I am contemplating putting together a vintage rig. The bike is an 1967 BMW R50/2 and has a sidecar ready frame. The sidecar is a Steib LS200, which was typically paired with this bike.
Here is my question. There appears to be two variations on the sidecar wheel for this combination:
1. The standard 18in BMW wheel and hub (with drum brake) as used on the bike. Sometimes the brake is hooked up, sometimes not.
2. The other is a 19in wheel that is full spoke and no drum brake/hub.
My question is: What is the mechanical advantage of using the drum brakeless 19in rim? It obviously weighs less, so there are less gyro scopic forces, plus it is also a bigger rim. Or are these not advantages at all?
Or is there no advantage other than it was probably a cheaper option?
It would seem to me that the 18inch rim has the advantage of being interchangeable with the other wheels, so if you have a flat you only have to carry one size tube.
I know alot about old BMWs, but not too much about the physics of sidecar rigs, so any insight would be appreciated.
The mechanical drum brakes aren't the most efficient system, so the 18" wheel with the brake would add to the bkaking ability of the rig, and if one had an onboard spare wheel and tire that would certainly be a plus if needed. The 19" wheel will support a larger tire which will allow heavier loading and sideloading plus have a longer tread life. Ride heigth of the hack will be about an inch higher. But, with poor brakes and that extra tube, I'd have to vote for the 18" with the brake.
But will the greater gyroscopic effect of the heavier 18in wheel and hub have a detrimental effect on handling?
Don't worry about the gyroscopic effect of the slightly heavier tire, it is minimal. The extra weight is concentrated near the center of the wheel which acts to furhter minimalize the effect. With regard to ride height, there is of courwse only a half inch difference in the two rim sizes. Chances are the variation in the height of the tire you pick would be more of a factor.I chose to go with the BMW wheel so that I'd be able to use my spare in any location. I haven't seen many of the smaller Steibs with a spare wheel but it is certainly possible.I believe that you are fretting over a non-issue here. Choose the wheel that pleases your estetic sensibilities and go with it.
Mole is correct of course. If you are not going to run a tire on the sidecar there will be only an increase of 1/2" in ride heigth on the hack.
Assuming the rim has been laced correctly and the axle is in the center of the wheel, 1/2 the radius and all that.
Come on you guys, cut an old man some slack here! LOL
>>Come on you guys, cut an old man some slack here! LOL <<
Oh allright...I will not say a word:-)
claude USCA#3563
Originally written by Mole on 10/14/2003 6:50 PM
Don't worry about the gyroscopic effect of the slightly heavier tire, it is minimal. The extra weight is concentrated near the center of the wheel which acts to furhter minimalize the effect.
I don't know Al, as you know that BMW hub is something like 22lbs. That's a pretty heavy flywheel mass to be spinning around way out there on the right. Especially when the Steib type hub weighs something like 2lbs. That's really my concern.
I guess all I can say is that it doesn't seem to create any significant problem on my rig (or the thousands of others so equipped) so I chose the BMW wheel for the convenience of interchangability. Also, BMW wheels are easy to find and used ones are generally available with either steel or alloy rims. (Steel is preferred for sidecar work)The 1/2 inch really isn't a big issue, my point was that the overall height of the tire would be more of a factor. I've found 15" tires that run from 23.5" to 26.5" in overall height. That's enough to make a difference.
The 19" wheel will allow the sidecar to have a slightly higher elevation. But you'll find a lot more 18" rear tires available. The gyroscopic forces on the sidecar wheel aren't an issue. Most importantly, the LS200 is relatively light, and adding some weight on the sidecar axle would be an advantage. Having a brake on the sidecar wheel isn't a big issue unless you regularly carry a passenger (or St. Bernard) I prefer a brake on the sidecar wheel, connected to a parallel lever next to the bike's rear brake pedal. If the brakes are balanced, it's easier to make a straight line stop.
My question to your question is whether the Steib hub is the same as the BMW hub. In other words, are the wheels interchangeable? In that case, you can swap wheels, or even carry a spare wheel that would work on either the bike or sidecar. That's what the Ural bikes do. You can use the same wheel on rear, s/c or front.
The LS200 has a 22mm axle and uses a bushing to get it up to 25mm wheel bearing size (if my memory is correct) while the old BMW wheels use something like a 17mm axle. Replacing the 22mm axle on the sidecar with a 17mm supported by only one side does not seem like a good move to me. I bought a new 18" wheel from Zweidramusuem and it looks great. BTW, it is NOT light, a lot more than 2 lbs! My sidecar came with a 16" wheel. Neither had a brake, but if you are runing it on a /2 you can use all the brakes you can scare up! I use solo gearing on a R60 and riding with the sidecar lightly loaded (camping gear or groceries) is not problem. I generally load my empty sidecar with 40-50 punds of sand in a Rubbermaid bin with handles so it is easy to get in and out of the car.
I THINK that the R50 might be marginal if there are hills where you live.
Ron
RANGERT MAKES A GREAT POINT ABOUT YOUR RIG BEING MARGINAL IF YOU LIVE IN AN AREA WITH HILLS AND INCLINES!!!!!!!YOU NEED DISPLACEMENT & TORQUE TO KEEP UP YOUR SPEED ON HILLS OR YOU MAY FIND YOURSELF LIMITED TO CERTAIN ROADS AND AREAS!! THIS MEANS YOU'LL NEED ANOTHER RIG FOR HIGHWAYS, HILLS ETC. CONSIDER A STEERING DAMPNER FOR STABLILITY AT HIGHER SPEEDS AS
A FRIEND OF MINE RIDES A R50/2 SOLO BUT DOES NOT LIKE GOING OVER 55-60MPH WITH IT. JUST TRYING TO HELP.
LENNY
Riding a vintage rig at interstate speeds of 75-80 is not in the cards for me. It would just be for around town. The usual solution to the R50/2 lack of torque is to substitute a lower rear end ratio and a sidecar transmission. This is basically the solo transmission with the 2nd gear replaced by the 2nd gear from an R27 single. Both mods are planned, so I'm not too concerned about the hills or the limited top speed as I have other bikes for that.
Just to be clear: I was talking about the weight of the BMW HUB vs the Steib HUB...not the entire wheel. Good point about the axles being 22 vs 17mm in diameter. A half centimeter is a substantial difference. Now I've seen many Steibs with the BMW wheel, and I understand that they were delivered from the factory with the BMW wheel and brake as a customer option, so what did they do differently? Perhaps a .5cm shim tube around the axle?
BTW: I also ride an R50/2 solo. It will easily and comfortably do 75mph. Top speed from the factory was supposed to be 82mph, but it revs so low you'd never know as it seems so understressed.
Your friend might be a tad on the conservative side.
R50/2 makes a great point about being conservative vs more agressive with riding. The r/2 series beemers are the nicest in my opinion.
Your intentions of using it around town and making the changes you stated above should make a fun rig. I have a 70 guzzi ambo with a velorex 562 for around town riding and for country roads.
Older beemers and guzzis make excellent around town/ local road hacks.
The extra weight is concentrated near the center of a wheel that still works minimalist effect. What ride height, there is only half courwse a difference between the two-inch wheel sizes. It is likely that variations in height of lifting the ring would be greater factor.
