Musky is a perpetual roller coaster of ups and down. I did it with a 53 in front and a 26-11 in the back, I wish I had a compact crank on, would have allowed you stay in the big ring longer.

With lots of up and down grades you'll stay in the middle section of the cassette the least. 53/39 with an 11-27 would be good for this course I think.

I've ridden a number of times and if you have a 53/39 I'd suggest an 11-27 cassette. I ride a 52/38 compact with an 11-27 and it is just enough to be able to spin up some of the rollers without needing to drop into the small chainring.

That said you will be using the small chainring so be sure that the FD is shifting well :)

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Rodney
TrainingPeaks | Altra Running | RAD Roller
http://www.goinglong.ca

Do you think an 11-32 is overkill?

I ride SRAM, so I can go up to 11-28, or jump to 11-32. Or, I could go 12-32 to give myself 14 back, but lose 11. On some of the decents, I imagine I will spin out on either an 11 or 12.

Nope :) Personally I'd rather have the middle gear than the 11. The longer descents are pretty technical so you won't be hammering down them in 53x11 anyway.

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Rodney
TrainingPeaks | Altra Running | RAD Roller
http://www.goinglong.ca

Important statistic missing here.... what's your Critical Power and W'?

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36 kona qualifiers 2006-'23 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
I ka nana no a 'ike -- by observing, one learns | Kulia i ka nu'u -- strive for excellence
Garmin Glycogen Use App | Garmin Fat Use App

Never calculated my W'. Feel free to educate me...

FTP = 265 (20 Minute test)
CP = 258

My training zones are setup as follows:

Active Recovery = 143
Aerobic End. = 144 - 195
Tempo = 196 - 234
Threshold = 235 - 273
Vo2 Max = 274 - 312
Anaerobic = 313+

50/34 FOR SURE

11-28 too depending on what some of those pitches get up to in terms of % grade.

when you say FTP is 265 is that the result of the 20min test or the derivative of the 20min test?

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36 kona qualifiers 2006-'23 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
I ka nana no a 'ike -- by observing, one learns | Kulia i ka nu'u -- strive for excellence
Garmin Glycogen Use App | Garmin Fat Use App

I did the 70.3 in 2013 and I believe had a 11-26 cassette with a 53-39 up front. It was a few weeks after IMMT and I rode around 3.4 w/kg, pushing around 25 less watts than normal for a 70.3. However, with the added distance (almost 60 miles for the 70.3) and elevation it probably made sense to aim for slightly less watts than I'd typically put out in a 70.3.

In your case, I'd think that one of the larger SRAM cassettes could work if you didn't want to change your front rings.

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Blog: http://262toboylstonstreet.blogspot.com/
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265 was the result of a 20 minute test.

Going down to a compact crankset is not really in the budget. I also just discovered if I go to a 32 cog in the back, I will have to swap out my RD for a Long Cage RD and also swap my chain.

Not sure if this is worth the $ for 1 race.

Looks like my best bet will be to increase to a 11-28 and keep my drive train intact.

you can put a 32 on there. Just take the B-limit screw out and put it in the other way (google this, it'll make more sense than i am). No need for a new RD. The girl and I each have a bike (one SRAM, one Shimano) that we've tinkered with to make this happen with no ill effect.

So being strongly conservative (your marathon thanks you) you've an FTP of about 240... with a race NP of somewhere around 165-170 that and your body weight on the climbs and the fact that running the marathon is kinda nice ;) you'll want as much range in the back as you can get. I snagged a SRAM 1050 11-32 on steep and cheap for 34 bucks yesterday.

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36 kona qualifiers 2006-'23 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
I ka nana no a 'ike -- by observing, one learns | Kulia i ka nu'u -- strive for excellence
Garmin Glycogen Use App | Garmin Fat Use App

The steep hills on the course are short. You will likely be spending some time out of the saddle climbing at low cadence pretty much regardless of your gearing. Definitely want to replicate this in training.

When you say the descents are technical, do mean there are actual switchbacks with braking etc?

Not so much switchbacks as short steep, really fast. Mostly in the first section from T1 to the start of the loop around the lake. With the rollers you are better off with closer gearing in the middle than you are with an 11 over a 12.

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Rodney
TrainingPeaks | Altra Running | RAD Roller
http://www.goinglong.ca

Not sure what brand or group set you're running, but you can get 105 compact cranks for ~$120. I obviously don't know your budget, but I've paid a good portion of that for cassettes before, definitely cheaper than a cassette plus a rear dérailleur. I raced Muskoka 70.3 and was very happy with the $/ability to spin and not ever burn out my legs--that's going to be a fun course on the second loop. I'm actually a huge fan of the 50 big ring on much flatter courses now; it takes a big hill to force me to the little ring. My FTP is within 10 watts of yours.

Thanks, I don't mind going 75kph on a tt bike but turning is a different story. That race looks awesome, trying to gather up some courage to sign up.

I just spent a week riding mountains with an 11-32 using a short cage 105 rear derailleur. Most likely it will work on his bike too.

jaretj

You can search for gears online also but few gears are essential like bike, tri suit, and other gears. You can also see here for more information on gears.

The descents are not technical. There are a couple of spots where there is a turn at the bottom of a hill but most are at most a slight bend.