I have a Trek 7.3 with 700x32cc tyres. I've been offered a set of SKS mudguards that are 35mm wide. These are only going to be 3mm wider than my tyres and I'm worried I'll still get a lot of spray off the sides?


  • 1
    The majority of liquid will come from the center. It wouldnt be perfect but better than nothing.
    – j0h
    Commented Jul 21, 2015 at 23:54
  • Aren’t they going around the tires?
    – Michael
    Commented Aug 20, 2015 at 19:26

3 Answers 3


3mm is definitely not enough, especially with plastic fenders!

A good rule of them is your fenders should be at least 10mm wider than your tires. I run 42mm tires on one bike and it has 58mm fenders. On my other bike I run 32mm tires and 45mm fenders. You also want at least 12mm between the inside of the fender and the tire. Ideally, you should have 20mm between the tire and point on the frame the fender bolts to (to account for fender thickness, protruding bolt heads and mounting hardware).

Keep in mind poorly fitted fenders can be a safety issue. If an object gets kicked up into the fender it can cause a crash.

Some good articles on fenders: https://janheine.wordpress.com/category/components/fenders/ (Jan probably knows more about fenders than anyone in the cycling biz!)


I have the 35mm mudguards with 28mm tires. They keep the spray away from me but are covered in dirt all over after riding in the rain. Slightly wider mudguards on my other bike look better. You also need to keep the mudguards completely straight, because the low margins make them rub at the moment they bend. For comparison, the S-blade from other answer is 52mm wide.


Probably not wide enough - but you could put a layer of duct tape down each side of the mudguard on both edges. Put the underneath one with adhesive facing up, and the top one with adhesive facing down.

If it feels a bit floppy you might lay some cable ties or similar between the adhesive before putting on the second layer.

If the road water still comes up and hits you, tape or pop-rivet some flexible plastic like a shape cut from the lid of an ice-cream container. This will make the whole mudguard longer.

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