Smaller wheels on the Vendetta?

[Shahmatt]

I've been reading up about smaller wheels and some articles seem to suggest that they could be faster than larger wheels.

http://www.livestrong.com/article/142026-the-advantages-small-wheels-bicycle/

http://hadland.wordpress.com/2012/06/25/small-wheels-for-adult-bicycles/

Since the Vendetta is now a record breaking bike, I wonder if smaller wheels have been considered to further improve its performance.

 

[Charles.Plager]

Except for extreme cases

Except for extreme cases (e.g. Dutch 83 mph streamliner, or changing rider angle for aerodynamics) smaller tires aren't going to help much. They have slightly less aerodynamic drag and slightly more rolling resistance. And, most importantly, much less selection in fast tires.

I wouldn't knock small tires, but I see no reason to put them on a Vendetta unless you want to change seat height (or seat angle by using different size tires and this might affect handling a lot).

 

[Shahmatt]

I was wondering what effect

I was wondering what effect there might be of only lowering the ground clearance to the rider by using smaller wheels (say 20").

That is, by still maintaining the same seat angle and overall position of rider while the stay lengths are reduced so that the rider is as low as possible to the ground.

Other than the possible net reduction in frontal tire area (reduction in height, increase in width?), would there be any other aerodynamic improvement in the general airflow profile around the bike?

Would the lowered position somehow lend to improved stability when cornering?

Would the reduction in stay lengths result in a significantly lighter bike through less material used?

Just some questions that popped in my head when trying to visualize a Vendetta with itty wheels!

 

[Charles.Plager]

Lower bike probably makes it

Lower bike probably makes it less stable (try balancing long and short sticks in your hand).

The difference in frontal area is minimal (its the difference in the area odd the tires that I was talking about above). The difference in weight is minimal (the difference in wheels and tires).

If you reduce the stays, you drop the feet making the position less aerodynamic, so your small weight gain hurts a lot).

I like small wheels add much as the next guy, but it's not the solution to any Vendetta problem.

 

[currystomper]

Also less suspension

Hi As an every day rider of small wheel (451 mm "14 inch") I agree that the Vendetta probably isn't the right platform.

Small Wheels give less suspension effect (because of the shorter length of spokes I presume) - so the Silivio would be a better choice for small wheels. Even then I'm not sure what performance advantage they would give you.

Acceleration is better with small wheels as there is less momentum to spin up - but that's not the generally an issue for out of town rides

 

[Charles.Plager]

Acceleration is better with

Acceleration is better with small wheels as there is less momentum to spin up

Assuming the weight of the wheel is all at the rim, this depends entirely on the weight of the rim/wheel. The lightest 700c wheels are very light and this is a very small effect (some 700c wheels/tires way less than most 20" versions)

And remember, it's the total weight of the bike/rider/crap you have to get moving and even though when accelerating wheel weight counts (almost) twice, this is still negligible.

 

[currystomper]

Angular_momentum?


Weight and distance from the rotational center,....

mmm seems I'm wrong

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

 

[snilard]

Small wheels can by faster in

Small wheels can by faster in theory, but in real world they this is not true. There are only few really fast 20" tires on the global market. And this fast tires cannot by compared with fast 700c tires. They are simple worse. Smaller wheel is slower on rough surface because it "jumps" more than larger wheel.
Some other points. It is easier to have flat tire by squeezing tire to rim on smaller wheels. When you use rim breaks tube is more prone to explode by breaking heat with smaller wheel.

What I really like on Vendetta are its large wheels.
On this years Cycle vision (recumbent competition in Netherlands) winner of 1h and 3h races in unfaired category was using highracer with 700c wheels.

 

[Charles.Plager]

For calculating the effect on

For calculating the effect on acceleration, it's easiest to look at energy calculations. (Yes, smaller wheels will have larger angular momentum...)

Rotational energy is 1/2 I w^2 where I is the moment of inertia and W is the angular speed (linear energy is 1/2 m v^2).

If all of the mass of the wheel is at the rim, I = mr^2. w = v/r so:

1/2 Iw^2 + 1/2 mv^2 = 1/2 m r^2 * v^2/r^2 + 1/2 mv^2 = 1/2 mv^2 + 1/2 m v^2 = 2 * (1/2 m v^2). (or, for acceleration purposes, you can count the mass of the tires/wheels as double).

The ratio of the wheel completely drops out (assuming all of the mass is all at the rim).

 

[John Tolhurst]

ah ha ... I sort of follow

ah ha ... I sort of follow the math. I definitely see the wheel has to be pushed forward, as well around and the angular speed is of course the road speed. Doubling the weight of the wheel in the power to acceleration calculation is a nice approximation as long as its all at the rim. You might improve that approximation by pretending the hub was not rotating and excluding it from the wheel weight? This would be a fairer approximation on a larger wheel. Am I on track?

 

[Shahmatt]

"If you reduce the stays, you

"If you reduce the stays, you drop the feet making the position less aerodynamic, so your small weight gain hurts a lot)."

Actually I meant lowering the overall position of the rider whilst still maintaining the same rider angle. Basically shrinking both the front and back wheels so that there is no change in the aerodynamic position of the rider.

My thinking was that, reducing the wheel size could help as follows:

1. Reduce wheel weight and tire weight (obviously)
2. Reduce bike weight by using less material in the wheel supporting structures (because frame to wheel hub clearances can be less)
3. Minimize turbulence caused by wheel spokes (would not smaller wheels equal less turbulence?)
4. Lower the rider to the ground (at the very least this makes it easier to put the foot down)

But if the tires, wheels and hubs aren't easily available then I guess that there's no point in designing such a bike for the mass market. Only for time trials and such maybe.

5. I read (link below) that records are broken by improving handling and rider comfort and this is where wheel size can matter. I wonder if the handling of the bike (rake and trail) be made more easy to adjust through the use of smaller wheels?

http://www.rodbikes.com/articles/web_articles/toeoverlap.html

 

[Robert Holler]

I can only see doing this for

I can only see doing this for a small rider. My 10 year old would fall over happy with a "Mini-V" as he likes to coin.

That said, a very strong rider will be faster on a 20" V than a weaker rider on a 700c V. And a rider who is comfortable on his/her chosen steed is always faster than one on a bike they feel too high/too low/cant get feet down safely on etc.

Many variables quantitative and qualitative. The engine is very important part of the mix. And gearing. And terrain.

 

[Charles.Plager]

You might improve that

You might improve that approximation by pretending the hub was not rotating and excluding it from the wheel weight? This would be a fairer approximation on a larger wheel. Am I on track?

Yup, that's it. So, for accelerating, you can double the (wheel + tire - hub) weights.

This is why having an IGH doesn't hurt performance. They're heavy, but they are at the center.

People ride Bike Friday's in pace lines. They aren't, in general, any better with the small wheels with the one exception that they can get that much closer to the bike in front of them because they don't have the big wheel in the way.

(The frame weight savings won't be that large on the Vendetta, particularly if you want to conserve wheel base - and I think you do).

I think RC^2 is right: The only real customers for this are short people and as kids don't generally have a large income, this probably isn't a winning move for Cruzbike right now.

All this being said, I would never try to discourage anybody from building something like this if they're curious. I have imagined a Vendetta-like lowrider.

 

[Robert Holler]

After my daughter had a

After my daughter had a chance to ride some laps at PIR with Maria Parker, she has constantly asked me, "Would I be as fast as Maria if I had a bike like hers?"


Oh yes... a future racer in the wings.

Robert

 

[snilard]

Vendetta-like lowracer? Like

Vendetta-like lowracer? Like this Zockra prototypes? http://www.zockra-factory.com/?page_id=64

 

[Eric Winn]

Vendetta 700C ride height is

Vendetta 700C ride height is already low enough that short people like me can put both feet flat on the ground when on the bike. With greater wheel selection in 700C I don't see much motivation to go to smaller wheels.

-Eric

 

[ratz]

Time will tell.

No need for a prototype, the new bike is set for launch, it is based on the TDP2 will be released at the World Cup This summer. After the first 10 go to French customers they will start building units for the rest of us. The first two US Units (supposedly #11 and #12) go to John and Jackie at Vitebiikes.com. So bikes 11 and 12 might hit the US around January-May 2015. Nobody know for sure how low they will be; nor how stiff nor how fast. Last time the conversation came up we where just excited that they are now real. I'm on the waiting list for spots 13 and 14; although Ryan (delcrossv) might be ahead of me in line I think we both called the day John @ Vitebikes announced them. We got those spots before our Silvio's hit the road this spring as a fall back. I thought we'd sell the Silvio's if they didn't perform.

After riding the Vendetta and enjoying the comfort of the Silvio's I'm not sure we'll keep those spots in line. We were seeking out the carbon for a comfortable long distance ride. We are already getting that from Silvios and they are fast; and The Vendetta is panning out equally great. The new Z's will have to come in as fast as a Vendetta and as comfortable as a Silvio to shake things up. Not to mention they will probably cost $2k more with equivalent components. The Schlitter Encore might be shaking things up on the carbon stick bike price front but, that's the cost exception. The Zockra and the John M FWD drive bikes will continue to be the extreme high end of the cost curve.

Right now, I can tell you the Vendetta is mightily low for a 700c bike, much lower in person than you would expect. With 50mm aero wheels she's going slice through the wind. You could easily put 650c TT wheels on the Vendetta if you use disc brakes. On a Small Frame (out of stock) which is what Maria is riding that's going to be a very very compact bike.

Robert needs to go build one for his daughter with 650c wheels as soon as the small frames are back (perhaps that will be the Vendetta version 3)....

It is great to have another MBB on the scene to drive innovation on the platform. If I am not the one to do a side by side test I hope someone does. Right now my money is on the V being faster because it is so stiff and the geometry is totally dialed-in after multiple iterations of the Cruzbike geometry...

Bring on the World Cup Anybody one to buy some spots in line?

 

[BentAero]

My employer spends *large*

My employer spends *large* sums of money each year on R&D of suspension systems for motorsports with the goal of being consistent, repeatable, and most of all, cutting lap times. Why? Because our customers will pay almost anything to drop their lap times.
Big money Tour de France-style cycling teams are no different. They spend huge piles of money testing aerodynamics of every aspect of the rider and bike. If small wheels were faster in a 40k time trial, they'd switch to 'em in a heartbeat.

 

[snilard]

Ratz, thank you for

Ratz, thank you for information from Zockra. I wanted to compete on World Cup in France. But competition fee is too high for me so I decided to skip it (fee on Cycle vision was 15€, on World cup it is 90€...). Meybe I am coming as visitor.

I am really interested in TDs from Zockra. But if the price will be higher than price of Vendetta I would buy Vendetta if I want new bike. From my point of view also Vendetta is not cheap bike.

 

[currystomper]

If small wheels were faster in a 40k time trial,

>Big money Tour de France-style cycling teams are no different.
>They spend huge piles of money testing aerodynamics of every
>aspect of the rider and bike. If small wheels were faster in a
>40k time trial, they'd switch to 'em in a heartbeat.



I'm not sure that they are 'legal' in the current UCI regs - I know the frame goemetery is pretty well tied up


...If it not allowable in the regs the big teams aren't interested (otherwise they would all be riding Vendetta's!!)

http://en.wikipedia.org/wiki/Racing_bicycle#Racing_components

"wheels must be of equal diameter, between 70 cm and 55 cm, and must have minimum 12 spoke"


..interesting to know if they are working at the upper or lower limit for wheels though!!