Gear

Technical FAQ: Wet riding, shock pressure, gear compatibility

Lennard Zinn answers questions about wet-weather riding, whether shock pump gauges actually work, and drivetrain compatibility

Dear Lennard,
Harry may want to try an Easton seatpost. Easton’s “Relief Area Design” places flat regions at the front and back of the post that create small gaps at the clamp areas to avoid contact. Not the best for keeping water out, but it’s just the ticket for “pinchy” frames!
— Ryan

Dear Ryan,
Good suggestion. And, regarding water getting into the frame around the seatpost, check out the simple suggestion in the letter below.
― Lennard

Dear Lennard,
‎On Haida Gwaii [British Columbia] at this time of year we often have wet roads … and occasionally water gets in through the seat post clamp keyway … even with fenders. My friend Terry Mitchell came up with this fix involving an old mountain bike tube. See photo above.
— Peter

Dear Lennard,
I frequently find myself picking bits of aluminum out of my brake pads. I suspect when tiny bits of dirt or sand get onto the pad, they scrape metal from the rim surface, which accumulates and embeds in the pad. I run Ultegra 6800 brakes with stock pads on Dura-Ace C24 rims, which have an aluminum braking surface. Despite keeping the rims and pads clean, I wore out my last pair of DA rims faster than I’d like. Should I try other pads?
— Scott
Portland

Dear Scott,
Probably you need to move someplace less wet if you want to be rid of this problem! Riding in the rain is when you get grit on the rims and pads, resulting in tearing up the aluminum braking surface and embedding the pieces into the pads. I doubt whether different pads will make a significant difference. Go on a cycling vacation in southern Arizona with new brake pads and see if they aren’t free of aluminum shards at the end of it!
― Lennard

Dear Lennard,
I have often wondered why in 2015 the industry has not created a better way to set air pressure in a shock/fork. I’m constantly having issues setting the correct pressure because a certain amount of air leaks out no matter how fast I try and remove the pump from the fill valve. So is there anything that might be coming in the future that would stop this silly problem? Just scratching my head looking for a better way to get truer air pressure settings.
— Thomas

Dear Thomas,
I wonder if you’re not misinterpreting air escaping from the pump hose as coming from the shock. Virtually all modern shock pumps have a no-leak head that allows the Schrader valve to close before it loses its seal around the outside of the valve. Air, at the pressure you pumped it to, of course escapes from the pump’s hose when you remove its head from the valve. But none should be coming out of the valve. You can have confidence that the pressure you measured before you removed the pump is in fact the pressure that is still in the shock after you removed it.

Convincing yourself of this afterward can be tough, because you can’t measure it anymore without reducing the pressure. When you put the pump back on the shock, yes, it will read a lower pressure than you had put in there, but that’s because air from the shock, which holds very little volume, has to fill the hose to the same pressure as the shock before you can get a reading on the pump gauge. But that doesn’t mean the shock was at that pressure; it only means that you changed the system by taking a measurement. That’s called the “observer effect” in physics, and it holds even if you just use a pressure gauge, rather than a shock pump, to measure it.
― Lennard

Dear Lennard,
I ride Campagnolo Super Record 11 on Zipp 404 wheels. I want to purchase some custom wheels for climbing, probably Reynolds wheels. I’m going to put Super Record [cogs] on Reynolds and Chorus [cogs] on Zipp. What are the chances I can swap the wheels back and forth without having to adjust rear derailleur?
― Mark

Dear Mark,
Chances are very good you can swap wheels and continue to have good shifting without any readjustment of your rear derailleur. I have 11-speed Campagnolo-, Shimano-, and SRAM-equipped road bikes, and I have many wheels with 11-speed cogsets, both Campagnolo cogsets on Campagnolo-compatible freehub bodies, and Shimano and SRAM cogsets on Shimano-compatible freehub bodies. I switch the wheels around on the bikes, and they have a variety of cog models as well as brands on them, including Record, Super Record, Chorus, Dura-Ace, Ultegra, Force, and Red. All of these 11-speed wheels shift fine on all of the bikes with no readjustment of the rear derailleur.

And while I did not have this compatibility across brands until 11-speed came along, I used to have compatibility between models of cogs within a given brand, no matter the wheel. For example, I still have dozens of cyclocross wheels of a wide array of brands that have 10-speed Campagnolo cogsets on them, from Record to Chorus to Centaur to copies from Miche and even to Shimano 10-speed cogsets converted by Wheels Mfg. to fit on Shimano freehub bodies yet be compatible with Campagnolo 10-speed drivetrains. All of them shift perfectly on any of my or my daughter’s Campagnolo 10-speed-equipped cyclocross bikes without any readjustment of the rear derailleur. I did have to put some spacers behind one of the Wheels Mfg. conversion cassettes one of the Shimano-compatible freehub bodies in order to get the smallest cog the same distance from the dropout. But once I did that, I could swap that wheel onto any of the bikes, and it, too, would shift perfectly without any derailleur readjustment.
― Lennard

Dear Lennard,
In your January 27 column you addressed a question about using SRAM 11-speed road shifters with a 10-spd MTB rear derailleur and an 11-speed cassette. I’d also been considering doing this, and finally took the plunge to upgrade our touring tandem to 11-speed using the XTR 11-40 cassette. I wasn’t certain how well it would work, but it seems to be mostly OK. I wrote a long report on the performance so far in the following thread in the tandem sub-forum of BikeForums; see the info that I gave in response #10 in particular. Keep up the excellent and informative work!

Chris

Dear Lennard,
I have a new Trek Domane with Di2 Ultegra components. I would like to go with the 11-32 rear cassette but the expense of buying the medium-cage rear derailleur, new chain, and cassette are holding me back. I see SRAM sells an SG-1190 with 11-30 gearing. While not inexpensive, if I could use my short cage derailleur and possibly existing chain, this would be a lower-cost alternative and provide me with some relief on the hills around my house.
Mark

Dear Mark,
I haven’t tried this, but, assuming you currently have an 11-28 cassette, I’m willing to bet that subbing in the 11-30 SRAM X-Glide 11-speed cassette would work with only some adjustment of the b-screw. It’s not worth risking cross-shifting and ruining that expensive derailleur by trying to use a chain that won’t reach over the big-big combination, though.
― Lennard

Dear Lennard,
Regarding some of your road tubeless points in various articles, I think in particular something I read in VeloNews … Using levers …

I’m sure you’re aware that it isn’t recommended to use levers on road tubeless because if not careful, you can deform the bead; that is bad. I had a mechanic try to monkey a tire off a rim with a lever once, he hadn’t realized it was tubeless until too late. Upon casual inflation afterward it blew off the rim. BTW, wearing earplugs when initially inflating is a pretty good idea. Ha!

In the article the scenario was roadside repair. If you are careful, and you use a plastic, or plastic coated lever, you can gently use it to help unseat the bead from the rim.

I find that roadside, if you need to install a tube because you forgot to top off on sealant … ahem … Carefully using a lever is a non-issue. The idea is to just get the lever under some already unseated bead and gently slide the tire off the rim. None of that up and down leveraging to pry the bead over the rim; unseat the bead and use the lever as a guide to gently slide the bead over the rim.
Martin