So I just bought a Bianchi Pista off my neighbor and got a great deal because he never rides it. I put a BMX freewheel on it and noticed that it threw the chainline off by about 10mm.
I was considering replacing the crankset anyway and noticed that the Sugino RD gives you a 45mm chainline with 103mm spindle length BB.
Currently the bike has a 103mm BB with a crank that gives it a 42mm chainline. So the Sugino crankset alone would get me 2mm closer to the proper chainline.
I noticed that the Sugino RD can also take a 107mm BB. So if i were to get a 107mm BB and the Sugino RD does this mean that It would move the chainring out a total of 7mm? Thereby giving me a much closer chainline, or is this completely convoluted logic?
I've searched the forum quite a bit and haven't been able to find an answer, or if I have it has gone right over my head because I'm pretty new to bike mechanics in general. Any answer would be appreciated, thanks.
if its really 8mm difference (thats a lot) you need to double that...so 103+16=119mm with the RD will give you the right chainline. VERY odd by the way. Maybe look into different freewheels? or get an EXACT measurement.
O.k. I see now that a 107mm spindle would only give me 2mm. But, wouldn't the RD alone give me 3mm? for a total of 5mm?
It's definitely pretty far off, at least 10mm. It's a regular shimano single-speed freewheel. I've seen that a lot of people here on the forums have used them on their pistas but I don't understand how they could maintain the same chainline since the freewheel is so much wider than the fixed cog. Pretty annoying.
This might be of help: http://www.sheldonbrown.com/chainline.html
scroll down to the tables.
If you know what hub you have you just add the hubs "chainline center to shoulder", with the freewheels "chainline from shoulder".
Myself I have an IRO hub 36mm + shimano 1/8" freewheel 8.67mm= which gives me a chainline of 44.67. Almsot spot on for my Sugino RD.
If this doesn't add up to reality for you, something might be incorrectly installed.
My hub isn't listed. It has the Bianchi hub that comes stock w/ the Pista. I'm confident that everything is set-up right.
It's a flip-flop hub and if I measure from the side of the hub to the center of the sprocket on the freewheel it is about 10mm longer than from the side of the hub to the center of the fixed gear on the other side. The problem is the thickness of the freewheel.
I just did some re-measuring. The freewheel is only about 3-4mm farther from the hub than the fixed cog but I did Sheldon Brown's technique for measuring chain line and the freewheel was about 7mm farther than the cog. I don't really know. I think I'm just too tired. I'll re-measure tomorrow.