This last week of July has been not much fun at all, with temps in excess of 30 degrees for each of the first four days, and the humidex regularly over 40. I spent a pleasant couple of days in the cool of my basement workshop, tidying up a couple of things on my city bike, and--more important and interesting--tweaking the gear ratios on my Raven. I installed a new, smaller chainring, replacing my Surly stainless 38T with a new Surly 36T, so that I now have a 36 x 17 chainring and cog; and added a new chain as well.
On Thursday, the weather broke with huge late afternoon rain-and-thunderstorm, and Friday was a classically beautiful Ontario summer day: 25, dry, sunny with occasional clouds and a 20 kmh wind from the NW. All the miasmas and airborne particulates from the Ohio valley and the gooey moisture picked up as the SW winds crossed the lakes were swept away and faded to just a bad memory. So I took the Raven for a nice 70 km unloaded test ride up into the Gatineau hills across the river, 3 1/2 hours of riding to check out the new gear ratios, covering all but one of the big hills.
The quick report:
1) The new ring went on quickly and easily.
2) Getting the chain length and adjustment was more fiddly, but presented no major problems.
3) The new ratios worked better than I had expected -- the 5 - 6% gear-inch reduction across the 14 gears of the Rohloff let me keep a much better cadence on climbs, and I spent much more time in both the upper range and in gears 10-11-12 than I normally would on this route with the 38 x 17 combination on the Raven.
4) So, the 36 x 17 is a keeper, and I won't bother re-fitting the 38T ring at the front. I'd planned to do a loaded test ride of the new combination in the more demanding hills of the Madawaska Highlands later in the summer or fall, and may still do that. But I've been so pleased with my first test ride that I can't see any reason to revert to the 38T ring--I think the lower ratios in #s 1 & 2 especially will make the tough hills that much easier.
5) The 38T ring was very little worn after about 4500 kms over less than 2 riding seasons, and the KMC 8.93 silver chain is less than 50% worn. (If anyone finds themselves within shouting distance of Ottawa, and needs a spare Surly stainless 38T ring, 110 mm 5-bolt pattern, let me know. It's yours for a bottle of braai wine, as we used to call it in SA.)
6) After just less than 5000 kms, the Rohloff is bedding in nicely, and gets quieter as the mileage increases. The freewheel on the descents still makes a bit of a racket: squirrels chattered at me as I sped down the hills in 13th or 14th, raccoons cursed (I assume) in their tongue, and even the usually imperturbable Bear managed the trick of raising an eyebrow while frowning. (Well, I don't know about any of that last sentence, 'cept for the freewheel's wail, but the critters' reaction seems plausible to me.)
7) Only question remaining is whether to fit the Hebie 'glider onto the smaller ring. I found that the portion of the 'glider covering the rear of the ring was binding a bit, even after I added more slop to the setup at the front end (top-to-bottom and fore-and-aft) by not setting all the tabs into their slots. I'm thinking to cut out that section (ignoring the fact that the result will look a bit weird) in the hope of getting rid of the friction against the rear part of the chainring, while still keeping the 'glider's frontal coverage against rain and grit.
Some additional notes on the changeover:
First, the change in ratios. I've attached two tables showing the gear-inch ratios for both the 38 x 17 and 36 x 17 setups. My Raven has Mavic XM719 rims and Marathon Supreme 26 x 1.6 tires. The diameter of the wheel + inflated tire is 25.75". The 36 x 17 shows 54.54 gear-inches in #11, a reduction of just 3 gear-inches from the 38 x 17, or 5.26%. The change in the feel of the bike seemed much more than 5% -- I found it a lot easier to maintain a comfortable cadence on both steep and more gradual climbs. (The Raven was unloaded, but I've ridden my usual training route often enough with the 38 x 17 setup to say that the new ratios felt noticeably better.)
Secondly, changing the ring was dead simple, a matter of maybe 15 minutes to remove the old chain and ring, clean the bolts and add a touch of blue Loctite, and then install the new 36T ring. I left centring the new ring until I had the new chain in place. When I had the new chain in place, I centred the new ring without much difficulty. Happily, the tight spot was limited and spread across about 10 - 12 cms of the new chain. One smart but not too heavy poke with my glassfilled rubber deadblow hammer did the necessary: tight spot substantially gone.
The only fiddly bit was the fitting of the new chain--getting the balance between the length of the chain and the adjustment of the EBB. I had hoped to leave the EBB fixing bolts alone, making the changeover just by calculating the ~ 1" difference in chain length required to fit a chainring which was 2T smaller. Well, no, not quite: I had some not-big-but-still-irritating problems similar to those described by Steve in his Mercury build. Without going through the numerical details, I had to work back and forth between my new chain (92 links, 2 less than the 94 on the old one, which of course had stretched a bit...), the placement of the EBB, and a couple of KMC Quick-links separated by a half-link. I think that, if I have to take a link out of the chain in the future, I'll be able to do so by removing the half-link and one of the Quick-links, and using the EBB to move the shorter chain backwards...Or maybe not. On va voir, as we say.
An intervening variable in all this is that during my short ten-day tour in Eastern Ontario in mid-July, I had noticed a bit of notchiness from time to time in my right crank arm. On a lazy day beside Lake Ontario, I did some close observation and push-and-pull tests on the crank arms, and found a slight but noticeable bit of play on each arm. Crank bolts were both very tight, but the axle of the BB seemed to move slightly. I thought I might have a worn Shim UN55 BB; not so. I asked Brad at Tall Tree Cycles, my LBS which had built up the Raven for me, for his reckoning of the health of the BB. He checked, and found that one of my 15mm EBB fixing bolts was loose, and that the EBB was thus shifting slightly in the shell. Yikes! We tightened the offending item, and during the replacement of the chain, I made sure that once the EBB was rotated for the right tension of the new chain, both bolts were fixed with blue Loctite and properly torqued. I then exhaled.
"Properly torqued" required finding a 15mm x 1/4 drive socket. My nice BBB torque wrench, bought from Wiggle Cycles on Andre's well-founded recommendation :-) lacked a socket of that size. I couldn't chase one down quickly in Ottawa, but found one for C$2.99 in, of all places, the online catalogue of Staples Office Supply, but was dismayed to find that they wanted $15 for shipping it from Tronna (??!!). Instead, I broke one of my usual rules and ordered one from Amazon.ca for $4.99, added a pair of Cane Creek rubberized bar-ends for my city bike for $50, and got the lot for free shipping from some unknown location, all within 48 hrs. Over the winter, I'll buy a couple of spare 15mm x M8 EBB fixing bolts from SJSC.
