53/39 crankset question.

Seadin

Hi guys,

Just wondering is it possible to put a 50 ring on inside of 53/39 ultegra crankset? In other words remove the 39 and put in a 50 there?


You might ask why I might do this? I just have a TT bike and part of the TT route we do has a slight gradient and into a headwind. At times I find that I can't get enough cadence at that section of the route with the 53 and lose speed and time.

Just asking here can it be done?
Thanks.

Cee-Jay-Cee

I'd imagine not as the 50T is designed to be the outer ring and so I can't see it mating correcting on the inside of a 53.

07Lapierre

Is changing the rear cassette an option?

youtheman

Standard 53/39 chainrings have a 130 mm bcd (bolt circle diameter).  Compact Chainrings (50/34) and Mid Compact (52/36) have 110 mm bcd.  So the answer to your questions is 'No'.

Lumen

youtheman wrote: »

Standard 53/39 chainrings have a 130 mm bcd (bolt circle diameter).  Compact Chainrings (50/34) and Mid Compact (52/36) have 110 mm bcd.  So the answer to your questions is 'No'.

This is no longer true with Shimano 4-arm cranks - all use 110 BCD.

Euppy

Of course its possible. Get a track designed 3/32 50t ring. You'll find it easily for the old school 5 arm cranks. Don't know if you'll get one for the modern 4 arm ones though - or it will likely be stupidly expensive.

Lumen

Euppy wrote: »

Of course its possible. Get a track designed 3/32 50t ring. You'll find it easily for the old school 5 arm cranks. Don't know if you'll get one for the modern 4 arm ones though - or it will likely be stupidly expensive.

But a track chainring won't have ramps on the teeth?

Plastik

Lumen wrote: »

But a track chainring won't have ramps on the teeth?

But the ramps are on the 53?

Euppy

Plastik wrote: »

But the ramps are on the 53?

Exactly, ramps and pins are needed on the outer chainring, not inner.

Not a necessity on the outer either but makes shifting much much better

cython

Lumen wrote: »

This is no longer true with Shimano 4-arm cranks - all use 110 BCD.

Still not gonna fit a 50t 4 arm chainring on the inside :pac:

Euppy

Thinking about it more, I wonder if the derailleur would hit any of the rings when going through its full range of motion.

But these small changes in front chainrings were done donkeys ago. But it's a question of whether modern f derailleurs can still do it.

From Sheldon:
Half-step Gearing
In the days of 4- and 5-speed freewheels, 8- and 10-speed bikes were commonly set up with chainwheels that were very close in size, for instance, 46/49, or 47/50. When used with typical freewheels of the era, the difference between the two front gears was about half as large as the difference between adjacent gears on the freewheel. (One reason for this was that early front derailers couldn't handle much more than a 3-tooth difference reliably!) With half-step gearing, the larger shifts are made with the rear derailer, and the front is for fine tuning. This allows an 8- or 10-speed set up to have a reasonable range with fairly close spacing of the gears. One downside of half-step is that it uses all possible combinations, including those that run the chain at a fairly severe angle. This was not a big deal in an 8-speed rig, but is kind of marginal for 10-speeds. Another serious disadvantage is that every other shift in the normal sequence is a double shift (front and rear derailers simultaneously). These issues are largely overcome with modern handlebar-end index shifters and narrow-spaced cassettes, but half-step requires mixing and matching sprockets these days -- no manufacturer offers an appropriate ready-made cassette.
Half-step gearing is most suitable for riding in flat terrain, where shifting is rare. It allows finer gradations to get as close to the "ideal" gear for the particular wind conditions as possible, and a wide range with even spacing.
Modern multi-range shift patterns use larger jumps on the chainwheels to select general ranges of gears, and fairly closely-spaced 7-or-more-speed clusters for the fine tuning. This greatly simplifies the shifting pattern, allowing constant adjustment to different grades in rolling terrain, with only occasional need for a double shift.

niceonetom

Feasibility aside, I don't think it's a very good solution.



Shifting from 53 to 50 on the front would have less effect on gearing than a single shift (say 23 to 25) on the cassette. If you're overgeared on the 53 you'll still be overgeared on the 50.

magicbastarder

07Lapierre wrote: »

Is changing the rear cassette an option?

i was wondering something similar - what cog on the cassette is the OP getting up to? is he worried about cross-chaining?

CramCycle

Different cassette and cross chain it. Modern set ups supposedly handle cross chaining reasonably well.

07Lapierre

CramCycle wrote: »

Different cassette and cross chain it. Modern set ups supposedly handle cross chaining reasonably well.

Hate to admit it, but I crosschain quite a bit.

OP what cassette do you have?