Final drive for R 69 S
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Jacques
Final drive for R 69 S
I'm looking for a complete final drive 7 x 25 for sidecar use. Offer welcome.
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Allan Atherton
Re: Final drive for R 69 S
I have not heard of a 7/25 final drive ratio. It might be very rare and hard to find. The proper sidecar ratio for an R69S is 6/26.
It may be easier for you to find a used complete final drive of any ratio, then buy the 6/26 gearset from Huggett or elsewhere, and have the final drive rebuilt with the new gearset.
It may be easier for you to find a used complete final drive of any ratio, then buy the 6/26 gearset from Huggett or elsewhere, and have the final drive rebuilt with the new gearset.
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Jacques
Re: Final drive for R 69 S
Thanks for your replay.
7/25 final drive ratio seems to have been mounted on R 50 S. From owner's advice, it seems to be better for sidecar use than 6/26. The reason is that 6/26 is really very short.
Nevertheless, I agree with your solution due to the difficulties to find a complete one.
7/25 final drive ratio seems to have been mounted on R 50 S. From owner's advice, it seems to be better for sidecar use than 6/26. The reason is that 6/26 is really very short.
Nevertheless, I agree with your solution due to the difficulties to find a complete one.
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Allan Atherton
Re: Final drive for R 69 S
Here's all the various ratios and uses:
26/6 4.333 (R69S sidecar)
27/7 3.857 (R60 sidecar)
25/7 3.571 (R50S)
27/8 3.375 (US Forks)
25/8 3.125 (Earles Forks)
The 25/7 would be better for the R69S than the 25/8, if the sidecar was small and light. However, if the sidecar was large and heavy, the 27/7 would be better. And if the sidecar was large, heavy, loaded with passenger, equipped with a windshield, and used in hilly country, the 26/6 would be necessary. BMW specifies the 26/6 for R69S with any sidecar.
I had an R69S with heavy Ural sidecar for five years and used the 26/6. The R69S does not have much torque at low to middle rpms.
I now have an R60/2 with a light LS200 sidecar. The R60/2 has so much torque at low to middle rpms that it could pull the sidecar pretty well with solo 25/8 drive. However, I also own an R69US and I moved its 27/8 drive to the R60/2, and this is perfect for the light sidecar.
There is a big difference in way that the R60/2 and R69S engines feel, especially when pulling a sidecar. The R69S does not have good torque and needs a high drive ratio like 26/6 to avoid "bogging down". And although the 26/6 ratio seems so "short" that it might rev-limit the top speed, the extra 1200 rpm of the R69S engine compensates.
If a complete 25/7 final drive from the R50S is available at a cheap price, and you have a small light sidecar, you might be satisfied. But I would not put much money into buying or building a 25/7 drive for an R69S sidecar outfit.
26/6 4.333 (R69S sidecar)
27/7 3.857 (R60 sidecar)
25/7 3.571 (R50S)
27/8 3.375 (US Forks)
25/8 3.125 (Earles Forks)
The 25/7 would be better for the R69S than the 25/8, if the sidecar was small and light. However, if the sidecar was large and heavy, the 27/7 would be better. And if the sidecar was large, heavy, loaded with passenger, equipped with a windshield, and used in hilly country, the 26/6 would be necessary. BMW specifies the 26/6 for R69S with any sidecar.
I had an R69S with heavy Ural sidecar for five years and used the 26/6. The R69S does not have much torque at low to middle rpms.
I now have an R60/2 with a light LS200 sidecar. The R60/2 has so much torque at low to middle rpms that it could pull the sidecar pretty well with solo 25/8 drive. However, I also own an R69US and I moved its 27/8 drive to the R60/2, and this is perfect for the light sidecar.
There is a big difference in way that the R60/2 and R69S engines feel, especially when pulling a sidecar. The R69S does not have good torque and needs a high drive ratio like 26/6 to avoid "bogging down". And although the 26/6 ratio seems so "short" that it might rev-limit the top speed, the extra 1200 rpm of the R69S engine compensates.
If a complete 25/7 final drive from the R50S is available at a cheap price, and you have a small light sidecar, you might be satisfied. But I would not put much money into buying or building a 25/7 drive for an R69S sidecar outfit.
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Jacques
Re: Final drive for R 69 S
Thanks for advices.
My side is from french make "précision", very similar in weight with the Steib LS 200.
My final drive is 25:8. My bike was built (probably!) in july 67 just before BMW changed the final drive for R69S to 27:8
Another fact is that the rubber is 110/90 x 18 that give also longer ratio.... As it is rather difficult to find correct size for tires, I prefer change the final drive.
27:7 choice has been given to me by a friend who rides his 69S with side since 25 years ! He says that 26:6 is really to short, and as he also own an R 50 S, lucky guy ! he can tell about this.
I believe in any way, that due to difficulties to find those parts, I must be prepared to compromise.
In that way, 27:7 or 27:8 would be correct to fit the bike. If you hear of some.....
Regards
Jacques
My side is from french make "précision", very similar in weight with the Steib LS 200.
My final drive is 25:8. My bike was built (probably!) in july 67 just before BMW changed the final drive for R69S to 27:8
Another fact is that the rubber is 110/90 x 18 that give also longer ratio.... As it is rather difficult to find correct size for tires, I prefer change the final drive.
27:7 choice has been given to me by a friend who rides his 69S with side since 25 years ! He says that 26:6 is really to short, and as he also own an R 50 S, lucky guy ! he can tell about this.
I believe in any way, that due to difficulties to find those parts, I must be prepared to compromise.
In that way, 27:7 or 27:8 would be correct to fit the bike. If you hear of some.....
Regards
Jacques