Trevski
Active Member
There have been quite a few posts, over the time I've had my Sofrider (Clarissa), about putting a triple chainring on the bike. I have always wanted a granny gear, and was leaning towards buying a 24 tooth 74mm BCD ring. To fit it, I would have to drill and tap the pads on the crank my bike came with (not sure if the new bikes have these pads). I've held off, because I was worried I'd make a mess of it. My next option was to get a triple crank from Bikesmith Design, as I wanted to retain the 160mm cranks. The final result was that I spent so much time thinking about it, that I never got around to actually doing it.....
Finally, after reading cplager's post about putting a triple on his bike, I decided to bite the bullet.After reading some of the spec sheets, I managed to convince myself that most Silvio builds have 170mm cranks, as would most conversion kits, so how terrible could 170mm cranks be?
The cranks I ordered were Shimano Alivio M410. The set I chose have 42-32-22 teeth, with a 50mm chainline on a 113mm bottom bracket. I measured the chainline on my bike and it was just under 50mm to the inner chainring, so I thought I might be in luck with the original bottom bracket. I put the new cranks on, lowered the front derailleur to suit, adjusted the limit stops and that was it! A simple bolt on solution. I did have to adjust the B tension screw on the rear derailleur to obtain clearance for the upper rear derailleur idler when in the 22-32 combination, but that was it. I then shortened the chain, so I could back off the B tension screw again.
So, to impressions. I chose this crank both for the 32 and 22 tooth chainrings. With the original 34 / 48 crank, I had 10 effective gears, with the following gain ratios - 2.1 2.4 2.8 3.2 3.7 4.5 5.3 6.3 7.3 and 8.6 (With thanks to Sheldon Brown). I don't have the strength to utilise the top 3 gears, so the 6.3, 7.3 and 8.6 were rarely used - I effectively had 7 gears.
Now, I generally just leave it on the 32. This gives me gain ratios of 1.9 2.1 2.5 2.8 3.3 4.0 4.6 and 5.4. Fantastic, I now have 8 useful gears, without having to change chainrings! Just having that 5.4 (32-11 combo) instead of the old 5.3 (48-18 combo, my most used gear) means I can bomb along at 35 kph on the flat with no wind. At that speed before, I would have been spinning out in 48-18 (5.3), then changing to 48-15 (6.3), losing speed and changing down, then repeating the whole process.
I find it hard to believe that such a small change in gain ratio would make such a huge difference in the feel of the bike for me, and I don't have any problem spinning at 100rpm+ with the 170mm cranks either, which was my main concern. And, if I do get the wind behind me, I still have two higher gears - 6.0 and 7.1.
And, when the ground stands up in front of me, I now have 1.7, 1.5 and even 1.3 waiting. I reckon that in the 22-32 combination, the bike would try and go up a lamp post!
In fact, I'm so happy with Clarissa, I've treated her to a set of SKS Chromoplastic mudguards as well, to keep the grot off my shiny new drivetrain!
Cheers,
Trev
Finally, after reading cplager's post about putting a triple on his bike, I decided to bite the bullet.After reading some of the spec sheets, I managed to convince myself that most Silvio builds have 170mm cranks, as would most conversion kits, so how terrible could 170mm cranks be?
The cranks I ordered were Shimano Alivio M410. The set I chose have 42-32-22 teeth, with a 50mm chainline on a 113mm bottom bracket. I measured the chainline on my bike and it was just under 50mm to the inner chainring, so I thought I might be in luck with the original bottom bracket. I put the new cranks on, lowered the front derailleur to suit, adjusted the limit stops and that was it! A simple bolt on solution. I did have to adjust the B tension screw on the rear derailleur to obtain clearance for the upper rear derailleur idler when in the 22-32 combination, but that was it. I then shortened the chain, so I could back off the B tension screw again.
So, to impressions. I chose this crank both for the 32 and 22 tooth chainrings. With the original 34 / 48 crank, I had 10 effective gears, with the following gain ratios - 2.1 2.4 2.8 3.2 3.7 4.5 5.3 6.3 7.3 and 8.6 (With thanks to Sheldon Brown). I don't have the strength to utilise the top 3 gears, so the 6.3, 7.3 and 8.6 were rarely used - I effectively had 7 gears.
Now, I generally just leave it on the 32. This gives me gain ratios of 1.9 2.1 2.5 2.8 3.3 4.0 4.6 and 5.4. Fantastic, I now have 8 useful gears, without having to change chainrings! Just having that 5.4 (32-11 combo) instead of the old 5.3 (48-18 combo, my most used gear) means I can bomb along at 35 kph on the flat with no wind. At that speed before, I would have been spinning out in 48-18 (5.3), then changing to 48-15 (6.3), losing speed and changing down, then repeating the whole process.
I find it hard to believe that such a small change in gain ratio would make such a huge difference in the feel of the bike for me, and I don't have any problem spinning at 100rpm+ with the 170mm cranks either, which was my main concern. And, if I do get the wind behind me, I still have two higher gears - 6.0 and 7.1.
And, when the ground stands up in front of me, I now have 1.7, 1.5 and even 1.3 waiting. I reckon that in the 22-32 combination, the bike would try and go up a lamp post!
In fact, I'm so happy with Clarissa, I've treated her to a set of SKS Chromoplastic mudguards as well, to keep the grot off my shiny new drivetrain!
Cheers,
Trev
