86 K100RS compared to 85 K100RT

[schrocketeer]

Please tell me differences I would notice between a 1986 K100RS, and a 1985 K100RT.
There's a high probability that I will have an unmolested K100RS join my fleet this weekend. Candidate RS photos attached.
Previously I had a 1985 K100RT (FYK) that I put 25k miles on, so I feel comfortable to receive responses relative to the RT.
My riding is typically a 40 mile, one way commute that is mostly back roads with a mix of interstate thrown in. Once I took the RT on a 700 mile, one way trip.

[You can berate me later for ever selling the RT, to trade for a GS1100. Does buying another RT and probably this RS pay penance? ;-)]

[Laitch]

Previously I had a 1985 K100RT (FYK) that I put 25k miles on,

Is that the one the you described in your latest posts that you haven't been able to get running very well?

[Laitch]

I wouldn't touch an '85 Brick in that condition with a telescopic pole that reached halfway around the world, unless I had nothing better to do with my days; even then, I would probably just sleep more.
 

[frankenduck]

I wouldn't touch an '85 Brick in that condition with a telescopic pole that reached halfway around the world, unless I had nothing better to do with my days; even then, I would probably just sleep more.
 

The on in the pictures is the 86. You can tell from the peg plates and seat.

[Laitch]

The on in the pictures is the 86. You can tell from the peg plates and seat.

Same pole, same outcome. 

[frankenduck]

Same pole, same outcome. 

I've brought bikes worse than that back to life. Two of them were bikes that sat under a tarp in the rain for YEARS in Seattle.

That one's just a little dusty.

[Laitch]

I've brought bikes worse than that back to life. Two of them were bikes that sat under a tarp in the rain for YEARS in Seattle.

That one's just a little dusty.

You have years of failure experience with multiple Brick's—failure from which you've learned some important lessons. That doesn't seem to be the case here but perhaps it will develop in that direction.

[schrocketeer]

My 1985 red, RT had been in a shed for 3+ years, that had gas with ethanol still sitting in the tank (what a funk). That's the one I put 25k miles on after I got it going. Bought some parts for it from Frankenduck.
Black customized RT (also an 1985) had a Previous Owner splice in to the harness, to feed the electric motor driven (not exhaust gas) "turbo" (maybe 2psi of boost?). Starting to think there were some other electrical "modifications" I haven't uncovered yet.
The dusty RS was running in November. Seller's brother owned the RS. Brother passed on. Now seller can't find where brother had put the key. Thinking I can pull the ignition switch and key from "turbo" and move it to the '86 RS, and have it hopefully running in a couple of hours (call me Mr. Optimist).

[schrocketeer]

[not sure why the right side turbo installed photo turned 90 deg in the previous post?]

[Laitch]

[not sure why the right side turbo installed photo turned 90 deg in the previous post?]

It's fixed now.

[schrocketeer]

RS vs RT ride difference is mainly final gearing, correct?
No differences of drivetrain substance, really?
Understand the aesthetic differences.

[schrocketeer]

Here's ChatGPT's answer:
Please include the final gear ratio, ostensibly in the rear differential, and provide data on 0-60 mph times, and also 40-60 mph roll on times, between the RT and RS.
ChatGPT
Final Gear Ratio
K100 RT:

Final Drive Ratio: 2.91:1
K100 RS:

Final Drive Ratio: 2.81:1
Performance Data
K100 RT:

0-60 mph Time: Approximately 4.7 seconds
40-60 mph Roll-on Time (5th gear): Around 4.3 seconds
K100 RS:

0-60 mph Time: Approximately 4.3 seconds
40-60 mph Roll-on Time (5th gear): Around 4.0 seconds
Summary
Final Gear Ratio: The K100 RT has a slightly higher final drive ratio (2.91:1) compared to the K100 RS (2.81:1). This means the RT has a marginally lower top speed but better torque at lower speeds, which is more suitable for touring. The RS, with its lower final drive ratio, is geared for better top speed and sportier performance.

0-60 mph Time: The K100 RS accelerates faster, with a 0-60 mph time of about 4.3 seconds compared to the RT's 4.7 seconds. This difference reflects the RS's sportier tuning and lighter weight.

40-60 mph Roll-on Time: In a 40-60 mph roll-on test in 5th gear, the RS is again quicker, taking around 4.0 seconds versus the RT's 4.3 seconds. The RS's gearing and engine tuning provide better mid-range performance for overtaking and spirited riding.

These figures highlight the RS's advantage in performance due to its sportier tuning and lighter weight, making it quicker in both acceleration and roll-on times compared to the more touring-oriented RT.

[schrocketeer]

Please tell me the differences between a 1985 BMW K100 RT, and a 1986 BMW K100 RS. I have put 25,000 mile on a 1985 K100 RT, so please describe RS differences relative to the RT. Detailed technical explanations are preferred.
ChatGPT
Memory updated
The 1985 BMW K100 RT (Reise-Tourer) and the 1986 BMW K100 RS (Rennsport) are both members of BMW's K100 series but are designed with different purposes and feature distinct characteristics. Here are the detailed technical differences between the two models:

1. Bodywork and Aerodynamics
K100 RT: The RT is designed as a touring motorcycle. It features a large, full fairing that provides extensive wind and weather protection for long-distance riding. The fairing includes an adjustable windshield, providing comfort and reducing rider fatigue.
K100 RS: The RS is a sport-touring model with a sportier design. It has a smaller, more aerodynamic fairing compared to the RT, focused on reducing drag and improving high-speed stability. The fairing is less extensive, offering less wind protection but enhancing the sporty aesthetics and aerodynamics.
2. Ergonomics and Riding Position
K100 RT: The RT has a more upright and comfortable riding position, suitable for long-distance touring. The handlebars are higher and closer to the rider, and the seat is designed for comfort over long rides.
K100 RS: The RS features a sportier, more forward-leaning riding position. The handlebars are lower and more forward, and the footpegs are positioned slightly higher and rearward, contributing to a more aggressive riding stance.
3. Weight and Handling
K100 RT: The RT is heavier due to its touring-oriented features, including the larger fairing, integrated luggage system, and additional comfort-focused components. The increased weight can affect handling, making it feel less agile compared to the RS.
K100 RS: The RS is lighter and more nimble, benefiting from its sport-oriented design. The reduced weight improves handling and maneuverability, making it more responsive in corners and at higher speeds.
4. Suspension and Brakes
K100 RT: The RT typically features a more comfort-oriented suspension setup, with softer springs and damping to absorb road imperfections and provide a smooth ride over long distances.
K100 RS: The RS has a firmer suspension setup to enhance handling and stability at higher speeds and during aggressive riding. It is designed to provide better feedback and control during spirited riding.
5. Performance and Engine Tuning
K100 RT and RS: Both models are powered by the same 987 cc, liquid-cooled, inline-four engine, but the tuning might differ slightly to suit their intended purposes. The RS may have minor tweaks for a more responsive throttle and sportier performance characteristics.
6. Instrumentation and Features
K100 RT: The RT comes with a more extensive set of touring-oriented features, including a more comprehensive dashboard with additional gauges and indicators, a larger fuel tank, and more storage options.
K100 RS: The RS features a simpler, more focused instrument cluster, emphasizing essential information. It prioritizes a sleek design and weight savings over additional touring features.
7. Windshield and Fairing
K100 RT: The RT has a taller, adjustable windshield that provides maximum wind protection for long rides.
K100 RS: The RS has a lower, fixed windshield designed for aerodynamic efficiency at higher speeds, sacrificing some wind protection for improved performance.
Summary
In summary, the 1985 BMW K100 RT is optimized for long-distance touring with its extensive fairing, upright ergonomics, and comfort-focused features. In contrast, the 1986 BMW K100 RS is designed for sportier performance and handling, featuring a more aerodynamic fairing, sport-oriented riding position, and firmer suspension. Each model caters to different riding styles and preferences, with the RT prioritizing comfort and the RS emphasizing agility and speed.

Please add more specifics on weight and suspension spring rates, between the RT and RS.
ChatGPT
Sure, here are more specifics on the weight and suspension spring rates for the 1985 BMW K100 RT and the 1986 BMW K100 RS:

Weight
K100 RT:

Dry Weight: Approximately 577 lbs (262 kg)
Wet Weight: Around 635 lbs (288 kg), including all fluids and a full tank of fuel
K100 RS:

Dry Weight: Approximately 535 lbs (243 kg)
Wet Weight: Around 590 lbs (268 kg), including all fluids and a full tank of fuel
Suspension Spring Rates
K100 RT:

Front Suspension: The front fork on the RT is designed for comfort with a softer spring rate, typically around 0.65 kg/mm. This softer setup is intended to absorb road imperfections better, providing a smoother ride over long distances.
Rear Suspension: The rear suspension also features a softer spring rate, generally around 100-110 N/mm, ensuring a plush ride that enhances comfort for touring.
K100 RS:

Front Suspension: The front fork on the RS is tuned for sportier performance with a firmer spring rate, typically around 0.75 kg/mm. This stiffer setup improves handling and stability during aggressive riding and high-speed maneuvers.
Rear Suspension: The rear suspension has a firmer spring rate, usually around 120-130 N/mm, which provides better feedback and control during spirited riding.
Summary
K100 RT: Heavier with a focus on comfort, the RT features a softer suspension setup with lower spring rates to ensure a smooth ride for long-distance touring.
K100 RS: Lighter and designed for sporty performance, the RS has a firmer suspension with higher spring rates to enhance handling, stability, and rider feedback during dynamic riding conditions.
These differences in weight and suspension setup contribute to the distinct riding experiences offered by the RT and RS models, catering to their respective touring and sport-touring roles.

[The Mighty Gryphon]

Having owned and put extensive miles on both models here are my thoughts:

The RT fairing is dryer and a little warmer in cold weather and a lot warmer in warm weather.  It also gets more damage when you go down(the part that goes down near your foot).

The RT is a bit easier on your back on long riding days.  I could go 24 hours on my RT, but the RS can get tiring after 6-8 hours. 

The suspension on my RT had an annoying brake/throttle dive that the RS didn't have as bad.  Never noticed any big difference in ride comfort on the highway. 

The only difference in storage is the RT has those little glove boxes in the fairing.  Saddle Bags, 22 liter top case and tank bags are the same between both models. 

The RT fairing is more top heavy and combined with the front end dive is a lot scarier to handle at low speeds. 

As far as the seat, if you want to rack up lots of miles, it's easy to swap the stock bench seat on the RS for a comfort seat.  There is one in my avatar photo.  You can also swap the RS bars for the C model bars that allow a slightly more upright riding position.  They're rare, but are out there if you are patient.

Performance?  Neither model is a rocket ship, and 4/10ths of a second in 0-60 time is pretty unimportant in the sum of the Brick experience.  Both will easily go fast enough to scare a sane person in the right situation. 

[schrocketeer]

[dusty black RS went to another rider]
Thanks for the inputs.