The back flap (left) aims to stop the high arc of spray that comes from your back wheel into the faces of riders behind you. The back flap is narrow where it attaches which allows it to bend without distorting your mudguard too much when you turn your bike up on its back wheel and catch the flap.
The front flap (right) is wider to stop splash coming from your front wheel over a larger horizontal area, protecting your bike’s transmission and keeping your feet a bit drier. The front flap’s wider top takes on the cross-sectional curve of the mudguard and gives extra rigidity; it’s only when you take the front wheel out that it needs to bend so you should be careful how you support your bike in that case.
To install RAW mudflaps you need to drill holes in your mudguard unless suitable ones exist - normally if there is at least hole within 2cm of the end of the mudguard you can make it work. The three pre-drilled holes are designed to work with some of the most common mudguards on the market that already have holes or some kind of flap attached.
Two screws are included for each flap as well as a small adhesive pad. One screw is normally adequate and, when done up sufficiently tightly, the flap will not rotate easily in normal use unless knocked. You can avoid the rotation by adding the small adhesive pad.
Using two screws offers the benefit that your flap will not rotate sideways but it is critical you get the two holes in line otherwise your flap will not be straight.
The following steps will guide you through drilling hole(s) and attaching your flaps.
Drilling Holes in the Mudguard
If your mudguards have no holes pre-drilled within 3cm of the end of the mudguard you will need to make at least one.
If you do have suitable holes which allow you to line up one of the holes in the flap with the hole in the guard and the fit line roughly with the end of the mudguard skip to Attaching the flap.
WHEN DRILLING THE HOLE YOU SHOULD NEVER DRILL THROUGH THE MUDGUARD WITHOUT REMOVING OR PROTECTING THE TYRE.
1. Before beginning choose either to:
i) Remove the wheel of the mudguard you are fitting to and support your bike using a work stand.
ii) Loosen off the mudguard stays and insert an old piece of wood between the tyre and the end of the mudguard.
iii) Remove the mudguard completely so you can drill into it on a work bench (probably overkill but the most accurate)
[Tip: Sticking a piece of masking tape on your mudguard where the holes will be drilled can help to mark the position of the holes and for the drill not to slip.]
2. Select which hole you will use: for one-bolt fixing use the central or bottom hole.
3. Hold the flap centred against the outside of the mudguard (pic.1) so that the fitting line lines up with the end of the mudguard. It needs to line up at the edges of the flap rather than in the middle so that the narrow top part of the flap is completely hidden. The back flap is shown here but the same applies to the front flap.
4. Make a mark on the mudguard with something sharp (or pen/pencil if using masking tape) in the centre of the hole you will use (pic.2).
5. Remove the flap and visually check the mark you have made is in the centre of the mudguard. If not correct with a deeper mark.
6. Drill a 4mm centred on your mark (pic.3). Take care as the shiny surface of the mudguard makes the drill slip easily. The mark in the surface of the mudguard should help.
[Tip: Depending on the mudguard material you may be able to use something sharp to make the hole instead of drilling but great care should be taken]
If you are using one screw move on to the “Attaching the flap” section or for two screws read on.
7. Place the flap against the mudguard again with your first holes lined up and the flap in line with the mudguard so that the flap is not wonky.
8. Make another mark through the second selected hole in the same way as the first (as in pic.2).
9. Remove the flap and check again the mark you have made is in line vertically with the first.
10. Carefully drill the second 4mm hole centred at your mark.
Attaching the flap
IMPORTANT: Button-head Allen Key screws have been selected as they have a low profile. You can fit the flaps with the screw head on the inside or the outside (better aesthetically) but you should always maintain the clearance between the screw head or nut recommended in your mudguard fitting instructions (in absence of this leave at least 1cm) to avoid things becoming lodged between the screw/nut and the tyre. If you are unable to increase the clearance, put the screw head on the inside as shown in the diagrams below.
If you are using one screw and wish to steady flap using the adhesive pad: peel off the red backing paper (as this hard to remove when in situ) and stick width ways along the top of the flap pushing down hard for 5 seconds. Then, make sure the inside of the mudguard is clean.
For screw head on the inside:
1.Put one of the washers onto one of the screws (or two screws for two-screw fitting).
2. Push the screw(s) through the hole(s) in the flap you have selected to use from the non-logo / non-coloured / rougher side of the flap (pic.4).
3. Then, thread the screw(s) through the hole(s) in the mudguard from the inside (pic.5).
4. Attach another washer to each screw on the outside of the mudguard and then a nyloc nut (pic.6).
5. Tighten the nut (which is 7mm) and screw using a spanner and Allen key as appropriate (pic.7).
For screw head on the outside:
1. Put one of the washers onto one of the screws (or two screws for two-screw fitting).
2. Push the screw(s) through the hole(s) in the mudguard you have selected to use from the outside.
3. Push the mudflap onto the screw(s) on the inside to the mudguard.
4. Attach another washer to each screw and then a nyloc nut.
5. Tighten the nut (which is 7mm) and screw using a spanner and Allen key as appropriate.
If using one screw and the adhesive pad, make sure the flap is straight compared to the mudguard wheel, then bend back the top of the flap. Peel off the white backing paper and push the flap against the mudguard for 5 seconds.
IMPORTANT: You should now adjust your mudguard stays to maintain the clearance between the bolt head and the tyre following the recommendations of your mudguard manufacturer as things could become lodged between the bolt and the tyre and potentially cause an accident. In the absence of those recommendations, ensure at least a centimetre of clearance.
Care / Usage
Take care when you turn the bike up on its back wheel. The flap can take a fair amount of punishment but repeated bending and scraping on the floor will cause it to snap off eventually. If you have mounted the flap higher than the level recommended above you may also damage your mudguard.
If you put your bike with flap on a rear mounted car rack and the flap protrudes from the side of the car, remove or secure the flap. The sideways force at motorway speeds will damage or snap it.
If you have a front flap attached, take care to lay or position your bike carefully when you take the front wheel out. Try to avoid resting it on the flap as this will put outwards pressure on the end of the mudguard and shorten its life.
If you have a coloured flap, the covering is a 4 – 7 year outdoor vinyl, which should stand up to the worst water, dirt and grime but, if scratched, dirt could collect in those scratches.
Do not attempt to bend your flaps to make them curved like mudguards particularly in cold conditions as this may cause them to snap.
Now you have your flaps fitted and are staying cleaner make sure the rest of your group reciprocates!
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