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Old 12-02-08, 07:33 AM   #1
donheff
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Changing chainrings

My wife and I ride Tricross comp triples. We love the bikes since they are comfortable for the roads and trails we ride on. The only thing we complain about is riding hills - if they get steep they are a challenge. My gear setup is front 50x39x30 and 12-27 rear. I'm not sure whether my wife's is the same but is probably similar - she got a newer bike and swapped the stock compact double for a triple. We generally ride in the middle ring, dropping into the granny for hills. I use the big ring fairly often but don't need the full range. My wife rarely goes in the big ring.

On our recent bike tour in Spain we both noticed that hills we would have found challenging at home seemed easy. I investigated and saw they were using MTB gearing (42x32x22, 11-30). We probably don't need something that extreme but a smaller granny gear would be nice for hills. Does anyone have any suggestions for what we should look for and what will work without drastic refitting? I would like to leave the cassettes alone so that councils something bigger than than the 42x32x22 would a 46x34x24 be good? How do you evaluate the proper combination and how do you figure out what will fit?

I would like to replace these myself over the winter. I can practice on my old beaters before messing with the good bikes. I figured I could get good advice from you old timers before I venture over to the mechanics forum
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Old 12-02-08, 07:34 AM   #2
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Get a 24 T FOR THE SMALL FRONT RING.
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Old 12-02-08, 08:10 AM   #3
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You may not be able to get there from here by changing chain rings. The bolt circle on a road triple crankset will not accept chain rings much smaller than the 30 you have now. (the bolt holes would be in the teeth).

You are probably looking at a touring crankset of about a 26/36/48 ring size to get what you want. Your road derailleur will still work ok with this crank. You can look at the Shimano LX series of cranks to see what this looks like although several other manufacturers also make such a crank.

To install such a crankset on a road frame will require you to know what your doing with regard to bottom bracket length.
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Old 12-02-08, 09:35 AM   #4
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I agree a 30t ring is inadequate for most riders in serious hills. 24t's bolted on both my bikes without changes, but I have an Atlantis and Rambouillet with Sugino XD cranks--not sure what the bolt circle diameter is these days on Shimano cranksets, which is probably what you have. That would be your limiting factor.
I suspect that since you're already running triples, you can swap down, and any bike shop could tell you in a second. You can probably figure it out for yourself: Look at the 30t rings and see if the bolt holes are way out by the edge, or if they're back toward the center of the ring a bit. I think (but don't remember for sure) that the bcd (bolt circle diameter) you need for a 24 is 74mm. Easy to check, in any case.
If you're uncertain, I'd just go to a bike shop. You may pay a little more for the part, but you'll save shipping, and you can consider it a fair charge for their knowledge and expertise (FWIW, I don't work in a shop. But sometimes it pays to use a pro).
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Old 12-02-08, 09:42 AM   #5
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Harris Cyclery has a 13-30 custom Shimano cassette that might be of use. I've run a mountain rear DR with the 30 tooth (LX or XT). However a medium range such as an Ultega GS triple will supposedly operate properly even though the published max is 27 tooth.

http://sheldonbrown.com/harris/k7.html

A swap of the rear cassette is the simple way to add some climbing gears. And its easy enough to go on up to a 32 tooth rear with the addition of a mountain rear DR.

Alternatively, I recently had a Deore M532 Hollowtech II trekking (48/36/26) crank set installed on a commuter bike for my son and it is a great buy. But if you have a road group front DR (105, Ultegra, etc) you may have front DR issues with the smaller radius rings, particularly if you drop to a 24 tooth small chainrings.

My recommendation: Casette changes and possible rear DR change if you go to a 32 tooth rear. Cheap, easy to reverse, easy to work with brifters.
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Old 12-02-08, 09:59 AM   #6
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Yep, a road triple (130/74) or touring triple (110/74) will go down to a 24T ring for granny. The larger of the two bolt circle diameters determine how low you can go for your middle ring, but have no effect on the large chainrings available -- you can get stupid-huge rings for either size. And, as I have found out, you have to stay within certain parameters when choosing chainrings:

1. The further away from 10T difference between rings, the worse it will shift
2. You still have to worry about total capacity. Most triple FDs only handle 22-24T difference from little to big, although that depends on the angle on the seat/shift tube.
3. As you get close to the derailleurs' capacities, getting chain length *just* right is important because just a link or two may make the difference between dragging your chain in a small/small combination or ripping your derailleur off by accidentally going to a big/big combo.
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Old 12-02-08, 10:08 AM   #7
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Quote:
Originally Posted by Velo Dog View Post
I agree a 30t ring is inadequate for most riders in serious hills. 24t's bolted on both my bikes without changes, but I have an Atlantis and Rambouillet with Sugino XD cranks--not sure what the bolt circle diameter is these days on Shimano cranksets, which is probably what you have. That would be your limiting factor.
I suspect that since you're already running triples, you can swap down, and any bike shop could tell you in a second. You can probably figure it out for yourself: Look at the 30t rings and see if the bolt holes are way out by the edge, or if they're back toward the center of the ring a bit. I think (but don't remember for sure) that the bcd (bolt circle diameter) you need for a 24 is 74mm. Easy to check, in any case.
If you're uncertain, I'd just go to a bike shop. You may pay a little more for the part, but you'll save shipping, and you can consider it a fair charge for their knowledge and expertise (FWIW, I don't work in a shop. But sometimes it pays to use a pro).
You are correct, there are rings available. The Shimano inner bolt circle is still 74mm. What do you use for a matching middle ring.
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Old 12-02-08, 10:24 AM   #8
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Originally Posted by maddmaxx View Post
You may not be able to get there from here by changing chain rings. The bolt circle on a road triple crankset will not accept chain rings much smaller than the 30 you have now. (the bolt holes would be in the teeth).

You are probably looking at a touring crankset of about a 26/36/48 ring size to get what you want. Your road derailleur will still work ok with this crank. You can look at the Shimano LX series of cranks to see what this looks like although several other manufacturers also make such a crank.

To install such a crankset on a road frame will require you to know what your doing with regard to bottom bracket length.
The crank as fitted now will take a smaller granny and I have done it on the OCR. For Ventoux last year I fitted a 28T granny but the rings may take some finding, Any LBS will be able to help you on sorting the right size on bolt spacing. Shimano only recommend a maximum of 22t difference on the front derailler but I have been using a difference of 24 on the tandem with no problem. As to whether it would be possible to make the difference more than 24 will be down to you to chance.


AND- As I wanted to set one bike up for the mountains- I recently tried to get a Crankset with 48/36/24 rings on the front. There is an MTB XT one that takes the latest type of crank bearings- but I did not want to pay the money. There is a deore version- but not a high enough quality for me and a bit weighty. Got a 105 triple with 50/39/30 on it and I will be changing the 30 to a 28----Or a 26 if it works.
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Old 12-02-08, 11:10 AM   #9
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Thanks for the feedback. I think I will visit the LBS. They are good and I bought the bikes there. I will do my learning/breaking on our old beaters
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Old 12-02-08, 11:52 AM   #10
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In the past, I've changed out the cranks set to mountain bike crank sets which have 22/32/44. My wife still uses one. My new bike uses an old TA design crank set which has 22/36/48.

My wife uses a 12 to 34 cassette which requires a mountain bike rear derailleur. I use a 12 to 27, but I keep a 12/34 plus a few extra links of chain and an extra SRAM gold link for a quick change-over if needed. I too use a long cage rear mountain bike derailleur.

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Old 12-02-08, 12:24 PM   #11
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The Deore Trekking crank is plenty good quality, but LX and XT versions are available if your ego requires that you spend more. I use a Sugino XD600 crank with 26/36/48 on my main road bike. It is a nice, old school cold forged design with 110/74 BCD, using a square taper bottom bracket.
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Old 12-02-08, 12:36 PM   #12
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Just short of a true mountain bike ringset, I've always liked the gearing of the touring crankset, which is the middle ground between a road triple and a modern mountain triple.

Last edited by roadfix; 12-02-08 at 01:51 PM.
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Old 12-02-08, 01:42 PM   #13
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AND- As I wanted to set one bike up for the mountains- I recently tried to get a Crankset with 48/36/24 rings on the front. There is an MTB XT one that takes the latest type of crank bearings- but I did not want to pay the money. There is a deore version- but not a high enough quality for me and a bit weighty. Got a 105 triple with 50/39/30 on it and I will be changing the 30 to a 28----Or a 26 if it works.
Over here, you can still get the internal bearing mountain bike cranks. When I built my wife's last mountain bike, she wanted a new crankset, so to avoid a "crank-set gap", I got two LX external bearing crank sets (one for me) as they were "only" $120 US at the time.

I then found out that you need to reface the bottom bracket on the older bikes that used the internal type. If you don't, the bearings will wear quicly as it's the BB surfaces that align the external bearings. Luckily, I have a neighbor who is an lbs mechanic and he ran over and did my frame.

The XT is about an ounce lighter than the LX and costs far more. I assume the oz is because it uses an aluminum 22 ring instead of steel one. I prefer steel as in the mountains, the aluminum small ring wears relatively quickly if you bike a lot.


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Old 12-02-08, 02:47 PM   #14
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Over here, you can still get the internal bearing mountain bike cranks. When I built my wife's last mountain bike, she wanted a new crankset, so to avoid a "crank-set gap", I got two LX external bearing crank sets (one for me) as they were "only" $120 US at the time.

I then found out that you need to reface the bottom bracket on the older bikes that used the internal type. If you don't, the bearings will wear quicly as it's the BB surfaces that align the external bearings. Luckily, I have a neighbor who is an lbs mechanic and he ran over and did my frame.

The XT is about an ounce lighter than the LX and costs far more. I assume the oz is because it uses an aluminum 22 ring instead of steel one. I prefer steel as in the mountains, the aluminum small ring wears relatively quickly if you bike a lot.


Al
I would have gone for the LX but it is not listed over here. It is either Deore- which I do not like- Or XT which is too expensive. The LX has always been good quality- far above Deore and not much below XT.
And on the rings- I always use Ally rings as I find the steel ones seem to wear out chains quicker. And I always buy Middleburn rings. This is due to the Tandem as That thing goes through crank rings at a tremendous rate- or used to. The middleburn rings are perfectly round and last twice as long as Shimano.
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Old 12-02-08, 03:03 PM   #15
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And I always buy Middleburn rings. This is due to the Tandem as That thing goes through crank rings at a tremendous rate- or used to. The middleburn rings are perfectly round and last twice as long as Shimano.
I use Blackspire rings. Canadian. Much better than Shimano for wear and tougher for "dragging" over logs.

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Old 12-02-08, 03:18 PM   #16
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I have a 52-39-26T front and 12-27 rear. It's about all I need, ever. You could go wacky with a SRAM 11-34 in back with that set up. I have a standard triple and 11-34 on my old bike. Both work fine.
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Old 12-02-08, 03:21 PM   #17
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I fitted a 26 tooth granny to my Ultegra cranks (replaced the 30). This places the total gear range outside of Shimano's recommendations (105 front dr) but it works perfectly - the recommendations are notoriously conservative. No other changes, just fit the smaller chainring. The labour for fitting it will probably be more than the cost of the chainring.

I made the change to the 26 after posting a similar question and getting a lot of responses from people who'd done just that. In my case, 26 was the smallest I could fit on the crank.

On the back, I've got one of SRAM's 11-32 cassettes (9 speed). Beautiful cassette. I use a DeoreLX rear dr because it has a extra long cage to handle the chain wrap over that range of gears.

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