…according to MBR:
The larger contact patch picks up more dog shit. 😀

In that case, anyone wanna swap my Lynskey 29er for a pogo stick with spd’s? No more poo spray for me.

i don’t understand the whole ‘larger contact patch’ thing.

contact area will be down to rider weight, and tyre pressure.

if you want a bigger contact area, let your tyres down a bit. or am i being thick again?

I have noticed that I’m getting more dogshit on me these days, in fairness. I thought it was more to do with more dogs shitting more shit though. How much I have to learn…

Perhaps they are on to something!

*waits for a ready supply of cheap 29er frames, wheels & forks to flood the classifieds* 😆

Someone should get Mythbusters to test that one out… 😛

if you want a bigger contact area, let your tyres down a bit. or am i being thick again?

nope.

29″ might change the shape of the contact patch (longer and narrower) but it won’t change area, given everything is equal.

http://en.wikipedia.org/wiki/Contact_patch

I find, for me anyway a 29er picks up more dog crap because, being a miserable fecker a 29er makes riding too enjoyable so I aim for dog crap to get sprayed in my face to dampen my spirits a little.

Simple really.

Completely untrue – all else being equal (tyre pressure, rider and bike weight) they will be the same. They may be a different shape, but they are the same size.

Follow that logic and buy a Roadie with 23C tyres then… 😯

ahwiles – Member
i don’t understand the whole ‘larger contact patch’ thing.

contact area will be down to rider weight, and tyre pressure.

if you want a bigger contact area, let your tyres down a bit. or am i being thick again?

29″ might change the shape of the contact patch (longer and narrower) but it won’t change area, given everything is equal.

Both are right up to a point.

Reducing tyre pressure will increase contact patch so you’re not being thick.
29er will elongate contact point but is not necessarily narrower so again it would generally increase contact patch.

Personally I think dogs should produce smaller turds to negate the effect… 8)

elongate contact point but is not necessarily narrower

Yes it is – all else being equal.

this thread has got really boring now.

Follow that logic and buy a Roadie with 23C tyres then…

or a moulton – even better

Mythbusters is a great suggestion. Kary on a 29er. Nutella to substitute dog shit in experiments. Perfect.

i don’t understand the whole ‘larger contact patch’ thing.

contact area will be down to rider weight, and tyre pressure.

if you want a bigger contact area, let your tyres down a bit. or am i being thick again?

Yes. This is why tractors use 26″ tyres.

Sam – Member

elongate contact point but is not necessarily narrower

Yes it is – all else being equal

So, a 2.3×26″ tyre would leave a wider footprint than a 2.3×29″ tyre?

[not going to dispute what you say Sam given your area of expertise 😉 , just my (very long time ago) schoolboy physics is struggling!]

Terra – I tried but the couch scientists didn’t miss a beat even after the Kery picture. Oh well.

So, a 2.3×26″ tyre would leave a wider footprint than a 2.3×29″ tyre?

At the same tyre pressure yes! This is one of the reasons you want to have less mechanical trail on a 29er, because of tyre deformation and the longer contact patch giving greater pneumatic trail and resistance to turning.

The contact area will be the same – pressure is force per unit area so the contact area has to be the same size if the load is the same.

The shape of a 29er wheel compared to a 26″ one means that the same area will be relatively longer and narrower (eg more oval/less round).

More importantly, most people who’ve ridden 29ers have noticed that they do seem to provide more grip than you expect. Some have theorised that it’s down to the different shape.

Clear as mud. Or should that be dogsh1t 😀

*cancels order for fat bike*

*cancels order for fat bike*

The difference being a fat bike uses *much* lower pressure.

Psling – think of the unit of measurement for pressure – lbs per square inch.

she’s a bit funny looking

I thought

A bigger wheel has a larger radius.

The transition is smoother to the contact patch comes at less of an angle relative to a smaller diameter.

This in turn causes less friction.

This means that

Wheel turns slower relative to a small wheel at the same road speed.

Tyre is moving slower so to displace the dog poo you need to go faster on a 29er to get the wheel turning at the same road speed as a 26

There is more tyre on a 29er giving more space for dog poo to be stored

It takes longer for the tyre to recontact the ground meaning there is more space to pick up poo

What this tell’s me is there is too much misinformation out there on 29er’s and most of it’s Poo 🙂

I don’t get it, how can it be the same size contact patch if the width and pressure are the same but the length is longer?

How far does this go, do 2.3×10, 2.3×20, 2.3×29 all have the same contact patch?

I’m not arguing, I genuinely don’t get it….

Forget base jumping, dog turd roulette is the ultimate extreme sport.

That is a man, isn’t it?

I’m not arguing, I genuinely don’t get it….

A 2.3″ tyre isn’t 2.3 wide on the ground, its a circle cross section 2.3″ diameter (ish, manufacturers measure different things).

So on the 29″ wheel only a small bit of that circle has to flatten out to make the nececary area to suport the weight of the rider. On the 10″ wheels kidies bike the wider patch required would result in more of the circle being flattened.

So for a 200lb bloke+bike.

2″ wide (contact patch, not tyre width, say its a 2.5″) tyre inflated to 50psi (for the sake of easy maths)
Assume a rectangular contact patch.

200(lb) /50(lb/”square) = 4 square inches, the tyre is 2″ wide so each patch is 1″ long.

Make that contact patch 2″ long (with a huge wheel) and it only needs to be 1″ wide.

29ers should be banned cos they look sh!t.
Lets face we all know having the best looking bike is more important that having fun or being any good.

It’s more the ultimate reason to buy mudguards.

The fashionable set may aspire to the dog egg spattered look, but fortunately for me, I’m deeply unfashionable.

That is a man, isn’t it?

or a woman that looks a bit manly….. she’s a ginge anyway, so a moot point

Nice red-trimmed Y fronts.

I thought the ultimate reason was because they were just another marketing ploy by the manufacturers to get you to buy another bike.
The whole different but better rubbish.

My primary reason for not buying something is that I don’t want it or can’t afford it.
If you want a 29er buy one, if not don’t.
Wonder if Kery up there is happier after investing in her larger orbs. Contact patch you say…….

Doesn’t it have something to do with tyre volume also? i.e if comparing a 2.3 x 26 it would have to be 2.2 x 29?

Reason being the relative pressure increases as the air in compressed when you sit on the bike. If the volume was smaller then the relative pressure would increase sooner.

Just thought I’d throw another spanner in… 🙂

But she has a penis in her pants!

she’s a bit funny looking

You’ve just never seen a woman smile before 😉

Most of us who ride 29ers are smart enough to avoid the dog eggs in the first place.

We leave riding through dog sh?t to those who still insist on riding around on kiddy wheels 😀