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More half step questions......

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More half step questions......

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Old 04-10-10, 01:55 PM
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thook
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More half step questions......

Since I've posted in the "show your 1/2 step" pics thread, I've done a lot of calculating and noticed it can be kinda hard to half step with 7spd's or more and still get a useful build with a wide range. I guess that's why it's vintage stuff.

Questions....

I've decided to only half step (for now) the Trek and Dawes Galaxy I have. I've really wanted to try and keep the Trek with it's original crank at 28/45/50, but it seems a 7spd cassette is impossible. At best I can build a 6spd, but I question the shiftability of such a build.

To illustrate...

At 45/50, that's give a ratio of 1.111%. This means an average of 4.2 tooth jumps in the rear. What I've come up with is 13/16/19/23/28/34. That comes to an average 1.106%. That's undershooting a bit. Or, 12/15/19/23/28/34. That comes to 1.116%. Overshooting a bit. Plus, the 50/12 is @ 112.5 gear inches. Pretty high, unless I have a nice hill to get going on. So, for the most part I'd be using the 45/12 combo. The other issue is all the big jumps in shifting. I suppose 3 tooth jumps is just fine, but the others are rather large. Would the fact that the cassette cogs are ramped and all help offset this? And, would the fact that the numbers don't match exactly in either cassette option make that much of a difference? I think if I even dropped the granny down to a 26, I'd be even better (wider range on the low end), but anyway....

It'd be nice if someone just said,"Oh yeah.....your fine.", and I could run with it, but facts is facts. Shoot me straight, please.
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Old 04-10-10, 03:07 PM
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Just noting that 1.116% and 1.106% are only a tenth of a percent apart. I guess I'd like to know what kind of tolerances to shoot for.
I just went a stuck a 11-34 7 speed on the back of my Trek 613 and didn't think too much about it. Now I'm thinking I shoulda thought about it.
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Old 04-10-10, 03:34 PM
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Well, right now I have the Trek on 27x 1 1/4's and a 13/15/17/20/23/26/30 freewheel in the back. It's not even close to an exact half step ratio to the crankset, but you can still feel a bit of a half step difference. This '82 614 came from the factory with a 6spd the averaged out around 1.08'something. I forget the exact numbers, but this according to the catalogue on the vintage Trek website. So, I would imagine not everyone made such a fuss about it. Maybe I am making too big of a deal about it and just oughtta get out and ride.
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Old 04-10-10, 05:26 PM
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Get out and ride before the sun goes down. Then get out your pocket calculator and a beer...
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Old 04-10-10, 07:45 PM
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>"The other issue is all the big jumps in shifting. I suppose 3 tooth jumps is just fine, but the others are rather large. Would the fact that the cassette cogs are ramped and all help offset this?"

Go for it. I don't see any reason why you'd have difficulty shifting between 28T and 34T cogs especially with ramped teeth, assuming your derailleur can handle a cog that big in the first place. I would also think that a 50/13 high gear will be more frequently useful than a 50/12, at least on 27" or 700C wheels. (650B, now that's another story.)

Half-steps are difficult to set up with anything other than the "perfect" 5-sp. freewheel of 13/16/20/25/31, limited as we are to whole numbers of teeth. As you are discovering, if you're off even a little, you get big holes and near-duplicates, the very thing that half-step gearing is intended to prevent. The "best" 7-sp. is 13/15/17/20/23/27/31 but even then, the ratio 15:13 is much bigger than 17:15. Anything starting with 13/14... will end up with a largest cog too small for a good low gear, especially since the chainrings will have to be something like 48/50. The other drawback is that when you're in the large-13 combo, you can't just half-step down to small-13 because that makes a cross-chain situation (although since you're not going to be in the 13T with either chainring more than a few minutes a year, perhaps it doesn't matter much.)

Note for that half-assed-perfect 7-sp., the correct chainrings are 50/46 (not 45.) Nowadays finding odd-size chainrings to replace the stock ones is very difficult unless you have TA Cyclotouriste cranks (no longer made) and a source for the still-available (in theory) TA chainrings.

Half-step gearing easily disappoints if set up using whatever cogs and rings you happen to be able to get a hold of. Fortunately, the more cogs you have, the less you really need to worry. Just go for a low-enough low and a high-enough high. A 7-sp. beats a 6 just because a duplicate or two has less detriment to your ability to find the perfect gear for the conditions.
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Old 04-10-10, 08:15 PM
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I think half step set-ups are best with close range frweewheels. I think common set-ups were 49/52 with 14-26 freewheel(5 speed). My first racing bike had 49/52 with a 15-24 freewheel. Had to use a 15 for Junior gear restriction. If you need alpine gears then throw a 36 on a triple front crankset, but keep the freewheel close range.

Three tooth differences on the chainrings seem to work best. How would a 45/48 work for you?
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Old 04-10-10, 09:01 PM
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^ I think a lot of elderly coronary arteries just went into spasm contemplating a "low" gear of 49 driving 24!
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Old 04-10-10, 10:06 PM
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^Thats a 55 inch gear. I'm a flatlander, we dont use anything below 70 gear inches.
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Old 04-10-10, 10:18 PM
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Originally Posted by big chainring View Post
^Thats a 55 inch gear. I'm a flatlander, we dont use anything below 70 gear inches.
Divide 55 in half and I'm interested. Went up this today....



With 70, or a 55 for that matter, I'm pushing not riding.
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Old 04-11-10, 12:16 AM
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Originally Posted by sailorbenjamin View Post
Just noting that 1.116% and 1.106% are only a tenth of a percent apart. I guess I'd like to know what kind of tolerances to shoot for.
I just went a stuck a 11-34 7 speed on the back of my Trek 613 and didn't think too much about it. Now I'm thinking I shoulda thought about it.
It doesn't take much deviation from the pattern before you have a gear pair that are only one gear inch apart.
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Old 04-11-10, 12:29 AM
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Originally Posted by thook View Post
Since I've posted in the "show your 1/2 step" pics thread, I've done a lot of calculating and noticed it can be kinda hard to half step with 7spd's or more and still get a useful build with a wide range. I guess that's why it's vintage stuff.

Questions....

I've decided to only half step (for now) the Trek and Dawes Galaxy I have. I've really wanted to try and keep the Trek with it's original crank at 28/45/50, but it seems a 7spd cassette is impossible. At best I can build a 6spd, but I question the shiftability of such a build.

To illustrate...

At 45/50, that's give a ratio of 1.111%. This means an average of 4.2 tooth jumps in the rear. What I've come up with is 13/16/19/23/28/34. That comes to an average 1.106%. That's undershooting a bit. Or, 12/15/19/23/28/34. That comes to 1.116%. Overshooting a bit. Plus, the 50/12 is @ 112.5 gear inches. Pretty high, unless I have a nice hill to get going on. So, for the most part I'd be using the 45/12 combo. The other issue is all the big jumps in shifting. I suppose 3 tooth jumps is just fine, but the others are rather large. Would the fact that the cassette cogs are ramped and all help offset this? And, would the fact that the numbers don't match exactly in either cassette option make that much of a difference? I think if I even dropped the granny down to a 26, I'd be even better (wider range on the low end), but anyway....

It'd be nice if someone just said,"Oh yeah.....your fine.", and I could run with it, but facts is facts. Shoot me straight, please.
What one is really looking for in a half step is to have an equal percentage jump from gear to gear with no wasted gears. it is possible to get this even progression with the gears being too close in the lowest or easiest gears. I think any step jump lower than 3 gear inches is probably too small a jump. But with this as a bottom end criterion, you will still end up with steps perhaps up to 10 or more gear inches at the top end. But this is ok, if the ratios are about the same.

If you want to make a 7-speed half-step, you should look at a 50/46 or 50/47.
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Old 04-11-10, 10:28 AM
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Many years ago I was riding 52/42 and 14/16/18/21/24 but lots of times I did not have the needed gear. I seldom used the real high gears so I did hours of calculations and decided to change cranksets and went to a 42/34 combo. I had 10 distinct gears and I had the ratios that I needed 95% of my riding miles. Since I am not a masher I rarely miss the big gears and never looked back. I now live in the low hills of TN and use mtb triples and love them. I have one bike set up with road triple but it is not as enjoyable to ride in the hills though it is great in more flat country. My local rides are better with the mtb triples.
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Old 04-11-10, 10:32 AM
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Half-steps are difficult to set up with anything other than the "perfect" 5-sp. freewheel of 13/16/20/25/31, limited as we are to whole numbers of teeth. As you are discovering, if you're off even a little, you get big holes and near-duplicates, the very thing that half-step gearing is intended to prevent. The "best" 7-sp. is 13/15/17/20/23/27/31 but even then, the ratio 15:13 is much bigger than 17:15. Anything starting with 13/14... will end up with a largest cog too small for a good low gear, especially since the chainrings will have to be something like 48/50. The other drawback is that when you're in the large-13 combo, you can't just half-step down to small-13 because that makes a cross-chain situation (although since you're not going to be in the 13T with either chainring more than a few minutes a year, perhaps it doesn't matter much.)

Note for that half-assed-perfect 7-sp., the correct chainrings are 50/46 (not 45.) Nowadays finding odd-size chainrings to replace the stock ones is very difficult unless you have TA Cyclotouriste cranks (no longer made) and a source for the still-available (in theory) TA chainrings.
Your calculations are correct, but finding a 31 tooth cog is impossible, and 27's are not too common. I have been running only a 3-tooth jump on the front rings (45-48, 44-47, or 42-45) on my 7-speed half-step set ups and that seems to work best for me (running 13-30/32 on the rear-end). I am also running 4-tooth front rings on some 13/14-28 six speeds becasue the rear derailuers won't handle larger cogs.

I have found that 7-speed is pretty much the most you can really do a half-step. I moved to Alpine gearing on 8-speed and above, but get frustrated because the middle of the gear range, the one you would expect to be in and through the most often, is stuck between the large and small rings. To compensate, you wind up with overlap between the two by a couple of gears. By doing this, why bother with 8/9-speed when you got the same gears with 7? Pondering this makes me inadvertently come to the same conclusion as Grant Peterson about not needing more than 7-speeds in the back

I have made a spreadsheet which figures all of this out for 5 to 8 speed rear ends, but I do not know how to post it here. It uses commonly available freewheel/cluster cogs, and all chainrings 32-55T.
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Old 04-11-10, 12:57 PM
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Originally Posted by sailorbenjamin View Post
Get out and ride before the sun goes down. Then get out your pocket calculator and a beer...
Haha.....well, I atleast had the beer.

Thanks.


Originally Posted by conspiratemus1 View Post
>"The other issue is all the big jumps in shifting. I suppose 3 tooth jumps is just fine, but the others are rather large. Would the fact that the cassette cogs are ramped and all help offset this?"

Go for it. I don't see any reason why you'd have difficulty shifting between 28T and 34T cogs especially with ramped teeth, assuming your derailleur can handle a cog that big in the first place. I would also think that a 50/13 high gear will be more frequently useful than a 50/12, at least on 27" or 700C wheels. (650B, now that's another story.)

Half-steps are difficult to set up with anything other than the "perfect" 5-sp. freewheel of 13/16/20/25/31, limited as we are to whole numbers of teeth. As you are discovering, if you're off even a little, you get big holes and near-duplicates, the very thing that half-step gearing is intended to prevent. The "best" 7-sp. is 13/15/17/20/23/27/31 but even then, the ratio 15:13 is much bigger than 17:15. Anything starting with 13/14... will end up with a largest cog too small for a good low gear, especially since the chainrings will have to be something like 48/50. The other drawback is that when you're in the large-13 combo, you can't just half-step down to small-13 because that makes a cross-chain situation (although since you're not going to be in the 13T with either chainring more than a few minutes a year, perhaps it doesn't matter much.)

Note for that half-assed-perfect 7-sp., the correct chainrings are 50/46 (not 45.) Nowadays finding odd-size chainrings to replace the stock ones is very difficult unless you have TA Cyclotouriste cranks (no longer made) and a source for the still-available (in theory) TA chainrings.

Half-step gearing easily disappoints if set up using whatever cogs and rings you happen to be able to get a hold of. Fortunately, the more cogs you have, the less you really need to worry. Just go for a low-enough low and a high-enough high. A 7-sp. beats a 6 just because a duplicate or two has less detriment to your ability to find the perfect gear for the conditions.
Yeah.... I had noticed that, when calculating, the higher the numbers being divided, regardless of the difference, the lower the resulting percentage (eg. 13/15 > 30/32)

One of the reasons I've been stuck on the idea of half stepping to a cassette in the rear on this rig is that I was told that freehubs are much stronger than freewheel hubs. I know from my own experience that they certainly shift better, and one can go down lower in tooth numbers, atleast. This lending towards a wider range to play with, of course. My lowest toothed freewheel gears are at 13. On the higher numbers side, I've seen the monster 38 FW cogs for sale on ebay, which would be fun to play with and give even more range, but then I'd need a monster rear derailleur to use it....haha. Pfffth! So, the cassette is the direction I've been trying to go in. Plus, that's the hub style on the only set of 700c touring wheels I have. I just don't feel like rebuilding to a freewheel hub, either.

One of the best 7spd HS set ups I've seen is 46/42/24 - 12/15/18/21/24/28/34. Lots of low and plenty of high. I could do that with a combination of Shimano and SR chainrings I have, but I've been trying to stick to the stock Sugino stuff........as I've mentioned. Now, if I had a Sugino 46 outer ring, I'd be much more inclined to do this. I'm still holding out because the Sugino finish is so much nicer than the Shimano anodizing. Note that in the end I may finally give up altogether on the personal satifaction of appearances and do the practical thing. Or, just as you encouraged, go for it.

Which comes to the other suggestions made here............

Last edited by thook; 04-11-10 at 12:58 PM. Reason: wanted to add something....thanks
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Old 04-11-10, 01:11 PM
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Originally Posted by big chainring View Post
I think half step set-ups are best with close range frweewheels. I think common set-ups were 49/52 with 14-26 freewheel(5 speed). My first racing bike had 49/52 with a 15-24 freewheel. Had to use a 15 for Junior gear restriction. If you need alpine gears then throw a 36 on a triple front crankset, but keep the freewheel close range.

Three tooth differences on the chainrings seem to work best. How would a 45/48 work for you?
You were half stepping race bikes? Didn't realize anyone was or would be doing that. I can see the implications therein. Unfortunately, I don't have much room for play with the SR Super Custom crank on my Lotus. 118 BCD and only 52/47/42/40/36 rings to work with there. I wonder if SR made 49 toothed rings!?!?!?

I agree about close freewheel ranges. I have a 5spd Suntour ProCompe with 14/17/21/26/32 and it shifts like total crap right in the middle where I need it to shift well. I was just wondering if the cassette cog ramps would eliminate that problem.

And, yeah....I do need alpine gearing. Mount Gaylor is like the pinnacle of cycling accomplishment around here. I happen to live right on the foothill of it. And, I've tried coming up with a good match for 45/48, but @ 1.067 to a 7spd with a low of 34 and a decent high end is not working for me. Haven't tried a 6spd or anything, though. Got any examples?

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Old 04-11-10, 01:48 PM
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Originally Posted by Road Fan View Post
What one is really looking for in a half step is to have an equal percentage jump from gear to gear with no wasted gears. it is possible to get this even progression with the gears being too close in the lowest or easiest gears. I think any step jump lower than 3 gear inches is probably too small a jump. But with this as a bottom end criterion, you will still end up with steps perhaps up to 10 or more gear inches at the top end. But this is ok, if the ratios are about the same.

If you want to make a 7-speed half-step, you should look at a 50/46 or 50/47.
You've mentioned this before, and I'm sure you're probably right. 47's not going to happen with 110bcd, though, and I'm still dancing around putting any Shimano rings on this Sugino crank. I have two Shimano 46 outer rings, but atleast one has to go on the mtn bike....haha. Meh.......I did see a Sugino inner 46 on ebay the other day. I just couldn't bid on it.

I guess I should ask one more thing since this little factor may determine alot of my decision here. Any one know if a Cyclone MkII Gt derailleur will work on 34 tooth cog? And, what would be the chainwrap capacity on it?
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Old 04-11-10, 02:09 PM
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Ah dang it.......according to what I just found the RD in question will only handle 34/36 max of wrap and a 32 tooth cog max.

Okay.....time for a tranquilizer.
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Old 04-11-10, 02:15 PM
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To find the widest range half-step, you first have to find the widest range freewheel you can get, and which has the most even fractional progression. I think Shimano makes a 13/15/17/19/21/24/28. I know I've seen a Sachs 12/28 and numerous others, but I haven't analyzed them all.

The mean step ratio for the Shimano is 1.136. It needs a chainwheel ratio of 1.068. If you have this freewheel and build it with a 50/47 crankset, you'll get a high gear around 104 and a low of 47, with a 27 inch actual diameter wheel.

If you can custom make an 11/13/15/18/21/25/30, you'll have a mean ratio of 1.182, and a total ratio of 2.73. The required chainwheel ratio is 1.091. For a 100 inch top gear you need 41 tooth large chain ring. Dividing by 1.091, you need a small chainring of 38 teeth. Again assuming a 27 inch diameter, you'll get a gear range from 34 inches up to 101 inches. It's not easy to make this, but it would be cool.

To really max out the range, a mathematical possibility is 11/13/16/19/23/28/34, for a mean ratio of 1.207 and a total ratio of 3.091. This requires a chainwheel ratio of 1.103. Using a 42 tooth large chainwheel for a top gear of 103, you'll have a small chainring of (again) 38 teeth and a low gear of 30 inches.

Many riders would see these as adequately wide ranges at least for some conditions, but you can add a granny ring down to 22 teeth if you really need it. With this last one, that would give a deep granny of 17 inches. But these are just mathematical exercises, and I haven't tried them. I'm planning to try one based on my 13-28.
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Old 04-11-10, 02:24 PM
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Wait.....I don't care what Disraeligears or even Suntour says. I've had this bike set up with the 50/45/28 and the ProComp 14-32 before and it handle everything just fine. The shifts in the back sucked, but that was due to the freewheel. What gives here?

Oh, and apparently if my RD hanger is 32mm or longer it can do the 34. But, I'd have to drop the top chainring down in size for chainwrap.

Anyway, anyone got opinions on what I've just posted in relation to CW and capacity?
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Old 04-11-10, 02:53 PM
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Originally Posted by Road Fan View Post
To find the widest range half-step, you first have to find the widest range freewheel you can get, and which has the most even fractional progression. I think Shimano makes a 13/15/17/19/21/24/28. I know I've seen a Sachs 12/28 and numerous others, but I haven't analyzed them all.

.
Keep in mind I'm using a cassette on the 700c wheels I mentioned. Right now it's on the 27"s, but I'm wanting to change that. Afterall, I bought some 32mm Panaracer TG's brand new at half cost. So, I gotta use'm....right?

Okay, so I'm limited to what I have right now. I don't have a 41 tooth chainring. I do have 2 @ 42, but one is an SR with 118bcd and the other is strictly an inner ring.........although @ 110bcd. I say strictly because it's kinda offset in how it fastens to the crankarm. The tabs, that is, are offset. It mates originally to a Sakae CR crankset. Maybe you've seen them before? They have the sort spiraling pattern to them?

Anyway, I could run that 45 as the outer ring (given what I've just learned about the GT's capacities) and the "offset" 42 as the inner with a 24 tooth granny. Then run 13-28? I have 2 oddly numbered HG cassettes and one evenly number HG cassette. So, I could easily build 13-28. It's kinda low on the top, but I don't suppose that's the worst thing in the world.
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Old 04-11-10, 03:29 PM
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Wow......someone had to throw derailleur capacity into the mix....lol.

Looks like my troubles are not over. If I can't squeeze my vintage gear into this little box, I'm going to use my Shimano Deore DX gear and put all my Cyclone/Sugino stuff on the Dawes. Then, I'll have some Suntour BL gear I won't know what to do with...haha.

Later, chaps.
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Old 04-11-10, 11:09 PM
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Originally Posted by thook View Post
Keep in mind I'm using a cassette on the 700c wheels I mentioned. Right now it's on the 27"s, but I'm wanting to change that. Afterall, I bought some 32mm Panaracer TG's brand new at half cost. So, I gotta use'm....right?

Okay, so I'm limited to what I have right now. I don't have a 41 tooth chainring. I do have 2 @ 42, but one is an SR with 118bcd and the other is strictly an inner ring.........although @ 110bcd. I say strictly because it's kinda offset in how it fastens to the crankarm. The tabs, that is, are offset. It mates originally to a Sakae CR crankset. Maybe you've seen them before? They have the sort spiraling pattern to them?

Anyway, I could run that 45 as the outer ring (given what I've just learned about the GT's capacities) and the "offset" 42 as the inner with a 24 tooth granny. Then run 13-28? I have 2 oddly numbered HG cassettes and one evenly number HG cassette. So, I could easily build 13-28. It's kinda low on the top, but I don't suppose that's the worst thing in the world.
I was just trying to provide some illustrations.

if you want to see what some of the options are with a 45/42, fine, I can show you some. I can't guarantee to only tell about what you can make with your hardware on hand, because I don't know what you have or don't have, or if you're willing to hunt on Ebay for the good, cheap solutions. But first you have to identify a small group of possible solutions. For that you need to kinda become your own designer.

PM me your email address and I can email you my spreadsheet for designing half-steps.
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Old 04-12-10, 12:03 AM
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45/42 on a 7-speed is what I am running on two rigs and I like it very much.
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Old 04-12-10, 08:25 AM
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Originally Posted by thook View Post
Since I've posted in the "show your 1/2 step" pics thread, I've done a lot of calculating and noticed it can be kinda hard to half step with 7spd's or more and still get a useful build with a wide range. I guess that's why it's vintage stuff.

Questions....

I've decided to only half step (for now) the Trek and Dawes Galaxy I have. I've really wanted to try and keep the Trek with it's original crank at 28/45/50, but it seems a 7spd cassette is impossible. At best I can build a 6spd, but I question the shiftability of such a build.

To illustrate...

At 45/50, that's give a ratio of 1.111%. This means an average of 4.2 tooth jumps in the rear. What I've come up with is 13/16/19/23/28/34. That comes to an average 1.106%. That's undershooting a bit. Or, 12/15/19/23/28/34. That comes to 1.116%. Overshooting a bit. Plus, the 50/12 is @ 112.5 gear inches. Pretty high, unless I have a nice hill to get going on. So, for the most part I'd be using the 45/12 combo. The other issue is all the big jumps in shifting. I suppose 3 tooth jumps is just fine, but the others are rather large. Would the fact that the cassette cogs are ramped and all help offset this? And, would the fact that the numbers don't match exactly in either cassette option make that much of a difference? I think if I even dropped the granny down to a 26, I'd be even better (wider range on the low end), but anyway....
Actually, I think you are mostly fine. Your 13-34 6-speed idea, if you have those cogs, is pretty good and I think it's mathematically a good match to a 50/45. It would give you a non-granny range of 43 to 104, which is pretty good. The gear inch steps are 4 inch smallest to 10 inch largest.

With your 12/34 idea, which also is a good match for 50/45, you'll get a range 43 inches to 113 inches. If you want the same 104 or so as the 13/34, you'll have to get a 46/41 pair. However, you didn't think that was practical.

Shimano (on the Harris site) has a 7-speed cassette, 13/15/17/20/24/29/34. That will get you a 52 inch to 108 inch range with a 50/46 chainring set. Having 7 cogs versus 6 pulls in the chainring ratio a bit, resulitng in a 4-tooth chainring diff rather than the 5-ring. Then because the small ring is one tooth bigger, you lose a little bottom end gear. Again the linear progression of this cassette is pretty good. Gear inch steps are 3.2 inch smallest up to 8.3 inch biggest. So another benefit of the 7-speed over teh 6 is closer steps. The transition to granny is at the 20 tooth cog for a 46 inch gear. I'd go for this one. You'll need to buy a cassette and a chainring, but this is all off-the shelf.
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Old 04-16-10, 04:09 AM
  #25  
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Originally Posted by Road Fan View Post
I was just trying to provide some illustrations.

if you want to see what some of the options are with a 45/42, fine, I can show you some. I can't guarantee to only tell about what you can make with your hardware on hand, because I don't know what you have or don't have, or if you're willing to hunt on Ebay for the good, cheap solutions. But first you have to identify a small group of possible solutions. For that you need to kinda become your own designer.

PM me your email address and I can email you my spreadsheet for designing half-steps.
Oh, I know that Road Fan. And, believe me........I'm appreciating all the help I'm getting from you and everyone.

I've been doing some homework a little here and there and would like to share a bit, but I'll have to post it all another time when I have more time.

PM coming promptly......

Later
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