Converting from 53/39 50/34 cheaply
louman999
Posts: 90
I currently have a 105 53/39 crankset. I have quickly realised I need a 50/34. Originally I was going to buy new chainrings but I can't find both chainrings sold together. Individually they are a ripoff for a piece of metal. I've seen some cheap FSA cranks but they are for BB30 and I have hollowtech II. Any suggestions on what to do ???
0
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Boardman Hybrid Team 2014
Fixed TT 2015-2016
your cranks are likely to be 130bcd, you cannot physically fit compact rings to 130bcd cranks, you need 110 bcd, so you'd need to buy a complete crankset
what cassette do you have? if it's an xx-25 then fitting one with a 28 would give you a gear almost as low as switching to a compact
Nope - spindle is different diameter. You can do it the other way round though with various adapted BB designs.
You can get adaptors to fit 24mm Hollowtech II (BB86 or BB90?) to a BB30 frame, but vice versa would seem less obvious, I can't find one at a glance but I'm not an expert, and whichever you are adding expense and complication.
Paul
going from 53 to 50 makes less difference than one cog on the cassette, not much return for such an investment
as you're putting a 12-30 cassette on, it's really only worth changing the crankset if need 34-30 instead of 39-30, i'd really wait and see how you find it before changing crankset
btw is your rear mech ok with a 30t maximum on the cassette? not all are rated for that
To me, going from standard to compact is really more about the spread of lower gears that the 34 (or 36) inner ring gives. I quite like a 53 ring but the 39 inner (38 minimum) that 130 BCD caters for just doesn't give a nice RANGE of lower gears for the steeper stuff.
I know that you can stick a longer cage rear mech and a 32 sprocket on a bike with standard gearing and get a lowest gear equal to some compacts, but you get larger gaps between the ratios. Also it's often just as much hassle and expense as buying a compact crank-set.
And 39 32 will always being a higher gear than 34 32. One of the daft things about cycle spares prices is that it's often as cheap (or cheaper) to buy a cheap crank-set as two brand new rings...
When you say the 53 is too big when are you using it?
If it's just the top end 53/12 or 50/12 there's not much in it. If you pedal at 100 rpm then in 53/12 you go 34.6 mph and in 50/12 you go 32.6 mph.
If it's because you're riding in the 53 on the flat at 'middling' speed and it's too hard then use the 39 ring. A lot of people use the 50 on a compact for most riding other than going up hill. Turning your legs at 90 rpm in 50/21 you will go about 16 mph. With a standard road you can use the 39 for these middling speeds. If you have 53/39 then use 39/17 and you will also go about 16 mph.