Gear

Technical FAQ: Disinfecting bikes, handling characteristics, tubeless pressure

When disinfecting — mild solvents like isopropyl alcohol, up to quite strong ones like acetone — are not going to damage a bike.

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

Dear Lennard,
With the current coronavirus pandemic, I’m sure many of us are taking closer care to our bikes after riding outside. Are disinfectant wipes or sprays or cleaners, etc. safe to use on bikes? Are alcohol, ammonia, or other types of cleaners particularly unsafe or preferred?
— Brad

Dear Brad,
All of those cleaners should be fine to use on a bike. In general, things to stay away from are extreme solvents like paint remover, which will dissolve paint as well as resins in carbon fiber composites. Well below that level of aggressiveness, mild solvents like isopropyl alcohol up to quite strong ones like acetone are not going to damage a bike. It’s good you’re already wearing gloves!

Water-based cleaners are generally fine as long as you don’t leave parts soaking in them for longer than a couple of hours, in which case you could inspire some rusting in steel parts.

Ammonia is actually very useful for dissolving oxidation on aluminum parts. For instance, it can be very effective in freeing a stuck seatpost.
― Lennard

Dear Lennard,
Here’s my conundrum: I own a 2016 No. 22 Great Divide Disc (I had one before they were cool), 56cm, which I like very much. However, I have two complaints: first, the fork-tire clearance does not match that of the rear end, and I’d like to run bigger tires — I’m currently running 28s that measure 30 — and second, I am a reformed road racer and have always wished the handling were a little sharper on this bike.

Fork spec

I have attached the stock fork and frame specs for your review, but here are the key stats for readers: 375mm axle to crown and 45mm rake. My options are either a Whiskey No. 9 road, which has a 367 a-to-c and a 45mm rake, or the Enve road disc, with a 370mm a-to-c and a 43mm or 50mm rake. I like the Whiskey for the price, rake, and lower a-to-c. I like the ENVE because of the bigger tire clearance.

My brand preferences aside, if I were to get an ENVE should I get the 43 or the 50? Or should I stick with the stock a-to-c that the Whiskey offers and assume the lowered stack height will give me the sharper handling I’m looking for?
— Andrew

Dear Andrew,
In general, to get “sharper” handling, you want to decrease the fork trail, which pushes the bike to lower stability and hence greater maneuverability. Using a shorter fork, which both of those options are, steepens the head angle, which reduces fork trail. Increasing the fork rake also reduces fork trail.

Your 56cm Great Divide Disc has a 72.5-degree head angle. With 700 X 32C tires (685mm diameter) and 50mm of fork rake, you would have 56mm of fork trail. With 43mm of fork rake, you would have 63mm of fork trail. The former should be fairly quick steering; the latter should be very stable.

So, if you want quicker steering with the ENVE fork, get the 50mm rake. The 3mm additional axle-to-crown length is not going to play a significant role.
― Lennard

Dear Lennard,
Your comments about severe bike shimmy left me wondering about my own experience this past summer with a 2019 model Trek Emonda SL6 with Enve SES3.4 tubeless wheels. With around 5k miles on the bike (flat Chicagoland roads), I took it to Boulder for a week of cycling on the front range. Heading out on my first ride on Old Stage Road (I suspect you know it well), the first descent makes a slight left on a somewhat bumpy road surface. I felt a gust of wind right-to-left as I entered the turn (not at full speed), which threw the bike into a severe uncontrollable shimmy — one that resonated the length of the bike front-to-back. Very scary, as I could literally feel and see the whole bike flexing across the top- and down tubes. I didn’t fall (though I was certain I would), but the shimmy continued unabated until I reached a near-complete stop. I carefully continued riding up to Jamestown, and descended carefully, not experiencing the shimmy again. But the next day as a test I rode up Old Stage and sure enough at the same place on the descent the combination of rougher road, a slight turn, and a gust of wind caused the same shimmy again. I was prepared though, and I controlled it quickly. Following that second experience I rode carefully for the week, perhaps doing another 25K vertical, being careful to firmly control the front end. In one instance the bike did weakly shimmy start again.

Now I should say, the previous summer I also rode a 2018 Trek Emonda SL6 in the same Rockies, doing more than 50K vertical with absolutely no hint of any shimmy. Same wheels. That frame developed a crack, which Trek warranted, ergo the 2019 replacement. So, I brought the 2019 bike back to Trek, and they were suspicious of what appeared to be carbon delamination in the head tube. They replaced the frame again (I switched to a Madone in the hope it will fare better.)

As you pointed out, it can be difficult trying to figure out what causes a shimmy, though I don’t believe in my case it has anything to do with the wheel, tire or sealant. I guess my point is, structural weakness in the frame can also increase the chance that an unpredictable triggering event blooms into a full-blown shimmy. You should advise cyclists such as the one who asked you about shimmy to have the frame carefully examined (on the inside). As you seemed to know, an uncontrolled shimmy at speed creates a very dangerous situation.
— Marty

Dear Marty,
I became a framebuilder due to a scary experience with shimmy driving me to try to eliminate it. Your narrative illustrates clearly how shimmy can be situational, and, given the right combination of road, wind, speed, and rider weight, a bike that had never exhibited it before can suddenly shimmy (nearly) uncontrollably.

And yes, your recommendation is spot on: by all means, if you experience shimmy under any conditions, have the bike examined carefully by an expert, particularly the frame and fork.
― Lennard

Dear Lennard,
I’m commenting on this VeloNews article — It appears that Tom exceeded the maximum pressure limit of the Pirelli Cinturato Velo 700 X 26C tire.

I did not find a pressure limit on the Pirelli site, but I found this who said that the maximum pressure for Pirelli tubeless is 87 psi.

Not safe for tubeless
Familiarity: I’ve used it once or twice and have initial impressions: I have concerns about the safety of your Cinturato tires. I recently purchased a Pirelli Cinturato Velo 700×26 tire that can be set up tubeless. I read several reviews on this tire before purchasing and the only consistent comment was that they tend to run oversized, i.e. the 700×26 is closer to a 700×28. I set the tire up on a DT RR440 rim with no problems and checked to see if it was indeed oversized. I measured the tire width at 25.7mm, which seems spot-on for a 26. Fast forward a bit and I’ve done a few rides and put a little over 100 miles on the tire, when I notice it is starting to rub against the top of the wishbone brake bridge on my Time RXRS. The tire looked noticeably larger so I measured the width and it came in a 27.6mm, the only two reasons I can think of for this is maybe the casing stretched or the bead stretched. Anyways, being I can’t use it on the rear, I decide to try the front, so I mount it on a Stans Alpha ZTR 340 and fill it up to 100psi when the tire explodes off the rim.

Yes, I now realize that Pirelli has two maximum pressure ratings on the tire, one for tubeless one for tubed. I looked at the tire before mounting and saw 116 psi max, and assumed 100 psi was safe; they list a max 87 psi for tubeless, the fact it blew off at 13 psi over is still scary. (Quick note: I have been running tubeless road almost since they first came out with no issues other than the occasion flat that sealant could not plug, I’ve put over 10,000 miles on this ZTR 340 rim mostly tubeless without an issue. However, I’ve always stuck with Hutchinson tires in the past, with the exception of one IRC (it worked fine also). The only reason I can think of for the Pirelli exploding off the rim is that the tire bead must have stretched, which I think would also explain the increase in width of the tire. If that is the case, and with the amount of comments on the Pirellis being oversize, it seems this could be an issue with all Pirelli Cinturato tires, maybe all Pirelli tires. In my opinion this is not a safe tire to run tubeless. I’m quite disappointed as I’ve had to purchase a new tire to replace it and have an almost new Pirelli that I don’t feel safe using.

The 100 PSI in a 26 mm tire does not exceed the manufacturer specs for the rim. BST-R rims offer maximum versatility with the widest range of tires and pressures. Compatible with 25mm to 32mm tires at pressures up to 115psi both with and without tubes, BST-R rims are also compatible with wider, higher-volume tubeless tires at pressures below 45 psi.
— Raymond

Dear Raymond,
Thanks for doing this investigation.
― Lennard


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is a custom frame builder and purveyor of non-custom huge bikes, 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 Bikes and Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a bachelor’s in physics from Colorado College.Follow @lennardzinn