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Thread: Lowering a 1977 r100rs

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    Lowering a 1977 r100rs

    I would appreciate your thoughts and ideas on the lowering an RS. It has a corbin 30 seat and is otherwise OEM. Two inches lower would be great. I am 5'9'' and pretty much on my toes at the stop. I'm new to MOA...just joined at the ralley in Salem. Jim

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    Jim: The easiest way to lower a bike are shorter shocks in the rear (or a lowering block) and sliding the fork tubes up in the triple tree in the front. You must be careful not affecting the geometry too much, it may cause ill handling. Also, in case of the RS, sliding the fork tubes may interfere with the fairing.

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    don't know for sure without pics of the saddle, but ditching the Corbin for a stock unit (or a stocker reworked by Rick Mayer or a Sargent) will probably help. Even tho the Corbin is thinner, they're usually wide at the nose, forcing your legs out and around before they can go down. i have a 30" inseam, and never had an issue with the stock saddle.
    Ride Safe, Ride Lots

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    Quote Originally Posted by EMSimon View Post
    and sliding the fork tubes up in the triple tree in the front.
    Is this possible on the standard BMW top triple tree? I've seen people do it on older Honda 750s and the like, but didn't think this was doable on our forks.

    Metric tires have a smaller radius than inch-sized tires.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
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    Quote Originally Posted by EMSimon View Post
    Jim: The easiest way to lower a bike are shorter shocks in the rear (or a lowering block) and sliding the fork tubes up in the triple tree in the front. You must be careful not affecting the geometry too much, it may cause ill handling. Also, in case of the RS, sliding the fork tubes may interfere with the fairing.
    I'd consider swapping out the shocks...anybody got the model or part #'s for short shocks?

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    Quote Originally Posted by 20774 View Post
    Is this possible on the standard BMW top triple tree? I've seen people do it on older Honda 750s and the like, but didn't think this was doable on our forks.

    Metric tires have a smaller radius than inch-sized tires.
    When these tires are due for replacement, I'll look at metric. Thanks.

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    Quote Originally Posted by bikerfish1100 View Post
    don't know for sure without pics of the saddle, but ditching the Corbin for a stock unit (or a stocker reworked by Rick Mayer or a Sargent) will probably help. Even tho the Corbin is thinner, they're usually wide at the nose, forcing your legs out and around before they can go down. i have a 30" inseam, and never had an issue with the stock saddle.
    Bikerfish, I have an OEM seat in the box of goodies. After looking at the two, I believe you are right about the geometry of the two seats. Swapping the seats will be my first step...Thanks

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    Quote Originally Posted by chippena.f View Post
    I'd consider swapping out the shocks...anybody got the model or part #'s for short shocks?
    aftermarket only. Probably only the pricier companies- Ohlins, Wilbers, etc- that offer shorter shocks.
    Ride Safe, Ride Lots

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    Quote Originally Posted by chippena.f View Post
    I would appreciate your thoughts and ideas on the lowering an RS. It has a corbin 30 seat and is otherwise OEM. Two inches lower would be great. I am 5'9'' and pretty much on my toes at the stop. I'm new to MOA...just joined at the ralley in Salem. Jim
    Welcome! I have a '77 rs with the stock seat and a 30" inseam. I can get down to the balls of my feet. I think the narrower seat might help a little. I have a friend who has a Harley Electra Glide with a 28" seat height, but because the seat is so wide, I'm still on my toes. I have considered sending the stock seat out and having some of the foam removed, but I'm concerned about comfort on long rides. I've owned the bike since '82. I just lean it to one side when I stop. Let us know if you come up with a comfortable/safe fix.

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    Shorty pants

    I am 5'6" on a good day with a whopping 28 inseam. Therefore the R100 was like being perched on a unicycle. The lowering I got was about 3 inches with the following: A billet top triple clamp from ebay (or an inverted lower triple clamp from an airhead). Grind off the stop lip so that the fork tube will slide up and through about an inch. The stock stamped metal upper triple has no clamping feature so if you just grind it out the tube will pass through but won't be held in place there. With The metric tire on the front that brings the whole front end down a good inch and half when you're sitting on it. R65 shocks on the rear end. I found some Konis that worked fine. Progressive sells a shock that will fit and I think it should be 13" from eye to eye. Again, the metric tire on the back. and you gain a little over an inch there. Cut as much foam out of the stock seat at the front as you can. I put in the gel pad from a bicycle seat and restored some of the comfort without a lot of added height. Cutting away the foam seems to narrow it as well which helps with the step-over distance.
    I can actually flat foot it if I let the bike lean a little when stopped.
    A drawbacks,- the stock center stand will be almost impossible to use.

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    Quote Originally Posted by FELAW View Post
    I am 5'6" on a good day with a whopping 28 inseam. Therefore the R100 was like being perched on a unicycle. The lowering I got was about 3 inches with the following: A billet top triple clamp from ebay (or an inverted lower triple clamp from an airhead). Grind off the stop lip so that the fork tube will slide up and through about an inch. The stock stamped metal upper triple has no clamping feature so if you just grind it out the tube will pass through but won't be held in place there. .
    No need to grind billet upper triple. I just boughht another one from CC Products (or San Jose BMW?) on fleabay, and their ad said they were also offering a version where the fork tubes slide thru; the holes are fully bored

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    Depending on how the handlebars are mounted, they may limit the amount you can slide the tubes.

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    Lowering

    Mike Simon is correct, but I used a set of bar backs (suburban machinery, I think- anyway the billet sort of triangle shaped ones) and it gives some clearance. Without measuring I would think my tubes, caps and all stick up an inch and the handlebars just clear. I'm told that my bars are K(or is it R?) 75 bars that have rise to them and are a little taller than the standard RS bars.

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    jimmy armour
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    lowering rs

    Hi ,check the fork springs they may have spacers on top i have progresives in my bike, and due to age ,knees etc removed the spacers completely, a little bit better,also move the right shock forward to the top front holes and drill out the blank left side, hope this helps,Jimmy

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    I really want to discourage you from doing this.

    First, at 5'9" you are not exactly short. Being on your toes isn't that unusual; some riders only manage one toe. You will get used to it but I will admit that your bike is not the easiest one to get used to that way. How much prior riding experience do you have?

    Second, two inches is a LOT to take out of a working suspension, and you will severely compromise the ride. The spring rate will be higher, meaning that the ride is bouncier and less compliant. You will lose cornering clearance in a major way.

    if you really have to lower it, think more along the lines of 3/4 inch. Slide a piece of 3/4" plywood between the wheels and straddle your bike with your feet on the plywood. I think you'll feel much more comfortable.

    I think you will want to undo the lowering pretty soon, so don't waste too much effort on it.

    EDIT: and you should try a different seat before you touch the suspension.
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