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Lennard Zinn Technical FAQ: Front brake thumping, removing stickers and malfunctioning Di2

Lennard fields questions about thumping front rims, removing stickers from carbon and malfunctioning Shimano Di2 shifters.

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Q. Lennard,
I am getting a thumping out of the front rim when brakes are applied. I put the wheel on the truing stand; the rim is true except about five spokes in from the valve stem it flares out on each side a millimeter or two. I don’t recall hitting anything hard but since I am heavy compared to most; maybe it’s just part of the deal.

What would you suggest? I was thinking of deflating the tire, placing a C clamp with little wooden shims on the braking surface of the rim and slowly see if I can bring in a bit. Is this a safe idea — can a rim take this?

A. Gary,
To do this right and by yourself, you really need the Morningstar Rim Rench.
Without it, you can’t deal with the bead hook.
— Lennard

Morningside Rim Rench
Morningside Rim Rench

Q. Lennard,
I have a pair of Dura-Ace carbon clincher road tubeless wheels with silk-screened graphics. I would like to remove the graphics. Is it OK to use lacquer thinner to remove the graphics?

I did a test and removed one of the four “road tubeless” graphics from the front wheel with lacquer thinner.

I am concerned that the lacquer thinner will damage the clear coat on the carbon.
— Mike

A. Mike,
As I’ve answered many times, usually in the context of how to remove rim cement: lacquer thinner, acetone, and similar solvents will not damage the carbon or its clear coat. Paint remover will damage a carbon matrix, so don’t use that.
— Lennard

Q. Lennard,
After using it a year, I have nothing but praise for the Shimano Di2 system. This past weekend, however, I was in southern Indiana for a team training camp, and had a problem. We had some pretty serious rainstorms one day, and there were many deep water crossings we had to cross, as some of the roads were flooded. The water was about axle deep (and dang cold too!). The bike worked flawlessly.

The next day’s ride started off well, but after 20-30 miles the rear derailleur acted up. When I pressed the “Y” button (to grab a smaller tooth in the back), it actually shifted to a larger tooth. After pressing the button a few more times it would sometimes go one way and other times the opposite direction, and other times unresponsive. The “X” button was unresponsive at times too, but then all of a sudden it would work for a few shifts. I never noticed the “X” button shifting the derailleur both ways … just the “Y” button.

This whole time, the front derailleur worked perfectly. The battery was freshly charged. Anyways, after returning home to Wisconsin, and driving through high 80 degree temps with lots of wind, things must have dried out or something. When I got home, I put my bike in the stand, and it shifts perfectly again. Needless to say, I’m a little nervous about getting caught out in the rain now. Unfortunately, I don’t have the diagnostic tool Shimano makes for testing. I know the shop I bought the bike from doesn’t either. I’m guessing the tool wouldn’t find anything anyways, unless it acts up again.

Would you or someone at Shimano have an idea of what’s going on?
— Steve

Answer from the guru of electronic shifting, Shimano’s Wayne Stetina:

There is definitely water in Steve’s system somehow. I had identical symptoms recently on a bike with a minor cut in the rear harness to the rear derailleur – minor visible damage. But it was only a problem in heavy rain, including delayed shifts, then occasionally multiple shifts.

It’s also possible the plug into the rear derailleur somehow leaked. For that, use air to dry it out completely, then use some electrical conducting lubricant and re-plug it in securely.

If you can’t find visible cable damage, the first thing to check if it ever malfunctions again is whether pushing the X and Y levers both indicate battery charge. If yes, and the front derailleur works normally, everything in front of rear derailleur cable (and rear derailleur) is good. Then try to unplug the rear derailleur, dry out any water (Kleenex or air?) then re-plug it in securely and see if it works again.

If you go to a shop with a Di2 system checker, you need to spray from the front derailleur back to the rear derailleur with a high-pressure garden hose until it malfunctions to diagnose that way.
— Wayne

RE: the bottom bracket seized in a titanium frame:

Dear Lennard,

I just read your latest Q&A column and noticed the question about a “seized” bottom bracket on a titanium frame … I suggest that the bike owner check to make sure that he is turning his wrench the right direction 🙂 ! My 1985 Eddy Merckx titanium frame (actually built by Litespeed here in the USA) has Italian threads on the bottom bracket.

I’m sure that Litespeed probably built more bikes like this. If the bike owner thinks that he has English threads and doesn’t realize that the bottom bracket threads are Italian, then he is only making it tighter when he tries to remove it!
— Roger

Dear Lennard,

Another possible cause of the cup sticking is Galvanic corrosion. If you look at a standard Galvanic series table you will see aluminum is highly anodic and titanium is very cathodic (or noble); opposites you could say.

Add a little water (gotta have an electrolyte for Galvanic corrosion) and the anodic metal will corrode. Oxidation causes volumetric expansion at the corroding surface of the anodic metal. That could contribute to seizing as long as the corrosion is not that advanced; given enough time and water the aluminum cup will corrode away and there will be another whole set of problems.
— Keith

Dear Lennard,

As I understand Ammonia (household cleaner type) can react with the oxidation and make a Ti/Al part break free.
— Dan

From the owner of the bike with the seized bottom bracket:

Dear Lennard,

Thanks to everyone that responded. The frame is an early airborne Valkyrie with English threads.

I am glad to say I got it off. I submerged the bottom bracket in PB Blaster for 12 hours. Best decision was to get the Park Tool bottom bracket tool as I could bolt it into the bottom bracket. The other brand did not allow this.

I then sat frame up on work bench with the stuck bottom bracket side over the edge. I put grandpa’s large pipe wrench on it and began gently striking it with a four-pound sledge slowly increasing force. About the 30th whack it budged. After 1/4 turn worth of bangs and budges it spun right out. Wiped it clean and the Ti is like brand new. I am working on rebuilding it now and the threads are in perfect shape. I used copper anti-seize.
— Tom

RE:MCipollini bicycles:

Dear Lennard,

In response to your letter about MCipollini framesets, I have read that their top-of-the-line frameset is actually made in Italy, not just painted or assembled there. I know that many companies use loopholes to label their country of origin based upon the final point of assembly or painting, but I know that it was a point of pride for MCipollini to actually manufacture their frameset in Italy (hence why it is gray market kidney money expensive … if you can find it).
— Todd