Regearing my 2015/16 base Turbo again

Douglas Ruby

Well-Known Member
I now have about 1000 miles on my "2015/16" base Turbo purchased in November of last year. As I am taking more rides over longer distances of 30-45 miles, I am thinking of re-gearing my Turbo again. When I bought the bike, I changed from the original SRAM 10 speed 11-32 cassette and 48T chainring to an 11-36 cassette and 44T chainring, While an improvement, I find that my current setup is "almost but not quite perfect".

1. When cruising on the flats I sometimes find myself caught between 9th and 10th gear, which is tiring. My base Turbo (and the 2015 Turbo X) has a maximum assisted speed of 42 kph (26.1 mph). If I want to hold that speed using full Turbo or ECO70, it puts me at a cadence of 79-80 rpm in 10th (where I am "pushing") or around 95 rpm in 9th (where I am spinning a bit too fast). Neither is quite optimal. My best cadence is between 85 and 90 rpm. I could change to the 48T chain ring and use 9th gear, but then I lose the benefit of my lower 44 x 36T 1st gear. A 12 tooth (100 gear inch) 10th gear on my cassette would be optimal, but then I lose the "over 30 mph" downhill 10th gear that the 11 tooth (110 gear inch) gives me.

2. On longer rides at ECO40 when I am trying to optimize for distance, I find that the lowest gear of 44 x 36 (33.5 gear inches) isn't always low enough, necessitating hitting the "Turbo" button to help me up the hill. If I could get a lower 1st gear that would be great.

Since I can't find an 11-12-13-...-36 in a 10 speed cassette, I am looking into the Shimano Deore XT system used on the 2016 Turbo S. The 1 x 11 speed 11-42T Shimano cassette will fit the standard Turbo wheel. The SRAM derailleur and shifter can easily be swapped for the Shimanop Deore XT system. If I swap back to the 48T stock chainring, I get a 101 gear inch 10th gear which provides 26.1 mph at a cadence of 87 RPM, ideal for me. I would still have a taller 119" 11th gear and a lower 31.3" first gear. Total cost is around $210 to upgrade the chain, derailleur, cassette, and shifter.

The gearing changes can be seen in using the web-=based calculator below:

http://ritzelrechner.de/?GR=DERS&KB...44&RZ2=11,13,15,17,19,21,24,28,32,36&UF2=2185
 
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jwb

Member
Thanks for posting this good info. I just got mine, but it's obvious to me that the gearing is totally weird. The 9th and 10th speed on the stock gearing are completely useless, and the 32T first gear isn't enough to get the thing up a mountain, either. I'm not sure what they were thinking.
 

Douglas Ruby

Well-Known Member
The stock base Turbo with 45-622 (2240 mm circumference) tires is geared with an SRAM 11-32 cassette and 48T chainring. This gives the following gearing compared with my current SRAM 11-36 cassette, 44T chainring, and 37-622 tires. As you can see, the stock 9th (112 gear inch) and 10th (122 gear inch) are not terribly useful unless you are descending. My 9th gear is 93.3 and 10th gear is 110 gear inches. Also, my current 1st gear is 33.7 gear inches vs stock 41.9 gear inches, a 20% lower 1st gear. This can be done cheaply, just for the price of the PG1050 cassette and a Vuelta 44T chainring. Don't need to change the chain or shifters.

With the move to the Shimano XT 11 speed described above, I am looking for a 100 gear inch 10th gear to provide ideal cruising on the level at 26-27 mph with a higher 11th gear for descents (122 gear inch) and a lower 1st gear (31 gear inch).

http://ritzelrechner.de/?GR=DERS&KB...44&RZ2=11,13,15,17,19,21,24,28,32,36&UF2=2200
 
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Douglas Ruby

Well-Known Member
Ok...today I got my parts. Good news and bad news.

Good News:
  1. The 11-42 cassette fits nicely on the stock Turbo wheel.
  2. The Shimano Deore XT RD-M8000 derailleur also fits nicely on the Turbo dropout.
Bad News:
  1. The Shimano Deore XT M8000 i-Spec II shifter is incompatible with the Formula C1 brake levers and the base Turbo control panel. No adapters are yet available to adapt i-Spec II to SRAM compatible brake levers.
  2. The Shimano 11-speed Dura-Ace chain needs special tools to insert the link pins. I don't have said tool, and the combination of 48T chainring and 42T rear cassette gear means the 116 link chain would probably be too short.
Solution(s):
  1. I will return the i-Spec II shifter to Nashbar and get the Shimano SL-M8000R "bar clamp" shifter instead.
  2. I will gift the Dura-Ace chain to my daughter who just got an 11-speed Shimano 105 equipped road bike.
  3. I will purchase two KMC X11 chains with reuseable missing links. Then I can easily use my current chain tool. I also can splice together a long enough chain to support the 11-42T cassete with the 48T chainring.
  4. Another solution would be to upgrade my front brake to a compatible Shimano XTR brake lever and caliper and keep the i-Spec II shifter. But I have gotten the Formula C1 brakes to work so well with the Kool-Stop organic pads that I don't want to mess with them.
 
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Douglas Ruby

Well-Known Member
Today I went on a morning breakfast ride by myself. Since I have put the 48T chainring back on my bike, my gearing in 9th and 10th with my SRAM 11-36 cassette is the same as it will be in 10th and 11th once I finish the switchover to the Shimano XT 11-42 cassette. Therefore I decided to do the entire ride in full Turbo mode to test out my theory about holding the cruising speed right at 26mph using the 48x13 (102 gear inch) 9th gear and using the 48x11 (120 gear inch) 10th gear for descents.

Worked perfectly. I was very comfortable cruising right at the edge of the assist cutout between 25-27 mph in 9th gear and hitting 33 mph in 10th without having to "over spin". For the entire ride of 15.5 miles, I was able to maintain an average of 21.5 mph, climb 652 feet, average cadence of 81 rpm with peak cadence of 101 rpm and peak speed of 33.1 mph.
 
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jwb

Member
Shame about the shifters not working out. Did you ever think about throwing out the brakes? The Formula C1 is garbage. I haven't looked into the integration, and I was told that the rear brake cuts the motor on the Turbo, but I don't know how that works or if it prevents the brakes from being replaced with something decent.
 

Douglas Ruby

Well-Known Member
Did you ever think about throwing out the brakes? The Formula C1 is garbage. I haven't looked into the integration, and I was told that the rear brake cuts the motor on the Turbo, but I don't know how that works or if it prevents the brakes from being replaced with something decent.

The brake/regen integration was in older versions of the Turbo S. Current version does not do that. I did look at replacing the brakes but pricey. I got the Formula C1 working great now in any case. It just took replacement pads. A different Shimano XTR shifter will solve the problem, so all will be ok.

By the end of this week I expect to be riding the 11 speed 11-42t rear cassette with the 48t chainring.
 

jwb

Member
My complaint with these brakes is they center poorly. In my experience the Shimano hydraulic disc brakes are reliably self-centering. But yes, ditching the i-Spec fiasco should also solve your specific problem :)
 

Douglas Ruby

Well-Known Member
Got the Shimano XTR SL-M9000 shifter in today around noon. By 2:00P the job was finished. Here are pictures of my 2015/16 "base" Turbo with Shimano XT 11 speed derailleur, shifter, cassette and KMC X11.93 chain. I have taken a short 1/2 mile test ride and all appears to work well. A few details:
  1. I kept the Formula C1 brakes, so I had to get the "bar clamp" shifter instead of the i-Spec II shifter.
  2. I purchased the RD-M8000 GS (medium cage) derailleur, even though I am using the 11-42 cassette. With a 1 x 11 setup, this is all that is needed even though Specialized says they use the SGS (long cage) on the Turbo S.
  3. I needed at least a 118 link chain. KMC makes a 118 link X11E Silver specifically for e-bikes, but it appears to be unavailable in the US. Further, I believe that Specialized uses a 118 link KMC for the 11-40 rear cassette. Since I am going two teeth larger, I bought two X11.93 Silver chains (116 link) and spliced together a 120 link chain. Sizing the chain around the 42 rear and 48 front sprockets, I had 4 links of overlap.
  4. I have not yet adjusted or used the "clutch" mechanism. The bike shifts nicely with it turned off.
20160831_140514.jpg 20160831_140421.jpg 20160831_140441.jpg 20160831_140547.jpg 20160831_140601.jpg 20160831_140636.jpg

I will try to get a few miles on the bike before I give you an update on function compared with the 10-speed SRAM X7 and 11-36T cassette.

NOTE: Careful examination of the pictures above shows i mis-routed the chain through the derailleur cage just like the Shimano manual says NOT to. This was caught before I hit the road.
 
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Senseiwai

Member
Got the Shimano XTR SL-M9000 shifter in today around noon. By 2:00P the job was finished. Here are pictures of my 2015/16 "base" Turbo with Shimano XT 11 speed derailleur, shifter, cassette and KMC X11.93 chain. I have taken a short 1/2 mile test ride and all appears to work well. A few details:
  1. I kept the Formula C1 brakes, so I had to get the "bar clamp" shifter instead of the i-Spec II shifter.
  2. I purchased the RD-M8000 GS (medium cage) derailleur, even though I am using the 11-42 cassette. With a 1 x 11 setup, this is all that is needed even though Specialized says they use the SGS (long cage) on the Turbo S.
  3. I needed at least a 118 link chain. KMC makes a 118 link X11E Silver specifically for e-bikes, but it appears to be unavailable in the US. Further, I believe that Specialized uses a 118 link KMC for the 11-40 rear cassette. Since I am going two teeth larger, I bought two X11.93 Silver chains (116 link) and spliced together a 120 link chain. Sizing the chain around the 42 rear and 48 front sprockets, I had 4 links of overlap.
  4. I have not yet adjusted or used the "clutch" mechanism. The bike shifts nicely with it turned off.
View attachment 9572 View attachment 9575 View attachment 9578 View attachment 9581 View attachment 9584 View attachment 9587

I will try to get a few miles on the bike before I give you an update on function compared with the 10-speed SRAM X7 and 11-36T cassette.

Hi

Those red cooling fins brake pads are they stock?
 

Douglas Ruby

Well-Known Member
Went on a nice ride into town for breakfast this morning as the first ride with the new 11 speed driveline. This is great! The bike shifts beautifully, has all the right ratios, a really low "granny gear" and is very smooth and quiet. I need to do a bit of adjusting to the position of the shifter relative to the grip, but I can tell I will like this. For anyone who has a base Turbo, or a 2015 or earlier Turbo S or X, this is a change that can be made for around $250 - $300 depending on the casette and shifter you use.
 

Charlie Rohlfing

New Member
Douglas, I did the 10 speed mods you first tried (44 crank, 36 cassette) and it is working great! Excellent advice. It is plenty low for the hills we encounter, and it seems like the other ratios will work fine for higher speeds. Thanks again for sharing!
 

Douglas Ruby

Well-Known Member
Charlie,

I am glad you like the new gearing. The nice thing is that you now have a 20% lower 1st gear and an adequate top gear. The ONLY problem for me was that I didn't have the ideal gear for my best cadence at the 26.2 mph limit of my base Turbo; 9th was too low and 10th was too high. That is why I changed over to the 11-speed Shimano XT with 48 tooth front and 11-40 rear.

I grew up in bicycling with a first edition copy of Eugene A. Sloane's The Complete Book of Bicycling, back in the early 1970's. In the day of the "10-speed" (i.e. 2 x 5 friction shift), everything was about knowing your best cadence and the type of ride you were doing that day. We calculated all of our gearing in gear inches and maintained a ready supply of alternate chain rings and free-wheels and the tools to change them. I still have 52, 45, and 42T front chainrings and 5 and 6 speed freewheels with 13-16, 14-18, 14-21, 14-24, 13-26, 14-28, 14-32, and 14-34 and two Camp[y derailleurs (Nuovo Record and Rallye) with which to use them. It all works pretty well too!

Today, with 11-speed rear and 1, 2, or even 3 front rings, most people don't need to bother doing gear inch calculations. I find it interesting that for many types of riding, particularly recreational, a 1 x 10 or 1 x 11 may be the best choice. Certainly, for serious road riding, the compact (50-32 front) and (11-28) 11-speed rear is great for almost all conditions for the average rider. However, it helps to do the calculations and know the optimal gearing, even for an old out of shape fogey like me!