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Technical FAQ: Handlebar aerodynamics, frozen seatposts, wide tires, and more

Lennard Zinn answers questions about cockpit aerodynamics, wide tires, and sticky components.

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Have a question for Lennard? Please email him at veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
Longtime reader, first-time questioner. I know narrower handlebars are all the rage on road bikes for their improved aerodynamics and I wanted to ask a quick question. If I were choosing between 2 bars, one with an aero profile in a 40cm width and a traditional round profile bar in a 38cm width, which one would offer the best optimization of rider and bar for a more aerodynamic package?
— Eric

Dear Eric,
I don’t have any data to back this up, and therefore may be wrong, but I would think bringing the arms in more, thus having them be less out in the wind by themselves and blocking more air on the chest, makes more difference than a flatter upper section of the handlebar.
― Lennard

Dear Lennard,
I have found lots of older information about tire width vs rolling resistance, however, I have not found anything current or addresses what I am looking for: I am finally thinking of moving from my road race bike to a gravel bike for the versatility to complement my mt bike. I want to be able to ride centuries, still retain the light nimble, road feel, etc.

I have tubeless 28 mm on my present bike. How will a 36 – 40 mm tubeless tire feel? Will it feel a lot more sluggish? I do realize the bike frame will also make a difference.
— Thom

Dear Thom,
I think you’ll be surprised at how un-sluggish bigger tires with smooth tread can feel. It of course depends on the particular tire, the tread pattern, and the pressure. I have three sets of wheels for my gravel/road bike; one of them has 28mm road tires with a file tread, and another has 42mm (Challenge Strada Bianca) tubeless tubulars slicks (the other set has 33mm cyclocross tires). On pavement, I run the 28mm tires at 70psi and the 42mm tires at 45-50psi. They both roll fast on pavement and feel similarly hard. And they should feel similarly hard, due to having similar hoop stress at these pressures.

On pavement, I am more careful on corners with the fatter tires. They grip and corner great, but intellectually I know that the leverage pushing on the tubular glue joint between the taller tire and the rim is so much higher than on a 23mm or 25mm tubular that I generally don’t rail corners. In any case, they definitely do not feel sluggish relative to the 28mm tires. However, if I use a knobby tire, it does feel more sluggish on pavement.
― Lennard

Challenge’s Strada Bianca tires are a plush treat. Photo: Ben Delaney

Dear Lennard,
I am considering getting a custom frame. I also want to run a smaller tire in the front (23mm) and a larger rear tire (28mm) – for aero reasons. My question is: Does this tire size difference affect steering in any (meaningful) way? Does it change trail and wheel flop? Background: The second picture of three bikes that handle differently where the rear is lifted — which decreases (effective) trail — got me thinking about this.

I thought a bit about it myself and the conclusion I came to is: if the rear tire is bigger than the front tire the (virtual) head tube angle increases and so trail and wheel flop decrease. But the effect is relatively small for the tire size difference I am considering (28mm vs 32mm): I calculated ~0.25° difference in (virtual) head tube angle assuming tire height changes 4.5mm (based on rolling resistance data).
— Nic

Dear Nic,
Your conclusion is correct. It does steepen head angle and decrease rake and hence increases oversteer and decreases stability at speed. Will it be enough to notice the handling difference? I doubt it.
― Lennard

Dear Lennard,
I crashed yesterday & snapped off a carbon post in a titanium frame. Saw a VeloNews article you did on getting them out, but this one is broken off a few mm above the seat tube. Have been trying to cut grooves in with hacksaw blade, but it is very slow, and the blade doesn’t really bite. Your article mentioned using a quill stem & handlebars for leverage. I have another bike with a custom long quill stem so may try that. Saw something online about pouring in concentrated sodium hydroxide solution from the bottom. No idea if that would eat the Ti. Do you have any suggestions?
— Tony

Dear Tony,
I don’t know whether it is necessary to use sodium hydroxide. Ammonia or Coca-Cola poured into the seat tube (frame upside down) from the bottom bracket will break down corrosion adhering the carbon post to the aluminum sleeve (often present in Ti frames to size the ID of the seat tube to the OD of the seatpost) inside of the titanium seat tube. Obviously, seal off the top of your broken-off seatpost so the ammonia or Coca-Cola doesn’t escape. Add enough volume so it’s deep enough that its level is above the bottom of the seatpost and continues to work overnight.

Ammonia or Coca-Cola will not damage the titanium or aluminum. I’m sure sodium hydroxide also won’t damage titanium; I don’t know whether it would attack the aluminum sleeve.
― Lennard

Dear Lennard,
It seems that each year I’m looking for a solution for lower gears on my bikes. I’m 68 and not the fittest rider out there, but I give it my best.

I have an Ibis Hakka MX with a PraxisWorks crank and a 38 tooth single front chainring. I want to lower my gears a bit (again!) and changing out all of the rear components (I’m maxed out on derailleur range) would get expensive. Praxis doesn’t make a smaller chainring than 38 in this type, would you know of an alternate product?

It’s a mechanical SRAM Rival derailleur. I’m not sure of the brand of cassette, but it is an 11 speed 11-46. There may be a derailleur extender on it to accommodate the number of teeth. You’d think that would be enough gears!

Every once in a while (not often), I hit a spot where I’m at my limit, I’ve usually dropped to just a couple miles an hour, and it’s always a very short section where the ramp is steeper than the other terrain. Would love to be able to get over those sections. The truth is, more fitness would probably be more practical!
— Don

SRAM Rival mechanical rear derailleur. Photo: VeloNews.com

Dear Don,
You should be able to put on a SRAM X01 or GX or NX derailleur for 1X11. Then you could run something like a SunRace MX8 11-Speed 11-50t cassette, Shimano CS-LG600-11 11-Speed, 11-50t cassette, or Shimano Deore CS-M5100-11 11-Speed, 11-51t cassette.
You’ll need a longer chain.
― Lennard

Dear Lennard,
I just read your article on Campy 11 spd rear derailleur compatibility [with a 34-tooth cog]. I currently use a Campy Chorus Medium rear with a Shimano 11-34 cassette with no difficulty at all. I noticed last year when I was installing a 11-32 cassette on my wife’s bike with a Potenza RD medium cage and as I adjusted the B screw, I noticed there was what I thought was enough room for a larger cassette. As we are getting ready for this year’s Triple Bypass, I decided to try an 11-34 cassette, and it worked without a dropout extension.

My wife had a Shimano wheel, so it was seamless. I have a Campy Shamal wheel and needed to replace the freehub with a Shimano-compatible one.
— Mike


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of The Haywire Heart,” and author of many bicycle books including Zinn and the Art of Road Bike Maintenance,”DVD, as well as Zinn and the Art of Triathlon Bikesand Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn on Twitter.