Rear mudguard bridge fitting

General cycling advice ( NOT technical ! )
SPB
Posts: 3
Joined: 17 Sep 2020, 10:09pm
Location: Wales

Rear mudguard bridge fitting

Postby SPB » 17 Sep 2020, 10:45pm

I’ve just invested in a new e bike (the hills were taking their toll in my 60th year!). I have had hybrids before and fitted top peak defender mud guards into the frame. Now I’m looking for full length guards for my new bike and considering buying SKS Beumel stingrays. However,looking at the screw holes on the bridges, the screw hole on the front bridge is in what I consider to be the right place to attach the mudguard to the bridge. However, the screwhole in the rear bridge is on the underside of the bridge pointing towards the tyre which has got me confused as I can’t see how the rear mudguard can be attached. Perhaps there is Some fitting with the SKS mudguards or some fitting I can get which screws into the underside creating a housing for the mudguard to be fitted.
I don’t have much experience of these new frames so any advice or knowledge would be appreciated.
SB

Brucey
Posts: 40913
Joined: 4 Jan 2012, 6:25pm

Re: Rear mudguard bridge fitting

Postby Brucey » 17 Sep 2020, 11:04pm

the idea is that you use a screw through a drilled hole through the mudguard, ideally with penny washers and rubber packing. The 'quick and dirty' method is to fit the bridge as normal, ignore the hole in the frame, and lash the bridge piece to the frame using a couple of zip ties instead. This actually works as well or better, and you don't have to faff about drilling holes or finding washers.

FWIW if you fit a screw without suitable washers, the mudguard is almost guaranteed to break sooner than it should do.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

tim-b
Posts: 1575
Joined: 10 Oct 2009, 8:20am

Re: Rear mudguard bridge fitting

Postby tim-b » 18 Sep 2020, 6:49am

Hi
You'll need to check the tyre/mudguard clearance before you start choosing screws and washers (egg-sucking, but not everyone likes eggs :) ) Overall the bridge is simpler but less neat
Regards
tim-b
~~~~¯\(ツ)/¯~~~~

SPB
Posts: 3
Joined: 17 Sep 2020, 10:09pm
Location: Wales

Re: Rear mudguard bridge fitting

Postby SPB » 18 Sep 2020, 11:02am

Thanks guys. I’m ok with following instructions when fitting bits and bobs on the bike or in the house. Past experience and my impatience says I’ll end up breaking something if I have to improvise but I think I’ll have to take the risk, order them and see what works best to get the right clearance. Don’t worry about the eggs Tim-b. This “granny” needs to be shown!

Jdsk
Posts: 2802
Joined: 5 Mar 2019, 5:42pm

Re: Rear mudguard bridge fitting

Postby Jdsk » 18 Sep 2020, 1:52pm

Brucey wrote:the idea is that you use a screw through a drilled hole through the mudguard, ideally with penny washers and rubber packing. The 'quick and dirty' method is to fit the bridge as normal, ignore the hole in the frame, and lash the bridge piece to the frame using a couple of zip ties instead. This actually works as well or better, and you don't have to faff about drilling holes or finding washers.


How about bending the bit with the hole? Might need a bit of packing to lower the bridge...

Image

Jonathan

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foxyrider
Posts: 5125
Joined: 29 Aug 2011, 10:25am
Location: Sheffield, South Yorkshire

Re: Rear mudguard bridge fitting

Postby foxyrider » 18 Sep 2020, 2:40pm

Jdsk wrote:
Brucey wrote:the idea is that you use a screw through a drilled hole through the mudguard, ideally with penny washers and rubber packing. The 'quick and dirty' method is to fit the bridge as normal, ignore the hole in the frame, and lash the bridge piece to the frame using a couple of zip ties instead. This actually works as well or better, and you don't have to faff about drilling holes or finding washers.


How about bending the bit with the hole? Might need a bit of packing to lower the bridge...

Image

Jonathan


Which could work unless its a plastic bridge! :lol:
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

mattsccm
Posts: 3443
Joined: 28 Nov 2009, 9:44pm

Re: Rear mudguard bridge fitting

Postby mattsccm » 18 Sep 2020, 5:02pm

Both ways. Cable tie it with the bridge to set it up then when it is and you are able to chgeck the clearance you can think about the washer and hole method. Much better once done. I use a whopping great washer and bend a slight curve into it and use pan head Allen bolts as they trend to be shallower

Brucey
Posts: 40913
Joined: 4 Jan 2012, 6:25pm

Re: Rear mudguard bridge fitting

Postby Brucey » 18 Sep 2020, 7:53pm

FWIW metal mudguard bridges tend to break at the bend or at the bottom of the mounting hole/slot. I suspect that the vibrations are usually largely radial, so flattening the bridge and trying to use a radial mounting bolt through the hole is unlikely to be structurally sound.

The mudguard itself can break near the bridge in any installation, usually because the mudguard has been fitted under strain, such that there is a high load in the mudguard onto which any vibrations are superimposed, resulting in a damaging combination.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

SPB
Posts: 3
Joined: 17 Sep 2020, 10:09pm
Location: Wales

Re: Rear mudguard bridge fitting

Postby SPB » 18 Sep 2020, 9:40pm

Thanks again to all. I like mattsccm’s idea of getting it in place with ties first then go to the washer option if I’m not happy. That sounds a good way forward.

mattsccm
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Joined: 28 Nov 2009, 9:44pm

Re: Rear mudguard bridge fitting

Postby mattsccm » 19 Sep 2020, 7:02am

My way is just a step to the bolt. Cable ties for set up only.

slowster
Posts: 1679
Joined: 7 Jul 2017, 10:37am

Re: Rear mudguard bridge fitting

Postby slowster » 19 Sep 2020, 10:37am

It's not that difficult to fit mudguards properly, but it's easier to do it badly and put the plastic and/or the brackets under permanent strain, such that they will fail sooner.

The first thing you need to do is determine whether you want the maximum clearance possible between tyre and mudguard. If you have a frame with clearance for very wide tyres and you only use a much narrower tyre, you may want to reduce the gap that there would otherwise be between tyre and mudguard. Personally I don't mind seeing daylight between tyre and mudguard, and at minimum there should be 10mm clearance. To do this, slide the bare mudguard without its fittings and bracket into place and judge for yourself whether the mudguard needs to be fastened directly to the chain stay bridge and seat stay bridge, or whether spacers will need to be installed in between them to reduce tyre/mudguard clearance.

Obviously if you decide you need spacers, then you will need suitable sizes and suitable length bolts. If you don't fit spacers, then standard M5* button head stainless bolts 16mm or 12mm long should suffice together with standard stainless washers and penny stainless washers, which you can buy from the likes of Screwfix and Toolstation.

* Assuming that the frame bosses have an M5 thread, since that is the norm.

It's easier to fit the mudguard if you've got a workstand. Remove the rear wheel, and bolt the mudguard to the chain stay bridge: penny washer between bolt head and the inside of the mudguard and a standard washer on the outside of the mudguard (or spacer if using).

Then offer up the mudguard to the seat stay bridge, without bending it or putting it under any strain. At this point you determine where the hole needs to go in the mudguard for the bolt into the seat stay bridge. Drilling a hole at the right location, where it results in no or minimal strain on the mudguard once the bolt is tightened is the main trick to fitting the mudguard.

After that fitting the mudguard stays is fairly straightward, i.e. it's easy to ensure that the mudguard is not under strain when you tighten the bolts securing the mudguard stays. All that remains is the tedious task of sawing off the protruding ends of the mudguard stays.

Brucey
Posts: 40913
Joined: 4 Jan 2012, 6:25pm

Re: Rear mudguard bridge fitting

Postby Brucey » 19 Sep 2020, 10:58am

I'm with Matt, in that I like to at least try the mudguard before I commit to drilling holes in it. Not that I particularly like drilling holes in mudguards thereabouts anyway.

Its also worth noting that on some bikes you can be pretty slapdash and still end up with something workable, but on others, there is less clearance and/or other features which hinder a neat strain-free installation.

For example frames with forward-facing dropouts are usually set up so that the wheel can slide an inch or so forwards without the mudguard fouling (so the wheel will come out) and this often makes it difficult to fit the mudguard such that it isn't strained at the seatstay bridge. Workarounds (such as a 'spring thing' from VO) exist, but they are always compromises of one kind or another.

If you need to reshape a rear mudguard to provide a strain-free fit, it is (IMHO) a much better idea to reshape the mudguard before drilling holes in it.

Also I would caution against using mudguards with one set of stays where two can be fitted: at the front the mudguard is more likely to fold up should something get trapped, and (IME) the rear mudguard is much more likely to break. One of the modes of vibration which breaks such rear mudguards is one where the mudguard swivels (laterally) around the fitting at the seatstay bridge. It should be fairly obvious that this shouldn't happen with two sets of stays (or one set and a second rearward mounting onto a rack). It should also be obvious that any such movement will quickly loosen a radial screw (under the seatstay bridge) and that once that screw is loose, the mounting will not inhibit such movement in any way.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Slowroad
Posts: 797
Joined: 28 Jun 2008, 9:58pm
Location: Nottingham, UK

Re: Rear mudguard bridge fitting

Postby Slowroad » 20 Sep 2020, 8:12pm

Useful advice on here!
Why is it that mudguards are such a pain?
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