Rear derailleur guard

[freiston]

What are people's thoughts on these (link to example here)? I noticed one on a photo today and it got me thinking. I've had a couple of tumbles in the past where my bike has gone down and the rear changer has got hit by the road. On one occasion, I suspect the derailleur might have gotten slightly out of line (the difficulty I had in getting positive accurate shifts disappeared with a subsequent change of cassette, changer and cables - so lots of factors that could have made a difference) Would this guard be beneficial in protecting the rear changer or hanger from getting bent? I'm thinking particularly about a steel bike and dropouts with integral hanger.

[gaz]

I had one that came on an MTB I rode in the 80's. Added to the faff removing/fitting the rear wheel. Wasn't long before I left it off permanently.

As with any such thing there will be sets of circumstances where it helps, others where it doesn't. IMO save your money.

[iandriver]

I'd associate something like that more with a folder to protect on trains etc.

Something like this might be more practical in a crash.
https://www.southwatercycles.com/m8b0s1 ... -Protector

I've got one that on-one used to do years ago but never put it to the test. Could never decide if something poking out would do as much harm as good.

[foxyrider]

IME they are more trouble than they are worth. Yes they stop the RM hitting the ground/wall etc but the guard often bends instead impacting the mech, at the very least interfering with its function.

[robgul]

Bike shops will tell you that the hanger - which is normally separate and replaceable on anything but the most basic of bikes - is designed to be the weak point if the bike falls over rather than damaging the frame - and that the so-called "guards" have potential to damage the frame/dropout.

My view is that they're a PITA if you take the wheel out - and look ugly too.

Rob

[freiston]

Thank you everyone for your inputs.

[peetee]

In my experience the majority of these hangers are designed for wheels with solid axles and securing nuts not quick release. The mating faces are formed from a crude pressing not machined flat so would not provide secure wheel location unless 'over' tightened with a nut and washer.

[pwa]

In more than fifty years of regular cycling I have never damaged a mech in a fall, so I'd give that piece of ironmongery a miss.

[freiston]

In more than fifty years of regular cycling I have never damaged a mech in a fall, so I'd give that piece of ironmongery a miss.

I put a gouge into a brand new rear mech first time out with it. It was rather silly and embarrassing - I went to a stretch of uphill on a little lane I know to test out my new low ratios, did a double change (front and rear) into bottom gear at low speed (but not low enough) then spun out and toppled over to the right. I ought to have changed down to the little chainring whilst staying a lot higher on the back. I felt very stupid and very annoyed with myself

[flat tyre]

I've never managed to damage the mech, however for time to time I've managed to bend the mech hanger (they're made of metallic cheese, there's a reason for this!), either by falling off or the bike falling over. I bought a derialleur alignment tool which has been very useful on these occasions.

[Brucey]

RDs get knocked all the time, so protecting them seems appealing, but using a guard is not without its consequences



the above is the most common type, and uses the axle or QR to retain it. You obviously need more axle threads to accommodate this, and it will get in the way when removing the wheel. It will protect the RD from minor knocks, but a fundamental problem is that a more serious load doesn't 'go away' it gets passed into some other part of the bike. They are cheap though; from 99p on ebay...

There are many variations on a theme for example this one



passes the loads into the rack/mudguard eyes on the dropout instead. This means the wheel is easier to take out but in the event of a prang the guard loads the dropout in a way that it isn't loaded normally, so guess what, the dropout bends/breaks instead.

This is a variation on a theme




in which the 'nut' on the QR is replaced and there is a 'prong' that engages with the RD mounting bolt; this will withstand small knocks and protects the (intentionally flimsy) hanger which is fitted to most modern frames. I think this type will usually only work if the hanger is exactly 30mm long.

So if you fit one of these contraptions you may avoid damage from minor knocks but in a more serious prang the damage may be moved into parts that would normally not be vulnerable such as the axle, the QR (or other mounting) and even the frame (£££££ ker-ching).

So on utility bikes/kids bikes that see rough treatment they are of some value but otherwise maybe they are more trouble than they are worth or indeed may be instrumental in causing more extensive (expensive) damage. RDs and gear hangers are not that expensive (although gear hangers are a complete rip-off for what they are...) and an RD -because it is sprung- may provide a softer landing for your bike than might otherwise be the case.

One place where I would fit one is to a SRAM clickbox; the guards required for this are shorter, so are less likely to wreck the (usually substantial) frames to which such gears are fitted. The clickbox parts are liable to go NLA anytime soon, so are worth protecting.

I've scuffed up dozens of RDs, bent a few of them and bent a few hangers too. For me, I don't remember this ever being a show stopper. But in the grand scheme of things the most likely cause of wrecking a RD wholesale is by stuffing it in the back wheel, and that can happen for a variety of reasons. Having a guard fitted does not preclude the mech going out of adjustment or being bent enough that it will go into the back wheel.

BTW checking/rectifying hanger/mech alignment is SOP; I don't think there is a bike out there where this hasn't been done (or needs doing....)

cheers

[freiston]

Thanks for your reply, Brucey - very informative and it confirms my suspicions re.transferring the forces in a way that could be potentially more of a problem than damaging the RD or hanger. My hanger is part of the steel dropout - which I understand should be capable of being bent back into alignment if ever it gets knocked out of alignment. I recall a thread (on these boards?) discussing using tools either designed for the job or fashioned out of to-hand pieces for it.

[simonhill]

One was fitted to my original MTB back in the 80s. It also had ball ends on the brake levers. Those plastic disc spoke protectors were another must have, not that I did. Cycling was dangerous back then.

However, I still use one, the second type in Bruceys pics.

I don't use it to avoid damage after a fall, but to protect the rear mech when in transit. This is when my bike is in a box for flying.

I have often had to bend it out so I consider it has done its job.

It doesn't interfere with rear wheel removal, only if I take the rack off.

As said above, made of cheese so bends easily.

I'm happy with mine and would recommend to anyone flying who doesn't want to remove the rear mech.

[Brucey]

If you broke the eyelets off the dropout (which I have seen happen) you would be as sick as a parrot though...?

FWIW when flying I simply undo the mech bolt and strap the mech under the chainstay. No danger of damage to anything.

cheers

[peetee]

I flew with my bike once. When I landed I wished I had bought one with suspension.