how many weeks is ideal for 1st IM?

Hrm not really enough information to give you any informed advice as you have no races or training in your logs and have no mention of your current fitness level.

From the couch 1-2 years is a good window for training for an IM.

If you have done marathons and HIM's within the last year and can currently ride 40 miles run 8 miles and swim 1 mile then 6 months should be alright.  You will probably want to have a base of running 25 to 30 miles a week, biking say 60-80 miles and swimming 2 miles a week before you start your offical plan.

So it really depends on your history in endurance sports.  I'm training a full year for my 4th IM with a couple of HIMs along the way and maybe a half mary.  Previoulsy it has been a 6 month build from a base level of training.  I am also not sure if you are recovering from a big race recently where you would need to take some time off to get healthy.  After a  mary I take 2 weeks after a HIM about 1-2 weeks after an IM I take a full month.  More info will help dial in the advice you get.

I have been participating in triathlons for two years (sprints, OLY and a 70.3). I'm doing my first IM on May 19th this year. I started training on December 1st. So it'll be 24 weeks and 2 days for me.  I count all the training and races I've been doing were training to train for IM. 

Feel free to look at my training logs to see what I've been up too.

Sorry I didn't give more background. I'm 47 years old, have been involved in triathlon on and off for 20 years, retired from marathons & triathlons about 8 years ago due to pressures of family, work and persistant achilles tendinosis. I started up again 18 months ago after 7-8 years of keeping in shape but not regular exercise. Now I have a little more free time and that feeling of unfinished business never having completed an ironman. I still have a niggle in the achilles so I've been careful with running. It's not bad though.

In the last 18 months I have completed two 70.3 races and a 2km/80km/20km triathlon which was a week ago. I'm managing to stay under the 5 hours 30 mins for the 70.3's, and ran a half marathon in 89 minutes last year. As I mentioned above, my big weakness is the bike - I struggle to hold 30km/hr (think that's about 18 mile/hr) on the bike for anything over sprint distance.

My current long rides are 100km (60 mile), long runs about 15km, and I swim 2500 metres once or twice a week plus a shorter recovery swim of 1500m the morning after the long ride.

I hope that helps.

Steve

Agree it depends a lot on your background & what your goal in an ironman race would be (e.g. just finish vs sub-12hrs etc.).  Sound like you have the right idea for working on your weakest sport before starting a formal program.  I did my 1st ironman last fall & used Intermediate program from Don Fink's "Be Iron Fit" book.  His plans are 30wks but start at fairly low training volume (e.g. 6-7hrs/wk for Intermediate). Other training plans are a bit shorter, but most all I've seen expect a reasonable level of multi-sport fitness when starting.  In the 2+ yrs before starting Fink plan I had done several tri's (inc a HIM), run 2 marathons, and had yrs of endurance cycling experience.  Swimming was (& is) my weakness, but I felt GTG starting the plan.  In retrospect I prob did not need 30 full weeks to train, but it worked out well for me.  Finished in 13+hrs (despite calf injury on swim & bad flat which destroyed a bike tire) & had a great time.

Good luck on your journey!!!

EDIT- You posted your background while I was posting.  Sounds like you are much more experienced than me, so you have plenty of time to do that IM!!!  Biking is mainly about time in the saddle (& decent bike fit if you haven't checked that already). 

5:30 HIM is solid.  Keep working on the bike, but I think you're in good shape.  Also IM Western Australia is a lot of legal drafting (3 loop bike course, completely flat).  You'll probably find your bike split turns out better than you'd expect, even if you hold back a lot.

Thanks everyone for the advice. After the initial elation from signing up for my 1st ironman some self-doubts have been creeping in, and i'm thinking how can i get ready in time. Going to move forward with a positive attitude from here on. My goal was just to finish, now i'm thinking why not set a target - perhaps 14 hours. Even more enthusiastic after seeing some of the 1st ever Melbourne Ironman on the weekend. I hope it stays on the calender for a couple of years, would love to race a local event. I don't think i'll be matching Craig Alexander's 7 hr 57 minutes though!

steve

I did IMWA this past Dec, and they were extremely strict about drafting. They have a 12 meter spacing, more than normal, and they are RELENTLESS about enforcing the no draft rules.

IMWA was my first IM. It was awesome. You'll love it. If you want any info from me, please PM me, I'd be glad to share. Also wrote up a race report on it, which is posted in my race logs.

As for my training, I had a base from the 70.3 I did in June, then trained up for XTERRA in October, with IMWA in the plans. The weeks following XTERRA were intense. So be prepared to put in the time the last 2 months, when the workouts are long.

Seems like you know what it takes to do HIMs...IMs are just a lot more work!

I think spudone was referring to legal drafting as passing slower riders.  With a 3 loop IM bike course, faster bikers are going to do A LOT of passing as they lap slower riders.  Every time you pass, you can roll up into the slower riders draft zone, pick up some free speed for 5-15 seconds, then sling shot past.  Rinse...repeat...maybe a few hundred times.

I was there also and it was pretty much a solid stream of bikes.  I think people made an honest effort to obey the spacing but it is still a 3 loop course.  So if you're stronger on the bike (or weak on the swim), you're passing people the whole time and you get quite a draft effect.

The only bad thing about the course is if the wind kicks up.

was a fun race, but I thought  the 12 meter draft rule was hard to obey.  the "draft police" on motorcycles seemed to pick people at random to penalize. I almost got nailed a few times..turned out to be the guys in front of me (whew).

I was sick, probably shouldn't have raced, still posted a 6:05 bike on 120 watts average... very, very low power for that kind of time.

Anyhow getting off track but to the original question, 8 months is PLENTY of time to build volume for someone who's already in good half-IM condition

Training consistently is key.

Will you be doing any other races prior to your IM?

What I think best is to have another race like a HIM that you build up to and race and then do an IM. 8-12 week plan is ideal for IM if you are training consistently before that.

Following a super long 16+ week training plan for one race tends to lead to burn out.

Hey Zed perhaps you, the OP and myself shoudl start some kind of group.  I start the 20 week program on April 8th.  It might be good for us to have someone to bounce how things are going type threads.  My first full course distance

I've read about 50 different training plans from beginner to semi-pro.

Typically they're 24 weeks long. That is assuming you have a base to work from.

Otherwise 32 weeks for people with absolutely NO base or perhaps need a chance to learn the routine before the meat of the traning kicks in.

Personally I use a solid 40 week plan but you'll run the risk of burnout if you're not mentally trained.

Whatever you can handle really.

I've seen plans as short as 16 weeks but that's assuming you were already mostly active. Really the 24 week program is 12 weeks base build, 12 weeks 'performance'. So when I say 16 weeks, that's because you may have had a 'B' race earlier and already carry a strong base.