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Gearing Questions II

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Old 12-12-17, 08:54 AM
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WNCGoater
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Gearing Questions II

I had another thread asking about gearing that got lengthy and this thread, while related, is a bit more specific.

So I've ended up with a 2017 Marin Four Corners. It has a 9 speed, 11/32 cassette and a 50/39/30 crankset on front. Having a ten speed 50/34 X 12/30 on my road bike, I can see for a touring bike, especially in mountainous areas, I haven't gained a great deal in climbing gear. Yes, it is a lower gearing, but considering this bike may see more climbing, I would like to investigate lower climbing gears. The 50t front ring is also no real advantage in front. (All of which a number of you indicated on the last thread)
So, to add versatility I see two possible options but I'm no mechanic or gear guru.

Can I remove the 30t inner ring and replace it with a Shimano 24t inner ring? Since that isn't a great jump, would it be reasonable to expect the rear derailleur to take up the slack? Here is a link to a chainring.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Only thing, that is considered a 10 speed and not sure if that is compatible.

Otherwise, I'm not against replacing the whole crankset, but I see not much readily available that would meet the need, except in "mountain bike" specific. Not sure if that would matter. I did find this:
https://www.amazon.com/dp/B002PTMOTE...24S&th=1&psc=1

It is 175mm x 48/36/26t 9 speed. I believe this is what I need, and I could just switch it out.

This seems a simple solution, though as stated, I'm not a mechanic and don't know if there is anything that would make this NOT work. I realize the BB may need to be changed or may need to shorten the chain?
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Old 12-12-17, 11:30 AM
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I don't know what drivetrain your bike has or whether it has enough capacity for the range you're suggesting. Going from 20 teeth to 26 teeth is quite a jump on the front ring though.

That said, 30x32 is a much lower gear than 34x30, and outside of fully loaded expedition touring, you will probably find 30x32 to be plenty. My road bike has a triple and it has 30x25 as its highest gear. My touring bike has 26x30 (trekking crankset like you're suggesting) and admittedly, I do use that even when empty, but I'm not sure I'd need any more than that unless I had a lot of weight on board.

If I were in your shoes, I'd probably try to install a mountain rear derailleur and a 9 speed mountain cassette, which was the common way to get lower gears before the pull ratios of road and mountain became different. Many touring bikes had mountain rear derailleurs and cassettes with road shifters before Shimano rendered them incompatible. It would be far easier to install a 36 tooth in the rear and perhaps a longer/new chain than to replace an entire crankset. If that wasn't enough, you can always go to the 48-36-26 crank afterward, which you'd probably find has a more useful range than even the 39 if you're a slower rider like me.
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Old 12-12-17, 12:15 PM
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For some reason, Amazon is not working on my computer right now so I can't see the chainring you cited.

But I can say that on two of my touring bikes I took off the 30T granny gear and put on a 24T. The sprocket was 5 arm 74mm BCD. Both of these bikes have Campy triples. I used a cheap generic 24T sprocket, not matched to the ramps and pins on my bigger rings.

That is a bigger range for chain wrap than you have now, my rear derailleur is a long cage XT and it does not quite take up all the chain but it is close enough so I use it.

I use friction front shifters, older flat sided front derailleurs on this setup. I have no idea if indexed shifting or if your front derailleur would work.

Two photos of two of my touring bike drive trains. My triple cranks are 46/42/24 (the 46/42 is half step gearing). Cassettes are eight speed 11/32.

I use chain catchers, not sure if they are necessary or not but it seemed like a good idea.

My upshift from the 24 to the 42 is not always smooth but for you from a 24 to a 39 would be a little less extreme. The downshift to the 24 is always just the way I want it.

I am running this gearing on bikes used for loaded touring. If you consistently have hills steeper than 8 percent grade for an unladen bike this might help. But if your hills are not that steep this might be more extreme than you really need unless you are carrying a lot of weight. You might consider a 26 instead, as that is less extreme.

Good luck.
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Old 12-12-17, 01:21 PM
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Realistically, most of my climbs on my regular routes do not exceed 8% except for perhaps some short 100' sections. I can climb most anything I normally ride with my road bike gearing.
But I would like to do some riding on the Blue Ridge Parkway. I rode the new Marin up a long 8 mile climb up to the BRP several weeks ago and there were a few steeper sections that the current gearing was just adequate. I should mention I'm not a powerful climber, preferring to sit and spin slowly up.

What I had on that Amazon link was a 24 tooth 4 bolt 64mm chain ring which seems to correspond to what I have. It's $16 bucks and seemed a cheap experiment to see if I can drop the 30t inner ring and replace it with the 24t. But I wasn't going to waste time to attempt it if someone said, "No way, that won't work".

In the meantime, I haven't even considered a Mtn rear cassette.

And to add, I DO want to try some touring perhaps if only overnighters. I think with a load and steep climbs lower gearing may be a necessity.
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Old 12-12-17, 05:02 PM
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Originally Posted by WNCGoater View Post
Realistically, most of my climbs on my regular routes do not exceed 8% except for perhaps some short 100' sections. I can climb most anything I normally ride with my road bike gearing.
But I would like to do some riding on the Blue Ridge Parkway. I rode the new Marin up a long 8 mile climb up to the BRP several weeks ago and there were a few steeper sections that the current gearing was just adequate. I should mention I'm not a powerful climber, preferring to sit and spin slowly up.

What I had on that Amazon link was a 24 tooth 4 bolt 64mm chain ring which seems to correspond to what I have. It's $16 bucks and seemed a cheap experiment to see if I can drop the 30t inner ring and replace it with the 24t. But I wasn't going to waste time to attempt it if someone said, "No way, that won't work".

In the meantime, I haven't even considered a Mtn rear cassette.

And to add, I DO want to try some touring perhaps if only overnighters. I think with a load and steep climbs lower gearing may be a necessity.
I have gambled on many setup changes, I wish they all cost $16 or less. That is a pretty low cost experiment. I think all the other surprises that you might come across I mentioned above.

I think the worst that could happen is that your front dérailleur does not play well with it or you find that when you are using the 24T sprocket that you can't use the smallest sprockets on the cassette if the rear dérailleur does not take up enough chain. But those gears are cross chained and might be duplicated with other gears you already have. I assume that you have verified that the chainring fits on your crank.

I am doing a van supported guided tour in April, one day is all uphill. Our luggage is hauled in a van, so I won't be loading down the bike. I planned to use a bike with a 30T granny gear on the triple. I looked at the elevation plot for that uphill day and I concluded that if I used the bike that I planned to use, I would probably swap that 30T out for a 24, at least for that one day. Or, might instead use my Titanium touring bike (drive train photo above) that already has a 24T granny.
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Old 12-12-17, 10:50 PM
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it should work assuming the bcd is the same. 10 speed is backwards compatible.

One thing to check is the chain wrap on the back derailleur. Also, I would definitely go to 46 or 44 big chainring if it's available
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Old 12-12-17, 11:33 PM
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Try out what you have...

...and adjust it when you see what does not work. Don't overthink this and consider everything you might do at some point in the future.

30x32 is plenty for climbing, and if it is not for you you might end up with nothing worse than walking/pushing a few steps. Find out yourself what works for you.

(If it was my bike I would probably install a 46/30 or 44/28 double and keep the standard 11-32 cassette.)
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Old 12-12-17, 11:48 PM
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I'd put on a FC-5502 Outer Chainring B-Type 130 BCD x 53T to replace that 50. It'll work fine with a 39T 10 sp. middle ring, which is what you probably have. Then replace the 30T with a 26T if you need more climbing cadence, but my guess is that you won't.
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Old 12-13-17, 12:58 PM
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Okay, thanks for all the tips. To start I'll probably try replacing the 30t inner with the 24t I have and see what happens. Going forward, I can decide which is the best direction to go based on more experience on some steeper climbs and climbing with a load.
Thanks again.
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Old 12-14-17, 02:32 AM
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Originally Posted by WNCGoater View Post
So I've ended up with a 2017 Marin Four Corners. It has a 9 speed, 11/32 cassette and a 50/39/30 crankset on front. (...)

Can I remove the 30t inner ring and replace it with a Shimano 24t inner ring?
If your existing crankset is a 50/39/30 then most likely it's a road triple such as 105 5703 or Ultegra 6703. Those are 110/74 BCD. Thus your inner ring needs to use a bolt circle diameter of 74 mm, not 64 mm like the MTB ring you have linked to.

Yes, you can replace the 30T with anything as low as a 24T but the smaller you go the bigger the risk of dropped chains on downshifts. This is not normally an issue on a 28T, but more so on a 24T. A chain catcher may become advisable.

With regards to ramps and pins, those take effect on upshifts, so a plain ring will do fine for the inner, provided it has the right dimensions.

Replacing the road triple crankset with a MTB triple may or may not work with your existing road FD. In some cases the FD may have trouble reaching far enough out to shift to the big ring. MTB triples usually have a chain line of 47.5 mm vs. 45 mm on a road triple. Also the channels in the cage of triple FDs are very sensitive to tooth count differences. If your new crankset has a different tooth count difference from your old one, your FD may no longer work properly. If you find that the FD doesn't work with a MTB crank then the next issue will be that road and MTB FDs use different cable pull.

So as others have suggested, upgrading the RD to a long cage 9-speed MTB RD and using a larger cassette (e.g. 11-36) is the more straightforward route.

A year ago I switched my crankset to a "compact plus" double (42/26T) with a FD CX70 front derailleur. It's a Sugino OX601D and it works great with what otherwise is a Shimano 11-speed setup. It gives me gears as low as on my previous 46/34/24T touring triple with 12-30 cassette (10-speed), but with much better shift quality. The only drawback was cost.
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Old 12-14-17, 04:25 AM
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My dear old Europa (before she died ) had an Ultegra triple crankset - 50/39/30 - just standard Shimano fare.
The front derailleur is Ultegra but from about a decade ago.
The rear cassette is a 9 speed 11-32

At one point, I took off the 30 and fitted a 26.
I already had a Shimano mtb rear dr (maybe an XT? but I don't remember) - this was replaced with a 105 rear dr (medium reach from memory) when the old one packed up.

I NEVER had troubles with this. I needed the 26x32 because my ride home featured a 10%+ climb. Equally, going the other way, I had to ride down that slope in the same lane as the traffic which is where the 50x11 was useful as I could maintain the 70 km/hr the cars were doing... despite the 60 km/hr speed limit.
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Old 12-14-17, 07:41 AM
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Seems like confirmation to try a smaller inner ring and see if the existing components can handle the shifting. If so, great! If not, then it will be time to consider more radical changes...or decide to go with what I have.
I'll have to go back and re-check but I thought I measured 64mm between the ring bolts.
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Old 12-14-17, 08:42 AM
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Distance between adjacent bolts is not the diameter of the bolt circle.

With 4-bolt cranks w/ square bolt pattern, the diagonal of the square is the diameter, however.
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Old 12-14-17, 05:11 PM
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For my 9 speed 30-39-50 with 11-32, the easiest thing to do was use a Deore long cage derailleur with a 12-36 cassette as the cable pull for 9 speed is the same for rear derailleurs.

Sora and Deore work great together out the back and you get a nicer climbing gear. I have a 26-36-48 trekking crankset and associated drivetrain compoments which I will put on my Specialized AWOL once the current Megaexo BB has given up the ghost, but for now, the 30-36 granny gear is okay.

Edit: I wrote the following with the Specialized AWOL in mind; however, the Marin 4 Corners is really similar, and the gearing on stock bikes is, in some cases, identical.



Lowering the Gearing on Drop Bar Adventure Bikes

Modern adventure touring bikes are commonly provided with Shimano Sora (9 speed) and Shimano Tiagra (10 speed) road groupsets, with some other components added on some builds, like FSA cranksets. The use of drop bars necessitates the use of road components, but on some models it leads to gearing that is much too high for an adventure touring bike required to climb paved and unpaved roads with a load. Some manufactures have recognized this, and have started to make some adjustments, but gearing remains problematically high on many adventure bikes, even with proactive measures from the manufacturers.

Thus, one of the most common questions I see here online is “how can I Iower the gearing on my bike?” It’s a good question, and one that is going to be asked increasingly, as adventure touring bikes become more popular. One can only hope that Shimano will listen, and produce an MTB groupset that is compatible with road shifters. Until that time, however, there are several things you can do.

These are ideas that you can use on your own, or more often, ideas that you can take to a bike mechanic to present to him or her as a solution to your problem. I initially wrote this based on a person starting with a Shimano Sora 3x9 drivetrain, namely a 30-39-50 crankset with an 11-32 tooth cassette shifted by STI levers, but I will try to include Tiagra here as well and 105/Ultegra etc in the future as I update the document.

1. You can use a mixture of SRAM road levers with MTB components.
SRAM Road and MTB components can play well together, allowing you to use STI-type shifting (SRAM double tap) with MTB drivetrain components. Some (note the “some”) SRAM MTB and Road components use 1:1 actuation, called “Actual Actuation” by SRAM, so SRAM road levers will work with MTB components. There is a wealth of information available on the Internet about mixing SRAM Road and MTB components.

2. You can mix Shimano road and MTB components.
9 speed MTB rear derailleurs work with 9 speed STI levers. With a front triple, either an FSA or Shimano 30-39-50 9 speed crankset, you can use an 11-36 or a 12-36 tooth cassette, shifted by a 9 speed MTB derailleur with a sufficient total capacity (an Alivio RD-M4000 for example) and a Shimano Sora STI lever. The 2017 base model and Expert model AWOLs use this configuration (30-39-50 crankset with 11-36 and 12-36 tooth cassettes).

The front derailleur is a different matter. Shimano road derailleurs have a different chainline to MTB front derailleurs, while road STI shifters have a different pull ratio to MTB gear shifters. People have kludged road triple front derailleurs to work with MTB triple cranksets, but shifting is never perfect. Please post pictures and notes if you make your AWOL work with a road derailleur and an MTB crankset.

There is a wealth of information online that you can look up on using MTB derailleurs with STI shifters.

You could also always go flat bar and use an MTB or Trekking drivetrain with trigger shifters. The AWOL has a lot of 29er MTB DNA, so the geometry can handle flat bars. With dropbars it has a short stem, so you can put a longer stem on it with flat bars and it becomes a rigid 29er or European style trekking bike.

Note for 2016 Specialized AWOL Elite owners and those with a front double with a 12 tooth difference or less: With the 46-34 crankset on 2016 Specialized AWOL Elite, you can use a Wolftooth Roadlink and a Sunrace 11-40 10-speed cassette, just those two things, because there’s only a 12 tooth difference between your front chainrings. Have your mechanic install the roadlink, increasing the effective length of your road derailleur, as well as the cassette and you’re good to go.

3. You can use MTB components with bar end shifters (9 or 10 speed indexed in the rear and friction in the front for both double and triple cranksets).
Microshift make bar end shifters that work with Shimano MTB components.

You could also combine rear 9 speed STI shifting with front bar end shifting. You could keep your rear STI lever to use with an MTB rear derailleur and use a bar end shifter to shift a front MTB derailleur on an MTB crankset. You could use the remaining STI lever as just a brake, or you could get a new non-STI road brake lever.

A Gevenalle Shifter is a road brake lever with a small shift lever attached to it. You could use one to shift an MTB derailleur up front with an STI shifter for the rear, or use two Gevenalle shifters, as they are sold in pairs.

Soma Gator bars are offroad dropbars with ends that accept MTB components (MTB bars are 22.2mm while road bars are 23.8mm). You could get a high rise stem and put some Soma Gator bars on your bike with their long ends loaded down with trigger shifters and MTB brake levers. You can put a small bar end at the top of the “hooks” and wrap it to give you a “hoods” hand position.


4. You can use other road components.
You could switch to a square taper bottom bracket and use a square taper triple crankset like a Sugino or an FSA model with a road chainline. The stock Surly LHT complete uses a system like this, namely a square taper bottom bracket with a Taiwanese OEM 48-36-26 road-type crankset, but I don't know how STI indexed shifting would work with such a set up, as the stock Surly bike has a Sora triple front derailleur like the AWOL, but it's shifted with a friction bar end shifter. The IRD Alpina-D front derailleur is often touted as a solution as a derailleur with a 45mm chainline optimized for smaller (48t/46t-26t/24t) road triple cranksets.

In this regard I do not know the correct type of square taper bottom bracket you would need for an your bike (68mm English thread is common, but there are a lot of different spindle lengths for the Shimano UN55. I think it’s a 113mm spindle for some triple cranks) or whether it would work with a 48-36-26 road crankset and STI levers, but it is an interesting possibility. Note that bar end shifting and square taper bottom brackets are quite popular for touring bikes as they are simple, easy to fix and commonly available off the beaten path.

5. Go 1x9, 1x10 and 1x11.
Shimano and SRAM both have 1x groupsets, but SRAM has a more gravel/adventure oriented 1x groupset (check out the AWOL Comp specs for ideas). SunRace, the Taiwanese company that bought Sturmey-Archer, continues to release wide range cassettes in uncommon speeds, such as 11-40 9-speed cassettes and 11-40 & 11-42 10-speed cassettes. If you used an 11-speed Shimano or Sunrace cassette, you could use one of the 11-speed Shimano rear derailleurs with a Wolftooth Tanpan, a device that allows you to use an MTB rear derailleur with a road STI lever.

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Old 12-14-17, 08:41 PM
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One of my bikes has the 52-39-30 triple. The 39 is perfect for flat to rolling rides, where I can stay in the 39 for most of the ride. On my local rides, with hills in the 200-300 foot high range, I rarely use the 52, only if it's a long shallow downhill that I want to pedal down. The 30-29 low is fine for even the 18% grades here, since those are short enough to stand up on.

My Campagnolo triple won't fit anything smaller than a 30, it's a "tripleizer" with the 30 bolted onto the 39. I've wished for lower gears than my lowest 30 front - 29 rear on some long climbs (and especially on gravel).

Triples
My preference is for closer range cassettes with the appropriate three chainrings. A small ring for the steeper climbs, and a middle ring to put my flat road cruising speeds just about at the top third of the cassette range. Then the big ring is for shallow downhills or big tailwinds. I like reasonably close shifts in the middle ring at my usual roads speeds. I wouldn't like a really wide range cassette to make up for a too-big chainring or rings.

I even have 12-25 cassette that I'll swap in for long rides without any steep climbs. It's really nice to have the exact cadence while cruising along.

Low enough?
I consider my gears low enough if I can stay seated and use quite light pedal pressure to keep moving. It might be a very low cadence, and I'm only going 3-4 mph, but I don't have to strain my leg muscles by mashing the low gear. My 30F-29R does this on at least a 10% grade, I'm not pressing very hard on the pedals at that fairly steep grade.

Your road bike's 34F-30R is 4.0 mph at 45 rpm.
Your triple's 30F-32R is 3.3 mph at the same 45 rpm. That's a big difference. A lot easier.
A 28F-32R is 3.1 mph at 45 rpm.
(I also like to compare what rpm will get me down to 3.0 mph. Much slower than that, and I'm really working hard to keep the bike upright.)

~~~

Try a 28 instead of a 30 chainring. An easy swap, and the derailleur "should" handle it. Your chain will be fine as-is.

Or the suggestion above for a new crankset 26-36-48. (But see the comment about mountain cranksets having slightly wider gaps between chainrings.) See how that 36 works for you, using the calculator.

For the Blue Ridge Parkway itself, you should be okay as-is. I don't think there's any grade steeper than 10% on the BRP. But since you live in the area, you may want to ride more of the side roads, and these can be way steeper.


Calculator
I like to try different combinations on Mike Sherman's Gear Calculator. All the charts update on the fly as you change gears or cadences.
Here's a 11-32 9-speed and 28, 30 and 39 chain rings. (I changed the calculator's 52 big ring to a 28 to get a direct comparison between a 28 and a 30 small ring.)

Link to this setup. The URL changes when you click "Bookmark this set" so you can save it and recall it later.

From the calculator:
I usually put "85-97" in the Speed Over RPM chart, to see flat road "spinning" speeds. But you are more concerned with long, steady climbing, which might be more in the 70-80 rpm range.

39 ring in blue, 30 ring in black, 28 ring in red.
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Old 12-15-17, 08:37 AM
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Originally Posted by PDKL45 View Post
...
You could also combine rear 9 speed STI shifting with front bar end shifting. You could keep your rear STI lever to use with an MTB rear derailleur and use a bar end shifter to shift a front MTB derailleur on an MTB crankset. You could use the remaining STI lever as just a brake, or you could get a new non-STI road brake lever.
...
On one of my bikes I have a rear brifter and for front I use a downtube shifter. That is another option.


Originally Posted by rm -rf View Post
...
My Campagnolo triple won't fit anything smaller than a 30, it's a "tripleizer" with the 30 bolted onto the 39. I've wished for lower gears than my lowest 30 front - 29 rear on some long climbs (and especially on gravel).
...
Keep an eye out for a good quality used Campy Race Triple, or Veloce Triple. Both use the same Campy square taper bottom bracket. If you have trouble finding a Campy bottom bracket, Origin8 makes a bottom bracket with the Campy taper. The two photos I had in post number 3 above, the first is a Campy Race Triple on a Origin8 bottom bracket (uses Shimano bottom bracket tools), the second photo is a Veloce triple on a Campy bottom bracket. I also have Mirage triple on two other bikes on Campy bottom brackets. I bought all of these enough years ago that I bought new, not used. But new ones are getting harder to find at a good price.
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Old 12-15-17, 01:57 PM
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Wow, great info! Thanks for taking the time. I think I'm going to print some of this out. Thank you again, very much!
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Old 12-15-17, 02:25 PM
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So this potentially could be as simple as putting a Deore Mtn bike rear derailleur such as
https://www.amazon.com/Shimano-RD-M5...eur&th=1&psc=1

And a 9 speed rear Mtn bike cassette such as
https://www.amazon.com/Speed-Cassett...ssette+9+speed

or...
Just put a 28t chainring on front in place of the 30t

Or maybe just keep what I got and pull off & rest if needed.
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Old 12-15-17, 05:24 PM
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Originally Posted by WNCGoater View Post
So this potentially could be as simple as putting a Deore Mtn bike rear derailleur such as
https://www.amazon.com/Shimano-RD-M5...eur&th=1&psc=1

And a 9 speed rear Mtn bike cassette such as
https://www.amazon.com/Speed-Cassett...ssette+9+speed

or...
Just put a 28t chainring on front in place of the 30t

Or maybe just keep what I got and pull off & rest if needed.
A 28 instead of a 30 chainring won't do much at all.

Regarding the 40T cassette, I have no clue what other components you would need but I am most certain that if you run a bigger cassette that you will need a longer chain to.

Is there some reason that you decided not to start your changes with the 24T chainring?
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Old 12-15-17, 08:16 PM
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Originally Posted by Tourist in MSN View Post
A 28 instead of a 30 chainring won't do much at all.

Regarding the 40T cassette, I have no clue what other components you would need but I am most certain that if you run a bigger cassette that you will need a longer chain to.

Is there some reason that you decided not to start your changes with the 24T chainring?
No, this is the first and simplest thing to try. I have a 24ring but picked up the wrong size. I got a 64 and needed a 74mm. Don't know how/why I had 64 in my mind but measured across the diagonal (per @HTupolev above) with a pair of calipers it measures 74.

There is a lot of info in this thread, and I am grateful for it, but it is a bit confusing trying to figure out what will work with what. Multiple solutions offered & I'm just trying to wade through it all. I don't have a problem working on the bike, repairing, changing components, adjusting, & rarely ever have had to get the LBS to do any work. But knowing WHAT to do and WHAT components that will work together, well, I am admittedly ignorant.

But yes, simply trying out to see if replacing the 30 front ring with a 24 is a cheap experiment and that is what I intend to do.

Thanks
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Old 12-16-17, 09:10 AM
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This may help.
https://www.sheldonbrown.com/cribsheet-bcd.html

and
https://www.sheldonbrown.com/gloss_bo-z.html

Note that 5 arm table has the 74mm, the 4 arm table has the 64mm. Shimano is making some asymetric cranks that are not covered on Sheldon's table but I do not know if any are triples.

All of my cranksets are older, thus five arm.

The Sheldon Brown website (he died a few years ago but others still maintain the site) have many good pages with basic information on bike maintenance and repair. So you may find good information there on other topics besides gearing. But sometimes it is a bit behind the times on newer equipment.
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Old 12-17-17, 07:52 PM
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Originally Posted by WNCGoater View Post
So this potentially could be as simple as putting a Deore Mtn bike rear derailleur such as
https://www.amazon.com/Shimano-RD-M5...eur&th=1&psc=1

And a 9 speed rear Mtn bike cassette such as
https://www.amazon.com/Speed-Cassett...ssette+9+speed

or...
Just put a 28t chainring on front in place of the 30t

Or maybe just keep what I got and pull off & rest if needed.
The Deore M591 may not work properly AFAIK, as it wants a largest cog of 28-34, rather than 36. An 11-40 cassette will not work with your current crankset either. By calculating total capacity (50-30=20; 40-11=29; 20+29=49), you would need a derailleur with a total capacity of 49, which doesn't exist. The largest you will find is a 10 speed XT trekking derailler with a total capacity of 47, but 10 & 11 speed rear derailleurs will not work with STI levers.

Shimano 9 speed stuff all plays together quite nicely out the back, though, and 12-36 cassette brings you in within the total capacity available (50-30=20; 36-12=24; 20+24=44) in Deore and Alivio 9 speed derailleurs.

Concretely, with a 9-speed 30-39-50 crankset shifted by Shimano Sora STI levers, you can use:

Rear Derailleur

Shimano Deore M592 Shadow 9 Speed Rear Mech; or

Shimano Alivio M4000 Shadow 9 Speed Rear Mech (steer clear of the T4000 trekking derailleur as the maximum rear cog is 34 teeth, while the M4000 can take 36; it's not a deal breaker, but the M4000 should be smoother).

Cassette

Shimano Alivio HG400 12-36 9 Speed MTB Cassette; or

Shimano Alivio HG300 12-36 9 Speed Cassette.

Chain
Use a 9-speed chain with 116 links (114 link chains may not allow for the 50-36 gear combo and might seize a 30-39-50 & 12-36 drivetrain in high-low combo).

Last edited by PDKL45; 12-18-17 at 12:09 AM.
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Old 12-18-17, 11:30 AM
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Originally Posted by PDKL45 View Post
The Deore M591 may not work properly AFAIK, as it wants a largest cog of 28-34, rather than 36.

Incorrect. I have been running a rear Deore M591 with a 11-36 cassette on one of my bikes for some 6+ years (roughly 12k miles). The B-screw allows for 36t in the rear with some room to spare, and shifting is great.



Originally Posted by PDKL45 View Post
By calculating total capacity (50-30=20; 40-11=29; 20+29=49), you would need a derailleur with a total capacity of 49, which doesn't exist.

Not a problem, since such a derailleur does not need to exist.
A sane and experienced rider won't need to use the 4 smallest rear cogs with the granny (nor the 4 largest rear cogs with the large chainring for that matter), meaning that the total capacity practically needed is much less than the calculation quoted.


Originally Posted by PDKL45 View Post
Use a 9-speed chain with 116 links (114 link chains may not allow for the 50-36 gear combo and might seize a 30-39-50 & 12-36 drivetrain in high-low combo).

Incorrect. More theoretical hogwash.
116 links is OK for 50/36 with up to 465 mm chainstay, which is a very rare breed of a bike. One of my bikes with 50/36 and 435 mm chainstay gets the full wrap with 112 links.
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Old 12-18-17, 07:08 PM
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Originally Posted by IK_biker View Post
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Not a problem, since such a derailleur does not need to exist.
A sane and experienced rider won't need to use the 4 smallest rear cogs with the granny (nor the 4 largest rear cogs with the large chainring for that matter), meaning that the total capacity practically needed is much less than the calculation quoted.
....
Agree with the concept but specifying four is a bit arbitrary. I try to avoid the two most cross chained gears for each chainring. That means that on my middle chainring on a triple I avoid the smallest and largest sprockets on the cassette. Thus my triple crank with an eight speed cassette instead of being a 24 speed is an 18 speed, where each chainring is used with six sprockets. Some of the six gears that I lose with my policy of avoiding cross chaining are duplicates, so did not really lose much.

But I still use enough chain links to make sure that if I accidentally shifted onto the big and big gear, I would not damage anything.
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Old 12-18-17, 07:15 PM
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Originally Posted by IK_biker View Post
Incorrect. I have been running a rear Deore M591 with a 11-36 cassette on one of my bikes for some 6+ years (roughly 12k miles). The B-screw allows for 36t in the rear with some room to spare, and shifting is great.
On your bike. One of the key factors in fitting a larger cog is the length of the hanger, which varies in both length and position between manufacturers. I've seen this lots of times.
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