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Gear Inches

Old 04-24-20, 05:26 PM
  #26  
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Originally Posted by djb
no prob
re building a wheel. Ive never done it, but I have replaced a rim that had cracks appearing at the drive side holes--I was able to get a rim that was the exact dimensions as the original rim, so the original spokes were the right length for the new rim.
So just be aware of the importance of figuring out how to get the spoke length for a given rim and hub, if not and you screw up you could end up with useless spokes because they would be cut too short....

and figure out if that crank can take a 24. My Kuwa crank could, it was a standard mtb triple 110/70 or whatever the bcd was, and 24 was the smallest the inner bolts could take.
again, its easy to ask google how to measure and calculate the bcd if not sure.
djb...I'll google my crank and see if I can find out the BCD. I would like to spin uphills instead of walk so the purchase of a smaller chairing is a no brainer. I have an old XTR 8 speed drivetrain waiting to be installed on a Specialized S Works chromoly frame so I might take the granny off of that crank until I can buy something new. If it's in good shape and not abused I will try it out. Until then the bike is good to ride as is, at least around the parking garage.
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Old 04-24-20, 07:01 PM
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Listen, one day you might consider putting that 42/32/22 on that bike. Makes a great touring crank when heavy. But need a wider bb and some 8 spd shifters....if the hub can take 8 speed...
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Old 04-24-20, 08:11 PM
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I've toured a lot with a mtb triple, and heavily loaded it works very well, especially with hills. I run out of gears at about 50kph but that's ok, pretty small percentage of time we ever go above 35kph.

you could just leave the bike with 7 speeds, no issues at all running 7 speed chains on 8 speed chain rings.
but you would need a wider bb, and shimano makes an inexpensive sealed unit called un24 I think, 20 25 bucks. Just have to get the chain line figured out, hence the wider , longer length axle.

no matter what, if your bike has the original ball bearing bb, if it's not in good shape, replace it with a un 24 or whatever it is. Sealed bb's are so much better than ball bearing ones, install and forget for years and years.

don't know what tools you have, but most is doable at home. Removing a ball bearing bb cup can be a bear though. Had to use my vice and rotate the entire frame of my wife's commuter bike to get the old bb cup out last year when I finally put in a sealed bb, the 20 25 buck one I mentioned.
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Old 04-24-20, 10:59 PM
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I have a Campagnolo Veloce 9-speed racing triple 30-42-52 on one of my bikes. I have an FSA crankset in my parts bin that also has 30-42-52 chainrings on it. To the best of my knowledge neither of those cranksets will take a chainring smaller than 30 teeth.

On my road touring bike I have an old-school Deore triple crankset from abck in the 1980s. That crankset has 24-38-48 chainrings. If I use a long cage Deore rear derailleur from the same era and a 32 or 34 teeth low cog on the rear, I'm set for almost all of my road touring needs/wants. That gives me a low gear of 20.3 or 19.1 gear inches with a standard 27" wheel.

Of course, an individual's gearing choice will depend on their level of fitness, planned distance per day, strength of headwinds, and weight of gear and how bulky it is.

Cheers
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Old 04-25-20, 09:34 AM
  #30  
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I think the lower the gearing the better. I would rather spin up a hill than walk it. I have a ways to go before I can take off my crank. I have some tools that I need to get first before I can do the job but it will get done at some point. Now that the idea is firmly planted in my head it's just a matter of time. I have an older Shimano something CX gruppo on the bike now that has a long cage derailleur on the back. It's meant to be.
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Old 04-25-20, 10:49 AM
  #31  
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Originally Posted by Chrisp72
djb...I'll google my crank and see if I can find out the BCD. I would like to spin uphills instead of walk so the purchase of a smaller chairing is a no brainer. I have an old XTR 8 speed drivetrain waiting to be installed on a Specialized S Works chromoly frame so I might take the granny off of that crank until I can buy something new. If it's in good shape and not abused I will try it out. Until then the bike is good to ride as is, at least around the parking garage.
Measure it! I suspect that it is a 130/74 (outer ring/inner ring). You can probably replace the inner ring with a 24. Measure first.
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Old 04-25-20, 11:30 AM
  #32  
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This is a good way to tell what chain rings fit which cranks.
https://www.sheldonbrown.com/harris/chainrings.html

But be careful with recent cranks that do not have evenly spaced crank arms, the above does not cover the four arm ones that are not square. And note that there are four arm and five arm 74mm chainrings that are not interchangeable.

Originally Posted by Miele Man
I have a Campagnolo Veloce 9-speed racing triple 30-42-52 on one of my bikes. I have an FSA crankset in my parts bin that also has 30-42-52 chainrings on it. To the best of my knowledge neither of those cranksets will take a chainring smaller than 30 teeth.
...
Most of the recent (last couple decades) square taper Campy cranks took a five arm 74 BCD granny gear. I have two bikes with those cranks with a non-Campy 24T aftermarket chainring.

The mid and large Campy rings are the ones that are a bit more rare with a 135mm BCD.
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Old 04-25-20, 12:27 PM
  #33  
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Originally Posted by djb
Listen, one day you might consider putting that 42/32/22 on that bike. Makes a great touring crank when heavy. But need a wider bb and some 8 spd shifters....if the hub can take 8 speed...
The weight depends on the crank. If the crank has steel rings, yes, it’s heavy. But if it uses aluminum rings it can be competitive with a road triple. If the crank is a Hollowtech, it’s even lighter.

As for the bottom bracket, the spindle may need to be longer or it may need to be shorter. Again, it’s best to measure it. I’ve often had to use shorter spindles when I use a mountain bike crank on my touring bikes.

Originally Posted by djb
I've toured a lot with a mtb triple, and heavily loaded it works very well, especially with hills. I run out of gears at about 50kph but that's ok, pretty small percentage of time we ever go above 35kph.

you could just leave the bike with 7 speeds, no issues at all running 7 speed chains on 8 speed chain rings.
but you would need a wider bb, and shimano makes an inexpensive sealed unit called un24 I think, 20 25 bucks. Just have to get the chain line figured out, hence the wider , longer length axle.

no matter what, if your bike has the original ball bearing bb, if it's not in good shape, replace it with a un 24 or whatever it is. Sealed bb's are so much better than ball bearing ones, install and forget for years and years.

don't know what tools you have, but most is doable at home. Removing a ball bearing bb cup can be a bear though. Had to use my vice and rotate the entire frame of my wife's commuter bike to get the old bb cup out last year when I finally put in a sealed bb, the 20 25 buck one I mentioned.
Another alternative is to go with an external bearing crank. A little more expensive...check Fleabay...but easier to work on and install.

On all of the 64mm BCD mountain cranks, you can convert them to a 20 tooth inner ring. The 20 is too small to bolt straight on but with just a little bit of filing. Here’s a video on how to do it on an external bearing crank


A 20 tooth 64mm BCD is fairly rare but they can be found. I have done this on several bikes and it works like a charm

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Old 04-25-20, 12:58 PM
  #34  
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cycc, I was typing too fast and not putting things down properly. I meant heavy as in the touring bike is heavily loaded.

and as per bb width, for square taper Doug64 explained to me years ago the details of road bike vs mtb shell widths, bb axle length differnces etc and all those details of putting a mtb triple onto a road bike, but i had forgotten the details, but as you say, certainly needs to be researched properly if ever going that route square taper wise.

and yes, for a bike that will be ridden lightly loaded or unloaded a lot, a mtb triple is not the best I guess, but they certainly are great for loaded touring---but in this case, I guess the smaller granny option is just the most simple and will work well.
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Old 04-25-20, 01:25 PM
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Originally Posted by Tourist in MSN
This is a good way to tell what chain rings fit which cranks.
https://www.sheldonbrown.com/harris/chainrings.html

But be careful with recent cranks that do not have evenly spaced crank arms, the above does not cover the four arm ones that are not square. And note that there are four arm and five arm 74mm chainrings that are not interchangeable.



Most of the recent (last couple decades) square taper Campy cranks took a five arm 74 BCD granny gear. I have two bikes with those cranks with a non-Campy 24T aftermarket chainring.

The mid and large Campy rings are the ones that are a bit more rare with a 135mm BCD.
My 9-speed Veloce triple crankset is from 2001. If it'll take a 24 teeth inner ring I'll be delighted.

Cheers
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Old 04-25-20, 04:16 PM
  #36  
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Originally Posted by Miele Man
My 9-speed Veloce triple crankset is from 2001. If it'll take a 24 teeth inner ring I'll be delighted.
...
Measure it first, but I think it will work. On two of my bikes I am running a half step plus granny drivetrain, 46/42/24 with Campy cranks. The 46 and 24 are aftermarket, the 42 is stock Campy ring. I use chain catchers to make sure that the chain lands in the right place when down shifting to the granny. The upshift from a 24 to 42 is a big jump, I usually have to over shift a bit and then back off, thus a friction shifter is best for the front.



Unfortunately the chain catchers do not show in these photos, are hidden behind the cranks.



I think both of the cranks above are officially 10 speed cranks, but I see no reason that they would have changed the BCD from an earlier crank. In both cases above, I am running 8 speed cassettes and chains.

I bought a Mirage Campy crank in 2004, I previously ran a 24T chain ring on that crank.

ADDENDUM ADDED LATER:

If you are running a 52/42/24, that means your derailleur cage might not take up all the slack when you are on the 24T chainring if you are also on one of the smaller sprockets. I am using older XT derailleurs and when I had a 52/42/24 with an 11/32 cassette, I could not use the two smallest sprockets on the cassette with the 24T granny because there was too much slack. Those gears should not be used anyway, too much cross chaining, but I just wanted to fore-warn you.

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Old 04-25-20, 04:33 PM
  #37  
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Originally Posted by djb
cycc, I was typing too fast and not putting things down properly. I meant heavy as in the touring bike is heavily loaded.

and as per bb width, for square taper Doug64 explained to me years ago the details of road bike vs mtb shell widths, bb axle length differnces etc and all those details of putting a mtb triple onto a road bike, but i had forgotten the details, but as you say, certainly needs to be researched properly if ever going that route square taper wise.
A few mountain bikes have wider shells but, thankfully, there are different bottom bracket shell widths available. Up until a few years ago, just about every bike out there used a 68mm bottom bracket shell with just a few funky 73mm's around. But what I was referring to was that many mountain bike cranks have arms that extend a long way out from where they are attached to the bottom bracket than road bikes. Road cranks tend to be straight from the bottom bracket to the pedal while mountain bike cranks aren't. You can kind of see what I'm talking about here

DSCN0940 by Stuart Black, on Flickr

The surprising result is that mountain bike cranks...especially square taper one...require far shorter BB axle length than road bikes.

Originally Posted by djb
and yes, for a bike that will be ridden lightly loaded or unloaded a lot, a mtb triple is not the best I guess, but they certainly are great for loaded touring---but in this case, I guess the smaller granny option is just the most simple and will work well.
A 48 tooth outer and an 11 tooth cog on the cassette give a really good high gear (115 gear inches) that is higher than we had 30 years ago. A 52/13 is only 105" and that was about all we could get back in the 80s. A 52/11 is 124" which is ridiculously high even for me.
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Old 04-25-20, 08:06 PM
  #38  
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Cycc, thanks. Probably because the cranks are set out more to clear wider chainstays for wider mtb tires?
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Old 04-27-20, 02:35 PM
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Originally Posted by djb
Cycc, thanks. Probably because the cranks are set out more to clear wider chainstays for wider mtb tires?
Could be.
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