Huge chainrings

[commuter ebikes]

I am currently running a 58T Vuelta USA chainring, but my pedaling spins out at 35 mph. I have a 110BCD. Vuelta USA sells a 60T chainring for only $40, but I was thinking of going up to 64-66T.

I know that tandem bikes use huge chainrings, and I found this page http://trisled.com.au/product-catego...uards-rollers/. They have 65T and 70T in 110BCD (the Aussies call it PCD), but I was hoping to find one for cheaper. I need a flat chainring for my 1X5 setup (as opposed to a ramped and pinned chainring).

FYI the smallest cog on my 5-speed freewheel has 14T. I don't have the room for a 7-speed freewheel, and 14T was the tallest gearing I could find in a 5-speed freewheel.

Does anybody know where to find a more affordable 110BCD 62-66T chainring?

For your entertainment, here is a picture of a 90T 110BCD chainring:

[commuter ebikes]

I might actually try that 70T in the link.

[commuter ebikes]

Using this formula,


I currently have 31.5" X (58/14) = 130.50 gear inches, which is spinning out at 35 mph.

If I use a 65T chainring, I will have 31.5" X (65/14) = 146.25 gear inches which will presumably spin out at [(146.25/130.50) X 35 mph] = 39.2 mph.

If I use a 70T chainring, I will have 31.5" X (70/14) = 157.50 gear inches which will presumably spin out at [(157.50/130.50) X 35 mph] = 42.2 mph.

[commuter ebikes]

So going from 58T to 65T (a 7T increase) adds 4.2 mph to the spinout speed.

Going from 58T to 70T (a 12T increase) adds 7.2 mph to the spinout speed.

Going from 65T to 70T (a 5T increase) adds 3.0 mph to the spinout speed.

In all three of these cases, adding 1T adds 1.67 mph to the spinout speed. This does not apply to smaller chainrings (the general formula below indicates that smaller chainrings experience a greater degree of increased spinout speed for added teeth).

[commuter ebikes]

The general formula for increasing the number of chainring teeth in order to raise the spinout speed would be:

New Spinout Speed = {1 + [(Number of Chainring Teeth Added)/(Initial Number of Chainring Teeth)]} X Initial Spinout Speed

I will probably go with the 70T chainring. So, using this formula, I get:

New Spinout Speed = [1 + (12/58)] X 35 mph = 1.2069 X 35 mph = 42.2 mph.

I would like this higher spinout speed because I need exercise. I rarely travel over 40 mph, so I can get exercise during the entire 30 minute round trip commute.

As it is now, I am traveling 35 mph most of the time and getting almost no exercise.

[commuter ebikes]

I called Vuelta USA and talked to Rex on the phone for a long time. They would make any chainring that I wanted, but the minimum order is a whopping 100 units!

Rex suggested that I keep the 58T on there, turn down the power so as to ride more slowly (and safely!) which would make for a good quadricep workout. Good advice, but I am going to buy the 70T from Australia and get the quadricep workout at higher speeds. Rex discouraged going to a larger chainring, indicating that this would increase the chance of lower back injury or ligament damage.

I also called my local machine shop for a one-off, and they said that they would need an AutoCAD drawing for the chainring.

Here is the 110BCD 70T:

[Kocho]

Why not drop the rear casette smallest ring to 11t? Maybe not as long-lived as a 14t, but 11t cassettes are readily available? You may even be able to just change the one ring, remove one of you less useful rings in your existing cassette and add an11t?

EDIT, just saw your 5 cog freewheel limitation ...

[MoneyPit]

I use a 60T Driveline chainring. Taiwan mfr. 7075 aluminum. Under $40. About $60 for a 68T

http://www.ebay.com/itm/Driveline-68T-CNC-AL7075-Road-Bike-Bicycle-Chainring-68T-BCD-130mm-Black-/142391752545?hash=item212735b761:g:jZEAAOSwYlRZJon1

However expect anything commercially available in this size is going to be 130 BCD. I'm frankly amazed you can find it in 110 let alone in larger-tooth sizes.

Here is a 70T. Also 130 BCD.

http://www.ebay.com/itm/Bikingreen-70T-Recumbent-Chainring-BCD130-CNC-7075-Road-Fixie-TT-Track-black-/161835033679?hash=item25ae1ea44f:g:xo4AAOSwwvZZW5Jz

Also found a couple 72's but look like one-offs and $100+


Here is a better gear calculator. Has a few more nice spiffs on linked pages like speed to cadence etc.: http://www.bikecalc.com/gear_inches

[commuter ebikes]

I use a 60T Driveline chainring. Taiwan mfr. 7075 aluminum. Under $40. About $60 for a 68T

http://www.ebay.com/itm/Driveline-68...EAAOSwYlRZJon1

However expect anything commercially available in this size is going to be 130 BCD. I'm frankly amazed you can find it in 110 let alone in larger-tooth sizes.

Here is a 70T. Also 130 BCD.

http://www.ebay.com/itm/Bikingreen-7...4AAOSwwvZZW5Jz

Also found a couple 72's but look like one-offs and $100+


Here is a better gear calculator. Has a few more nice spiffs on linked pages like speed to cadence etc.: http://www.bikecalc.com/gear_inches

That 70T is exactly the link I was looking for. I can find a 58/130BCD or 110/130BCD spider easily enough. I am currently using a 58/110BCD spider so switching over to 130BCD would be easy peasy.

I would be very interested in links to the one-offs. Thanks!

Here's a guy with a 77T. He also has a really long crank arm and probably a 130mm BCD:

[commuter ebikes]

I was able to find a few spiders, but only in 110/130mm. I could not find a 58/130mm BCD spider anywhere; I don't think they exist! I am already using a 58/110mm spider, and I don't want to use two spiders for three reasons: cost, weight and unnecessary complexity.

So I pulled the trigger on two of the 110mm BCD 70T chainrings from Australia. The price was $225.06, including delivery.

I have room for a chainring up to 15" in diameter, and I calculated the diameter of a 70T chainring to be 11.14".

A chain link is 1/2" long, so a 70T chain is 70 X 1/2" = 35" in circumference. Since C = π X d, it follows that d = C/π so the diameter would be 35/3.1416 = 11.14.

Note: answer #6 here https://bicycles.stackexchange.com/q...umber-of-teeth states that two links are 25.5mm long. I used 1 inch (25.4mm) because I was taught that each link is 1/2". Close enough.

Picture from the link:

[commuter ebikes]

Forrest Carver at Bath Cycle & Ski (aka Bikeman) expressed a concern about putting a 70T on any spider, let alone a Surly Mr. Whirly spider. He has broken one of these spiders with a 50T ring installed. He thinks I would be better off making a custom 144mm BCD ring to put on a track crank.

The 58/110mm Surly spiders come in two styles pictured below, both of which are aluminum. One style is not a full circle. I have the spiders which are a full circle.

[commuter ebikes]

Here is a collection of pictures of broken Surly spiders:

[calfee20]

I found some 13 tooth freewheels on ebay. http://www.ebay.com/sch/i.html?_odkw...13%2F&_sacat=0 One tooth in the rear will make a huge difference. You won't have to go so big in the front.

[calfee20]

I found this on the bike forums.

"Most of my freewheels are custom built using the Suntour Winner system, which allows building 5 or 6 speed freewheels for 120mm hubs and 6 or 7 speed freewheels for 126mm hubs. The system has different width spacers, permitting regular or narrow (ultra) cog spacing. I purchased a "shop board", which came with freewheel bodies, cogs and spacers that allow an almost unlimited variation in gearing setups. I recently even used this system to build a single speed freewheel for a restoration of a 1970s Mercier. The advantage of this method over just buying a single freewheel is that I could achieve a near perfect chainline to within +/- 0.5mm and could choose cogs from 15T to 21T."



here is the link. http://www.bikeforums.net/classic-vi...reewheels.html

[commuter ebikes]

Very helpful! Thanks, Bud.

[commuter ebikes]

I see that IRD (Interloc Racing Design) makes 5-speed freewheels (English thread for threading onto hub motors) with a 13T small cog and a wide range of gearing (for a 5-speed, at least): http://www.interlocracing.com/casset...eels-567-speed








I bought a used one on eBay http://www.ebay.com/itm/IRD-Interloc-Racing-Design-Freewheel-5-speed-13-32-Teeth-Road-Used/391866406874?ssPageName=STRK%3AMEBIDX%3AIT&_trksid =p2060353.m2749.l2649 to see if it fits in the limited space that I have available.



If it fits (and shifts with my index shifter), the bike will have 169.62 gear inches with a projected spinout speed of 45.5 mph which is just about the top speed of the bike.

With the 130.50 gear inches that I have now (31.5" tire diameter, 58T chainring, 14T smallest cog), my bike is in the tallest gear all the time and I get almost no exercise because there is no pedal resistance above 35 mph with the highest reasonable cadence.