Why are rear wheels dirtier?

Question

I have noticed that my rear wheel is always considerably muckier than my front one, after a wet commute.

Why should that be? They both travel the same distance and terrain. I assume this is a common experience.

Bike has mudguards.

The rear wheel runs through the same dirt as the front wheel AND gets the spray from the front wheel. — Carel, Mar 07 '16 at 13:40
There is another reason, assuming the bike has fenders. A front fender typically covers only about 1/4 or 1/3 of the wheel diameter, while a rear fender covers more than half. This give the front wheel more opportunity to "sling" mud off without the fender simply throwing it back at the wheel. — Daniel R Hicks, Mar 08 '16 at 02:42
Mudguards (fenders to some) will make your wheel muckier, because its not spraying the mud/muck off so easily. The mudguards are to keep you and the bike's mechanisms cleaner. — Criggie, Mar 08 '16 at 06:49

legowave440 · Accepted Answer · 2016-03-08T02:04:20.440

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As mentioned in the other answers, there could be several reasons that your rear tire is always muddier than the front after a wet commute.

The front tire splashes mud on the rear of the bike.
There is more weight on the rear tire, causing it to sink deeper into mud.
Your power is being transferred to the rear tire, creating more friction than on the front.
You're probably using your rear brakes, causing your rear tire to slide. If so, it's probably better to use more of the front brake.

One more thing... the mudguards are probably not keeping your wheels and tires clean. They're there to keep you from getting splashed.

edited Mar 08 '16 at 02:04

answered Mar 08 '16 at 01:41

legowave440

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I am not sure I get the distinction between 2. & 3. It is self-evident that there is more friction from things like tyre wear. Is wear the result of friction, therefore rubber dirt, what you are implying? – gaijintendo Mar 08 '16 at 19:02
@gaijintendo Yes and no. The additional friction is, as you say, evident in tire wear. I forgot to explain that this increased friction can be overcome by the mud, causing the tire to slide--even insignificantly--and throw around the mud. I'd say, however, that (3) probably contributes to the dirtiness least among the other points. – legowave440 Mar 08 '16 at 19:42

score 0 · Answer 2 · edited Mar 08 '16 at 20:58

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My guess is, although the front and rear mudguards are within 2 inches of the respective tyres, the front one is primarily to the back of the wheel, and the rear one above. As a result, crud will fall onto the rear wheel more regularly.

edited Mar 08 '16 at 20:58

Móż

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answered Mar 07 '16 at 11:23

gaijintendo

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I am trying to imagine a bicycle where the front and rear mudguards are within 2 inches of each other... – Penguino Mar 08 '16 at 20:22
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@Penguino it's better to edit the question so the wording matches the intent than make snide remarks. – Móż Mar 08 '16 at 20:58

score 0 · Answer 3 · answered Mar 07 '16 at 11:53

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The mudguard is not perfect. Mud will still get flung up from the front wheel onto the backwheel. It just doesn't end up in your face; which is good enough for most people.

answered Mar 07 '16 at 11:53

ratchet freak

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score 0 · Answer 4 · answered Mar 07 '16 at 12:32

Most likely cause is shape and size of the mudguards.

Some other affecting factors are:

Front wheel's direction to frame changes when steering, rear wheel goes straight
More weight on rear wheel
Rear wheel "moves" the bicycle hence there is more friction between tire and ground

Maic López Sáenz · Answer 5 · 2016-03-09T23:50:31.737

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The rear tire may be dirtier that front tire, regardless of mudguards or rain, because it is closer to the chain. The chain is a dirt magnet and some of it will splash to the wheel by the mere proximity to it. For instance look at the chain stay on the chain side, it is always dirty just because of being next to the chain.

edited Mar 09 '16 at 23:50

answered Mar 08 '16 at 19:52

Maic López Sáenz

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I would imagine the reverse - the muddy tire transferring dirt to the chain. – Vorac Mar 10 '16 at 14:03

Why are rear wheels dirtier?

5 Answers5