Jsnaggle

Building somewhat of an oddball bike setup from a 92' Bridgestone MB-1 that I snagged for $20 on Craigslist. I've got the original Ritchey Logic triple crank (172.5) but it only came with a single ring that was spent. I plan on running a 14-34 - 7 speed freewheel and already bought a 24t granny chainring since I would like to be able to climb anything in front of me and do some trail riding when off pavement. My question is what would be an appropriate size for the mid and outer rings? Would 24/38/48 give enough range? Wheels will be 26x1.5

niknak

48/38/24 would be fine. I like a gear inch range from the mid 90s to the high teens. Combined with the 14-34t cassette your bike would go from the high 80s to high teens.

bikemig 

Bridgestone catalogs are available online. You can always check to see what was on it originally to see if those gear ratios work for you. Great deal on that bike for sure.

https://www.sheldonbrown.com/bridgestone/1992/1992.pdf

Of course, pics or it didn't happen. This is my '93 MB 1

Jsnaggle

Thanks niknak, I think I will go for the 48/38/24 as I have my eyes on a couple of steel chainrings in that size. Figured I'd compromise on the high end to get me a few cm of ground clearance. Bike was in sad mechanical shape but frame is good (minus 1 small dent in top tube) and the Ritchey cranks and sealed hubs were worth the $20 alone. Won't be a showroom bike but will make a good user! Looks like I need a few more posts before pics.

staehpj1

I agree that is a very reasonable setup. I have managed with less on both ends and a full load back when I packed heavier and it was fine.

timdow

I personally would consider 24/36/48 to avoid the 14 tooth jump, although this may not be so much of an issue with friction shifters. Still a big jump though, and it might not be a smooth shift.

indyfabz

48/36/24 shifts fine in friction mode.

staehpj1

We used 46/36/26 cranks with 12-32, 7 speed cassettes on the TA, but two of the three of us swapped out the 26 for a 24. They shifted great with brifters. Completely trouble free.

The 24 tooth was probably a good swap, but I managed okay with a 26. The 46-12 high gear was adequate as well.

79pmooney

I'm running 50-38-24 with a chainwatcher on one bike and it shifts (friction) just fine. (I do narrow the FD cage by removing the bushing over the screw at the bottom with a shorter stack if small washers. Got thwarted with my best bike's Dura-Ace FD because Shimano doesn't use the screw SunTour and others used for decades but has a formed "U" that we creative types cannot alter. Taped some steel flatbar I had lying around to the inside of the cage to get the same effect. (Drawback to narrowing the cage is more FD/chain rub but I will take that for faster, more secure shifting.

Ben

djb

depending on the price involved, I also would strongly suggest getting a 36.
I ride a 26in bike with 44/32/22 which is fantastic with panniers on it, but the 32 can be a bit undergeared for light riding.
I also ride a 700 bike with a 42/34/24 which I find the 34 to be a great size
I also ride a 700 bike with a 50/39/26 and when loaded with panniers, the 39 is frankly too tall and one finds oneself a lot of the time at the larger cogs in the back.

dont know if you can find reasonably priced 36t rings for your bolt pattern, but Id really recommend that.

look up html gear calculator, you can put two diff setups in it, and compare.

oh, if you can go to 8 speed, consider it, it would be easy to find some used 8 spd shifters

what bars are you thinkig of doing?

Jsnaggle

Thanks for the suggestions. Definitely going to look into 36. For the amount of time I'll be using the middle ring I want to make sure it's not too tall. Thinking of either the Surly moloko bar or some other trekking bar.

djb

Don't get me wrong, for light load riding and no load, a 38 would be fine.
And the very often used on touring bikes 48/36/26 crankset that can easily take a 24 or even 22 if wanted, is a great crankset.
One of out bikes has this crankset, along with a 10 speed 11-36, which on a 26x1.5 wheeled bike, has a really good, real world range of gears and a nice low gear of 18 gear inches.

staehpj1

Just a caveat... Not sure which cranks you are referring to, but many cranks take a 24 as the smallest ring that fits their inner bolt circle. That includes all of the ones I have experience with that came with combinations like 48/36/26 or 46/36/26. So check before assuming a 22 will fit. It may not.

djb

Absolutely, my old 1990 crank I put a 24 on is probably at the limit. The one I’m referring to is the modern deore 48 36 26, stock on lots of touring bikes. I know one of the fellows here, gauvins, changed his to a 22, stock deore crank on his troll.
i always forget the bcd numbers, but can be easily checked.

but yes, one must check and be sure, but at least with older triples, getting to a 24 is probably a safe bet, but not a 22 as you say.

But even a 24 34 combo on a 26x1.5 bike must give under 19 gear inches, which is pretty good.

saddlesores

single chainrings get expensive, often can buy the whole crankset cheaper.

something like a 22-30-40?

staehpj1

It really varies wides depending on what you are looking for, but buying a single small or middle ring can often be pretty cheap. For many applications I have been happy with the shifting with plain tooth profiles and inexpensive rings are often available. A quick google search shows some rings for pretty cheap including FSA, Ultegra, Sram, Race Face, and others in the $12 range for small and middle rings. I have usually found small rings for about that price that I have been happy with.

Buying a crank that has a set of rings that are designed to work together can have advantages. Some may have special tooth profiles that aid in smooth shifting. That may favor buying a crank with the gears you want already installed since otherwise you'd be buying a full set of rings which may cost almost as much as a new crank.

Pricing on this stuff can really be all over the place so you really need to check before deciding which way to go.

djb

that is certainly been my experience looking into rings. All over the place in prices, and at times, a new crankset comes with a bb, which then really makes it worth it perhaps.....

Miele Man

I used a 48-38-24 with a 14-34 on my MTB for touring on Northern Ontario Canada mining/logging roads near Kirkland Lake and Matachewan Ontario. I had swapped out the original 28 with the 24 because I wanted a lower gear when climbing the steeper loose surface dirt roads where a lot of times the rear wheel would turn a couple of times before biting and moving the bike froward. It sure beat walking and trying to push a loaded for two weeks unsupported riding MTB up those hills.

Cheers

stardognine

That's also what's on my Cannondale, 48-38-28. I'm going to a small bike shop tomorrow, looking for a 36 & a 24, or close. Might get lucky. 🤔

Jsnaggle

Glad to hear the 24/34 is not too low. Will give piece of mind having even if I don't use often. I live on top of a gigantic hill so it's always a climb back and usually on a steep trail or unpaved hill.

Miele Man

Whether it's low enough for you will depend on your fitness, steepness of the hills and length of the climb. My 24-34 was on a fully loaded MTB with about 40 pounds of gearplus my 160 pounds body weight.

Cheers

Tourist in MSN

I think you need to look at the specific sprocket sizes of your freewheel and run some calculations on potential chainring sizes. I have seen over the years lots of new bikes from the factory with lots of duplicate gears because some idiot in the bike company thought that what looked good on another bike for either a cassette (or in your case freewheel) or crank would work but they did not bother to run the numbers.

I do not have a good suggestion for on-line gear calculators since I do my calculations on a spreadsheet that I developed. But perhaps some others that know of good on-line calculators will suggest something?

On my derailleur touring bikes and on my rando bike, I am running a triple crank and eight speed cassette. On all those bikes I avoid the two gears that are most cross chained on each chainring, thus I am only using six gears for each chainring, which with a triple means a total of 18 gears that I am using. When I only have 18 useable gears, the last thing I want are a bunch of duplicate gears.

bikemig 

I like the online Sheldon Brown gear calc. https://www.sheldonbrown.com/gear-calc.html

OP: is that 14-34 7 speed freewheel the shimano megarange? If so, you will want to do some gear calcs because that freewheel has a heck of a jump from 24 teeth to 34.

In setting up my cannondale ST 400 recently, I decided to go with a 13-28 7 speed freewheel and 48/36/24 rings up front. With 7 gears in the back, you are making some trade offs and I wanted a decent progression in my gears with a pretty good low. That gave me a 99.7 inch high, a 23.1 inch low, and jumps between the gears are pretty decent.

Run some numbers through a gear calc and see what you think.

djb

html gear calculator is the neat one that you can change stuff on the fly , as well as comparing two setups.

good ol sheldon brown gear calculator is still good because on the final calculated page, it shows clearly the percentage jump between shifts, which I find nice to know and to see easily and clearly

Cougrrcj

I like this gear calculator - you can change things on the screen to see how that affects your gearing. tire/wheel size -- Doubles, triples -- and no limit on rear cogs. You'll waste spend hours working out your combo!

https://www.gear-calculator.com/