You do not need a CX rear derailleur if you are able to set up your standard derailleur correctly. I have run bigger than 28t rear with a standard derailleur.

I will be running a standard RD 11-28 and a 54 tooth 9 speed front chain ring on my TT bike this year. 170 crank length. I never have problems with cross chaining

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I would also assume you would want a Narrow-Wide chainring like what was used on Rapps bike.

The purpose of the CX rear isn't so much to clear the 32 but for chain retention (the one on Rapp's bike is a clutch-type RD). The downside, iirc, is the increased chain tension induces frictional losses.

I was thinking of 53 x 11-30 or 32 so could a regular RD accommodate that? Thanks!

How do you know that? I've been wondering the same thing. I had an xo clutch RD on my cx bike, and it *felt* like it had more friction based on my oh-so scientific spinning the cranks backward in the work stand test. This got into my head, so put a wifli on instead (I've never dropped a chain with the wifli as a side note).

Are you aware of any actual testing of the clutch RD in terms of friction? Apparently friction-facts tested the narrow wide rings, and there were no significant losses.

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I can't seem to find any narrow wide chain rings that are bigger than 44t for cross bikes. Anybody know of any narrow wide rings that are standard sized (52, 53)?

Friction Facts did some testing with chain testing a while back. IIRC it was when they tested the Gates Carbon Belt Drive. Higher chain tension led to higher frictional losses. I don't recall the number though.

I think Wolf has them in 130 but not 110 now.

Cool. thanks. I wasn't aware of that. It would be nice to see some numbers to put some context into the friction losses they found.

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This... Plus the narrow wide front chainring. Otherwise you run a high risk of chain drop. Sram CX1 and prototype chainring that Jordan is using is built specifically for 1x optimization. I will have more info for you soon. :-)

Are you guys concerned about the friction losses of the clutch-style RD?

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[/quote]Are you guys concerned about the friction losses of the clutch-style RD?[/quote]
I haven't seen any evidence at all yet to show any loss, and given the clutch style RD there shouldn't be!

Are you guys concerned about the friction losses of the clutch-style RD?[/quote]

I haven't seen any evidence at all yet to show any loss, and given the clutch style RD there shouldn't be![/quote]
Given the clutch style RD, there *should* be some pretty significantly losses. I'd suggest taking a more proactive approach to the question vs. "I haven't seen any evidence".

Wolf does have a 110BCD ring with 50 teeth...

http://www.wolftoothcomponents.com/...yclocross-chainrings

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Remember Luddites are people too...

running a chain watcher on the front would eliminate the need for the expensive wide-narrow chainring and clutch rd. K-edge makes some nice ones or modify an old FD and set it to sit lower. Your normal RD will handle a 30 without issues. You might not need such a huge chainring either which would allow a little closer ratio in the back, I suspect you could win most tris on a 52 or even 50

Yep, they do a 50t in 110 and a 52t in 130.

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/kj

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what if the chain falls off to the outside?

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I run one of these on a cross bike and it seems to work, but you have to set it carefully. You could run an outer guard with the ring on the inner side if the chainline would work and the ring would clear the chainstay

http://www.acecosportgroup.com/k-edge-chain-catchers/cyclocross/cross-single-xl-chain-catcher.html

I guess the other question is why would someone want to TT on a 32 tooth cassette? You lose the 15, 17, 19, 21,23 etc. That's a lot of jumps

I've made a bunch of chaincatchers and one that would cover both the inside and outside would be easy to do (think an inverted "U" shape). That said, I run a 1x9, with a Wolf chain ring and have never had an issue with a dropped chain.

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Remember Luddites are people too...

Go single for marginal weight and aero advantage.

Lose some/all of that advantage with fancy chain catchers or extra chain tension?

hmmm

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I personally feel like the additional losses to increased chain tension are minimal. It's worth buying the Friction Facts reports (all of them). He has one on frictional losses as a function of load. It's actually surprising how little it varies as a function of tension due to applied power, and we're talking substantially increased tension from say 100w to 400w. That dwarfs the sort of increase in tension you'll see from a clutch RD.

Friction Facts hasn't done and specific testing and what testing SRAM may or may not have done, I do not know. But looking at what you can glean from existing data on frictional losses as a function of chain tension, I think the whole "clutch RD introduces frictional losses" is being way blown out of proportion. I wouldn't even be surprised if it was almost totally offset by the proportional increase in jockey wheel size to 12T vs 11T.

This is all just my own guesstimates and opinion, but I absolutely feel like this is a non-issue. I think people have this sense that it's multiple watts or even tens of watts. I'd be shocked if it was even fractions of a watt.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Good point re the friction-facts load test. With a little maths we should be able to make a reasonable guess as to the impact from, and it does look like it would be super minimal.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter