Just wondering as I followed a scrambler bike on a trailer why it’s wheels weren’t an inexplicably large diameter?

Surely if bigger wheels are better…..

Because they’r not obsessed with fashion and the media?

Fork travel, handlebar height, rear suspension travel, seat height, wheel base.
Take all those in to account and you’ll find they generally have the biggest wheels they can fit.

Because they have 250cc and loads of travel. The front wheel, the one that hasn’t got the engine helping out, is bigger than the back.

Big wheels don’t steer so quickly – ask anyone who has ridden a Fireblade with the original 16 inch front wheel!

Because they aren’t better. 26 inch is the perfect size for general trail riding imho. 29 seems to be the racing choice and i really can’t see how 650 is so much better than 26. It is purely about the big manufacturer’s trying to sell more bikes.

motorcycle manufacturers do the same by changing colours or spec every few years rather than wheel size!

And yet, trials bikes, which regularly go round much sharper corners than Fireblades, have got 21″ front wheels.

Wasn’t the original Fireblade problem head-angle related ? Ah, that was the last fad, wasn’t it…

Motorcycles, especially racing ones are contuinually looking for the best wheel size, along with anything else that will give an advantage:

http://motocrossactionmag.com/Main/News/THE-20INCH-TIRE-REVOLUTION-1858.aspx

and GP bikes went through many sizes before settling (currently) on 16.5″

Come to think of it, the difference in usage between a trials bike and a motocrosser is more pronounced than the difference in use between a DH and XC bike.
Yet both trials and motocross are pretty much standardised on 21″ front and 18″ rear wheels.

Honda did produce some trail bikes with 23″ front wheels back in the 80’s, they didn’t catch on. Probably not helped by crap tyre choice.

The other problem with big dia. wheels on motorbikes, is the gyroscopic effect. Not a problem on a lightweight cycle wheel at low speeds, but at speed on a motorcycle, a large dia. heavy wheel would have quite an effect on steering .

If big wheels are not better then why don’t motorbikes have 10″ wheels?

Why do tractors have BFO wheels?

Ground clearance and contact patch within a given width.
Two things that don’t directly translate to bicycles.

Why don’t shopping trolleys have bigger wheels? They’re a nightmare on the towpath.

They make the towpath come alive, though bigger shopping trolley wheels would roll right over the old biddys that get in your way at Tescos…

@kayak LOL!

Think of the inertia of a massive 29″ moto-x tyre!

Think of the inertia of a massive 29″ moto-x MTB tyre!

Engineering design is full of engineering compromises as you want properties from a product that are in contradiction to each other. You want something that is light, but strong, powerful yet economical, aerodynamic yet roomy. There is no such thing as a perfect design. If you could invent a wheel that changes diameter then that would be perfect, but you can’t so you select the wheel size that best suits what you want to do with it – if you’re a downhiller and want long travel suspension, then 26″ is what you want, if you’re a wheels on the ground cross country mile muncher, then 29er is what you want, if you’re indecisive and just want to try to cover all bases then 650B is for you 😉

The extra inertia of a 29 inch wheel though calculable is irrelevant in the real world. especially when you factor in that you don’t have to accelerate the wheel as much to get the same forward acceleration and you don’t have to accelerate the wheel as long to get the speed you want. It cancels itself out. So forget inertia in the 26 vs 29 inch debate – its irrelevant.

I probably meant gyroscopic effects of big wheel + heavy tyre, rather than inertia. Whatever.