Ask Nick: Shimano’s Di2 gearing compatibility, water bottle code, Ti seatpost

The trick is in the b-tension screw

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Editor’s Note: VeloNews tech editor Nick Legan is a former ProTour mechanic who most recently wrenched for Team RadioShack at the 2010 Tour de France and elsewhere. His column appears here every Thursday. You can submit questions to Nick at, and be sure to check out Nick’s previous columns.


I can’t seem to get a precise answer to my questions regarding Shimano’s Di2. I am currently running an oversize compact in front 52-38 and a 12-27 cassette in the rear. I would like to run a 11-28 cassette in the rear but had heard that the Di2 can only handle a 27 as the largest cassette in the rear per Shimano’s website. I have seen bikes equipped with Di2 with a 28-tooth gear in the rear but a standard 53-39 in front. I have concerns that since I have a 52-38 there will be a gearing compatibility problem. My concerns run into the future as well if I decided to put a 50-34 in front and try to run an 11-28 in the rear. Please clarify what gearing combinations can be safely run on the Di2 in all situations including cross chaining.

—Johnston Wu


I emailed with Wayne Stetina at Shimano regarding your question. He’s been successfully running some pretty wild gear combinations on his Di2 bike. The quick answer is that you’ll be just fine using the 11-28 cassette with either of those crank options.

The recommendations on Shimano’s website are made based on old horizontal dropouts. As such, the numbers are all very conservative.

Stetina has actually been using 12-32 cassettes with 53-39 chainrings on his Di2 bike. The trick is in the b-tension screw. Make sure that you, or your mechanic, screw it in all the way. If you need addition clearance, remove the screw and put it in backwards.

I’ll be trying this setup pretty soon on an Ultegra Di2 bike. But in the mean time, rest assured that with careful setup, you’ll be just fine running any of the setups you mention.


it’s a hoot to pick up a few water bottles from the various pro teams at stage races. Some of them have markings on the tops, like “W” or “X” etc. So, what gives? What’s the secret code?

— Richard Nance


When soigneurs make bottles before the race, they mark all the bottles with an electrolyte or sugar drink with an “X” on the top. The unmarked bottles are filled with water. This lets the mechanic know what he’s handing to the director if a specific order has been radioed in. It also helps the rider who’s collecting bottles know what he’s handing out to his teammates.

So, there you go. Just be sure to wash the heck out of those things before you use them!


I have a 15-year old Trek OCLV 5500 frame. I’ve used an equally aged American Classic aluminum seatpost in it, with no issues other than the sweat-flaked paint on the seatpost-to-saddle clamp. At the same time, the American Classic Ti post from my 16-year old Trek OCLV Pro Issue mountain bike has been sitting in a drawer for almost 15 years, since I installed a RockShox suspension post.

Can I use the Ti post in the road frame without cutting it down to the standard 135mm post length, or should I cut it down to protect the frame from damage?

I’d like to use the old Ti post that’s otherwise wasting in a drawer, lighten up just a smidge and “soften” the ride of my road bike.

Clay E. Ewing


Go for it. If you can achieve your position without cutting it, you’re good to go. If, on the other hand, the post hits one of your water bottle bosses, you’ll want to chop it.

If you don’t think that you’ll ever install the titanium post back on your mountain bike (and let’s be honest, if you haven’t in 16 years, you probably never will) I would cut it though. You’ll save a bit more weight and allay your fears about frame damage.


When a rider has a mechanical, flat, or needs to switch bikes, the rider pulls over, stops, and waits for their car, which in some cases might be a ways behind them. Wouldn’t it be of a slight advantage, especially on mountain stages, if the rider briskly walked up the road as they wait for their team car to arrive?

I’m not sure of the UCI rules and regulations. Maybe there’s a rule that states a rider can only advance in the race if he/she is on the bike?

— Phil Newby


I see your point. But in truth, it wouldn’t save that much time. Ideally a rider stops only at the last possible moment, when his team car is right behind him. If a bike is unrideable, the rider can always get a quick wheel from neutral support. If a bike change is needed, he’ll have to wait.

But here’s the thing. Officials don’t usually penalize a rider for drafting a team car after a mechanical. So, while it’s a bit of work, a good director can get his rider back into the fold with minimal effort.

And there’s always the risk of falling down, trying to shuffle along in cycling shoes. No one wants to risk the embarrassment of that on television!

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