hurriedly dismounted, and found that: which it wasn't. I have had this as a result, I realised later, of a broken axle. Tyre against chainstay slows progress to zero. Release QR, recentre wheel (horizontal drop outs) and super-retighten. Make it back home. Started servicing hub: (one third of) axle falls out with cone, spacer and locknut still attached! LBS for new axle, get the left/right correct, and ride on.

 

[alicat]

What make and range of chainrings and cassette/freewheel are you using? What gear (xx numbet front and xx number back) were you running when it happened? How come you were able to get off rather than falling off? Some more info might help us diagnose what happened.

 

[cougie uk]

I've pulled my wheel across climbing a few times but as has been said - the wheel stays there.

Your frame is ok ? No cracks on the chainstay ?

 

[bikingdad90]

Something damaged in the freehub?

 

[Paulus]

Bent or broken axle?

 

[Tigerbiten]

As it get worse the more force is applied and the wheel jams.
That sounds like there's something bent/broken in the hub itself.
As the more force that is applied the more the bent/broken part shift until something rotating jams with something that's not.
The first guess would be bent/broken axle.
Outside possibility is a bearing is doing the same trick.

Luck .........

 

[Low Gear Guy]

Does the frame have vertical or horizontal dropouts?

 

[Ian H]

I've pulled my wheel across climbing a few times but as has been said - the wheel stays there.

Your frame is ok ? No cracks on the chainstay ?

That was my thought. Cracked or a joint come loose. Might need careful inspection to find it.

 

[Arrowfoot]

Classic chain suck - mechanical, sudden and increase load at the start of a climb. In my case, first ride after air travel using a bike bag. Due to possible knock during baggage handling, misalignment - bent derailleur. Bike was fine for 10 kms until the start of the climb. A real shock.

 

[gbb]

Bearings can lock up as noted by Tigerbiten, particually cheaper cageless varieties, I've seen it on my own bikes in the BB. A quick backpedal usually looses it. I think the balls in a worn bearing jam against each, instant lock up.
Its a potential cause, chain suck I've never experienced but does seem a more ,popular / likely theory.

 

[Ajax Bay]

Reading the OP yet again (but noting the OP hasn't been back here since Friday noon, posting (their first post)):

At any rate, they replaced the (temp) QR skewer with a nutted one, and there has been a mild improvement.

I'm going to guess that the LBS thought this might be a broken axle. Well was it? And if not why did they replace it. What do you mean by a "(temp) QR skewer"? In what way temporary?
Why was the middle ring replaced? The OP would not have been in the middle ring up a steep hill (assumed at 4-5mph).
This is a new rear wheel, with a new cassette and chain to boot. The inner chainring is worn (making this assumption since the LBS decided the middle one merited replacement). See chain suck table above.

 

[Maharg]

Some clarifications: the replacement middle chainring is incidential to the problem (I should never have mentioned it - my fault) since I'm always on the innermost ring* when climbing this hill and others like it. The term 'chain suck' is a new one on me, and right now I'm absorbing what it means. I guess the real lulu about the problem is that it should replicate itself, despite having a completely new back wheel, including new cogset, tyre, axle, bearings (plus new chain) fitted to the bike. So all that's left now is the rear mech, bottom bracket and the frame itself. The frame itself, which is steel, is a 1960/70s Falcon which I've owned these last forty-odd years. Indeed, the only original part of the bike now left is the frame and its period-piece Weinmann centre-pull brakes (minus levers). Yes, the frame is definitely showing its age and there is some rust on the rear stays. This means it should be replaced forthwith. It's taken this thread for me to realise it, I guess. Still, I'd like to know, if only for form's sake, how exactly a frame's rear stays could cause the above problem. . . flexing under pressure perhaps? I don't know. Many thanks for the helpful suggestions, by the way.

*Visually at least the steel 26T chainring checks out fine. If the tools were available I'd swap it for the 24T inner ring on my Surly tourer, just to make sure, but quite honestly I think that's unnecessary.

 

[Ajax Bay]

the replacement middle chainring is incidential . . . . I'm always on the innermost ring* when climbing this hill . . . . I guess the real lulu about the problem is that it should replicate itself, despite having a completely new back wheel, including new cogset, tyre, axle, bearings (plus new chain) fitted to the bike. So all that's left now is the rear mech, bottom bracket and the frame itself. . . . . , how exactly a frame's rear stays could cause the above problem. . . flexing under pressure perhaps? I don't know. Many thanks for the helpful suggestions, by the way.
*Visually at least the steel 26T chainring checks out fine. If the tools were available I'd swap it for the 24T inner ring on my Surly tourer, just to make sure, but quite honestly I think that's unnecessary.

Humour us (me): so why was the middle ring replaced, incidental or not?
You said in the OP the problem WAS replicating. This is what chain suck does. IT has Zero to do with the other stuff (freewheel block, tyre axle bearings RD BB frame): just chain (new) and ring (worn). As you say: how could the Falcon's chainstays cause the symptoms described?
As an aside try climbing Wrynose and Hardknott (with a new 'sensible chap changed it before a long ride 1000km' chain), chain sucking twice, and then knowing that any moment the b*****y cranks are going to dead stop on a 1 in 4 corner and you're (I'm) clipped in, 'eading for a fall - only solution to climb in the 42t as opposed to the 28t ring, and wear out cleats as and when.
Aside number two: my sixth form bike was a Falcon (drop handlebars with esoteric bar-end shifters): I still have its Brooks, for high day and holiday use only.
Since the inner ring "checks out visually fine" it's clearly not worth changing. Bounce your bike up and down a few times and then go and ride up a steep hill, clipped in and see if the problem, however caused replicates. All part of your personal development plan.

 

[andrew_s]

I had a similar set of lockups once, when riding with the rear QR undone.

Vertical dropouts and gravity made sure the wheel stayed put during normal riding, but if I got out of the saddle on a steep climb, the lack of weight on the rear wheel meant it didn't take much of a bump to lift the rear enough to allow the axle to drop out of the dropout.
Chain tension then pulled the wheel hard against the chainstay bridge and mudguard bolt head, and it locked. The bike skidded (briefly) to a stop, and I got off, but the loss of chain tension as I did so allowed the axle to move back into the dropout, so there was no obvious cause, and the wheel moved freely.

It happened 3 times, all on the one hill, before I worked out what the problem was and did up the QR.

It's not going to be chainsuck - that will lock the cranks, but not the rear wheel (it won't happen on fixed).
It also normally leaves the chain jammed between chainrings and chainstay, so it's obvious what the problem is.