CliffordK

This is always ridiculous that whenever anybody wants higher gearing, so many people come out of the woodwork saying that nobody actually needs that high of gearing.

In this case, the OP's PR on a bunch of downhill segments doesn't even get him close to the top 50 riders.

The triple setup on the OP's bike is interesting, 30-39-50 & 11-x?
What is the low gear? Say 11-25 or 11-32? 9s? 10s? 11s?

According to Sheldon Brown's gear inch calculator,
50/11: 119.9 gear inches, 39/11: 93.5 gear inches, 30/11: 71.9 gear inches

The 39/11 overlaps between 50/14 and 50/15
The 30/11 overlaps between 50/18 and 50/19

Thus, the 39T sprocket is completely unnecessary, and with anything other than a straight block cassette, there is huge overlap throughout the cassette.

Put on, say a 60T first ring, 143.9 gear inches.
One still gets overlap with the 39T between 16T and 17T, and with the 30T at the 22T.

So, really, it is not that the OP really loses much by going with a larger big ring. He still gets overlap between the large and small rings.

One of the issues is that the larger rings push the capacity of the derailleurs.

So, jumping from the 50T to 54T will increase the radius by about r=d/2π, so 4T = 2", and the 54T should be about 1/3" larger in radius.

It will also pull about half that more in chain, or 2T or about 1" more chain.

So, just check you have the reserve capacity in both the front and rear derailleurs, as well as the ability to raise the front derailleur between 1/4 and 1/2".

And a $50 chainring, is one of the cheapest upgrades/experiments that one can do on one's bike.

reggieray

This was on a recumbent with a 15-20mph tailwind on the -2% grade. I kind of gave up pedaling for a lot of the segment when I was feeling very little resistance on the pedals in 50x11/100rpm. Also, spinning the legs at that cadence at that speed has to create more drag than at a lower rpm.

According to bikecalc, a 28mm tire in 50x11 at 105pm is less than 38mph.

My question had to do primarily with compatibility, as far as being able to fit on the crank I have and working with the SRAM 9-speed chain.

Does anyone know what the N10 means? It's on some of the rings I have seen online.

It's this crank

reggieray

It's a Bacchetta Corsa with 50/39/30 / 11-32.

Most of them come with 52 or 53/39/30, but I ended up with a 50 somehow.

You are correct, the middle ring does nothing other than allow me to go from the 50 to the 30. The shift from 39 to 50 is smooth though.

I'll just email Bacchetta and ask them if the parts on the bike will take a 53 or 54 and how much chain to add.

WhyFi

Lol. Okay, I thought that this thread might be taking the piss and now I know.

chaadster

You know what they say about that word "assume"...

CliffordK

If they supply it with 53/30 chainring setup, then yours should be able to take a 54.

Just look at the bike.

Can you fold the chain over so that the rear derailleur takes up 2 more links slack when in the big/big combination? If not, how much tension does the derailleur have when on the small/small combination? Does the chain drag on itself?

If there is a front derailleur hanger, can the front derailleur be raised by 1/4 to 1/2 inch?

Do you have at least 1/2 inch clearance for the chain over the tail of the front derailleur when in the small/small combination?

You can look up capacity and chain wrap for both front and rear derailleurs for most derailleurs, often slightly conservative.

One issue that you will run into is that if you get a matched set of chainrings, they will shift slightly smoother than a mismatched set, including the possibility of chain suck. But, it is often only a very minor annoyance. You should be able to shift 39 to 54, at least if you have a good ramped&pinned chainring.

CliffordK

Did you mention how many rear sprockets you have?

N10 may mean 10 speed, as I believe there are very few 11s, triple combinations available.

As mentioned earlier, a matched set of rings will probably shift a little better with less chance of chain suck, but a mismatched set may be fine too.

CliffordK

What size of wheels do you have on your bike?

I see the Corsa comes with anywhere from 24" to 700c. Other models have mixed wheel sizes.

reggieray

9 speed cassette.

Wheels are 700c, same as road bike. 28mm Michelin Power Competitions, latex tubes.

Front derailleur is on the derailleur post.

The chain is very, very tight in 50x32. I could only get half of one link to fold back over the half link behind it.


I rode most of the same course again today and pedaled harder and faster than yesterday. This time I was for sure spinning out 50x11 at roughly 110rpm. Bike was shaking and moving up and down. That gear at that cadence was barely good enough for 39mph.

https://www.strava.com/activities/91...ts/22354924613

I believe I could win that segment relatively easily with a 54.

Trsnrtr

I had a 54 ring on a 650C Corsa one time and it worked fine. Be sure to check that chain length after installing a bigger ring and adjusting your front derailleur. Don't want to inadvertently rip your rear derailleur off with too short a chain.

CliffordK

That explains a lot. For example, I was wondering about the triple and really big cassette on a "road bike". But, I've heard the recumbents need a bit lower gearing.

A lot of PR's and a couple of top 10 segments in that last ride.

Check the chain length and front derailleur clearance with the small/small combination. It sounds like you'll probably need to add at least 2 more links to your chain (new chain?).

It looks like you have the vertical FD adjustment on the post you need to go to quite a bit larger of a chainring.

Trsnrtr

I worry more about the big/big. You can rip a derailleur off pretty easily if the chain is too short.

CliffordK

In theory yes, but the OP has already said he probably needs to add a pair of links to the chain, so time to look at the other end.

If the derailleur can tolerate the cage being flattened out, I'm not sure how much "ripping" there would be.

Carbonfiberboy 

Big rings are good. Some tandems run 60T. I always run 52 or 53 on my road bikes. When I spin those out it's because I'm descending and I'm faster getting my body out of the wind and coasting, so I don't need anything bigger. On a recumbent you might be able to go even larger.

On a Shimano 9-speed if you're running a 42 middle, you need the 52T Type A ring, which you probably can't find. If you are running a 39T middle ring, you need a 53T Type B ring. Amazon.com or ebay. I run 53-39-26 now on all my Shimano road bikes. The small granny allows a closer spaced cassette which keeps your cadence jumps smaller.

To measure chain, wrap the chain big-big but not threading through the RD, just straight. Then add 1 link to allow for the RD. Ignore small-small. You should never go past the middle of the cassette in the granny ring. Also ignore ratio overlaps. Who cares? You put it in one ring and run through the cogs until the next ring is usable, then run through the cogs until the next ring is usable. I never saw anyone shift a triple in the front anything like as often as they shift the back. It's not a 60's half-step rig.

reggieray

Add one link even for a long cage RD?

Cross chaining isn't really an issue on a bent.

TimothyH

I have always added two links, one only if using a quick link.

Carbonfiberboy 

That's what I do with my XTR. I don't think they come any longer. Or add 2, doesn't really matter, but no more.

No, cross chaining isn't really an issue except that you want to always use the least chain tension, which means the largest applicable ring, except that I never run lower than 3rd cog in the big ring on my bikes.

fietsbob

Online, or a proper bike shop, do make some effort.

reggieray

Experience has dictated to me that this is a contradiction in terms, in most cases.

merlinextraligh

This. Pedal hard and fast at the top, coast when you get up to speed.

I've done P,1,2,3 races with 50x11 gearing.

I find it difficult to believe that gearing is holding many people back.

merlinextraligh

I think the OP's Strava chart implicitly confirms this. His maximum speed was coasting at 49 mph. His high cadence immediately before that was 94 rpm at 23 mph.

So OP quit pedaling and coasted well before reaching a cadence of 109.

Having had a 53 tooth chainring would likely have made no difference to the OP's high speed on this ride.

With a 50x 11 and a top cadence of 110, OP runs out of gear at 39 mph, and with a 53x11 at 41 mph.

In either case, coasting would still get him the 49mph, both above what he can spin at 110rpm in either gear.

merlinextraligh

Further, the OP is rarely if ever over 100rpm during the ride, and when he is in the high 90's its typically at a speed in the teens or low 20's, when he still has plenty of gear to go bigger if he wanted or needed to.

There's just nothing in that file to suggest the lack of a higher top end gear is holding the OP back.

He obviously can spin 95- 100 rpm on a sustained basis, given that he elected to so on sustained portions, where he was not in his biggest gear, and had the option of gearing up and going to a lower cadence.

50x11 at 100rpm is 35mph at 100rpm, and 39mph at 110. There just aren't many situations where its profitable to pedal above 39mph.

Carbonfiberboy 

It depends on the gradient. I have some descents where I'm fastest spinning my 53 at 115 rpm, others where I'm fastest coasting. I would not be able to achieve the same speed on shallow descents spinning a 50 at 115. A 53-39 crankset became standard because it gave the best results. Were that not true, the standard could have become 50-34. That new "standard" came into being because the wider variety of individuals with varying cycling abilities in the present demanded easier gears.

PepeM

Loving the in-depth analysis of the Strava file.

Dan333SP

I'm not touching the gearing/rpm debate, but kudos to @reggieray for that ride! 50 miles with that much climbing at that speed, on a 'bent or not, is very strong.