Gearing Suggestion

Brian Hagan

Is there a website that you can enter course, IF target, FTP, weight and get a suggested chain ring size / cassette combination?  Is there some scientific way of determining this, or is it just based on feeling on training rides on similar terrain?  I currently have a 175mm crank on a 53/39T Quarq with a 28/11 cassette.  I am thinking of getting a compact for IMMT, but not sure. 

Attila Matyas

I would maybe start by looking at the gear inches to see how different combinations will affect your ride.  I use a compact crank with various casettes depending on course.  For going downhill only on really long and straight descents do I ever spin out.  Usually because of turns etc. you have to coast anyway so unless it's a really flat course and you are really strong to push the 53/11 for a long period of time I would say go with a bigger back cassette at a minimum if you are keeping the 130BCD cranks. For climbing I find it much more comfortable to spin up a hill than grind at a low RPM but this is a preference and I'm also a bigger dude so I'm happy with the 32 in the back. 

I think the more gears you have in general the better.  When I first switched I felt like I was shifting constantly to try and find the right gear but over time I got used to it and it also helped raise my RPMs, I was much more of a grinder when I used the 130BCD. 

If you were to switch to compact going to a 50/34 is sometimes a big jump and takes some getting used to.   In that case you can opt for the alpine double which is a 52/36 and pretty close to what you have now in the 130BCD setup.  The benefit is that you can now put a bigger cassette in the back to get up the hills and have 3 fewer teeth with the 36 in the front and this combo might be enough relief on the bigger hills.  With a long cage derailleur in the back or if you back out the B-tension screw you can easily fit a 36 cog with no shifting issues.

You can use this site to plug in some options and take a look at how it will change your speed based those choices at particular cadences.

http://www.bikecalc.com/gear_ratios

One more:

https://www.stevehoggbikefitting.com/cycling/2011/05/compact-cranks-vs-standard-cranks-gearing-implications/

One last thing would be to read through the race reports from previous IMMT racers to see what they did.

Brian Hagan

@Attila Matyas Thanks! This is so helpful. I think I remember @Coach Rich doing a webinar on this last year, so I am going to look for that as well. Your response was very helpful!

scott dinhofer

@Brian Hagan - not sure of how big of a person you are, but on my tri bike i went down to 165 on the crank to open up the hips... helped dramatically. Aside from that, I'd pretty strongly recommend a 52/36 for IMMT with the 11/28 you have in the back.. 
just an n of 1 chiming in here from experience on that course and LP.. 

Brian Hagan

@Scott Dinhofer that's interesting.  I may talk to my bike fitter and see what he says about the 165.  I am 5'10" and 160 lbs.  I have been playing with Best Bike Split, and I am going to see if I can do some steeper longer climbs without going over the watts they recommend for the climbs.  My road bike has basically the same drive train, so I will get a good feeling at BRC.

Clark Mitchell

@Brian Hagan Where did you net out on this subject?  I'm getting ready to switch to a 50/34 for IMMT from a 53/39.  Just curious to see what you're thinking and if you know anything about IMMT vs. what we climbed during BRC.  Thanks!

Brian Hagan

@Clark Mitchell I ended up getting a compact 50/34. I am no longer doing IMMT, but if I were I think it would be perfect. My FTP is roughly 3.6 w/kg and with an 11/28 I can spin up those climbs without exceeding my goal watts with a few exceptions. With a standard crank my TSS would probably have been 350. I do spin out a little more than with the 53/39, but I'd rather do that than spike on every climb. 

Clark Mitchell

Thanks @Brian Hagan, this is really helpful.