FLO 90 / FLO Disc Combo

I'm going to be purchsing the same combo after the new year and can't wait. As for stems just buy valve extenders so you can carry the same size tubes

Carry a tube that will work for the disc and buy an extender that you will need to get the extension for the 90mm wheel.    

Putting the extender on takes a minute and you do need the small tufo tool, but it is small and light. I put the tool and the extender into small plastic bag and tape them right to the tube in my seat bag.  Put the extender on if needed when you flat. Not perfect solution but as good as it will get with different wheels.

I highly recommend the Tufo extender and to use tubes with a removeable valve core. 

Your disc will not need an extender and will probably need a standard length valve stem.

Buy the valve extender for the front that works with the standard stem tube also...then you use the same tubes for either tire, which you wisely concluded you should do.

You won't need to carry an extra extender as you can pull the one off your front stem and put it on your spare when changing the front.  Just know that if you put the extender on too tightly you won't be able to get it off with your fingers during a tube replacement on the road.

The 'standard' valve stem length is right around 42mm.  You want probably 20mm of stem above the rim so you are looking for about 70mm valve stem.  Zipp sells a 74mm extender for their 808s.  HED sells a 75mm extender for their 90mm wheels.

Boyd 58/85 combo here, I need a valve extender on the back, long valve on the front.

The spare tube I keep has the extender on it, and I keep a wrench with it.  I like the "true" extenders over the sleeve type, where you unscrew the valve core, put the extender on, then screw the valve core back into the extender.  This way you have access to the valve.  With the sleeve type, you have to leave the valve open, then screw the extender on, covering up the valve core.  When I tried that, my pump wouldn't seal, and it seemed like more air was leaking out than going in the tire.

haven't flatted yet, so I haven't been through and on-the-road change, but at home haven't had any issues.

Also the removable core tubes aren't sold everywhere.  You can tell them by the wrench flats near the valve.

One thing disc-related that I just found out this weekend; bike racks can be an issue; the strap that goes through the wheel; disc could be a problem there!

Both the 60 and the 90 have similar aero numbers according to Flo.  I also know the real gains from the 90 will be at faster speeds.  No I am not at the faster speeds....yet    I also like the look of a deeper wheel on the front.

Thanks for the info folks.  I pretty much guessed a standard tube for the disc but will need extender for the front.  Web sites aren't that upfront with the valve lengths on the tubes.

Just to give an alternative pespective.  Carrying an extra extender (while a pain in the neck) means that all you have to do is put an extender on one tube, not remove from one first, to then put on another.  This isn't a huge time saver, but it eliminates a step. Another reason is that the "o"ring on the extenders sometimes degrade and get a little chewed up if repeatedly installed and reinstalled. Remote risk, but an extender seal failure would not be a good thing. I agree with getting around 110 mm total with the extension and the stem.

Yes, you want a minimum of 20mm of valve extending beyond the rim so you can get the head of your pump on it. (25mm is about 1 inch)

Great question.  We've put together a YouTube video about valve extenders here http://www.youtube.com/watch?v=Sx8aLQBPD-M

AND... if you are interested in carrying only 1 length valve, I've come up with the following combinations for my own wheels.  I wanted to carry one type of tube with a valve extender for my 60mm wheels and for my 90mm wheels. I found by using the following parts and pieces I could limit the "stuff" I needed to carry.

Tubes: http://www.michelinbicycletire.com/michelinbicycle/index.cfm?event=Airstop.view

In this size... 700X18-23C / A1 / 52mm presta valve / 98g 

Extenders: http://www.amazon.com/Sram-WE-Valve-24-SRAM-Valve-Extension/dp/B003WOQ974

In a 48mm for the FLO 60s and a 74 for the FLO 90s.