1. No you cant swap out chainrings between the two. New crankset. You will want as easy as gearing you can get, if you arent a STUD on the bike.

2. not sure exactly, im guessing brockway was the longest from what i remember. look at strava or garmin connect or mapmyride. there will be tons of maps.

if you are strong you could kinda get a way with a 54/39 and 28 but your run would appreciate something easier. First loop wont seem too bad, but that second time up brockway...... But then again that was last year, and i hear there is 1000 ft or so less this year with the slight course change.

You can swap to 50/34 on 6800. The new 4 bolt cranks use a 110mm bolt pattern. Totally interchangeable. FWiW I'm running 52/36 with an 11-28 cassette at IMLT. I guess we'll see how that goes...

Thecipollinis is correct. The latest generation of Shimano 4 arm cranks (Dura Ace 9000, Ultegra 6800, 105 5800) can run all sizes of chainrings.

The older generations have two different cranks with 130 mm or 110 mm bolt center diameters and are not interchangeable.

On a side note: What cassette are you running? A cassette change may get you a lower end than a chainring change at a cheaper cost.

You cant swap the rings unfortunately. This was my issue at IMLT last year. Instead I put an 11-32 on the rear and ran with my full size crank. I was fine with that setup.

Steepest grade is probably the top of Brockway, but it's not really anything to worry about. The Brockway climb is going to be the longest climb of the day (and you get to do it twice). Just be glad they took out the Martis climb (although sadly I think that was the prettiest part of the course, it was also one of the toughest parts).

Hmmm...conflicting answers on the Ultegra. It is the new 11 speed. I will ask my LBS where I got the bike, but if it means anything I haven't been able to find anywhere online where you can buy the compact rings to switch out.

I'm pretty sure I have 11/23 or 25 in the rear. I live in eastern MA...we got nothing mountain-wise, everything is rolling and I can spin out the big gear on some of my preferred training rides. Thanks for the climb info. I did the LP course with the current set up w/a bum rear wheel (flexed into frame when out of saddle) and it wasn't that bad. Are the two courses comparable? LP like 6000 feet or so of uphill.

Yea the 11-speed Ultegra may pose a problem. I swapped my 10sp Ultegra RD with a Tiagra to accommodate the 11-32. I put the Ultegra and my normal 12-25 rear back on after the race.

Changed to a 50/34 11/32 which I use for all my races. Why anyone doing hills would want less makes no sense to me unless you are Lance. (But mine is bigger than yours)

Now, you did ask the correct question, which is one needs to run after well. For all the folks who say they did the race with more manly sized gears, ask them what their marathon
run time was and their age. My gearing might have helped me pass 400 folks on the run, but wait, they had more manly gearing so .... :o)
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Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep

If you're a strong cyclist (and decent climber) you'll be fine with a 53/39. I ran a 53/39 with 11-28 in the rear last year and was ok. There are alot of flat sections on the course where you'll appreciate the 53.

Or you could, you know, stop being a dick about it and realize that some people had good reasons for keeping their big crank on there. I have a Quarq as my crank, so my choice was to either swap the whole thing out for a compact and run with no power meter, or just deal with the big crank and race with power. Since I trained with power all year, suddenly going without would have been a much bigger mistake. And you know what, in the end the big crank didn't make a difference. My marathon sucked anyway but I seriously doubt you could pinpoint overbiking, since my NP was something like 58% of FTP.

Dude...the only way to answer your question is to have you tell us your bike power level. If you have a power meter, what is your FTP, or what is your goal IM power?

If no power meter, tell us some recent bike splits in races that went well for you.

No answer will make any sense till you tell us more.

FWIW -- I'll be riding the Tahoe course at a goal power of ~165 watts. I have a 50/34 and 11-32. And I will be in that 32 a fair bit. If you have the stock 6800 rear derailleur, you might be limited to a 28. No biggie.

as the guy that I was running with in LP said: Everybody looks pretty on the bike ;)

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The entire event (IM) is like "death by 1000 cuts" and the best race is minimizing all those cuts and losing less blood than the other guy. - Dev

Only form of "power" I have is the Strava calculations based off of weight, speed, segment, and whatever else they throw in their formula.

Last few rides it's been between 168-190 average watts. My last few rides have been a century w/8000 ft of vertical in 5:50, average speed was 17.1 mph. I did a 40km TT route with 1200 ft of vertical averaging 21mph, and this AM 30 miles, 19mph with 1500 ft of vertical for some rough stats. I'm leaning towards the compact with 11/28 in the back if able to switch out the rings keeping the price down. None of these efforts has been all out hammering...just staying fairly comfortable pushing here and there.

It's always nice to have a bailout gear.

http://kevinmetcalfe.dreamhosters.com/ironman-lake-tahoe-bike-calculator/

My FTP at sea level is a bit over 5 W/kg right now. I'm a bike racer, not triathlete. If I was doing this triathlon and wanted to do a good run my current 36x28 bottom would barely fit the bill in keeping my power where it belongs on Brockway at a reasonable cadence.

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Kevin

http://kevinmetcalfe.dreamhosters.com
My Strava

I did imlt last year and my suggestion is get the 32 (if possible) save your legs for the run.

also keep warms cloths in t2 or run special needs bag to stay warm because once the sun dropped it got cold. granted I came from so cal and we had a hot summer so I trained in 90+ heat which I felt with low temps in Tahoe.

great race so enjoy!

jim

Compact rings with 11-28 cassette works with stock 6800 Ultegra group. They *say* that you need the medium-cage derailleur to use a 32 cog. Don't know if it's true or not.

But yes, you definitely will be a lot happier with the 34x28 low gear.

Not sure why people are saying you can't change out chain rings for an Ultegra 6800 crank. Maybe they are not aware that this is the 6800 series you are asking about or they were told incorrectly.

Here is the parts list for the Ultegra FC-6800 crank. http://si.shimano.com/...EV-FC-6800-3609A.pdf You can see there is only one version of crank spider per crankarm length. The parts list shows the 50/34 and 53/39 fit on the same crank spider. If they were not interchangeable you would see two versions and a crank labeled FC-6850 which does not exist. The shimano website also has a dealer manual showing you how to interchange the chainrings.

I have Dura Ace 9000 and have both sets of DA 53/39 and 50/34 chainrings that I have easily swapped over. The design is similar to Ultegra. Although the tolerances or dimensions may be slightly off as an Ultegra 6800 chainring did not seat perfectly on my Dura Ace 9000.

They are available on ebay as well as BicycleBuys. Typical prices appear to be around $175 for the set.

Now regarding new chain rings ($175) vs cassette ($75). Here are the gear inches for the respective chainring x cassette cog combos.
30 x 23 = 39.3 gear inches
30 x 25 = 36.2 gear inches
39 x 28 = 37.1 gear inches
If you have a 11-23 cassette changing to 50/34 would not give you lower gearing than keeping your 53/39 and getting a 11-28 cassette. If you have 11-25, then a compact would get you lower gearing.

Edit: I now see an earlier post that you plan to go with compact and 11-28. So disregard my last paragraph. I had assumed you were going to keep your current cassette.

Unless you have ridden a similar route to the race course (at altitude), there is no way to know how your normal rides will compare to it.

So you basically only have to ask yourself a couple questions:

Can I afford to make changes to my gearing if I decide them to be appropriate?
Would I rather have lower gearing, and possibly wish I had higher during the race, or the other way around?

I went the cautious route: 50/34 and 11-32. It was also my first Ironman so I just wanted to be extra safe. I rode in zone 1 or VERY LOW zone 2 for most of the non-climbing sections of the course. I spun up the hills without much stress in low zone 3 for me and felt comfortable the whole time. It was nice to be able to spin up at 80-90 rpm going up a sustained climb. Brockway isn't super steep, but it is about 2.75 miles of "up" from the turn onto 267 from northstar drive.

The part you will need your "high gear" is the 1-2% average downhill section from Squaw to Truckee, and the new section by the truckee airport. The brockway descent is too steep, and you will out-gravity your gearing regardless. I was coasting in an aero-tuck going 50+ mph pretty easily. I'm not sure how fast you plan on riding from Squaw to Truckee, but if you can find a -1% grade section near you, you can estimate it. If you are not at altitude, you may actually go a tiny bit faster (thinner air = less resistance) but I'm hesitant to think it would make a whole gear change of difference.

I passed a lot of people on the run (~250), and I wasn't even running that fast. I apparently had more left in my legs than the average person that I started the run with. Maybe too much. But I'd rather have too much left for the run than not enough.

Yeah you can switch them out just confirmed w/the LBS...apparently Shimano limited where you can get them from or distribution.

I will try bicycle buys, dealer could get them for 185$ for the 50 and 22$ for the 34, apparently the 50 uses carbon. Def gonna run the more climb oriented gearing. I am a transfer into this race...damn it got expensive fast! Thanks everyone for the advice.

Good post.

Keep in mind that the section from Squaw to Truckee should be taken as fast as possible WHILE STILL KEEPING YOUR POWER IN THE PRESCRIBED RANGE. So, are you going to spin out that 50x11 at 80% of your (sea level FTP*.9)? For the VAST majority of people the question is can you spin out your 50x11 on that stretch of road on 200 watts or less. Even at 80 RPM that's 28.8 mph. On Age Group Ironman wattage, I don't think that's likely.

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Kevin

http://kevinmetcalfe.dreamhosters.com
My Strava

Who needs a power meter for the race? Never used one. For most folks who spend all the money and training to get to a tough race, IMO, and so many others I have talked with, to be under geared just makes no sense to me, but just my opinion. I sure would not call anyone dick if they want to do it differently since we all can do well with different setups.

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Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep

I've never used this place before. But google shopping showed bikepartsexpress with $118 for the 50 and $18 for the 30. I didn't check shipping.

http://www.bikepartsexpress.com/mm5/merchant.mvc?

I have barely used 6800 Ultegra 50/34 I could sell you. (I found that 52/36 11x28 ended up being the sweet-spot for me and my legs.)
PM me if you're interested.

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/Howie Nordström

I just did boulder at a whopping 136 watts (5:50)....rode a 50-34 and I think my race wheels have a 11 or 12-25. I ride mountains all the time and simply drop my cadence to 60 or so while climbing. Are you going with the easier gearing to keep your cadence up on climbs? Think it helps the run? Its already embarrassing how slow I climb in races; not sure going slower is even feasible....just too hard on the psyche:).

If I went easier, I assume I'd need a new chain, a new cassette, and a new derailleur....I think my derailleur wheel and my cassette already essentially are touching in my largest cog.....

Debating signing up for IMLT as its just up from me:). I had fun in boulder; another IM sounds good.

Dave

That's a nice bike split on that power. Well done.

I like to keep cadence up around 70. Just preference, that's all. When I drop to 60 my power starts to falter at a given perceived effort.

I'm doing the half at Tahoe, hence the higher goal power. I'd be looking at 145 or so if I was doing the IM.

I *think* my 165w might get me right close to 3 hours. Hard to tell, but I'm planning on 3 - 3:15. Would like to finish around 6 hours. Fingers crossed.