Showing posts with label Rohloff. Show all posts
Showing posts with label Rohloff. Show all posts

Friday, March 11, 2011

How to select your chainring for a Street Machine GTe with Rohloff

After riding my HP Velotechnik Street Machine GTe I realized that I want lower gearing than stock.

My stock setup is 46T chainring and 16T sprocket on a Rohloff IGH.

Gears from 1-7 are quite noisy and feel "draggy". The noisiest is #7. My cruising gear on flats is somewhere between #7 & #8. Direct drive on Rohloff is #11. 

Ideally, #11 should be my main cruising gear.

First I went to Sheldon Brown's gear calculator and figured where I was at.

For 26 X 1.5 / 38-559 / MTB tire with 155 mm cranks

With Custom Sprocket(s) Cassette

With Rohloff 14-speed Speedhub Rear Hub

Low2345678910111213High
19.9
22.6
25.7
29.2
33.2
37.8
42.9
48.8
55.3
63.0
71.5
81.2
92.4
104.9

So my cruising is done between 48.8 and 55.3 Gear Inches.

So this would be my "ideal" setup.

For 26 X 1.5 / 38-559 / MTB tire with 155 mm cranks

With Custom Sprocket(s) Cassette

With Rohloff 14-speed Speedhub Rear Hub

Low---------11--High
13.5
15.3
17.4
19.7
22.4
25.5
29.0
32.9
37.4
42.5
48.3
54.8
62.4
70.8

If I would like to move my cruising to gear #11, I would need 33T chainring and 17T sprocket. But Rohloff insists on 38T chainring as the smallest with 16T cog, as going smaller would go beyond 2.4 ratio suggestion from Rohloff. What to do?

Doing more research I realized that Rohloff recommendations includes tandems and super fit riders who can really crank on their pedals. In recumbent situation I don't have jolts of force applied to the pedals (I can't stand on them, I am just "spinning").  There are articles that suggest you can go lower in gearing, but Rohloff will not honor the warranty.

So, if I decide to go with "unapproved" ratio on gearing, what are my options for chainrings and sprockets?

Standard sprocket from Rohloff is 16T. For lower gearing they have a 17T sprocket available.

17T sprocket costs $50-60 USD, then you need a chain whip ($10-30 USD) and special Rohloff tool to remove it ($53). 

What if I leave the sprocket at 16T, and just change the chainring?

T.A. Specialites does make a 33T chainring, but it is designed for inside of the shiftable cluster. It might work, but I don't want ramps for shifting on the chainring.

For 34T chainring, there are more choices. Again, I am avoiding rings with pins and ramps. You can have a Surly stainless steel chainring, or numerous aluminum ones. The hardest aluminum alloy is 7075-T6.

How does aluminum  compare against steel? Surly uses 304 steel. It is harder than 7075-T6 aluminum, but also it is heavier. As I am going for reliability, so weight is not that significant for one piece. I would go with Surly. Surly is also reversible -  just like the Rohloff sprocket.

For $30 I can get a Surly chainring and get much closer to the "ideal" range.


For 26 X 1.5 / 38-559 / MTB tire with 155 mm cranks

With Custom Sprocket(s) Cassette

With Rohloff 14-speed Speedhub Rear Hub

Low---------11--High
14.7
16.7
19.0
21.6
24.5
27.9
31.7
36.0
40.9
46.6
52.8
60.0
68.3
77.5

Would this work? There is only one real way to find out.

Monday, December 20, 2010

Wet weather riding

After couple days cooked up at home I could stay no more.

I got my rubber/neoprene riding shoes (Keen Commuters), synthetic REI stretch pants and synthetic long sleeve top, and I was off!

At first I was ecstatic. I was riding, and there was pretty much no one on the beach. Figures, it was still raining, but not hard.

I rode North, towards Malibu.

As I approached Santa Monica Pier, I expected some flooding. Well, "some" turned out to be a lot, and I ended up riding through what I think was up to 4 inches of water. I figured I could just downshift and power through the water. The concrete path was still there, just underwater.

Riding through water feeling was great. There was increased resistance, but I knew where the path was so I was not concerned with road disappearing. Good thing, it did not, and I safely forded the water barrier.

After my water experience, I decided to test my weather resistant disc brake.

BB7 brake has turned to mush. There was no fiction to stop, then the calipers started to drag on the rotors, then the lever would not spring back to neutral.

Slowly, the brake sponged back to semi neutral so it was not making scraping noises, but whenever I tried to use it to slow down the bike, it was pretty much useless.

If I was touring with a load and going downhill, and that was my only brake option, I would be in deep trouble.

So much for "improved wet performance" over rim brakes. On my front wheel I had Avid V brake, and it was still functioning. Granted, it took a moment for the brake to start breaking, but the friction was still there.

My dry lube (right now I had Finish Line dry lubricant, in the past I used Boeshield T9 with good results) got washed out and I could hear sand crunching on my chainring and middle drive chainrings. I stopped at the shower and tried to wash the sand, and that helped for 30 yards, then the sand was back.

I think I pair of fenders would have slowed down the sand working it's way from the water and sand slury into the chain. Also, I will use wet lube for my next wet ride.

What did work extremely well was the Shimano LX derailleur. It did not skip a beat through my shifting, no problem whatsoever. I was waiting for sand induced noises, but all was in vain. Noises were coming for lower bracket/chainring area, but not from derailleur.

Lessons learned:

  1. Riding in the rain could be fun. Way better than being cooked up at home in front of the computer!
  2. Horses for courses. You have to have wet weather clothes and wet weather lubricants on your bike. Fenders don't hurt either. You have to keep sand laden water out of the drive train!
  3. Brakes that work in wet, not only in dry. I always thought of my BB7 disk brake as my best defense against weather. Not so - it has failed to live up to it's expectations. On my next bike I am sticking with rim brakes.
  4. I am very impressed by Shimano LX derailleur. I was set to get Rohloff Speedhub for my next bike build, but now I feel I need to rethink my convictions. I still think if money is no option Rohloff is the way to go, but my newly regained respect for Shimano keeps them in the running.
  5. My hat is off to all of you in Northern climates - snow and ice are not cyclists friends. I do have a friend who moved from California to New England and was riding his bike (with studded tires and all) through the winter. Go Winston!