Technical FAQ: Shimano brakes with Sram eTap

Dear Lennard, I run a Specialized S-Works Tarmac with a mix between Ultegra and Dura-Ace components. I’m thinking of a switch to an electronic system with Di2 the obviously choice because I can keep my calipers and chainset. However, the SRAM eTap looks like a good option but I…

Dear Lennard,
I run a Specialized S-Works Tarmac with a mix between Ultegra and Dura-Ace components. I’m thinking of a switch to an electronic system with Di2 the obviously choice because I can keep my calipers and chainset. However, the SRAM eTap looks like a good option but I don’t want to spring for the whole groupset.

Can I mix the eTap and Shimano groupsets to keep the costs as low as possible? Ideally, I’d like to keep the calipers (I assume the pull will be sufficient?) and the chainset; I’m running a Stages power meter and don’t really want to change.

So I’ll look to change the levers, front and rear mech, cassette and chain.
— Ryan

Dear Ryan,
You can basically do that, with one caveat: The Shimano brakes will not work ideally with the SRAM levers.

Current Shimano calipers are built with higher leverage (longer lever arms) and are paired with a low-leverage lever that pulls more cable. So the SRAM lever, which has higher leverage and less cable pull than the Shimano lever, will not get the pads to the rim as quickly; they will need to be set up with the pads closer to the rim to get the same range of lever movement, and they will make the brake system more powerful than it was designed to be. That said, I used to have a bike set up with Dura-Ace ST7900 (10s) levers and SRAM Force calipers, and, once I got used to it, I had no problems whatsoever with it.

If the bike is currently 11-speed, there will be no reason to change the chain and cassette, if they’re not overly worn. The Stages crankset will work fine.
― Lennard

Dear Lennard,
I turn 68 this summer and live in the peak district in Derbyshire England. I have always had bikes, currently three road and three mountain.

I do a lot of my own work on bikes, (physics degree like yourself).
I am riding a 1963 steel 531 frame which I have modified with compact chainset, long-reach dual pivot brakes and cold-set rear fork stays put in a longer QR axle in rear wheel and changed from 5 speed to 14 speed. I have 34/34 as my bottom gear.

I have a very nice Ribble bike with 53/39 Campag Chorus groups set 10 speed cassette 11-26t. It gives me 39/26 bottom gear, but it’s not low enough. I have tried to find a way to alter it.

Could I replace back wheel with Shimano hub and freewheel and somehow change rear derailleur and cassette to give me lower gears. It just seems rather expensive to do anything and impossible with Campagnolo kit.

Is my only option a whole groupset change??
Think I might just sell it and put money to another bike!
— Mike

Dear Mike,
Well, you could certainly increase the capacity of that rear derailleur to 29T merely by getting a long-cage Campy derailleur. And you could probably get away with a 30T and perhaps more than that by messing with the Campy equivalent of a b-screw, which is a screw at the lower knuckle that winds its return spring tighter. Of course, you then have the issue that Campy makes no 10s cogs larger than 29T, so if you want to push beyond that, then you have to do some mixing and matching.

Without going to a non-Campagnolo derailleur and shifter, if you want a larger cog than 29T, then you will need to get an aftermarket one that is spaced for Campy and fits on a Campy freehub body. Otherwise, you’re looking at a new drivetrain, or a new bike.
― Lennard

Dear Lennard,
I have recently found some NOS Stronglight 49D crankarms in 175mm length! They would be for my vintage Peugeot Competition PKN 10E 1980 Reynolds 531 road machine. I will have to pay close to $250 to acquire them, but since they match the vintage and look of my French bicycle I am really tempted. My question then is; should I expect a long life out of these or have they ‘aged’ as to limit their serviceable lifespan? From all appearances they have never even been mounted before.

— Dziwei

Dear Dziwei,
As long as they aren’t corroded from being in a caustic environment or something or heated to high temperatures, their lifespan will not have been reduced by sitting in a box.
― Lennard

Follow-up on freezing cables on disc brakes and rolling resistance of tubulars:

Dear Lennard,
Regarding Dave in Cincinnati and his problem with sticky brakes on his Trek Domane, the cause is the position of the rear brake on the chainstay. The cable housing is effectively facing skyward where it enters the rear caliper, which allows moisture easy entrance. Once in there, it’s not coming out without assistance, and it will freeze when the temperature drops. This isn’t a problem on the front brake because moisture is unlikely to get into the housing where it enters the front brake, as that hole faces downwards.

There is a relatively simple solution to this problem, though. Placing a V-brake bellows on the exposed brake wire between the caliper and actuating arm almost completely prevents dirt and moisture from getting into the housing. I have used this setup on Hy/Rd brakes during a couple of New England winters and have had no freezing problems.
— John

Dear Lennard,
I had similar problem for the first time ever on a road bike with disc brakes a year ago. I was riding in Dublin Ireland every day and majority of those were wet but rarely freezing. However, on one freezing morning my brakes froze in place and would not release. At first I thought it was the mechanical disc caliper but roadside defrost didn’t work… It happened again a few days later and I decided it was the cable and when defrosting the part under the BB it work. Once home that evening I took it apart, greased it, and CHANGED THE CABLE Routing.

The thing is, with disc brakes, cable routing runs low on the bike, frequently under the BB and chainstay in a housing (unlike derailleur cable). My assumption was, because of the low routing, moisture was entering the cable at the caliper stop and unable to drain out as it would with a normal rim brake (cable runs down from top tube so water doesn’t settle. Prior applications the cable exit was always the lowest point in the cable system. In many new disc brakes, cable routing the exit is actually higher than a good section of cable.

Front brakes, rim brakes and disc brakes with seat stay routing wouldn’t be a problem as cable exits at the low point and moisture can’t settle into a low point and freeze.

I greased the cable liberally, rerouted the cable over the top of the BB and zip tied to top of chain stay and didn’t have any future problems.
— Dan

Dear Lennard,
Just read a question from one of your readers looking into Crr of tubulars.
You might already know of it, but Tom Anhalt has a blog which he has independently roller tested a lot of tires (clincher/tubular) out in the market.

He is one of the few independent sources that released data on this topic. His willingness to go deep into this has been a good reference for myself when I am looking into data on maximizing potential tire-wheel combos.
— Ron