Login required to started new threads

Login required to post replies

Musings on using a frankenstein junior cassette and big front ring
Quote | Reply
I see this a lot in the British TT forum. For same ratio we know the bigger diameter cogs and rings, the more efficient. Ok, I'll run with that for now.

I run 1x already, so cross chaining is out of the discussion of efficiency here. I'm not going back. So, that simplifies this.

I'm thinking of experimenting with drivetrain optimization now that my aero setup is pretty good for now.

I'm thinking of buying a pair of R8000 cassettes to frankenstein together and a new pair of larger chainrings.

Right now I run a 54T 1x with either a 12-25 (flat TT) or an 11-28 (hilly TT). This seems to work well. I'm rarely in the 11, 12, or 25/28. I'm usually in the "meat" of the cassette with a decent chain line.

Currently chain line looks "optimal" on the 4th cog. So that would be either the 14t or 15t depending on the setup.

Now, the conundrum. My old Felt seems to not like big chainrings. The 54 looks fine right now. But the 58 or 60 I'd like to run for the "junior cassette" experiment seems I'd need to space the big-ring out. Then, it would line up best with the 3rd cog instead of the 4th.

Who has gone down this rabbit hole, and where did you end up?
Quote Reply
Re: Musings on using a frankenstein junior cassette and big front ring [burnthesheep] [ In reply to ]
Quote | Reply
burnthesheep wrote:

Right now I run a 54T 1x with either a 12-25 (flat TT) or an 11-28 (hilly TT). This seems to work well. I'm rarely in the 11, 12, or 25/28. I'm usually in the "meat" of the cassette with a decent chain line.

Where are you most often? If you're already usually in the 14th, that's kind of a sweet spot already, for both chainline and cog efficiency. Hard to beat that.
Quote Reply
Re: Musings on using a frankenstein junior cassette and big front ring [trail] [ In reply to ]
Quote | Reply
trail wrote:
burnthesheep wrote:


Right now I run a 54T 1x with either a 12-25 (flat TT) or an 11-28 (hilly TT). This seems to work well. I'm rarely in the 11, 12, or 25/28. I'm usually in the "meat" of the cassette with a decent chain line.


Where are you most often? If you're already usually in the 14th, that's kind of a sweet spot already, for both chainline and cog efficiency. Hard to beat that.

Yes.

Agreed. I was working on keeping that same chain line but increasing the diameter of the normal rear cog used by increasing the chainring also.

Some of the UK guys run a 60T up front and a modified junior cassette in back (14-28) for the flatter TT's.

I would wind up in a 60/16 instead of 54/14 or 60/17 instead of a 54/15. Definitely more than a watt. I thought it was a % of power output.

This may be a fool's errand though as it appears to me the rear seat stay may be too close for a 14t in the outermost position. I need to measure.
Quote Reply
Re: Musings on using a frankenstein junior cassette and big front ring [burnthesheep] [ In reply to ]
Quote | Reply
I have actually thought about the is a decent amount. With companies like SRAM and 3t going towards smaller tooth cassettes (and 12sp groups) for the superior gear ratios, this is hurting drive train efficiency. I’ve thought about what if you took it the other way as well, specifically with shimanos 14-28 cassette. If you do the math, using a 64t big ring would be nearly identical to a compact crankset with a standard 11-23. For tri’s, many would find occasions where they would spin out. Therefore, you’d need a 68 or 70t big ring. At that point, I feel aero losses would be worse than any gain in improved chain line efficiency, if you could even fit a gear like that.
Last edited by: Driva77: Nov 18, 20 13:20
Quote Reply
Re: Musings on using a frankenstein junior cassette and big front ring [burnthesheep] [ In reply to ]
Quote | Reply
burnthesheep wrote:
trail wrote:
burnthesheep wrote:


Right now I run a 54T 1x with either a 12-25 (flat TT) or an 11-28 (hilly TT). This seems to work well. I'm rarely in the 11, 12, or 25/28. I'm usually in the "meat" of the cassette with a decent chain line.


Where are you most often? If you're already usually in the 14th, that's kind of a sweet spot already, for both chainline and cog efficiency. Hard to beat that.


Yes.

Agreed. I was working on keeping that same chain line but increasing the diameter of the normal rear cog used by increasing the chainring also.

Some of the UK guys run a 60T up front and a modified junior cassette in back (14-28) for the flatter TT's.

I would wind up in a 60/16 instead of 54/14 or 60/17 instead of a 54/15. Definitely more than a watt. I thought it was a % of power output.

This may be a fool's errand though as it appears to me the rear seat stay may be too close for a 14t in the outermost position. I need to measure.

Use the same optimal chainline cog for all events, just pedal faster for the shorter stuff.

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
Quote Reply
Re: Musings on using a frankenstein junior cassette and big front ring [Driva77] [ In reply to ]
Quote | Reply
Driva77 wrote:
I have actually thought about the is a decent amount. With companies like SRAM and 3t going towards smaller tooth cassettes (and 12sp groups) for the superior gear ratios, this is hurting drive train efficiency. I’ve thought about what if you took it the other way as well, specifically with shimanos 14-28 cassette. If you do the math, using a 64t big ring would be nearly identical to a compact crankset with a standard 11-23. For tri’s, many would find occasions where they would spin out. Therefore, you’d need a 68 or 70t big ring. At that point, I feel aero losses would be worse than any gain in improved chain line efficiency, if you could even fit a gear like that.

Imagine if we had 1x since the beginning of bikes instead of 2x... we'd be heaping praise on the inventor of 2x and dancing in the streets.

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
Quote Reply
Re: Musings on using a frankenstein junior cassette and big front ring [ericMPro] [ In reply to ]
Quote | Reply
Quote:
Imagine if we had 1x since the beginning of bikes instead of 2x... we'd be heaping praise on the inventor of 2x and dancing in the streets.

2x is pretty nifty when you've got this on the back:



________
It doesn't really matter what Phil is saying, the music of his voice is the appropriate soundtrack for a bicycle race. HTupolev
Quote Reply
Re: Musings on using a frankenstein junior cassette and big front ring [Driva77] [ In reply to ]
Quote | Reply
My math didn't have me going to anything like a 70T front. Just 60 or 62. I pretty much spin at 95 during a TT. And am OK going up a hill around 75 if I must.

Perhaps first I'll work on my rear derailleur setup.
Quote Reply