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Thread: Rear End Gear Ratios

  1. #1
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    Rear End Gear Ratios

    I have a ‘57 R60 that has a 2.91 (ratio) and it is much too high for the hilly area that I live in. I’m in the foothills of the Blue Ridge Mts and the closest city is nicknamed the “Hill City”. All fine and good for a lower ratio rear end but the 2.91 rear end needs riding the clutch and visions of nice flatlanders terrain.

    I would like a lower Rear End. Barrington’s says that that year also had a 3.18 ratio. And surprisingly no ratio for a sidecar.

    I’m curious as to options. Are some, if not all Rear Ends from ‘55 to ‘69 interchangeable. Probably dreaming. Do other Crown Gear Sets fit the earlier bikes. Like wouldn’t it be grand/lucky if the /5 gears fit the older housings. Anyone want to let go of a little knowledge to help me make this bike more enjoyable in this area.

    Everything is appreciated

    Charlie

  2. #2
    Liaison 20774's Avatar
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    I very much doubt that anything past 1969 is going to work. The brakes will not match as the width of shoes and drum material are different. I suspect that the mate between the drive shaft splines and the input to the final drive are also not compatible.

    The early R60 had the 32/11 solo and 27:7 sidecar. The later R60/2 had the 25:8 or 27:8 for solo and 27:7 with sidecar. 25:8 is 3.13...maybe that's what you meant based upon what Barrington told you. I suspect that anything available during the '55-'69 period would be usable. You would need be sure the wheel splines are suitable otherwise it would quickly wear the new drive. And the speedometer would need to change in order for the readings to be correct.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
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    Just hoping on the post ‘69 driveshafts fitting. After all the post rear brake shoes, although more narrow worked as a temporary measure while replacing pad material on stock pre 1960 shoe pad holders.

    Yes, I did mean a 3.13 ratio.

    Still would like to know if all pre 1969 Rear Ends are compatible.

    Saw a 3.13 pop up for sale after my original post, but I’m a few weeks away from being able to buy. Just bad timing right now.

    Charlie

  4. #4
    Liaison 20774's Avatar
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    I think all pre '70 final drives are pretty much the same. I tried this...I opened up RealOEM for a '67 R60/2 and R50/2. I compared all the internal part numbers for the "right angle gearbox". They're all the same part numbers. A little difficult to compare all models across all years. Maybe give Vech a call??
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
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    Talked to “Vech” and his opinion was that the Rear Differentials from 1955 to 1969 are interchangeable.
    That’s an important piece of information for the enthusiast/custodian/owner.

    The 32/11 (2.91) Differential that I have is not compatable with the very hilly area that I live in, nor the country type of riding that I do.. I hope that a 25/8 (3.12) ratio will suit the terrain where I ride I a little better. At least make first gear engagement less of an event and city route choices a non issue.

    Thanks for your input also Kurt.

    Charlie

  6. #6
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    Do not forget the tire size is important component of overall gear ratio

    Do not use a 4:00x18 rear tire

    Do use both 3:50x18 tires

    Suggest 27:8 rear end with 3:50x18 tires for hilly area - that is what I have been
    using on my 1967 R50/2 and or 1968 R60/2 for my annual Black Hills visits

    The shorter stroke R50/2 is actually better than the R60/2 for aggressive mountain riding

    Mountain riding seldom use the 4th gear under 50mph - these bikes like to spin up
    more rpm than you might think to get good power
    Attached Images Attached Images

  7. #7
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    Very good recommendations.
    And from personal experiences that relate to the same type of riding/terrain that I was looking for.

    Thanks a lot 44006.

    Charlie

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