strange_intp
New member
Hi, longtime BMW owner (R1200C) but new to BMW MOA and the forums. Also a new owner of a '78 R100RS (though the fairings have been replaced to look like an 'S'). The speedo on it is busted. The previous owner said he'd actually fixed it once but it broke again soon thereafter and he gave up. He mounted a GPS unit, which conveyed with the bike. I'd rather get a working speedo put in.
OEM/OE speedos go for $250 on e-bay, and I'm not willing to spend that on old parts when I can likely get newer [aftermarket] parts for much less. I also would prefer to update the instrument panel to a more modern and slimmed down look anyways.
After doing a bit of research, I've become familiar with the caveats with putting non-original speedos in. Unfortunately, most manufacturers don't seem to give much guidance on working around those caveats, mostly seems to be set ratios. I think I am settling out with the Acewell digital multifunction speedo and tach from Dime City Cycles (DCC): https://www.dimecitycycles.com/black-acewell-reg-md-052-digital-multi-function-speedometer.html, especially since it provides both speedo and tach and most of the indicator lights (although turn signals work on the bike, the instrument panel indicators don't, so that's another thing I'd like to fix). So I think I can replace the entire dash with that one meter.
Their speedometer-only analog meters are set for 60mph @ 2240 rpm, which doesn't seem to work for this bike (I read elsewhere on the forum anecdotally that the R100 is about 70mph @ 4000 rpm. even allowing for some uncertainty, those ratios are just too far apart. It's also shown with a sticker on the back "M=2.1" which I assume is the ratio, whereas the R100s have either 3.0 or 2.91)
So, questions:
- I spoke to someone at DCC and they seemed pretty confident that I would be able to get the digital meter (but not the analog) working with the bike, via the programming functions. But I thought I'd ask around before dropping the $150 (or more). Does anyone have experience with converting over to this instrument? Have you had success?
- The digital multifunction meter comes with parts to install a magnetic sensor on the front wheel. Alternatively I can get the Acewell Digital Speedometer Conversion cable ($19) and hook it up between my existing mechanical speedo cable and the meter, and use the programming functions for calibration. For $19, that seems preferable to installing another sensor and having to get that calibrated correctly, though that calibration seems to be just a matter of programming the front wheel circumference into the meter. Suggestions or recommendations?
- I have *not* done research on tachometer replacement, so I don't know what the potential caveats are there. (Honestly, I'm not too concerned with having a working tach, I'm not going to race it; but if I can get one working "easily", I might as well.) Is that a straightforward conversion/hookup? Can I just rewire the input to the existing tach into the digital multifunction meter?
- Are you aware of other aftermarket solutions that work out-of-the-box (and that cost less than $150)?
On a sidenote, it seems like speedo conversion should not be so difficult! Maybe it's just the engineer in me, but even for analog meters, I'd think you could just reprint the gauge face with a different range to have it reflect speeds for different ratios. In other words, if speed is linear with (proportional to) some frequency input, why couldn't you just change the spacing between the dial marks to "calibrate" the dial for the right ratio? You might peg high, or the reproportioned gauge may reflect speeds you can never reach, but that's something I'd live with to get a working speedo that is somewhat accurate. It'd be an ugly hack-job if I did it myself, but seems like something the manufacturers could pick up on....
anyways, thanks in advance for any input!
OEM/OE speedos go for $250 on e-bay, and I'm not willing to spend that on old parts when I can likely get newer [aftermarket] parts for much less. I also would prefer to update the instrument panel to a more modern and slimmed down look anyways.
After doing a bit of research, I've become familiar with the caveats with putting non-original speedos in. Unfortunately, most manufacturers don't seem to give much guidance on working around those caveats, mostly seems to be set ratios. I think I am settling out with the Acewell digital multifunction speedo and tach from Dime City Cycles (DCC): https://www.dimecitycycles.com/black-acewell-reg-md-052-digital-multi-function-speedometer.html, especially since it provides both speedo and tach and most of the indicator lights (although turn signals work on the bike, the instrument panel indicators don't, so that's another thing I'd like to fix). So I think I can replace the entire dash with that one meter.
Their speedometer-only analog meters are set for 60mph @ 2240 rpm, which doesn't seem to work for this bike (I read elsewhere on the forum anecdotally that the R100 is about 70mph @ 4000 rpm. even allowing for some uncertainty, those ratios are just too far apart. It's also shown with a sticker on the back "M=2.1" which I assume is the ratio, whereas the R100s have either 3.0 or 2.91)
So, questions:
- I spoke to someone at DCC and they seemed pretty confident that I would be able to get the digital meter (but not the analog) working with the bike, via the programming functions. But I thought I'd ask around before dropping the $150 (or more). Does anyone have experience with converting over to this instrument? Have you had success?
- The digital multifunction meter comes with parts to install a magnetic sensor on the front wheel. Alternatively I can get the Acewell Digital Speedometer Conversion cable ($19) and hook it up between my existing mechanical speedo cable and the meter, and use the programming functions for calibration. For $19, that seems preferable to installing another sensor and having to get that calibrated correctly, though that calibration seems to be just a matter of programming the front wheel circumference into the meter. Suggestions or recommendations?
- I have *not* done research on tachometer replacement, so I don't know what the potential caveats are there. (Honestly, I'm not too concerned with having a working tach, I'm not going to race it; but if I can get one working "easily", I might as well.) Is that a straightforward conversion/hookup? Can I just rewire the input to the existing tach into the digital multifunction meter?
- Are you aware of other aftermarket solutions that work out-of-the-box (and that cost less than $150)?
On a sidenote, it seems like speedo conversion should not be so difficult! Maybe it's just the engineer in me, but even for analog meters, I'd think you could just reprint the gauge face with a different range to have it reflect speeds for different ratios. In other words, if speed is linear with (proportional to) some frequency input, why couldn't you just change the spacing between the dial marks to "calibrate" the dial for the right ratio? You might peg high, or the reproportioned gauge may reflect speeds you can never reach, but that's something I'd live with to get a working speedo that is somewhat accurate. It'd be an ugly hack-job if I did it myself, but seems like something the manufacturers could pick up on....
anyways, thanks in advance for any input!
