I've just finished re-building the e-bike ready for summer commuting. Part of the rebuild was an all new handlebar setup because I wanted stripped back, no clutter bars due to my old setup being very "busy". To achieve this I fitted new, wider bars with new grips and I removed the throttle, ignition key barrel and regen/kill switch. This enabled me to fit a trigger shifter under the bars in place of the old over bar SIS shifter along with the new SRAM Guide RE brakes, which are awesome by the way!
Anyway the point is that without a throttle, I now rely on PAS for power but I'm spinning out at 16-18mph due to the available gear ratios with the 1x7 setup. I'm stuck with the 7spd freewheel (Shimano MF-TZ21) threaded on to the hub motor so I have to address the chainring. I currently have a 38T raceface narrow wide ring fitted on the inside of the crank spider that originally held a 3x setup. This gives a perfect chainline and I have no chain retention issues.
Yesterday I ordered a blackspire 46T chainring and a new chain before realising a problem - the larger chainring will interfere with the chainstay if fitted on the inside of the crank spider so it will have to go on the outside which is going to push the chainline out by about 10mm (guess). This means quite a crossed up chain in the lower gears. Also, the new chainring is not narrow wide so I wonder if it will try to derail - at least it is not a ramped chainring, it's a 1x specific DH type. I'm using a 9spd chain and don't think I can go to a more flexible 10/11spd as they may be too thin for the old-school 7spd freewheel.
I "think" with the chainring fitted to the outside of the crank spider it will be positioned roughly between the original middle and big ring. I suspect I will spend most of my time on the bottom half of the freewheel which is OK, but there are some steep uphill standing starts on my commute due to cycle gates which are a pain and will require 1st gear and a high PAS level.
So I guess the question is, do we think a 9spd chain will drop off the chainring when on the larger rear gears, with a chainline 10mm out from perfect?
Anyway the point is that without a throttle, I now rely on PAS for power but I'm spinning out at 16-18mph due to the available gear ratios with the 1x7 setup. I'm stuck with the 7spd freewheel (Shimano MF-TZ21) threaded on to the hub motor so I have to address the chainring. I currently have a 38T raceface narrow wide ring fitted on the inside of the crank spider that originally held a 3x setup. This gives a perfect chainline and I have no chain retention issues.
Yesterday I ordered a blackspire 46T chainring and a new chain before realising a problem - the larger chainring will interfere with the chainstay if fitted on the inside of the crank spider so it will have to go on the outside which is going to push the chainline out by about 10mm (guess). This means quite a crossed up chain in the lower gears. Also, the new chainring is not narrow wide so I wonder if it will try to derail - at least it is not a ramped chainring, it's a 1x specific DH type. I'm using a 9spd chain and don't think I can go to a more flexible 10/11spd as they may be too thin for the old-school 7spd freewheel.
I "think" with the chainring fitted to the outside of the crank spider it will be positioned roughly between the original middle and big ring. I suspect I will spend most of my time on the bottom half of the freewheel which is OK, but there are some steep uphill standing starts on my commute due to cycle gates which are a pain and will require 1st gear and a high PAS level.
So I guess the question is, do we think a 9spd chain will drop off the chainring when on the larger rear gears, with a chainline 10mm out from perfect?
