Coker Reliability

I have a coker from coker tire with the stock steel rim. I was looking through these threads the other day and it seems like people think these are junk. I am about 220lbs and my primary use is bike trails, streets and jumping an occasional curbs My question is based on what I’ve read in the threads and my use pattern do I need to update to a stronger wheel, etc. Does anyone have any long term experience with these stock cokers. Thanks.

I rode mine most of last season without any trouble. I’m over 200 lbs and only use it only on the street (no jumping curbs for me). I upgraded to the airfoil because I found I was using it more and more and wanted to lighten up. I would say use it till it dies, then worry about replacing.

I muni’d with my coker all last season, and a lot of urdan/street miles on it. I am about 180-90 with gear on, and go over curbs and stuff, as well as through technical MUni trails.

The rim is definetly the weak point to the unicycle, but it is far from ‘crap’.

You do, however, need to be more concerned with proper spoke tension, if you plan on throwing curbs and things into your ride.

My Coker has been through quite a bit, and the rim is still ‘true’ (true enough)

Here is a 18mb Video of me showing the wheel almost taco’ing, then springing back into shape again. Very little spoke tensioning was required when I got home…it’s still going strong.

However, if I were to buy a new Coker, I’d get it with the aftermarket Airfoil rim right from the start, I’m sure it would be a wise move…because then you wouldn’t have to worry at all. But as stated by the other poster, I won’t replace mine with the aftermarket until mine dies.

Finesse overcomes the wheel’s weaker points.

Well, are US pounds the same as proper English ones? Coz I’m only 149 pounds (as of today) and I think I need to lose a few more.

Be that as it may, I’ve ridden my standard Coker on and off road, up hill and down dale, through the merry greenwood and down by the riverside, and all I do is get the local bike shop to true the rim every few months.

I believe I’m right in saying that steel is stronger than aluminium alloy, weight for weight (I recall this from my scuba diving days when steel tanks were lighter than the aluminium equivalents), but the problem with the stock Coker rim is that it is a very simple design, rather hastily thrown together. Add to that that the wheel is machine built, and the structure can be weak. Hand tensioning of the spokes by someone who knows what (s)he’s doing makes quite a difference.

If my standard Coker rim Croke-d, I would probably pay the extra for a better one, but not before.

149 pound (US) = 10.6428 Stone (UK):smiley:

So a pound’s a pound, either side of the pond. But no Englishman would put a decimal point in a weight in stones. :astonished:

:stuck_out_tongue:

149 pound (US) = 10,6428 Stone (UK)?

149 pounds = a little over ten and a half stone or ten stone six.

Sarah ( UK)

Re: Coker Reliability

“Mikefule” <Mikefule@NoEmail.Message.Poster.at.Unicyclist.com> writes:

> I believe I’m right in saying that steel is stronger than aluminium
> alloy, weight for weight (I recall this from my scuba diving days when
> steel tanks were lighter than the aluminium equivalents)

Actually, aluminum alloy and high grade steel are comparable in
tensile strength/weight. Aluminum parts are often stiffer than steel
because they have to be made thicker for the same tensile strength,
and so the aluminum resists bending better. Steel is less expensive.
So, aluminum rims can be lighter and stronger than steel. Steel tends
to be used for inferior rims to save money.

Ken

Re: Coker Reliability

On Sun, 4 Apr 2004 16:35:32 -0500, “sarah.miller” wrote:

>149 pounds = a little over ten and a half stone or ten stone six.

What does the six refer to? Six tenths of a stone? That is a decimal
point in disguise.

Klaas Bil - Newsgroup Addict

I think profile should make some stronger 145mm cranks - Ryan Atkins

Re: Re: Coker Reliability

A spy decimal point!!!:smiley: :astonished:

I bet it even has an evil laugh.:stuck_out_tongue:

Re: Re: Coker Reliability

A little clarification: The ratio of strength to weight is about the same for steel and aluminum.

Steel is three times stronger (in tension) and three times heavier than aluminum. So an equivalent aluminum part is generally three times thicker. This is the secret behind the stiffness of Cannondale and Klein bicycles - since there is more aluminum to work with the tubes can be made in larger diameters which are MUCH stiffer because the material is further away from the centerline and has more leverage against the bending.

But getting back to rims, they don’t fail in tension. They twist and “buckle,” which means that they fold up under compressive loads. Think of what happens to a rim when the wheel tacos - it picks up four gradual twists. And if you’ve ever seen a broken rim you can see it has picked up three distinct folds - one in and two out. Both of these deformations are the rim’s way of escaping from the huge compressive loads that tensioned spokes create.

Torsional resistance and buckling strength are very dependant on the geometry of the part. A thick-walled tube, like an extruded aluminum rim, is much stronger under compressive loads than a thin sheet that has been formed into a C-shape, and MUCH, MUCH more resistant to twisting loads. My structures professor demonstrated this with a cardboard tube from a roll of paper towels. The torsional stiffness of the tube disappeared when he slit it lengthwise.

So the stock Coker rim is weak because of it’s shape, not because of the material. Aluminum rims are stronger because aluminum is easily extruded into those nice tubular shapes. Those nice rim sections could be done in steel but it would be prohibitively expensive.

What does the six refer to? Six tenths of a stone? That is a decimal point in disguise.

10 stone 6 means 10stone 6lbs(pounds) where there are 14 lbs in a stone
Oh the joys of imperial weights and measures

Roland

That is my point. 149 lbs should be 10 stone 9, not 10 stone 6. More proof that the imperial system is confusing even to the English - as if we need more proof.

Klaas Bil

I weight about 200 lbs. For the longest time my Coker (completely stock), was my only unicycle. I beat the hell out of it, and never had any problems. Until I bent the crank, which I believe are just cheap lascos. So that’s certainly no fault of the coker. I have found the coker to be quite durable.

Absolutely - I was lazy and didn’t look at the figure that was being converted assuming that the good folk of England would still have their dark ages measuring hats on and so would have got it right :slight_smile: Just as well we went decimal on the coinage or ordering unicycle bits on the web would have been a nightmare

Roland

I wouldn’t rush out to buy a new rim, but if I broke the one that I have I would upgrade to the airfoil.

carjug

149 pounds is 10 stone 9.

1 stone = 14 pounds
10 stone = 140 pounds

1 pound = 16 ounces.
Just to make it easy.

No one would normally express 10 stone 9 as 10.6 stone.
This is because the deciomal point would imply a decimal system, and clearly a system of 1/14 and 1/16 is not decimal.

In the USA, they use pounds, rather than stones. Hence, an American would say 149 pounds and an Englishman would say 10 stone 9.

My question which started all this was (facetiously) whether US pounds were the same weight as UK pounds. Not an entirely daft question as US gallons are different from UK gallons. It was prompted by several people referring to their own weights as being about equivalent to the weight of me carrying all my unicycles and a bucket of heavy water.

:wink:

Now I’m really confused! All that Stone stuff had me going, and now we have to figure out the weight of “heavy water.” Normal water is about 8.34 lbs/US gal, but i guess we’ll have to ask Harper about heavy water.

Just to stay somewhat on topic…i’ve had my standard Coker for about 4 years now. It doesn’t get ridden on any real tough terrain, but it has worn out two tires with no rim problems. I’d love to have the airfoil rim, but like others have said, i probably won’t upgrade until i fold the stock one. One thing, though, i wouldn’t recommend trying to use brakes on the stock rim. I tried it for a little while, but my rim has such a bulge at the weld that it is impossible to modulate…sent me flying too many times!

Chuck

I put a slight bend in my stock steel Coker rim one week before I got my Airfoil wheel back from the wheel builder. That was almost perfect timing. :slight_smile:

I bent my stock Coker rim on a bad mount. I mounted, was off balance to the side, and did a slight side hop to recover. It was only a slight bend and was still rideable afterwards. I took it to a local bike shop that specialized in unusual bikes and he was able to bend it back true. The wheel works, but I don’t trust it any more. I expect it to bend again in the same spot.

The stock Coker wheel is weak. The steel rim can’t take very much spoke tension so the spokes have to be loose. The stock hub is very narrow which doesn’t help matters any. The stock wheel works, but given the opportunity it will bend. It’s a wheel failure waiting to happen.

The Airfoil is an immensely better rim. It’s stronger. You can tension the spokes to very high tension and it won’t buckle. It’s stronger. Did I mention it’s stronger. I’m willing to ride mine down stairs and go on single track with no fears that the wheel is going to fail.

Put the Airfoil rim on a w-i-d-e hub and difference between it and the stock wheel is dramatic. With a strong wheel build and a wide hub the rim does not flex even when pedaling hard up a hill. That means that the rim will not rub the brake pads when climbing. The wheel is solid. It gives you confidence to ride it harder. But the cost of such a wheel is more than the entire stock Coker.