I am running a tiagra compact 50/34t front with a sora 12/32t rear,
I am still finding the long steep hills a problem, is there a alternative available without going tripple. IE lower front chain rings.
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2I think you are currently at the limits.– paparazzoCommented Sep 22, 2014 at 15:13
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I think you are pretty much at the limit as regards vanilla Shimano options. But really, all this means is that you need to start thinking "outside the box". For example you can get smaller chain rings, its just that you'll need to do some research as to the number of teeth, the bcd etc - they won't be conveniently labelled "Tiagra" or "Sora". It might help to check out some single speed chainrings, then to look at how you could fit them together into a double chainring.– PeteHCommented Sep 22, 2014 at 15:22
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For example, on my favourite single speed site (Velosolo), I can see some 32T rings which might help you. Also there must exist 30T rings which are used on triples. But whether they could fit onto your double, and importantly whether you'd still be able to shift effectively, I don't know.– PeteHCommented Sep 22, 2014 at 15:49
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@PeteH A 30T is not going to work. That is smaller than the bolt circle - 110.– paparazzoCommented Sep 22, 2014 at 16:14
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@Blam was assuming a crank change too.– PeteHCommented Sep 22, 2014 at 16:42
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1 Answer
Your only alternative is to get a crankset with a different BCD (bolt circle diameter). You have a 110mm bcd, and while it is possible to use a 33t gear on the front, it won't help much and they are difficult and expensive to find.
IMHO, if 34/32 is not low enough, then by far the most straightforward thing to do is go to a triple.
However, that is not your only choice. You could try using various 2x cranks from the MTB world. The problem there is the large ring size is limited and getting the shifting working correctly can be tricky. 42/28 is probably the best you can do, although with some searching you might be able to get a big ring up to 48t. Shifting that big a gap will also present problems.
There are these cranks which offer a compromise btw Road and MTB doubles.
http://store.velo-orange.com/index.php/components/cranksets/grand-cru-50-4bcd-crankset-mkii.html
They have a 50.4 BCD and can use chainrings from 28t to 62t. The problem is they don't shift quite as smoothly as more modern chain rings with ramps.
Middleburn also makes some double cranks with BCD smaller than 110,
http://www.middleburn.co.uk/products/cranks/road-touring-cyclo-x
Surly's Mr Whirly cranksets also come with "spiders" that could be used to create a smaller crankset up front.
http://surlybikes.com/parts/drivetrain/mr_whirly_crank
Lastly, you could consider expanding the gearing out back. There are Mountain Cassettes that go up to 42t these days. You'd likely need a new rear derailleur, I'm not sure about the shifting.
All in all, going to a triple is by far the simplest and will actually get the gears you need. All any of these solutions provide is at best 2 more lower gears.
I highly recommend switching to a 110/74 triple with something like a 24/36/48. If you do get a "road" triple with the standard 30/42/53 gearing, swap the inner 30 for a 26t.
answered Sep 22, 2014 at 16:02
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The triple option is quite an expensive option for most people given that you need to buy a triple front shifter and a triple derailleur on top of the triple crankset. I'd probably say try a bigger cassette in the back even if you need a new RD, since thats significantly cheaper, or just try harder.– BatmanCommented Sep 22, 2014 at 16:16
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I see a 32T@110 bcd on a single speed site, but I totally agree with you - this is a <10% gain, you could spend your time and money and find that it doesn't feel a whole lot different.– PeteHCommented Sep 22, 2014 at 16:26
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The derailleurs that work with 42t cassettes don't work with road shifters( or at least not out of the box). Lot's of good info on this page: velonews.competitor.com/2014/02/bikes-and-tech/technical-faq/… Commented Sep 22, 2014 at 19:22