HIGHPATH ENGINEERING

 

 

EGG

EGGring Oval Chainrings

page 1 : General Information

 

 

 
I regret that I've stopped making chainrings and sprockets.

Thank you to all my loyal customers who have sent me so many interesting
orders over the past 25 years. I almost feel that I know some of you
personally - indeed some of you have become good friends!

On this page you can see some of the things I used to make...
 

 

How Ovals work
Why aren't Ovals more popular?
How to choose Ovals
More questions answered

page 2 : Technical information
page 3 : History

 

hillOval EGGrings allow you to pedal more effectively, powering your legs in greater comfort. They offer advantages in the following situations:

  • climbing hills
  • pedalling a high gear at a slow cadence
  • maintaining traction on slippery surfaces offroad
  • overcoming the bobbing effect on suspension bikes

But you don't get something for nothing - an oval chainring simply allows you to pedal more smoothly and to work harder when you demand more power.

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Click on the photos to enlarge them.

 

How Ovals work

As you turn your pedals, you encounter two dead-spots where you can achieve very little output. You will notice them when pedalling slowly up a hill - your cycle lurches forwards in spurts corresponding to each stab on the pedals, slowing down each time your feet pass the dead-spots.

Ovals reduce this effect by providing a lower gear to speed you through the dead-spots. You spend longer in the power-stroke, where your legs can push the hardest, which means you can pedal more powerfully too.

 
Power-stroke
power stroke   power stroke
You push the hardest when your pedal is here. The Oval behaves like a larger round chainring, giving you a higher gear.
 
 
Dead-spot
dead-spot dead-spot
You can't push much here. The Oval behaves like a smaller chainring, providing a lower gear to help you round to the next power-stroke.

 

The benfits are most noticeable when you turn the pedals slowly, particularly when climbing hills or when pushing a large gear at a slow cadence. An Oval helps you pedal through the dead-spots, allowing you to keep going while you've still got some energy left. Ovals also transfer power to your back wheel more smoothly, reducing the stop/start effect which causes wheelspin on slippery surfaces and the bobbing effect which occurs on some suspension bikes.

dales

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Why aren't Ovals more popular?

Although Oval chainrings were invented in the 1890's, today most manufacturers only make round ones. One reason is that Ovals don't lend themselves to mass-distribution because of the large number of variations that has to be catered for. Different cyclists ride different machines, from small-wheeled bikes to recumbent trikes, and each of these requires differently orientated chainrings.

A lone engineer making something that really works, without the huge advertising budget of the big manufacturers and without resorting to the hype which has become today's norm, has little chance of influencing the habits of the millions of cycling comsumers. Nevertheless, a few Ovals are currently being mass-produced, specifically for racing cyclists - these are Osymetric and Q-rings.

It should be noted that Shimano gave Ovals a bad name in the 1980's by orientating their 'Biopace' chainrings back-to-front. There's more information about these and other designs on the Oval history page.

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EGG

How to choose Ovals

 

Every Oval EGGring is unique, custom-made to suit your cycle and your style of riding. The following notes will help you to specify your Oval.

Number of teeth

Ideally you should choose the same numbers of teeth as you would for round chainrings. However the smallest Oval that will fit your cranks will be a few teeth larger than the smallest round chainring (see Minimum size). I will check your order carefully and let you know if there are likely to be any problems.

Ovality

This specifies how oval a chainring is, as the following four 38 tooth chainrings show:

0% 10% 20% 30%
0% ovality (round) 10% ovality 20% ovality 30% ovality

(note:  if the round ring doesn't look round then you need to change your computer's screen resolution)

Round chainrings (0%) work well when you spin the pedals fast, whereas large ovalities suit slow pedalling rates. So your smallest chainring, used for climbing hills, should be more oval than the others. You can mix round and Oval on the same crank but, to maintain your rythmn when shifting gear, don't exceed a 15% difference between adjacent chainrings.

The table below gives various recommendations. Choose the ovalities which match your style of riding...

  type of cycling outer
chainring
middle
chainring
inner
chainring
 
   road racing double chainset
fixed-wheel
round
7%
-
-
7%
-
 
 road touring double chainset
triple chainset
hub gears
20%
20%
10%
-
30%
-
30%
40%
-
 off-road racing
touring
trials
round
20%
30%
7%
30%
45%
14%
40%
70%
 BMX   10% - -
Your cycle and riding style

When you order an Oval, I ask you several questions about your cycle and riding style. Your answers will help me to get the orientation correct. (See Crank orientation for more information about this.)

And, because Ovals must be mounted correctly, each one is permanently marked with the correct crank position for your setup. This won't necessarily be the same as that for a different cycle or another rider. In particular, Ovals are orientated differently on standard upright bikes, small-wheelers and recumbents.

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EGG

Oval chainrings - more questions answered

 

Round or Oval?

Nothing's wrong with Round chainrings and they remain a good choice if you always spin your pedals fast, working flat-out all the time. This is how track riders compete - if you ride like this then you could stick to round. But if, like most cyclists, you keep something in reserve and only push your hardest when absolutely necessary, then Ovals could be an advantage for you.

Ovals also make it easier to maintain traction on slippery surfaces offroad, because they deliver power to the rear wheel more smoothly (see Smoother power transfer).

Many riders mix round and Oval chainrings on their chainsets (see Ovality above).

Do Ovals feel strange?

You may notice a difference at first, just like when wearing a new pair of shoes. But after that your pedalling will feel perfectly natural - you may simply notice that it's easier to climb hills.

Several riders have told us they didn't notice any difference until they tried round rings again, and that these felt dead in comparison. That's when they finally realized what Ovals are all about!

Are Ovals more efficient?

The shape of your chainring doesn't alter the mechanical efficiency of your cycle, but Ovals do allow you to pedal more effectively by continuously changing the gear ratio to match your effort while pedalling. The slower you pedal, the more advantage is gained (see Efficiency).

Will my derailleurs still work?

Your rear mech will work normally but you may need a larger front one (see Front derailleur capacity).

What about recumbents?

Ovals are particularly helpful on recumbent cycles since the dead-spots are more noticeable and you can't push harder by standing on the pedals. But an Oval designed for an upright bike won't work on a recumbent as its orientation will be wrong.

Can I use an Oval with hub-gears or a fixed-gear?

Yes, and you won't need a chain-tensioner if the ovality is small. I recommend a maximum of 15% for hug-geras and 7% for fixed-gears.

Small chainrings

The smallest Oval that will fit your crank is a few teeth larger than the smallest round ring (see Minimum size).

You may therefore be tempted to increase the number of teeth when specifying your Ovals. Don't do this - reduce the ovality instead, a lower gear taking precedance over ovality. Better still, choose a crank which allows smaller chainrings - this will also allow the same size chainring to have a greater ovality.

Other systems

Over the years several other devices have been offered in the quest to increase the efficiency of cycle transmissions. Some of them appear to work, some make no difference at all, and others actually make matters worse. It should be noted that, unlike an Oval chainring, any device which intoduces extra mechanisms (such as a cam, rubber bush or cog) inevitably reduces the overall mechanical efficiency of any machine, including a cycle.

Ovals in the 21st centurey

Today there's renewed interest in Oval chainrings and 3 makes to choose from (Osymetric, Q-rings and EGGrings). It's a pity that one manufacturer has seen fit to promote their own Ovals with text copied directly from my webpages and literature while, at the same time, claiming that EGGrings themselves aren't very good. Surely there's room in the market for more than one good product? A mass-produced item will never be threatened by a custom one, nor a custom one by a mass-produced one - in fact they compliment each other very nicely.

More information

Technical information about Oval chainrings.
Brief history of Oval chainrings.
General information about EGGring custom chainrings.

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Chris Bell
HIGHPATH ENGINEERING
Cornant, Cribyn, Lampeter, Ceredigion, SA48 7QW, Wales, UK
Wales
©  Chris Bell