Technical Q&A with Lennard Zinn – Sure it’s tubeless, but eventually it goes flat, too

Dear Lennard,The question is simple enough: What is the quickest/best way to change/fixa tubeless tire? While I love the ride characteristics and generally betterflat resistance of tubeless, fixing a flat--when it eventually does happen-orsimply swapping tires for another tread pattern is nothing short of anordeal. Skinned knuckles, broken tire levers (which you're not supposedto use anyway) and at least a half-hour's worth mano-a-rubber WWF styleaction seem to be the minimum commitment. On a recent ride, a friend who used a tubeless sealant nicked his sidewallon a sharp rock, adding a

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By Lennard Zinn

Dear Lennard,
The question is simple enough: What is the quickest/best way to change/fixa tubeless tire? While I love the ride characteristics and generally betterflat resistance of tubeless, fixing a flat–when it eventually does happen-orsimply swapping tires for another tread pattern is nothing short of anordeal. Skinned knuckles, broken tire levers (which you’re not supposedto use anyway) and at least a half-hour’s worth mano-a-rubber WWF styleaction seem to be the minimum commitment.

On a recent ride, a friend who used a tubeless sealant nicked his sidewallon a sharp rock, adding a gooey, gloppy, messy component to the whole process.Any wisdom to share?

Dear Don,
I am convinced that it is not only a matter both of technique but alsoof tire and rim selection. It can be elegantly accomplished and withoutmess, hassle, tools or skinned knuckles.

If the tire bead’s circumference is undersized, it can definitely bea bear. One UST tubeless tire with which I have struggled mightily is theIRC Serac. I don’t know whether it was just a tight batch, but those wereREALLY tight.

I have also found that the rim matters a lot. I have a number of setsof Mavic UST tubeless rims – ones I have built up myself onto hubs as wellas ones incorporated into pre-built CrossMax wheels. All of them are easyto mount tires on. They require no rim strip, as the spoke holes do notpierce the rim’s outer wall (the nipples or nipple inserts thread intothe wall of the rim’s inner diameter). I have had trouble mounting tireson Bontrager UST rims, which were standard rims that became UST rims bymeans of a permanent plastic rim strip that sealed the spoke holes. Theproblem, as far as I could tell, was that the rim ledges for the tire beadswere standard diameter, but once they had the rim strip over them, thecircumference was increased and required the tire to be stretched farther.Furthermore, the rim valley was narrower and shallower, due to the rimstrip taking up room throughout this area as well, making it harder forthe fat UST beads do drop down into the center, particularly both of themat the same time, which makes pushing the bead over the rim wall at theopposite edge of the rim easier.

I find that with Mavic UST rims requiring no rim strip and most USTtires – Hutchinson, Michelin, Continental, Geax, etc., I can easily mountthe tire by hand. The Shimano UST wheels also do not have spoke holes inthe outer-diameter wall, so those may be similar, but I have not triedthem. Let the opposite bead drop into the rim valley as you push it overthe wall on your side. Start opposite the valve and finish at the valve.Also, wet the tire edges first. And if you put Slime or another sealantin them, which I recommend, this lubricates the installation of the finalfew inches of bead as well.

If you are using Mavic rims and many different UST tires and still havingthese troubles, your technique needs work. You should be able to easilyinstall them without tire levers. My new book described below covers thisin great detail, and so does my existing “Zinn and the Art of MountainBike Maintenance”, in almost as much detail.

Tubes, tubless and tubeless with tubes?
Dear Lennard,
I recall reading a piece you did for VeloNews a while back outlingalternative tubeless systems. I’d like to know the advantage of using tubelesstires and why one would use tubes with tubeless tires.
Thank you,

Dear Karl,
The tubeless advantage is to be able to ride with lower pressure (whichprovides better traction and lower rolling resistance on rough surfacesand side hills) while not having to worry about pinch flats. Furthermore,with Slime or a liquid latex sealant solution inside, you don’t need toworry about thorns or small tread punctures, either.

The most dependable system I have found, allowing you to ride throughanything without concern for flats as well as to leave the bike unusedfor extended periods and still have tires that hold air, is to use USTtubeless tires on UST rims with a sealant like Slime inside.

Weight is not an advantage of UST tubeless systems, because the tirehas a thick butyl layer inside that is as heavy as a tube. However, Stan’sNoTubes system, which consists of a rim strip and some sealant solutionthat you can use on almost any tire and rim, ends up being lighter thanUST tubeless systems as well as tires with tubes. I have found that itrequires more maintenance and TLC, though.

These two questions segue into an announcement of my latest book. Sincelast fall, at the expense of much of my usual amount of skiing, particularlyof my ski racing, and, now at the expense of much of my usual riding, Ihave been working long and hard at the biggest book project I have everundertaken. Zinn’sCycling Primer: Maintenance Tips and Skillbuilding for Cyclists willbe out in June (provided I keep returning those pages coming back fromVeloPress’s production and copy-edit folks in a timely manner-?). It ismy “top 50” list of things you can do to get more out of cycling, be itriding faster, more efficiently and more comfortably, or having more funand having fewer mechanical problems and crashes. The mechanical sectionscontain things like tips on tubeless installation and tire changing, andnumerous other adjustments and upgrades you can do to your road and mountainbikes to have them run better and more reliably.Encompassing the first 13 (of 50) parts of the book (which I call “blocks”since they build upon each other) is the most extensive bike fit sectionthat I have ever seen in any book. Following those are blocks on gettingthe most out of your body and properly caring for it, from diet, to training,to supplemental exercises and stretching, to various kinds of bodywork.Then there are skills, like cornering, descending, climbing, even jumpingand doing stunts for road and mountain bike riders. And then the mechanicalsections cover upgrading and tweaking of road and mountain bikes – beyondthe kinds of things I covered in the “Zinn and the Art of” road- and mountain-bike maintenance books.Anyway, it has been a labor of love and a labor, indeed. Much of the inspiration for each individual section came from your questions, so I particularly wanted you to know about it. Like this column, it incorporates much of what I have learned over the past 30 years of riding and working on bikes. I intend it to be a book about what people who love riding really want to know. This link has a bit more about it.
Look for it in June!

About bent cranks and pedals
I was amazed at the flood of mail I received following up on last Tuesday’scolumn about methods to check for straightness of pedals and cranks. Icould not begin to post all of them, and many of them describe some ofthe same methods anyway, but I wanted to give you a sampling. Some of themare quite innovative!
Thanks for sending them.

Dear Lennard,
Many years ago when I was starting to learn how to be a good mechanicI was shown some pedal axle plates, and had some made for myself. Thesework by having a pedal thread machined into a approximately 10mm thickaluminum (steel would be fine) disc. The face needs to be square to thethread.

Once the disc is screwed onto the (removed) pedal, hold the pedal toa hard surface and spin the plate. The disc will appear to wobble if theaxle is bent.

Dear Lennard,
A simple method for measuring bent pedal axles is as follows:
1. Remove the pedal from the crank and clamp it in a fixtureof some type.
2. Measure the face runout of the flat surface adjacent to thethreads with a dial indicator as the pedal axle is rotated.

Dear Lennard,
One way of detecting a bent crank or a bent pedal spindle is to pedalbackwards. As others have observed, after a while, the body gets used tothe irregularity, and so it becomes the norm. However, unless you’re ridinga fixed wheel, pedalling backwards always (for me) reveals any bent spindle.

Dear Lennard,
I think Hans has the simplest method for checking for pedal and crank”trueness”. He should attach the laser pointer as he originally described,leave the pedal firmly screwed into the crank and rotate the crank (keepingthe pedal alignment with the floor constant). If the pedal and crank aretrue, the circle made on the wall by the laser pointer will have a diameterof exactly twice the crankarm length. If it is not this size, either pedalor crank is bent.

Here is a method for checking bottom-bracket axle straightness:
1 – Mount both cranks pointing in the same direction and measure thedistance between them at the pedal end with a vernier caliper.
2 – Remove and remount them on the next facet of the axle.
3 – Repeat for the last two facets.
Any significant variation in the measurement would indicate a bentaxle.

Technical writer Lennard Zinn is a frame builder (, a former U.S. national team rider and author of several books on bikes and bike maintenance including the pair of successful maintenance guides “ Zinn & the Art of Mountain Bike Maintenance” and “Zinn & the Art of Road Bike Maintenance.”Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.

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