Modifying a rear mech for road 1×10 and a 11-40t cassette (Part 5)

One final piece in this puzzle is the rear mech or derailleur: no Shimano road-shifter compatible mech was designed to reach a cog even as big as 34t, much less 40t. In fact, cassettes with 36t have only become common in the past few years when 1×10 mountain bike drivetrains started to appear. SRAM has this under wraps since their10 and 11 speed  road shifters are compatible with MTB 10 speed rear mechs as well as 11 road mechs (but not their MTB 11 and 12 speed mechs). With Shimano 10 speed road shifters, rear mech compatibility is restricted to 8, 9 & 10 speed road mechs and 8 or 9 speed MTB mechs, except for 9 speed Shadow: though the cable pull should be the same, I have not been able to get these derailleurs to shift correctly on a road setup (I tried several combinations).

See the followup. This is arguably not a great solution…

What I ended up doing was modifying a Shimano XT RD-M761 mech, increasing both the main pivot tension and the B tension springs. Some blogs will suggest the use of a longer B tension bolt, but I find this rarely works as it falls off the tab it’s meant to push against on the mech hanger (see pic below). Dismantling a higher-end derailleur is pretty easy: to remove the B pivot, pop off a circlip. To remove the main pivot, there is a hidden allen bolt on the knuckle. When removing the main pivot, pay attention to what hole the spring was engaged in, and make note. You will want to put it back together using the other hole. It is my understanding that these two settings were designed for cyclocross/pave use, though it is also plausible they were a longevity feature for when the spring started to wear out. At any rate, clean off all the pivots, remove any dirt and grease, then regrease things before assembly.

RD-M761 spring tension modification


Modifying the B tension involves drilling a small hole about ¼ rotation from the original. I tried it further, but found the spring was under too much tension to assemble. If you remove the B tension bolt, the tab it screws into can be put in the jaws of a vice. Punch a centre for your drill bit, either using a punch or a wood screw.


To reassemble the B pivot, insert the spring into the main body of the mech, engaging its hole, then put the plastic washer on, then engage the modified plate in the correct hole. Using either plumber’s grips or vise-grips hold the tab you had in the vice and rotate it until it gets past its stop, and push the assembly together: hold with one hand whilst pressing the circlip back in place.


Reassembling the main pivot is similar, but much easier since the cage acts as a lever, and you only have to push a little pin in place to hold it together.


After 1400km of commuting daily, this derailleur has died (30/4/18).

Though the initial modification worked, I had to make minor adjustments almost daily. It turned out that one of the main issues was that I had (previously, whilst chasing drivetrain noise) substituted the stock jockey/pulley wheels with Tacx cartridge wheels. These are great, but only as tension wheels as Shimano shifting needs that floating jockey wheel, which aftermarket products don’t seem to offer. I replaced the stock XT pulleys, and shifting returned to near perfection for a whole two days (about 40km). The modified B tension has broken – I assume the spring has sheared.

My planned solution is to get a Wolftooth Roadlink and, if I can, a short cage 105 5700 derailleur to match the shifters in exact generation. I worry that the road link will put more stress on the hanger, but if it brings a more reliable shift, then I will be pleased.

More soon.

Tobias Feltus:

Shimano ST-5700 exploded view & throw modification (Part 4)

If you happen to have taken apart your shifter, here is an exploded view of how it goes back together. It’s not that hard, but it is really fiddly. The upper two plates interact with the shifter ratchets and ratchet plates: they are the business end. I took it all apart and cleaned it with alcohol, then reassembled it dry and lubed it with TriFlow. This is not an ideal lubricant for a wet climate, but I am currently building this for the desert. Fortunately none of the springs need to be under load when you slide everything together, and once everything is together and the springs are loaded, you can take the pivot bolt out, push the assembly into the composite frame, then reinsert the pivot.

ST-5700 exploded view

The one interesting thing about taking this apart is learning how easy it is to modify the shift lever throw of the smaller paddle. The throw is less of an issue for me on these as compared to the older style of shifter (with external shift cable).

ST-5700 throw modification

Tobias Feltus:

Converting Shimano ST-5700 105 shifters to 1×10 (Part 3)

1x drivetrains should only have a shifter on the right-hand side, for the rear mech, in my opinion. I mean, otherwise you have pointless machinery cluttering your cockpit, right? On a mountain bike you just take one shifter pod off, but converting Shimano road levers to a 1x does involve removing a shift paddle, in my books. The internets would suggest that no one has ever tried this. Removing the shift paddle from the left hand shifter is actually remarkably simple, takes about 10 minutes, is reversible and leaves you with only a tiny bit of brake lever play.

Removing ST-5700 brake lever

Remove brake lever assembly per Shimano’s instructions (see illustration), which involves moving a circlip from the inside end of the shift pivot pin: I used a flat object like a butter knife to raise the clip, then push or tap out the pivot pin. Removing the lower shift paddle involves the removal of another circlip, then it all slides out. Reassemble the brake lever, and the job is done. There is a lever-return spring which you may need to hook into its little hole on the composite frame, but I found this to be pretty easy with a small flat-blade screwdriver.


Tobias Feltus:

1x drivetrains for road: selecting gearing (Part 2)

Selecting the gear ratios is the easy part. You go HERE and input what you are currently riding, then try and mimic this with a single cassette.


I am of the firm opinion that all bikes are sold with bigger (longer, greater gain ratio, or bigger Gear Inches) gears than the average strength rider can push. I know that I have never spun out a road bike with a 50/11, and the descents into Bartlett Lake are among the longest and fastest descents I’ve ridden, barely spinning out a 46/11 at over 40mph in an all-out effort. So I think it is fair to say that I don’t really need anything over 100 Gear Inches.


My CrossCheck had a 34/46 with an 11-32 cassette (8 speed), my new setup is a 40t Origin8 narrow-wide and a Sunrace 11-40 cassette. I dropped a couple of gear inches off the top end, and gained a couple at the lower end, based on how I use the gears. In detail, I had 29-84 gear inches and 39-114 gear inches: now I have chosen to have a single sweep from 27-99 gear inches. From riding, it seems like at the lower end of the ratios I have an rpm difference of around 5 between sprockets, and at the higher end it is around 10: this is vaguely comparable to a road setup and oddly similar ratio spacing to my previous setup, but its all on one shifter, simple and linear.

This is my gearing comparison HERE.

After a few commutes, my only comment is that the 40t is too close to the 36t in pedalling rpm, so I may opt for the 11-42 on my next build (the only difference is the biggest ring), sticking with a 40t chainring, rather than changing the tooth count on the chainring (this will probably be a gravel monster, SRAM equipped and with a power meter).

Tobias Feltus:

Shimano 105 1x drivetrain considerations (Part 1)

Despite the fact that SRAM has been touting 1x drivetrains for a few years, killing off the MTB front mech and making road shifter compatible clutch rear mechs as well as selling left-hand levers which don’t have shifter internals, Shimano seems to have closed its eyes to this trend, as have all forum discussions on the topic. This has all become more pertinent now that, for the 2018 road season, team Aqua Blue Sport has signed up with 3T to be the first pro team (road) to race on a bike which is unable to use a front mech or rim brakes. This makes road 1x systems a very real present.


In my quest to run a drivetrain where I use all of my available gears efficiently/equally – and after choosing the gearing on our touring bikes which was both arduous and aimed at a specific task, I decided to try a road 1×10. I was given a pair of heavily used 105 ST-5700 shifters, which are what I consider to be 2nd generation 10 speed, or SLR-EV levers, which have a slightly different brake cable pull compared to old Shimano, SRAM and Campagnolo. I believe they have an improved ergonomic design compared to the older hoods, and it is nice to have all the cables under the bar tape. I am a little frustrated with the inferior braking performance with the majority of brakes on the market, despite the fact that Shimano launched this cable pull in 2008 with the Dura Ace 7900 series, there are very few fully compatible brake options. Seriously, 10 years later and I am not aware of a single third party brake lever which is labelled as being deliberately compatible with the cable pull of these levers.


My list of tasks were:

1: Select gear ratios that will not be compromising.

2: Remove the shift paddle from the L/H lever

3: Clean/lube shifter mechanism.


I’m going to break this up into separate posts.

Tobias Feltus:

Instax 100 with a manual twist.

A few months back I got round to hacking an Istax 100 to pieces and reassembling it with manual focus, shutter and aperture. Despite having posted almost nothing, I have got a lot of interest on Flickr, then Georg (Polapix) made his own version from my notes, and I thought I might as well write a wee bit about it.

a PhotoBooth snap of myself with the beast

I had originally wished to keep as much of the original Instax as possible, and just replace the shutter and exposure unit. I failed at this whilst trying to identify the flash trigger. I think the flash uses an IGBT chip, or is rather overly sophisticated for the camera. Also the flash control board seems to be combined with exposure and shutter control. Odd design, as usually even on digital compacts, from my experience, the flash board has been separate. Even in a Nikon SB600 the inverter board is separate from the control board. So, yea, trying to identify the trigger I ended up loosing all of the electronics within the Instax, blowing a couple of components.

But all was not lost. The barrel was not rigid enough to move the weight of the tiny Vaskar 105mm anyway, so it is best to have it glued in rigid.

I believe the Instax 100 is a simpler chassis design than the later models, from what I gather. So, the microswitch which I have
drawn in my diagram is at the bottom and back of the camera, on the lowest gear in the drive mechanism. it fits into a cam to break contact. what I have written as “shutter switch” I then re-wired through the bus to the PWR button, the red one, on the back of the door, as the eject, as I thought there was less of a chance of me hitting it by accident. Again, I identified the bus contacts by ohmmeter, and just use the lower circuit board to for the bus contacts. So the red button initiates contact, and the cam closes the circuit, continues its cycle, then breaks the circuit once the film is ejected. I would recommend that you don’t solder onto the bus contacts, as I did, as things are too small, and a bump later shorted this out and ejected half a pack of film. So look for larger solder points on the board, if you plan to use this switch. obviously using the existing shutter button would be easiest, as it is large and already has wires coming off of it. After I blew the main circuit board i just cut all of the wires connecting the boards to the battery, to avoid any issues. The diagram and notes are in this scan of my Moleskine. The camera is a bit of a hassle to use, as it is a clunky machine with a rather small viewfinder, however it can be used with studio lights, and does produce images. Below is one example.

And here are a few more images of the camera in parts:

Tobias Feltus:

Graflex RB Super D: converting the back to take “standard” accessories.

Finally, after a couple of years lusting after one, I have a Super D (thanks to Bob Crowley and his find). It is in very good condition, in fact, almost new, and hardly used if at all. The only issues were need for a bit of lube in the shutter, and some minor cosmetic issues (like the leather coming loose on the lens door, due to retraction). However the Graflex standard back is not too useful today, or at least, it is not much use to me, as I want to use some Polaroid, and a Grafmatic sheet loader. The normal approach to this adaptation seems to be along the lines of what Bob did with his, involving taking a Grafloc back, cutting it down, and gluing it into the RB’s back. But I saw little point in this as Grafloc backs are expensive, to me, and also there is little need for a springback on a reflex camera.

The differences that I found in the Graflex back are:

the accessories are 6.5mm wider than the international standard

the accessories do not have a light trap lip sticking out, but rather a recess in them.

So, I had to shim the whole plane of the mount up by 1mm to create a groove to accept the light trap, and move in the tongue sliders. For most accessories they are fine the way that they come, however my Polaroid 545 back has two slots in either side, so I had to cut my sliders into the typical two-eared shape. I did this with a dremel and files.

But from the start, clean everything up, and the edge of the tray needs filing back by about 1mm so that it sits flush with the new raised level.

I then cut a piece of 1mm black styrene that I had to fit, and cut out the slot for the light trap. Then I glued this in with contact adhesive. The component has no structural value nor requirements. Then I drilled out and countersunk all of the necessary holes, including four new ones to move the lower screws that hold the slider supports in place. They had to be moved 3mm in, so I moved them diagonally to avoid weakening the frame. The slider bar supports are made of mahogany with brass inserts. To move them in the necessary 3mm I cut thin strips of 3mm plywood and glued these into the existing rebate with aliphatic resin, but any good PVA will do the trick. Then I primed and painted the brass tray with the new plastic shim, and the enhanced supports.

Re-glue the felt onto the base of the tray (cutting 4 new holes where the new screws go), and reassemble the base and rotating components. Screw the slider supports back in using the same screws, and reassemble the whole caboodle.

The last thing to do is to shim the ground glass and fresnel assembly. I just used two thin strips of the same 1mm styrene, as this was the only change in the focal distance made.

And now I have a Super D which can take all manner of film holders, including Fidelity double darkslides, as they are grooved on the side so they can be gripped by the sliders.

Tobias Feltus: