Bent Rear Mech - or Frame?

[thirdcrank]

The key is that for a while now, the hanger has been treated as what I believe is called a sacrificial part. I come from a generation when "lightweight" frames had a hanger as part of the RH dropout. My first Campag Super Record rear mech came without a hanger; in those days "loose" hangers = cheapo. Much more recently when I was baffled trying to sort out the shifting on one of my grandchildren's Islabikes, I asked at my LBS (Sowerby Bros, Mirfield) and the immediate suggestion without seeing the bike was to check the hanger. I got a new one - Islabikes stock them to fit their own bikes, which says something - and once fitted, problem solved. The difference between original and replacement was imperceptible to me so any misalignment needn't be glaringly obvious.

[Jupestar]

If it was me I'd buy a new one and then spend way too much time trying to repair the old one anyway. I find it very difficult to throw anything away! !

yep. did exactly this with a 9 speed. Spend ages tweaking it with a vice, hammer etc to get it straight. got it 'working' but never WORKING!. after losing a few hours/days of my life, fitting, unfitting, fitting..... . I ended up chucking in the scrap metal bucket.

[Mick F]

Good morning guys.

Thanks for your replies.
No cracks, just a scratch and some muck.

The answer has been staring me in the face, as so wonderfully pointed out by Mrs Mick F the other day. Chuck the bent one out and fit the new one. She says I'm nearly 70 for goodness sake!

I was/am reluctant to fit the new one because these M772 XT mechs are completely sold out worldwide. I had this idea that eventually I could sell it as brand new and get my £70 back.
Everywhere you look, they are all gone. Sadly, because they are a superb rear mech. They are ostensibly 9sp, but work 10sp admirably.

https://www.wiggle.co.uk/shimano-xt-m77 ... derailleur

It's obvious that I'm not getting any younger, so the new one will be on the bike this weekend, and as I'm feeling better all the time, I'll be out on a test ride early next week.

Meanwhile, I'm going to strip it down, if only for the jockey cage (both sides) and the jockey wheels. Plus the fixings and the swivel hanger as well. The rest, can sit on a shelf.
https://www.manualslib.com/manual/21047 ... tml#manual

[Mick F]

Kitchen table job!

Stripped it easily and was horrified to see the lack of lube in the jockey cage hinge.
Big spiral spring and axle shaft completely devoid of grease.

Dunno if it was like that from new and it was washed out over the thousands of miles, or if it was badly lubed to start with.
It's not easy or quick to fit more grease. All it would need would be a seal and/or a grease insertion point.

I'm gonna have to strip the new one to check ............. and lather with grease.
Having stripped the old one, and then rebuilt it, I now know how it's done.

Pull the cage forwards and remove the anchor stop. Crosshead screwdriver.
Allow the cage spring to unwind.
Remove the pin in the bottom of the parallelogram. Small Allen key.
Pull the cage away and reveal the spring and the innards.

Refitting, is the reverse but paying attention to which way round the spring goes. Narrow end towards the cage. Also, there's two spring anchor holes in the cage. Tighter or looser.

[NickJP]

Can't see from your photos if this is a "shadow" RD. If so, and if it's the hinged part that bolts to the frame that is bent, you could replace that with a goatlink: https://www.wolftoothcomponents.com/products/goatlink.

[pq]

I haven't bothered reading this thread, so it's probably been said already, but I had a similar problem, and quickly found that trying to straighten things by eye didn't work. I bought the cheapest alignment tool I could find (a cyclus), and while it's crude, it was completely effective. I then checked the alignment on all my bikes and discovered that most of them were a bit out of whack, so straightened them too, improving the shifting in every case. It was a very good investment of time and money.

[Mick F]

Update.
Photos later today/tomorrow perhaps.

Fitted the new one, and it's fine. Refitted the old one, and it's bent. I very much think that it's not the cage that has flexed, as the cage seems true and straight.

Stripped the new one, only to find there was zero grease in there. Maybe a pitiful tiny bit of an oily deposit, but that's all.
Shoved a good finger of grease in, and then reassembled, and fitted to the bike.

Meanwhile, cleaned the chain. I'll fit the chain and photograph. Bike is upside down.

Then, I'll fit the old one, and photograph.
Then, I'll remove it, and swap the hinge pieces over and refit the old one.

I predict, that it's not the hinge piece, but the parallelogram of the old one.

Back later!

[Mick F]

Can't be bothered to do any more.
The mech is bent, and that's it.

Swapped the mechs over and photographed each.
Big ring, small sprocket on both.
Guess which is which.

[pwa]

I screwed it in and out on both. The cage is on a parallelogram and follows a straight a parallel path. It's just that on Bent, the cage isn't aligned correctly. Going in and out doesn't alter that ............. or that's the way it seems on New and on Bent.
No wobbly play on Bent, as it's not floppy or rubbish at all. It's just not straight.

Having a beer and siting in the livingroom, and looking and thinking.
Part of me thinks that I should just chuck it into the parts bin, and then fit New and forget about Bent.
Another part of me, likes to fix things.

It's not the top unit or the bottom unit, or the parallelogram specifically, or play in the the whole thing.
It's just "bent" and "stretched" perhaps, making the cage not be inline with the chain. No damage to the cage at all.

The whole thing took a whack when I slammed into the tarmac and it became "twisted" perhaps.
I think I have nothing to lose by attempting to "un-twist" it.
Sort of diagonally mounting it into the vice and giving it a squeeze.

Tomorrow job but only after I've been to the nurse to have my dressings changed. I wonder if she knows anything about bike mechanicals?

I'd fit the new mech for now, and keep the old mech as a spare, minus the knackered part. You have a replacement for the knackered part, but it is currently on your new mech. So long as you don't break that one too, it will be transferable to your old mech if and when you ever want to use it again.

[philvantwo]

Are you going to fit some decent tyres as well Mick F, instead of those cheap nasty budget things you got for £3 off ebay!

[Mick F]

Excellent tyres, thank you.

The roads are a terrible mess hereabouts. Greasy and slimy, and I am in no doubt whatsoever that there was a diesel deposit. It's the first tight righthander since I saw the diesel a few miles earlier on the tight bend after Gunnislake bridge. By the time I got to the mini roundabout, I'd forgotten about it.

I won't forget in future!

What we need is a few days of rain. Not had any rain to speak of for over two weeks.

As for my cycling glasses, they have had it. The lens is scratched and where the frame has broken, it's right on the hinge. The prescription for them is about three prescriptions ago, so they are well out of date. They are worn too with the nose pads all squidgy and falling apart. The arms are worn and the hinges floppy.

I'm due another prescription soon, so Optilabs will be getting an order from me. May not wait for another prescription as my normal varifocals are fine. I may wear them when I tentatively venture out this week. Moulton is now in one piece and fully checked over.

[Mick F]

Update.

Just come back from an hour's ride. New rear mech is fine, The indexing needs a tiny bit of a tweak, but the gears instantly selected at the flick of the lever.

The bike overall was fine, and the cranks haven't been bent - thank goodness. No damage at all to anything ................. except the rear mech of course.

[NATURAL ANKLING]

Hi,
And your pride
Neither my road or tourer has seen any daylight in the last two years, three this july.
Its the skip trainer only and I have another hanging up as a reserve.

If your just riding and just riding then its matters not, how heavy or expensive looking it is.
My brakes work and the gears too, hybrid tyres the way to go.
Little point in slicks if the bike is a substitute for a fly trap

[Mick F]

Fixed it!

Having spent the last few days stewing over it, I took the bent on into the workshop and gave it a good eyeballing.
I'm convinced that the parallelogram is out of whack, and even after removing a rivet to open it, I was unable to do anything.

All there was left, was to fit it on the bike, fit the chain, and give the whole mech a good twisting. It was surprising how much force and flex there was, and when I let it go, it was basically un-moved. Eventually, I managed to get the chain to run sweetly.

I'm not too sure what I'd done, but perhaps a twist in the cage and a twist in the parallelogram too, but it's fine now - though not a good as the brand new one - but it should be ok.

Test ride early in the week. Horrendous weather out there now. Don't even want to take the dog out!

[cycle tramp]

Kitchen table job!


IMG_1007.jpg


Stripped it easily and was horrified to see the lack of lube in the jockey cage hinge.
Big spiral spring and axle shaft completely devoid of grease.

Dunno if it was like that from new and it was washed out over the thousands of miles, or if it was badly lubed to start with.
It's not easy or quick to fit more grease. All it would need would be a seal and/or a grease insertion point.

Did you end up drilling one?