Need lower gearing, but which gears ??

Discussion in 'Rack Mounted Engines' started by Bill P, Dec 17, 2014.

  1. Bill P

    Bill P Member

    Thanks LR, I was looking for that old post but couldn't find it !
     

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  2. LR Jerry

    LR Jerry Well-Known Member

    Bill what is currently your largest chainring?
     
  3. LR Jerry

    LR Jerry Well-Known Member

    A 7 speed 28-14 is a freewheel not a cassette. Here is what you want to get.

    http://www.ebikestop.com/dnp_epoch_...vtt_YAwgQYggdZNWqmLNbtdX38ThfAeHSAaAuxz8P8HAQ
     
  4. LR Jerry

    LR Jerry Well-Known Member

    Your post is somewhat confusing. Did you switch from a freewheel hub to a cassette hub?
     
  5. Bill P

    Bill P Member

    I didn't switch anything, it must be a freewheel, my terminology is just off.Anyway, my largest chainring is a 42t, if I can a freewheel that starts with a 10 or 11 I think I would be fine. I would need to get a 7-speed freewheel as I can't really afford to start changing everything right now, my rear wheel took a hit the other day and is gonna need replacing, maybe I can buy 12 gauge spokes and relace it myself....Thanks

    another issue I have is I cannot access the 14t on the freewheel because the bolthead for the vertical rear support is in the way.
     
  6. LR Jerry

    LR Jerry Well-Known Member

    Last edited: Dec 23, 2014
  7. LR Jerry

    LR Jerry Well-Known Member

    Bill, here is what I need to know. What speed and size freewheel are you using in the rear? What front chainrings are you using? What size gear is on your gearbox. Do you have lots of steep hills? Are you under 250 lbs. What size tires are you using. Once I have a clear picture of this, then I'll be better able to help you.
     
  8. Bill P

    Bill P Member

    Smallest is 27t, I don't even think of using that I'm always on the large C.R and #6 or #5 on the shifter.If I could get that freewheel you posted and eliminate the bolthead blocking mr i would be fine. The gear on the G.B., I went down to a 10 tooth.
     
  9. Bill P

    Bill P Member

    27,37,42 = C.R.'s
    185 lbs= ME
    Lots of steep hills
    14-28 = freewheel
    26" tires
    10t = engine gear
     
  10. LR Jerry

    LR Jerry Well-Known Member

    What you need is a 17t gear on the gearbox. You'll need to move your rear wheel over to the left using washers so you'll have access to the 14t sprocket. That means you'll have to adjust the rear derailleur. This will be your shift pattern: Entering a uphill climb at a slow speed 1(1,2,3). Level ground 2(3,4,5) 3(5,6). Downhill overdrive 3(7). The shift points for the front chain rings are when you're in 3 or 5 in the rear. For stops going up a hill be in 1(1) before stopping. Then use that as a starting gear. All other stops be in 2(3) before stopping then use that at a starting gear.

    You could use a 15t gear on the gear box. This would give you more hill climbing ability but 3(7) will be the 100% gear instead of 3(6). You'll lose the overdrive gear. However a 15t is what you'd want to use with a 8 speed 34-11 freewheel should you ever decide to use that setup.

    How to adjust your bicycle's rear derailleur and …: http://youtu.be/gCP9i8eWt78
     
    Last edited: Dec 23, 2014
  11. Bill P

    Bill P Member

    Thanks Jerry, my rear wheel is quick release, very short axles and no room for spacers as is.

    Wouldn't the 10t produce a higher rpm with my current setup compared to the 17t ??
     
  12. LR Jerry

    LR Jerry Well-Known Member

    Just the opposite. Engine rpm 7000÷18.75=373.33... (373.33...x 10/44= 84.84... cadence.) (373.33...x 17/44=144.24... cadence.) (373.33... x 15/44=127.27... cadence.)
     
  13. LR Jerry

    LR Jerry Well-Known Member

    Since you can't move your rear wheel over go with the 17t on your gearbox. You just won't have an overdrive gear. You won't be able to shift into 7.
     
  14. Bill P

    Bill P Member

    I thought when I changed to the 10t on the gearbox I was gaining low end ??
     
  15. LR Jerry

    LR Jerry Well-Known Member

    Low end means you gain torque but lose speed. A small gear on your gearbox means you can climb really steep hills or pull really heavy loads. A large gear means you'll go faster but may have to assist going up a hill. With a 17t gear on the gearbox the only way you'll need to assist while in 1(1) is if you're pulling a heavy load behind you. Here is what you'll have with that set up 7000÷18.75×(17:44)×(42:16)×(13÷168)~29.3 mph. Would be your top level ground speed. If you're going downhill let off the gas after 29.3 mph. You'll just be over reving after that. With a 10t gear this is what you'd have. 7000÷18.75×(10:44)×(42:16)×(13÷168)~17.2 mph.
     
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