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Final sidecar gears

rmichel13
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Joined: Thu Jan 26, 2017 10:25 am

Final sidecar gears

Post by rmichel13 »

Anyone have / 4.33 final drive gearing for sale :?:
Bob Michel

rmichel13
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Joined: Thu Jan 26, 2017 10:25 am

Re: Final sidecar gears

Post by rmichel13 »

Sorry I need gear ratio's 26/6 4.33
Bob Michel

rmichel13
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Re: Final sidecar gears

Post by rmichel13 »

I am considering putting a sidecar on my r60/2.
any advice as to what will be needed in the way of gearing ect.
Bob Michel

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schrader7032
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Re: Final sidecar gears

Post by schrader7032 »

This page suggests 27:7 with sidecar. What about a transmission? Generally to go along with the rear drive, a transmission is used which has better gearing to pull the extra weight. Also shown on this page.

http://www.bmbikes.co.uk/specpages/R60-2.htm
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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palica
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Re: Final sidecar gears

Post by palica »

There are several mods to be made according to BMW user manual:

- transmission (4.33 instead of 3.13 on the R50/2, 3.86 on the R60/2)
- Reinforced springs (actually, the standard rear springs can go to the front shocks and you can buy reinforced springs for the rear only)
- Large handlebar
- Steel rims (no aluminum)
- 4.00 x 18 rear tire

I would add that sidecar reinforced tires (with a flat profile. Well, not a flat tire)

My sidecar is attached with an R50/2 with original transmission (3.13) and I must say it can handle it perfectly. But my sidecar is very light (approx 40 kg). Considering the cost of a 4.33 transmission, I will leave it as is. Another solution (cheaper?) would be to have a smaller wheel on the pusher but I do not like it, purely for aesthetics reasons.
1967 R50/2 with Duna sidecar
1974 R90S

mcsherry1328
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Re: Final sidecar gears

Post by mcsherry1328 »

I have an R69S with a Steib S500 sidecar. Initially I installed the recommended 26/6 rear drive. For me it was way too low geared. I then bought & installed a 27/7 ratio rear drive & I love how it works. I can walk away from just off idle & cruise at 65 all day. Also I have the stock gearbox which works fine. Just wanted to share my experience with you on ratios.

Daves79x
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Re: Final sidecar gears

Post by Daves79x »

I talked to Richard at Vech's about this topic recently. He also said 26/6 was too low for any of the models, and only appropriate for the R50 if you are climbing mountains all day pulling a TR500. He said too that the 27/7 ratio was a much better choice for most applications. You just never find them used out there, I'm likely going to spring for a new 27/7 crown set and matching speedometer in KPH (none available in MPH) for my R50. It's an expense, but what choice do we have?

Dave
Dave

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Flx48
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Re: Final sidecar gears

Post by Flx48 »

A lot of personal choices to make when hooking on a sidecar.

The factory and owner's manuals have differed through the years; in earlier days the 7/27 gears were called out for the R60, but later on it was the 6/26 gears, which may be confusing.
The higher ratio (to me) makes more sense as the R60 (and R60/2) are torque engines, their power is developed at lower rpms than the R69/R69S engines and so tend to like to run at lower rpms than their counterparts.

If numbers make sense to you-
The solo final gearing in 4th gear is 4.67. (that's 3.13 final drive+1.54 trans 4th gear)
The s/c 7/27 final gearing in 4th gear is 5.40. (3.86+1.54)
The s/c 6/26 final gearing in 4th gear is 5.87. (4.33+1.54)
So bearing in mind those numbers, realize that 4th gear, when using the 6/26 final gearing, is basically the same as being in 2nd gear (2nd gear is 2.72, assuming your trans is marked "S" for sport) with the solo (8/25) final gearing the total ratio is 5.85. (3.13+2.72=5.85)

Meaning- if riding your stock solo bike, and wanting to simulate driving with a 6/26 final gearing, drive around in 2nd gear instead of 4th.

This is the reason many of us opted for the 7/27 gears, which is close to (though just under) 3rd gear on a stock solo gearing. (5.40 compared to 5.07)
Lower rear gearing than solo is preferred of course, because an empty s/c is the same as dragging around 1-2 passengers, (depending on the chosen s/c) and when occupied the same as having a 3-4 passenger payload.
The 6/26 final gearing would probably feel good if all driving were in mountainous terrain or conversely, only in an urban setting, but 7/27 works very nicely here in the hills of New England.

As for further s/c gearing advice:
Perhaps seek out a pre "S" stamped trans; this will give you the same 4th gear (1.54) as the "S" but will have a 5.33 1st gear instead of the "S" 4.17 1st.
This makes moving off from a stop a bit easier, (kind of like the old VW bug's creeper 1st) particularly easier on the clutch when forced to a stop in a line of traffic at a light on very steep hills.
(And a technique to deal with that situation, regardless of what 1st gear you have is: after coming to a stop, roll backwards turning to your right, so being perpendicular to the traffic as if going to drive across the oncoming traffic lane; then when starting off you are starting on the flat and driving around the s/c before actually pulling the weight of the s/c)

And further s/c thoughts in general:
S/C tires on all three wheels; it is no longer a two wheeler, it now is steered around corners rather than leaned through, so more flat road contact patch is preferred, just like with a car, for more solid control. (for the /2 that's the Metzler Block K 400-18)
Steel wheels; instead of the soft alloys, and also the wider steel rim for the bike rear for more road contact, or newer alloy rims all around, which seem much stronger than the original Weinmanns.
Wide handlebars; even though using the Earles swingarm in the forward position gives easier steering, (less trail equals less effort) there is still more effort required to steer a rig than lean a solo and that inch and a quarter less trail also means less self-centering effect, so more leverage is good.
S/C springs on the bike; the heavier the s/c you choose, the more you will appreciate stiffer springs on all four corners of the bike.
Speedo matching the final drive ratio; I did this when doing the rear gear swap, but consider it a vanity as I drive much more by feel and sound than by any information provided by the speedo. (and I'm certainly not concerned about speeding when on the outfit...)

Back when setting up my rig (thirty some years ago) almost no one had multiple bikes, except maybe a few with both a street bike and a dirt bike.
So I had visions of swapping back and forth solo and s/c, but the real life practicality of doing that doesn't exist. (at least not in my world)
So I came to doing all of the above slowly as I realized what made the rig a nicer ride, and also realized another bike was needed for solo riding pleasure, so like many on this list multiple rides clog my barn these days.
Best-
George

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Re: Final sidecar gears

Post by mcsherry1328 »

George, Thanks so much for the very thorough & informative explanation of sidecar set up. All important & critical knowledge necessary for correct & safe sidecar operation. I learned much of this over time.
I didn’t want someone just beginning to set up there rig to go to the expense of buying pricey 26/6 gearing & then realize it’s too low.
One question I have is do they make sidecar type tires other than 4:00 x 18 ?
,Michael

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Flx48
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Re: Final sidecar gears

Post by Flx48 »

Michael, other than the Metzeler 400-18 for the /2, there is the Avon 350-19 that I see on Steibs, and /3s, and the Russian rigs.
And a few guys in the past took it a step further and laced up the /2 hubs with 15" rims to use 125-15 car radials all the way around, I believe Buchanan's was doing that work, kinda like the EML rigs did on their solid wheels.
I know some chairs run smaller dia. rims, but I am not familiar with what's available for them, you could probably find them on the google.
The above is just what I'm familiar with, I'm sure there is more out there, and perhaps others will chime in.
Best-
George

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