Fastest wheel size combo?

[Cyclaholic]

All else being equal, what would typically be the fastest wheel size combo?

I'm in the middle of buying a Toscana 20/26 OSS, it's like Europa's but with a 20" front wheel. The interesting thing about it is that the 20/26 and the 26/26 share the same frame, it's the fork and front wheel that changes.

That led me to thinking about different wheel combos. From what I've read in the forums it seems that larger wheels will tend to be faster, so I'm wondering if there will be a benefit in going to a 26/26 or even a 700c/26" setup?....ignoring any necessary frame modding issues to get the 700c size wheel to work in that frame, but from a speed/performance/handling point of view.

Gab.

[John Lewis]

Hi Gab,

All else being equal I think the larger dia. rim should be faster. There are a number of articles on the net though that suggest this is not always the case. Eg a small wheel may accelerate quicker. Do a bit of a search.

I think the real determining factor is your leg length. The seat height on my 20/26 is about 680 mm and is just a bit high for vertically challenged me. It is a bit uncomfortable when starting and stopping.

I looked at Kalgrim's bike a few weeks back. He has dual 700's I think and it would have been way too high for me.

From my perspective I need to go with the 20/26 to get a fit as much as I'd like a highracer.

Best advice would be try before you buy if you possibly can.

John Lewis

[Uba Tracker]

G'day Gab,
That's a really interesting question and regrettably I have no published scientific evidence to say conclusively one way or the other which is the fastest. However, some years ago I was involved in manufacturing a Go Kart or more accurately a 'Billy Cart' with a class from one of our local schools. The goal being to achieve the highest possible speed on a controlled descent. Now we tried all sorts of combinations but eventually found that a larger diameter wheel with thin tyres inflated to their maximum pressure achieved the best result. It was faster by a significant margin too. We ascertained our combination reduced rolling resistance by overcoming such influences as wind resistance, road engaging friction and bearing hub resistance. I am not saying that this is conclusive proof but it's worth noting.
cheers
Harry

[Kalgrm]

For what it's worth, my 700c wheels (23mm tyres) are about 10% faster than my 26" MTB slicks on the the same bike. I believe the reason is the larger diameter allowing smaller rolling resistance and the lower wind resistance of thinner tyres.

Cheers,
Graeme

[Cyclaholic]

Thanks everyone for the replies. Sounds to me like there's plenty of room for experimentation here. I have the parts and the opportunity so I guess I'll just have to try out different combos and see for myself then. Of course I'll post my results here, subjective and un-scientific as they'll be.

[Leigh_caines]

Well if one could buy 20” wheels as light and narrow as 700 by 23 and the tyers to match…
But they don’t seem to be out there

[Kalgrm]

Well if one could buy 20” wheels as light and narrow as 700 by 23 and the tyers to match…
But they don’t seem to be out there

I have seen 1" wide 20" wheels and tyres - the guy who makes Logo trikes fits them to his sporty models. However, it's not the width or weight making the 700c wheels roll more easily. It's the diameter.

A good analogy is to roll a marble and a basket ball along a road surface. The basketball sits on top of the chips and rolls smoothly, while the marble drops into the gaps between each chip, slowing it down as it bounces up and down.

The narrow width of 23mm tyres makes them more aerodynamic, which only really becomes significant above 30km/h.

Cheers,
Graeme

[Leigh_caines]

Having only ridden heavy recumbents with heavy chunky wheels and tyres….
But I’ve a feeling that if one could lighten it all up….
It’s not like small wheels [20”}don’t go fast…
like down hill I’ve hit well over 70 many a time…
But along the flat or up hill it is harder pushing a 35k bike + my 73k’s then it is my fixy that weighs 10ks with it’s 700 by 23….
One day….