Adding a 12t sprocket on a 5 spd freewheel?
 

I'm maxing out the top gear (14t) on my Miyata 110 and would like to add a 12t sprocket. Its a suntour 2 prong freewheel. Would I need anything other than the Park freewheel remover to do this? I was thinking of removing the 2nd largest sprocket to make room for the 12t?

Afraid you may need a custom machine shop to make it..

#1.. suntour 2 prong freewheel puts it back to being 30 years old.

(I toured Europe, with a 50:14, a lot. the High 95" gear was fine.. 3.5:1)

put a huge chainring on the crank , or better, buy a new bike.

modern cassetes on road-racer wannabe start at 11t, with a 53t chainring
4.818: 1..

120 dropout frames, the 5 speed era , are good for fixie conversions,
so you can find a buyer for your old frame and old parts.
[value is what they are willing to pay ]

As far as I know, there are no 5s freewheels with a body small enough for a 12t sprocket. 12t started with 6s freewheels as an extra sprocket overhanging the outside of the body and mounted inside the 2nd sprocket.

I was thinking 8 speed , 12 screws into a 13, 13 screws into a 14, then the 14 screws onto the body,
at least that was the Sachs - Malliard ARIS Freewheel Plan.

Find a bike co-op and dig though their box of freewheels and look for a ultra spaced 6 speed freewheel. I imagine it would have a smaller cog but I really don't know. The spacing of a ultra type freewheel should fit in place of the 5 speed wheel hub without needing to respace anything.

In 3 years of cat3/4 criterium racing I did not max out a 14 tooth cog. In fact I placed 4th in a criterium that averages 29mph when I was on an extended tour and had reduced my outer chainwheel to 48 teeth. So I assume by maxing out you are referring to either going downhill or being unable to crank higher than about 90 rpm.

If you are convinced you need a 12 tooth I would also advise finding an ultra 6 (13 tooth cog) or selling the bike and purchasing a used one with that small a cog. Probably less time and money net.

Sounds like a plan - for broken axles.

Ultra 6 freewheels (6u) also cannot use a 12t sprocket for the same reason as 5s. In a 6u freewheel the 1st sprocket is on the body itself so the large body diameter limits the minimum size. On some older freewheels it's 7s, on later freewheels they shrank the body diameter so it could accept 13t, but that's the limit.

As CNY-Bikeman said you shouldn't need larger for most purposes, and should be able to spin a 52/13 to about 30mph (if you're strong enough). But if you need bigger gears (or think you do) then your only option is a larger chainring, or spreading the frame, re-spacing the wheel and going to 6s (not 6u) or 7s.

BTW- many people think they need a higher gear, but in fact run out of torque rather than speed, and can actually go faster in the next gear lower. It's kinda like your car, which may have little throttle response in overdrive, and must be downshifted for passing power and speed.

Maybe I'm mistaken but I recall installing a 13x28 6-speed Sun Tour Ultra Freewheel on my '85 Bridgestone 400 in 1987 or thereabouts. The bike was spaced for a standard 6-speed freewheel (126 mm) but the ultra was cheaper at the time as it was NOS.

You're not mistaken. A 6u will fit on a 126mm hub, giving you the option of leaving it inboard with the 6mm or so on the end where the 7s outer sprocket would go empty (the 13t 6u sprocket would need to be replaced with a 7s, then one added, other sprockets are the same). Or you could respace the hub around the 5s/6u width and have a nearly dishless wheel.

However the OP wants 12t, and that requires a overhanging sprocket s on regular 6s or 7s.

Thanks for the info guys. We really don't have many hills to speak of, but I ride around the lake and benefit from a gusty tailwind for several miles on each lap. I'm certainly not going 29 mph but still could use a higher ratio. My plan was to make this a rain bike all along. Guess that will happen sooner than I wanted.
Btw is a 13t freewheel findable?

Yes, there are many 5s freewheels starting with 13t. I have a large stock of NOS Sun Tour 5s freewheels with a 13t, but the low ends are all 22 or 23t and smaller, so if you can use a 13-23 5s your in good shape, and I can give you a good deal. OTOH if there are climbs involved you'll want to seek out a 13-26 or 13-28 (or bigger on the internet)

A freewheel (FW) remover only removes the FW from the hub. You need a pair of chainwhips to remove cogs from the FW body. Your not likely to find a 5spd FW with a 12T small cog you might find a 13 though.

As mentioned a 6spd FW may fit on your bike easily enough.

What year is your bike that it only has a 5spd FW?

Are you maxing out down hill?

What are your chainrings? 42/52? or more like 38/48? Or smaller? A bigger ring might be a solution.

-Its a 1981. But my dad's Raleigh Sportif is from the mid 80s and has 5 speeds as well.
-Yes, going down hill its the same problem as with a tail wind. Just have to spin the pedals too fast for my liking.
-The outer chainring is a 50t. I thought about replacing it but they are like $45 for a 53t, and I'm not even sure I could find one that fits.

13T was the standard high gear on 5speed freewheels, I just found a somewhat rusty Regina Oro that was on my old touring bike when I lived in the flatlands the summer of 1975, its 13-15-17-19-21. as soon as I moved back to the coast, I returned to saner gearing, 13-26 or so. the crankset on that bike was 54-42.

If you really have a 14T a 13T may not make that big of a difference. a new chainwheel would make all you gears slightly 'bigger'. The trick is what size your crankset is.

more htan you might think. here's gear inches for a 13 and 14 rear with a 50, 52, and 53 front (OP said he has a 50T), and assuming a 700x32 tire...

gear inches[TABLE="class: mytable, align: center"]
[TR]
[TD="class: c0n, align: center"][SUB]front[/SUB][SUP]rear[/SUP][/TD]
[TD="class: c1n, bgcolor: #CCFF66, align: center"]14[/TD]
[TD="class: c2n, bgcolor: #CCFF66, align: center"]13[/TD]
[/TR]
[TR]
[TD="class: c0n, bgcolor: #CCFF66, align: center"]50[/TD]
[TD="class: c1n, align: center"]96.5[/TD]
[TD="class: c2n, align: center"]103.9[/TD]
[/TR]
[TR]
[TD="class: c0n, bgcolor: #CCFF66, align: center"]52[/TD]
[TD="class: c1n, align: center"]100.4[/TD]
[TD="class: c2n, align: center"]108.1[/TD]
[/TR]
[TR]
[TD="class: c0n, bgcolor: #CCFF66, align: center"]53[/TD]
[TD="class: c1n, align: center"]102.3[/TD]
[TD="class: c2n, align: center"]110.2[/TD]
[/TR]
[/TABLE]

to the OP, your existing crank, are the chain rings 4 or 5 bolt, and how many mm apart are two adjacent bolts (center to center)? $45 seems rather high for a low end chain ring. These numbers (bolt count and spacing) will give us the 'BCD' of your chain rings, which is needed to know what will fit. for instance if its 5 bolt and they are 76.4mm apart, its a 130mm BCD crankset, thats a very common old school road bike size

also to the OP, when you're going too fast to pedal, that's where you coast and take it easy, saving your strength for the inverse conditions :)

According to Sheldon Brown's Gear Calculator, wth 27" wheels and a 52/13 gear, if you are turning the cranks at 80 RPM (considered by many to be a little slow) you should be doing 41 km/h. If you are turning the cranks at 100 rpm (considered by many to be a good target cadence for most road riding) you should be doing 51 km/h.

Unless you are training for the olympics, you don't need to get a higher gear, you need to teach your legs to spin faster.

btw, you might give this gear calculator a try.... (its the /2nd/ hit on google for 'bicycle gear calculator', behind Sheldon's)
http://www.machars.net/bikecalc.htm

I like it better.

and yeah, I totally concur re: the rest of what you said. learn to spin.

As we're throwing out gear calculators, I like this one as it is a bit more visual:
http://www.gear-calculator.com/#

axles bigger than 10 mm were a partial solution..
but the problem was solved SRAM took over Sachs Group
an threwMalliard and all the European manufacturing under the Bus,
they are on Taiwan now also .. exported the production machinery.

the freewheel, French company, not included. they went Poof! gone.

hmm, that is slick.

What crankset is on there (pics)? You might be able to find a whole used crankset for that much. I definitely agree with putting on larger chainrings rather than smaller freewheel sprockets, if you really need to increase the gearing. Larger sprockets are more efficient and last longer. :thumb:

There is no advantage without disadvantages and the same goes for a larger chainwheel.

Positives:

• Minimally more efficient, but if that were the concern the OP should first address it by learning to spin faster, which is more efficient both for body and bike.
• Slower wear - again, technically true but proper riding in the small cog, even at slightly low rpm's, involves very few miles of usage.

Disadvantages:

• Gear ratio increase - as shown in the chart earlier (and easily seen if one looks at percentage change) one needs to add 4 teeth on the chainwheel to equal 1 tooth difference on the rear cog.
• Front derailleur adjustment - The front derailleur must be raised and readjusted, often requiring a new cable.
• Flex - So much for efficiency, as a larger chainwheel will have a greater distance between teeth and the end of the spider, so will tend to flex a bit more.
• Chain length - to be safe in case of shifting to large large one will likely need to add links to the chain.

Of course if one goes the rear cog route it would not be surprising if a new chain is needed, but a new chain always feels so good, and in fact is more efficient.

A used crankset is unlikely to have more than 52 teeth, for only a 4% increase in gear ratio, or about 1mph greater speed at equal rpm's. Even the 53 tooth just adds 1.5 mph. It also may not be compatible with the current BB/spindle.

I know, the OP says he's not "comfortable" pedaling faster, but that can be learned in most cases. Admittedly we don't know what his rpm's are now or what physical limitations he may have, but if we assume he's pedaling at 90 rpm he only needs to up that to about 100 to add 2.5 mph or more to his top speed with no change in gearing. In the bargain comes better heart exercise, greater efficiency, lower drivetrain wear and in most cases a further increase in averatge speed as one gets into better shape.

Sounds like a Regina freewheel to me.