[PetaWatt]

A little background

I started cycling to work in 2014. I continued the healthy lifestyle till mid of 2016, then cycling was gradually stopped because of my poor time management skills. Initially, I was getting an average of 16 kmph in 28 km round trip to my office and by the time I left cycling, I was getting an average 20 kmph in 32 km round trip to my office. On plane roads I was able to touch 35 kmph and on up-hills speed was decreasing to 14 kmph. On down-hills I used to touch 50 kmph in crouch position pedalling at max speed in top gear. One day a guy overtook me on his road bike when I was doing 52 kmph on the downhill, then I realized my performance is limited by the gear ratio of the hybrid bike.

Last week, I started cycling again. I reached office(16 kms away) without any problem and got the average speed of 19kmph (not bad after a gap of almost 2 years). While returning back, just a km away from my home, I rode over a small rock in such a way that one spoke of rear wheel broke which caused wheel to bend and touch the frame. When I gave the wheel for repair, the repairing guy suggested me to get all the spokes changed as I have ridden the bike for more than 10000 km and spoke broke because of the fatigue.

I thought to use this opportunity to upgrade the drivetrain of my hybrid bike. I own 2013 Fuji Absolute 2.3 but this upgrade can be done for the similar hybrids.

Drivetrain details of the 2013 Fuji Absolute 2.3

• Crankset: 48/38/28T
• Front shifter: Shimano EZ Fire 3 speed
• Front derailleur: Shimano Tourney
• Rear Freewheel: 14-34T, 7-speed
• Rear shifter: Shimano EZ Fire 7 speed
• Rear derailleur: Shimano Altus, 7/8 speed

The plan

The standard gear ratio range provided with the bike is 28/34 - 48/14. The first gear ratio(28/34) gives the max torque and min speed, which helps going up-hill. I was not worried about this extreme torque ratio as while coming out of my office basement parking I was using just 28/24 gear ratio. The second ratio(48/14) gives the least torque but max speed. I was interested in increasing the second ratio value to increase the top speed of my bike on the downhill at minimal possible cost. Just for reference the second value for most of the road bikes are 52/11 = 4.73, which means for one round of pedal, wheel will rotate 4.73 times. My bike had poor ratio of 48/14 = 3.43, which explains why was I overtaken by the road bike even when I was doing my best.

To keep the cost low, my target was to decrease the number of teeth on the smallest wheel of the rear cog from 14 to 11 to achieve the high speed gear ratio of 48/11 = 4.36 which is very close to road bike ratio.

Executing the plan

When I started the search for 7 speed cog with 11-3x teeth (where x is a value from 1-9), I learnt the following things:

1. 11-3x teeth configuration is available only in the 8 speed onward cogs
2. All the 11-3x, 8+ speed cassette comes in Freehub design
3. The gap between cassette gears is same on a 7 speed Freewheel and 8 speed Freehub

Because of the point 1 above, I was suppose to change the rear drivetrain system to 8 or more speed which includes 8+ speed cassette, matching rear derailleur, matching chain and matching rear gear shifter. I selected to upgrade to 8 speed cassette because the standard derailleur on my bike is 7/8 speed and chain can be used in a 8 speed drivetrain as well. Also, 7 speed shifters can be used on the 8 speed cassette excluding either the high torque gear(the biggest one) or the high speed gear(the smallest one) on the cassette. As I wanted to increase the speed of my bike, I planned to exclude the high torque gear. I will switch to 8 speed shifter only when there is need of high torque in my day to day ride or the current 7 speed shifter finishes its life.

There was one more problem, rear wheel of my bike had 7 speed Freewheel cassette and all the 8 speed cassette were available only for Freehub configuration. Anyway, I had to get all the spoke replaced, so I thought I'll replace the hub too with a Freehub one on which I can get the 8 speed cassette installed. But all the available Freehubs were in 32 holes configuration which cant be installed on the rim of my bike which has the 36 holes on it. So I decided to buy a new wheel itself (hub+spoke+rim). I bought the Btwin Freehub wheel and 8 speed SRAM cassette from Decathlon for Rs 2499 and Rs 849. I don't have tool to install the cassette on the wheel's hub so I asked a service guy to install it. As all the decisions made by me were based on the theory and indirect information I convinced the service guy to take back the cassette if it doesn't works well with my 7 speed drivetrain.

I reached home with my fingers crossed. I removed the old wheel from my bike and clipped on the new wheel(without tyre and tube) on it. I kept the wheel off the ground all the time to save rim from getting damaged. I started rotating the pedal with my one hand and tried shifting the gear from 7 to 1 and 1 to 7 using the other hand. To my surprize, chain on the cassette shifted swiftly from smallest gear to the second largest gear and from second largest to the smallest gear on the cassette without even adjusting the rear derailleur. This is exactly I was expecting with the 7-speed shifter with a 7/8 speed derailleur and 8 speed cassette. I took the new wheel off the bike and put the tube and tyre from the old wheel and installed it back on the bike. Immediately I went down to try the upgrade and it worked flawlessly. On the same downhill where I was able to touch 50 kmph in top gear now I am able to touch 65 kmph.

Outcome and other photos

The 7 speed shifter on my bike



The 7/8 speed derailleur



The old 14-34T 7 speed Freewheel - this is what I replaced with 11-32 8 speed Freehub cassette



The new 8 speed SRAM 11-32 cassette mounted on the new wheel



Result: Bike in max torque gear combination with 7 speed shifter. Notice, chain is on the second largest gear wheel of the cassette



Result: Bike in max speed gear combination. Gear ratio upgraded from 3.43 to 4.36

[GTO]

Thread moved out from the Assembly Line. Thanks for sharing!

[Aditya]

It's good that you have shifted to a cassette. It's far more in keeping with today's time compared to a freewheel.

The smaller cogs will certainly give you more speed if you use them. But, don't think that your hybrid will go faster than a road bike. Many factors including aerodynamics, size of chain ring and rolling resistance of tyres work in a road bike's favour. To give you an example, over 100 km, I average ~ 30 km/h on the road bike and ~ 27 km/h on my mountain bike.

The only issue I see is that the shifts between the different cogs of the 8-speed 11-32 will not be jerk-free. I use an 8-speed 11-32 on my road bike. It's not quite as smooth as the 10-speed 11-34 on my mountain bike. There are times when I feel I could do with a couple of more cogs to fill the gaps. The difference is felt most on steeper inclines. These gaps can get irritating even in traffic.

Also, if possible, do upgrade the rear shifter to an 8-speed unit so that you can use the largest cog as well.

[AlphaKilo]

Originally Posted by PetaWatt

I started cycling to work in 2014. I continued the healthy lifestyle till mid of 2016, then cycling was gradually stopped because of my poor time management skills. Initially, I was getting an average of 16 kmph in 28 km round trip to my office and by the time I left cycling, I was getting an average 20 kmph in 32 km round trip to my office. On plane roads I was able to touch 35 kmph and on up-hills speed was decreasing to 14 kmph. On down-hills I used to touch 50 kmph in crouch position pedalling at max speed in top gear. One day a guy overtook me on his road bike when I was doing 52 kmph on the downhill, then I realized my performance is limited by the gear ratio of the hybrid bike.

Try the new Deore tourney or XT set of cogs and they come with a rapid shift mechanism, where the spring is replaced by a direct shift mechanism. The shifts are unnoticeable, especially downshifting is a dream. To increase speed, try upgrading the wheel bearings and the pedal bearings to a more newer one. You can squeeze out 1 - 2 kmph more out of the bike. As mentioned already, hybrids have inherent limit and don't push them beyond it as the will reach this stability limit sooner or later.

Out of interest, which bike do you use? How much do they cost? I had until recently no idea that our country has such a big user base for such cycles other than our trusted Hercules .

[PetaWatt]

Originally Posted by Aditya

But, don't think that your hybrid will go faster than a road bike.

That was never the plan, I understand the term 'drag coefficient' . Just wanted to increase the top speed of my bike on downhill. In future, will switch to thinner tyres to increase the top speed on level roads.

Originally Posted by Aditya

Also, if possible, do upgrade the rear shifter to an 8-speed unit so that you can use the largest cog as well.

Yes, will upgrade as soon as the current one goes out of order. Currently there is no need to use the largest cog as I am able to come out of my office parking effortlessly using the second largest cog. When I will upgrade the shifters I might go for 11 speed drivetrain to decrease the gear ratio gap between the adjacent gears which will help in finding the comfortable pedalling speed easily.

Originally Posted by AlphaKilo

Out of interest, which bike do you use? How much do they cost? I had until recently no idea that our country has such a big user base for such cycles other than our trusted Hercules .

Currently I am using 2013 Fuji Absolute 2.3 hybrid bike. I bought it for 29k as far as I remember. Got the fender installed for 5k. In my school days I used Hero ranger swing (Full suspension 3x6 speed), Hercules RockShox(Front suspension fixed gear) and small Avon cycle.

[AlphaKilo]

Originally Posted by PetaWatt

That was never the plan, I understand the term 'drag coefficient' . Just wanted to increase the top speed of my bike on downhill. In future, will switch to thinner tyres to increase the top speed on level roads.

Since you are in the process of upgrading, also try to upgrade the tektro's to Magura brakes. You are sure to stop even with lot of dust and dirt. There are non-hydraulic rim brakes available from magura which have a dirt free model. I was using tektros for a long time and here in winter they are sure to fail and in summer, the fine dust accelerates their wear a lot more. My experience was really bad with them especially in wet conditions.

Rockshoc used to be my favourite but never had the necessary vitamin M to buy them those days.

[anandpadhye]

Great thread. Good info. Excellent upgrade! I have huge respect for DIY stuff!

I faced a similar problem/urge after riding my hybrid for @500km and bought a road bike:

http://www.team-bhp.com/forum/shifti...ml#post4416084

Regarding downhill speed - yes it's a function of gear ratios (my Scott metrix 10 has 48-11 versus the 50-11 on the B'Twin Triban 540 that beat me everytime on downhills). However, I think it's also a function of the rider's strength (on flats and uphills) and wheel bearings on the downhills.
Let's take the following situation:
- I am at 30kmph at the top of the hill just before starting the descent.
- My friend is also at 30kmph at the same spot.
- We both stop pedaling and let our bikes freewheel on the descent.
- Triban is lighter than Metrix by 2 kg, but my friend is heavier than me by 5kg.
- Triban rides on 25mm tyres that are sparsely treaded, Metrix rides on 38mm tyres which are decently treaded.
- Both of us never pedal or brake throughout the descent and no dog or pothole or any other obstacle comes in the way of either of us
- Yet, his Triban reaches the bottom faster than my Metrix

What gives?


P.S. It will be interesting to see what happens by installing the exact same tyre (say 28mm) of both Metrix and Triban when both are ridden by the same rider (or riders of same height and weight).


Cheers!

[PetaWatt]

Originally Posted by anandpadhye

I faced a similar problem/urge after riding my hybrid for @500km and bought a road bike:

Congrats for your new Ultra 700 AF. I had similar urge, so I test rode few road bikes and found that I was not comfortable on any of them (my weight was 90 kgs then). I even planned to go for flat bar road bike, then I thought lets convert my hybrid into a flat bar road bike gradually

Originally Posted by anandpadhye

Regarding downhill speed - yes it's a function of gear ratios (my Scott metrix 10 has 48-11 versus the 50-11 on the B'Twin Triban 540 that beat me everytime on downhills). However, I think it's also a function of the rider's strength (on flats and uphills) and wheel bearings on the downhills.

Let's take the following situation:
- I am at 30kmph at the top of the hill just before starting the descent.
- My friend is also at 30kmph at the same spot.
- We both stop pedaling and let our bikes freewheel on the descent.
- Triban is lighter than Metrix by 2 kg, but my friend is heavier than me by 5kg.
- Triban rides on 25mm tyres that are sparsely treaded, Metrix rides on 38mm tyres which are decently treaded.
- Both of us never pedal or brake throughout the descent and no dog or pothole or any other obstacle comes in the way of either of us
- Yet, his Triban reaches the bottom faster than my Metrix

What gives?

P.S. It will be interesting to see what happens by installing the exact same tyre (say 28mm) of both Metrix and Triban when both are ridden by the same rider (or riders of same height and weight).

In the scenario you mentioned above, tyre thickness, tyre pressure and high drag coefficient(you are sitting in upright position on a cycle with higher drag coefficient) are the major contributors to the Metrix slowness. You on your Ultra 700 AF might still be a bit slower that Triban in the same scenario because of the extra 5 kg your friend got.

[Lambydude]

Originally Posted by PetaWatt

[b][u]

Last week, I started cycling again. I reached office(16 kms away) without any problem and got the average speed of 19kmph (not bad after a gap of almost 2 years). ]

Good decision to start commuting on bike again. Which route do you take?
I used to pedal to office in 2014-16 atleast thrice a week. My office was in EGL and it was easy to travel through Koramangala roads from Arekere BG road. However, in 2017, I changed my job and my new office is in Marathahalli. I'm too scared to travel on a bicycle on ORR.
Should do it one day and overcome this fear.
Happy pedalling!

[vinodvayyat]

Originally Posted by Lambydude

I'm too scared to travel on a bicycle on ORR.
Should do it one day and overcome this fear.
Happy pedalling!

Fit a rear-view mirror on the bar end (since you are using a straight handle bar) - Decathlon mirror is the best (affordable, wide view) and pedal to get you some confidence. You can take service road most of the time on ORR. My wife and myself had cycled to work for almost an year and she was doing it from Spice Garden till Devarabeesanahalli on a daily basis.

Originally Posted by PetaWatt

I thought to use this opportunity to upgrade the drivetrain of my hybrid bike.

Wishing the best. This gives me motivation to DIY shift from my bar end shifter (touring setup) to Shimano STIs in my Surly CC.