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Sidecar gearing

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weh8127
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Sidecar gearing

Post by weh8127 »

Hi all; I've recently added a sidecar to my R60/2 which is an old ambition realized and I'm enjoying it quite well. I'd like some input and advice based on experience.

For now I'm using the solo transmission and 25/8 final drive which works pretty well; I really don't feel the need for a sc transmission. However, the overall gearing feels a bit high. With only 30hp available I expected to slow down on hills, which it does, and to pull a long grade at 40mph 3rd gear is necessary. On a long, flat straight road with a passenger in the car and the windshield in place top speed is 58mph indicated. (I don't know if the 4.00x18 block K tires create any speedometer error or not.) With a 50# sandbag for a passenger and the opening covered by the tonneau the rig will go over 60 but not the 66mph that Snowbum's page says yields 4200rpm with this final drive.

The issue here is not speed but overall drivability. According to the Barrington manual the 27/7 final drive which is most often used on R60/2 sc rigs makes for an unpleasant busy feel to the whole rig and that the 26/6 is a better choice. But, things aren't terrible now. So what I'd like to know from other's experience is the degree of difference to expect if I go to the trouble and expense of making a change. Maybe 27/7 is the way to go after all and the 26/6 is only a so-so improvement, or maybe it's fantastic. Maybe I'm best off with things as they are. I'd love some feedback.

Thanks in advance.
Bill Husted
Barre, MA USA
1963 R60/2 w/ 1955 Steib S500
1973 R75/5

mcsherry1328
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Re: Sidecar gearing

Post by mcsherry1328 »

When I first got a sidecar over 30 years ago I read that 26/6 was the ratio to have. I have an R69S with a Steib S500. I bought the 26/6 rear drive and immediately decided it was way too low. Then I bought the 27/7 ratio and feels it's perfect. The sidecar will walk away just off idle and cruise at 60mph no problem. I have the solo transmission which is fine I wouldn't change that. Something I would do is upgrade the suspension. I used Koni shock absorber inserts with sidecar springs front and rear. It's also important to use steel rims, not aluminum.

Daves79x
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Re: Sidecar gearing

Post by Daves79x »

I think you have the ratios mixed up. Barrington thinks the 26/6 is very 'busy', from my recollection. It is lower than the 27/7, which I think they endorse. You should have a matching speedometer for either of those, but they are impossible to find in mph. I personally think a sidecar transmission is the way to go, and you can make one out of a solo /2 trans and an R26/27 trans. The single's trans has the exact same ratios as the sidecar /2 trans.

Dave
Dave

weh8127
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Re: Sidecar gearing

Post by weh8127 »

Yes, I mixed up the drives. The bike is fitted with w-p shock inserts and upgraded front brake from Scottie Sharp as well as steel rims and heavy springs. The performance Mr. McSherry is describing is what I'm looking for. I wish I could find a plotted graph of hp and torque curves for both models but can't seem to find any.

Bill
Bill Husted
Barre, MA USA
1963 R60/2 w/ 1955 Steib S500
1973 R75/5

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Flx48
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Re: Sidecar gearing

Post by Flx48 »

Feels like I posted something like this not all that long ago, so if a repeat of what you've already read or learned, well, so be it.

If memory serves the factory manual for the R60 era listed the 27/7 for sidecar use, and then the R60/2 era manual listed the 26/6 gears.

I think it's a horses for courses scenario; a mixture of the environment in which you intend to drive, and your own expectations; the Earles bikes simply don't have the power to be high speed and have low speed tractability.
When I first set up my rig, like yours it had the solo trans and 25/8 rear. I found it to be lacking at both ends of the spectrum, it worked fine but was not what it could be.
Starting off from a stop was difficult on the clutch in too many situations, and fourth gear was just not utilized that much. My riding environment includes a passenger 80% of the time, and is hilly with numerous hilly stop signs, so that made the creeper 1st gear a no brainer to use in my situation.

For the rear gears, here's my take-
Your stock gears give you an end ratio of 4.67 (that's the rear 3.13 plus 4th 1.54) which may put you in 3rd more than 4th, or perhaps more than you'd like to be, and 4th is where you'd like to be most of your time. (that's why 4th is a direct drive on the trans shafts)

The 26/6 gears give you an end ratio of 5.87 (that's 4.33 rear plus 1.54 4th gear) which is a good setup for driving always in an urban setting, or conversely always in the mountains.
If you want to simulate a 26/6 rear using your stock setup, simply drive around without taking the trans higher than 2nd gear.
The 26/6 rear plus 4th gear is 5.87, while 25/8 plus 2nd gear (2.72) is 5.85, making them virtually the same.
So the 26/6 is great for instant top speed, which would be nice for always bopping around the block or crosstown quickly, or handily making it through a mountain pass, but the low top speed is not that nice for most touring about.

The 27/7 gears give you an end ratio of 5.40 (3.86 rear plus 1.54 4th) which is a compromise that puts you in the neighborhood of driving around in 3rd gear with your stock ratios; 5.40 vs 5.07. (3.13 rear plus 1.94 3rd gear)
This is my preference, as I'm never on a highway, and it gives comfortable mid-50 mph on the larger 2 lane roads.

Another option, if you want just a little more latitude than the stock gearing gives, is the rear out of a US /2, (27/8) which gives an end ratio of 4.92. (3.38 rear plus 1.54 4th)
That puts you about one third of the way from the stock 25/8 rear to the 27/7 rear; perhaps good enough if your driving is primarily unhilly terrain; and it's no doubt more economical to find a used US rear and reseal that, than purchase new gears and rebuild the rear.
Best-
George

weh8127
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Re: Sidecar gearing

Post by weh8127 »

Thanks much, guys. That's exactly the perspective I was looking for.
Bill
Bill Husted
Barre, MA USA
1963 R60/2 w/ 1955 Steib S500
1973 R75/5

johnlacko
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Re: Sidecar gearing

Post by johnlacko »

There is a 27/7 rear drive for sale on ebay now if you decide to go that route. jl

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