HiYoSilver

I have this setup:

Triple TruVativ Elita ISIS, 30/42/52
derailleur Front: Shimano 105, Rear: Shimano LX
shifters Shimano 105, STI, 9
speedlevers Shimano 105
cassette SRAM 12-23.

Is it possible to create a new triple of 20/38/52 ?

Thanks in advance for your advice.

LordOpie

why not go with a stock mtb crankset. I think it's 22/32/44? Sure, you lose a lot on the downhills, but there ya go.

What're your goals? Is this doubling as a loaded down touring bike?

sydney

Assuming your granny ring has a 74BCD a 24 is the smallest and it may not shift well if at all since you are greatly exceeding the derailer capacity. A 26 granny often works. The 105 triple front may not handle the 38 very well.

Retro Grouch 

The truth is I don't know. There are a number of potential problem areas that I can anticipate.

1. I think to accept the 20 tooth granny gear, you're going to have to use a mountain bike crankset.
2. You will need to keep a road front derailleur to handle the 52. I'm not sure but you may find you drag the chain on the back of the derailleur cage when you're in the 20.
3. I wouldn't bet on what kind of shifting you are going to get from the 20 to the 38 using STI or going the other way for that matter. You'll probably have to use a chain watcher or something similar to keep from throwing the chain all the time.

HiYoSilver

Not sure of goals. I started commuting after setting up the bike as a smooth ride. It is more fun than I anticipated but I have lost low end gearing and wanted to finish configuring the bike with the option of loaded touring. Thus the idea of changing the triple. But for commute the 52 is almost too small on way home, it's a bit downhill and it's fun to fly.

22 would work. Thus, the 22/38/52 might work? The 38 is the most workable ring for the commute.

LordOpie

do you need the tighter gearing of the 12-23? What about keeping the crank, but get a 12-27?

late

or a 12-34.

Velo Dog

I'd ditch that 12-23 in a second, for something like a 12- or 13-28. I wouldn't use a 12-tooth cog once in 50 years.
There are several ways to approach this, of course, but here's what worked for me: A compact crankset, 46-36-24, and an 11-28 eight-speed in back (I don't need the 11, but that's how the cassette came). It gives me a high gear of 113 inches (yours is 117, but do you really use it?) and a low of 23 inches (yours is 35 now; with a 20 ring it would be 31). Assuming you can use a 28-tooth cog with your existing derailleur, about $30 would give you a low gear of 29 inches. You could also swap the small chainring for a 24, which I think (not sure) is the smallest that will fit on your crankset, for a low of 28 gear-inches with your existing cassette.

sydney

22 won't fit a 74BCD and I wouldn't even recommend a 24.Maybe a 26. Get a mtb RD so you can switch out to a 34 cog for touring and forget trying to work the whole business around that 12x23 cassette.

53-11 alltheway

If he has a LX rear derailleur already I would go with a 12-34 XT cassette......$65 at supergo.

HiYoSilver

so in summary you're saying go back to stock 11-32 cassette

53-11 alltheway

I thought you had a 12-23 cassette on there? Now that you tell me you already have a 11-32 cassette and a LX rear derailleur isn't that plenty low enough to go with a triple?

Your low gear will be 30-32!! I didn't use the gear calculator, but I'm guessing it may be lower than 25 gear inches!!

LordOpie

good call.

collegeskier

30-32 is give you 0.94 wheel revolutions per pedal turn whereas you get 0.87 for 20-23. That is a difference but it is a much cheaper option and will probably work better if you want the same gearing you would need a 34.5 mathametically but I would switch out the cassette, and if you want the ease for climbing and are itching to spend money get the tools to change the cassettes out then you have have the best of both worlds depending on what you need.

53-11 alltheway

He can't run a 20T chainring on 74bcd triple anyway. 24t is the smallest you can you.

HiYoSilver

53..

I do have a 12-23 cassette. I had the LBS swap out the std 11-31. My lowest gear currently is 36.0 inches. I'm dropping to about 55-60 rev on 2 short hills. Now if I start biking beyond just the commute, then a long hill might cause problems.


Dropping to a 24 chainring would make lowest 28.2 with current cassette. I need advise. I've heard for long road trips and loaded touring you need a granny in the neighborhood of of 20 GI.
I've heard CO has a few good mountains.

HiYoSilver

Oh, also what is the ideal % change in GI for smooth gear shifting. Currently I am running about 8.4% and it is feeling great. Some people have commented that 10.0% is ideal.

I am not in great shape and biking is still a good workout, even for just 5 miles. What do you think? Is the changing for smooth shifting a waste and it doesn't make much difference as long as you are between 8.4 and 10%, or what?

lala

Go double compact!

HiYoSilver

**********

sydney

Stay out of the Colorado mountains.

LordOpie

I didn't realize you were here (Location: 5280).

Ride the city trails: Cherry Creek, Platte, highline, c-470 and you'll be good to go when the snow melts next year. I'm not in good shape either and I have a bad knee. There are few few areas where I have any trouble with a 30-27. While you can ride the east side of the front range, it looks to be a snowy year, so even if you wanted to ride the mountains now, you'd need some good handling skills to deal with the snow and ice.

Oh, you do not need easier gears for long distance. Any gear you can spin over 5 miles, you can do (eventually) over much greater distances. I wouldn't worry about loaded touring until you're comfortable doing unloaded rides of >50miles.

If you ever wanna hook up for a ride, just PM me. I know, you're probably not very fast, neither am I.

HiYoSilver

Why? Maybe you should stay out of the ocean.

When you live along the front range of the Colorado side of the rockies, you have to enjoy the scenary.

My best ride so far was with a Gold Wing on I-70 thru the passes. I'm not ready for that with a bike. But look forward to the packing the bikes up and driving up higher into the mountains and taking a ride this fall.

HiYoSilver

Good to know the 30-27, i.e. 30 GI, is not low enough. I don't want to ride in the snow. Comfort biking. More like a short ride in the early fall next year.


Not concerned about loaded touring, but tired of fussing with gears. I would like to get an ideal setup for current and potential future needs and then stop messing with gears and just ride.

Problem is on those hills, I'm just barely pushing 5.5 mph and that's only because pushing so don't have to stand pedal or get off the bike. At that speed there's a problem with side to side stability, ugh.
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ok, thanks

LordOpie

Syd got told yo!

Careful, you may fall in love with pedaling so much that your motor will sit idly by. During the summer, I was riding my road bike and didn't get in but two motorcycle days (1986 BMW K75).