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Technical FAQ: Road tubeless tires on rim-brake carbon rims, Ultegra drivetrain compatibility, and more

How to service Phil Wood Hubs, clean disc brake calipers pistons, and praise for Di2 ‘triples.’

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

Dear Lennard,
Can you tell me if it’s safe to run tubeless tires on traditional clincher rims (e.g., Campagnolo Bora Ultra 35)? I’ve talked to lots of people and read countless forum posts on this question. The answers I found are nearly equally split between “it’s completely fine, I’ve been doing it for years” or “don’t do it if you value your front teeth”. What’s the scoop?
— Michael

Dear Michael,
I can’t tell you unequivocally if it’s “safe” or not. What I can do is tell you what I would do and my reasoning for why or why not.

While I was a proponent of road tubeless from the get-go on tubeless-specific wheels from Campagnolo, Shimano, and Fulcrum with the original UST road tubeless tire from Hutchinson, I cooled my jets considerably on this when riders started using tubeless tape on standard rims with “tubeless ready” road tires. I had seen and heard of enough disasters of tires coming off at speed to swear off of this setup. I explain here, in response to another scary blow-off, why I think using tubeless tape on a standard rim can be problematic. Now, I’m more comfortable with it. Why?

The European Tire and Rim Technical Organization (ETRTO) sets standards for the sizing of rims and tires for the European Union. Many tire and rim manufacturers in the past seemed not only to not adhere to those standards closely but also to not participate in the annual ETRTO meetings and discussions leading to their continuous revision. Rim manufacturers looked at tire blow-offs as the fault of the tire, and tire manufacturers blamed them on the rim. Now, there is considerably more buy-in on strict adherence to the standards and to keeping them current by both rim and tire makers. It should be obvious that the tire’s bead diameter and the rim’s shelf diameter have to be the exact right sizes in order that air cannot leak out under the beads, the beads cannot move once at riding pressure, and the tire can be mounted without damaging it.

On your particular setup, I lean more toward the “don’t do it if you value your front teeth” camp, especially if you happen to be a heavy guy who rides in the mountains. The Campagnolo Bora Ultra 35 is a carbon rim-brake wheel, and, as such, is prone to the rim heating up more (and hence heating the air in the tire more) on descents than an aluminum rim-brake wheel and way more than a disc-brake wheel. If that super-heated tire, now at up to 50 percent higher pressure than it was at the house due to being heated to over 300F° by the rims brakes when ripping down a steep mountain and slowing down hard for a switchback under a heavy rider, doesn’t just blow straight up and off of the rim, its tight grip on the slick rim strip lubricated by slippery sealant will be lightened, and then the side force of hard cornering can open a slight gap along the rim wall and burp some air. Unlike on a big, tubeless mountain bike tire running at low pressure that burps and just lets a small amount of pressure out with each quick burp, a burp on a road tire at high pressure drastically drops the amount of air in the tire.

I don’t think it’s wise to run tubeless road tires on rim-brake carbon wheels. I’m sure I’ll hear from people who do this all of the time with no problems, and maybe you would fall into that category as well, but I won’t do it.
― Lennard

Shimano Ultegra crankset
Shimano R8000 chainrings should fit on a 6800 crank. (Photo: Dan Cavallari | VeloNews.com)

Dear Lennard,
Would you know if the Ultegra R8100 and R8000 big rings can be installed on a 6800 crank? At first glance, it looks possible, was just curious if you have tried at least an R8000 ring on a 6800 crank.
— Steve

Dear Steve,
I haven’t tried it. It should be possible, and there will be a mismatch in both color and shape. The bolt pattern is the same, and I would guess that the bolt length, diameter, and thread pitch would also be the same. The shape of the arms and mating area of the chainrings are different, so you won’t have a smooth transition from spider arm to chainring. The top ridge on the arms of the 6800 crank is wider than that of the 8000-series cranks. Obviously, the color is different, too.
― Lennard

Dear Lennard,
I have a Mercier with Phil Wood hubs, and the rear has a bit of play that I haven’t figured out yet how to adjust. Are you familiar?
— Monte

Dear Monte,
Yes. Here are the instructions for adjusting Phil Wood hubs.
― Lennard

Another testimonial (“the natural next thing”!) to Shimano Di2 electronic-shift triples:

Dear Lennard,
I just read Tim’s reply to Bob’s question of 3×11 STI on a loaded tandem. I have done this – I bought a 1992 Burley Tandem from Goodwill and, because of the long length of cable from the front handlebars to the rear derailleur and a flexy steel frame, I had rather inaccurate shifting. So, I did the natural next thing – I upgraded a 1992 tandem to Shimano’s 3×11 XTR Di2.

The biggest problem I had was finding a crank to replace the 1992 crank that would work with newer components (long story short, I ended up making a double-sided crank from 2 RaceFace Turbine module cranks and a transmission bearing as a bottom bracket – don’t laugh; it works really well). I will point out that I think the front derailleur on 3×11 is only recommended for a 44T large ring or smaller – so a 46 or larger probably wouldn’t shift all that great. That said, I tried a 48T and it shifted better than the original FD from 1992 – mileage may vary on newer tandem setups though. I believe now I am running a 42T. The range I would think would be great for what Bob has in mind, but the Di2 is expensive, and the triple Di2 FD is somewhat hard to find.
— John

Dear Lennard,
I just read the column in VN and noticed a detail that may need clarification: Does it make a difference to lubricate the caliper pistons with mineral oil or DOT fluid? Or do you use like for like to ensure there is no possible contamination with the fluid in the system?

Interestingly, Hope brakes recommend using silicone oil, whether it is a mineral oil or DOT system. > Align and Lubricate calipers > 1:05 in the video.
— Carl

Dear Carl,
When I wrote, “Ideally before pushing the pistons back in their bores you first cleaned the protruding sides of each piston with a cotton swab dipped in the same brake fluid that’s in the brake,” I had thought I had specified to use “like for like” when cleaning the piston. Maybe that wasn’t clear. Yes, clean and lube the piston’s outside with the same fluid that is pushing on it from the inside.

Also, Hope brakes use DOT fluid, and I didn’t see on that video where Hope was also promoting silicone oil lubrication for mineral-oil brakes.

Having no idea what silicone oil is, I found that you can also use it for creating “stunning cell effects in your paintings” by mixing it with acrylic paints. Using silicone oil seems like an extra PITA to me. I just clean and lube the pistons with the same fluid that goes into the brake.
― Lennard

Dear Lennard,
Somehow the link I sent for the front derailleur on the Cycles Marinoni online store got changed. It should be: https://store.marinonicycles.com/productmodel/219
— Harry


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.

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