lower gears

[bentbuilder_jawnn]

I need a lower gear than he 17.6-gear inch I now have (24 sprockets front divided by 34 rear). Some one told me that I could get an even bigger gear for the cassette. But it may be easier to get a 22-sprocket chain ring for my 5-hole 74mm bolt circle road crank? I don’t want to use a Mt. Tamer adapter unless that’s the only way.

Does any one know where I can get these?

[TheKid]

You may have to change the whole crankset. To my knowledge, there are no freewheel casettes with a larger than 34 tooth cog. I haven't been able to find a 22 tooth 5 hole 74mm chainring either. You don't say what kind of bike you're riding, but if you need gearing that low, I'm assuming it's a trike or a quad, or you're pulling a trailer with a bike.
The gear inches you mentioned are for a 26" wheel. If you could switch to a 24" rear wheel, you'd be down to about 16 gear inches, and 14 with a 20" wheel. The 22 tooth chainring will also give you about 16 gear inches, so that's probably the easiest way to go, if that's low enough. Here are some links for the cranksets:

http://www.jensonusa.com/store/product/CR307A02-Shimano+Alivio+Fc-M410+Compact+Crank+Set.aspx

http://www.ebikestop.com/sugino_impel_150x_175mm_22_32_42_78_spd_silver_arm s-CR8894.php

http://www.bikemannetwork.com/biking/p/COMPCRNKMTNSETSG/CR8894

[robertwb70]

I've never seen anything bigger than a 34 freewheel/cassette either but I do have a 22 tooth front but it's not the bolt on kind it came off a one piece crankset that was riveted together-maybe you could drill it out and make it work?
it might also be possible to do the same thing to a 22 tooth gear taken from a rear freewheel/cassette but either way it would take some ingenuity.

probably best to just buy a new crankset with the gears you want though especially for $35.

[bentbuilder_jawnn]

what is the highest gear I can get on a mt bike crank? I would need about 50 sprockets....maybe I should try the 48. I'm not in hurry.

I load my short hybrid bike down with about 350lbs combined weight.

[SirJoey]

The pair of drivetrains I'll be using on the KC, have 24s for the smallest chainrings, & 30s for the largest freewheels. With 20" wheels, I should have low enough gearing, right?

[TheKid]

That would be 16 gear inches. Consider that your DW weighs 65 lbs., so the KC will be at least 10 lbs. heavier. Assuming you used the same gearing on the DW with 24" wheels, your low gear would be 19 gear inches. I found it difficult to ride my quad, which weighed over 80 lbs. with 16 gear inches when in low gear. When I added positraction, it was much easier, especially when making a left turn uphill. If you ride by yourself, 16 gear inches may make it a little strenuous on hills, if your disabilities are similar to mine.

[SirJoey]

On the DW, the smallest chainring is 28, the largest freewheel is 34, so which one is geared lower? Or are they the same? I'm thinking they're both the same, since both ends went up by 4 teeth. Right? (not considering wheel size here)

In other words, is the 24 & 30, the same as the 28 & 34, if both have the same size wheels?

[TheKid]

19 gear inches for your DW, whether you use 24/30 or 28/34. If you go to 24/34 on the KC, you'll get down to 14 gear inches. Crank those (14 or 16 gear inches) at 100 rpm, you'll get to 4 mph. On level ground, it's easy to get to 100rpm. The hills were the killers. On some, I could barely get the quad to 60 rpm, which is 2 mph. I sometimes found it easier to push it up a hill.

[SirJoey]

So, since the two gearings are actually proportionally the same, I'll still gain with the KC, by using the smaller 20" wheels. What would it then figure out to be? Never mind. Sorry, you've already answered that, thanx.

[robertwb70]

This page can provide at least a few minutes of entertainment
http://www.sheldonbrown.com/gears/

[TheKid]

I use that one sometimes, but I have one I downloaded that's easier to use, because I don't have to go online. It's not quite as accurate as Sheldon's, because it rounds up. I can't find the link anymore. I know it's in the old forum somewhere. I also use Sheldon Brown's internal gear calculator:

http://sheldonbrown.com/gears/internal.html

[bentbuilder_jawnn]

For 350lbs combined weight using a 26" drive wheel and 170mm cranks, 17.6 gear inch is the maximum low gear I need.

But with 150mm crank arms I need 12% lower gears. So I need a 15gi on the low end and 82gi on the high end. So a 48-20 crank set is needed.

The short cranks are for spinning faster to make up for the lack of ability to stand onthe pedals.

[TheKid]

Shorter cranks are also used by some of us who have knee problems, especially if the BB is above the seat.