New Speedo Drive Bad

[Red]

On a trip this weekend my speedo drive failed. Worked fine when I stopped the bike at a store and did not work when I resumed travel. Called the nearest shop at Sierra BMW Reno. A three hour detour and they got me right in to check the problem. They found the fault in minutes and ordered a new drive. By 11 AM the next day I'm on my way. That's the happy story.

I'm going 10 over on the freeway back on my way to the Quincy, CA rally and everyone, even camp trailers going uphill, are passing me. My cornering ability on the mountain roads all of a sudden really got better! Well after about 4 hours of just feeling odd on my bike, I pulled over at a highway milepost marker and set my trip meter to zero. I went 80 miles according to the markers. My odometer showed 93 (exactly) miles. That is a 16.25 % difference. So, when I thought I was doing 75 on the freeway, I was actually doing just a wee bit under the 65 limit. I don't have a gps or I'd have done a test on that function as well. I am going to assume that the data for speed should be directly proportional to the distance error. I understand that BMW speedometers are set to read 3 to 5% high. 16+% is not within acceptable standards IMHO.

The part number on the invoice shows a Speedo Drive 2.6 part number 62122306078. I checked this against the online parts schematic at the A&S BMW (Auburn,CA) web site and it matches what ought to be in an 1100RT. So, what is wrong here?

I am now home and 400 miles from Sierra BMW. Theories on what the actual problem is and recommendations on how to proceed are very welcome.

Nearest bmw shop to my home is Big Twin in Boise, ID 185 miles. Changing O & F or removing tupperware to get at the battery is about the limit to my mechanical repertoire.

[dirtrider]

Afternoon Red

 

Did they put JUST the drive gear in? It's possible the incorrect drive gear was installed but was on the shelf or in the bin marked 62122306078.

 

You either have the wrong gear for your wheel design, or wrong gear for your tire size, or the drive gear isn't the correct drive gear for your driven gear, or your spedo head is not working correctly.

 

You can't always say that the error is the same for the odo & speedo as one is a direct drive & the other (spedo) is a magnetic drive.

 

Any chance they still have the old gear to compare to your new drive gear?

 

[Red]

Dirtrider,

I'm sure the old part went into the trash/metal recycle bin when removed.

Repairs were last friday. Comparing the old part to the new part would be problematic as I am now 400 miles from the shop.

I too had the thought that they ordered the right part but got a different part and installed the new part w/o checking it was the correct one. Would be easy to do.

Different tire size occurred to me as well. I checked the specs for the 1150's thinking their front wheel got bigger and maybe that was it.

No joy,looking at old specs for 1150's, the 1150's also have a 17" front. I haven't checked a parts schematic for 1150's. Now way for me to know if the speedo gearing is different.

Could it be that the part is simply defective somehow? It does read consistently and smoothly. It's just not correct.

Would other speedo units for other models/years install and operate in my bike?

[dirtrider]

Afternoon Red

 

You wouldn think that a defective part just wouldn't allow the speedometer to work.

 

The 1150 uses 62127650348 drive gear (same 2.6:1 ratio just different part)

 

Would other speedo units for other models/years install and operate in my bike?

Possibly but without trying it for the fit & function then no way to know.

 

You might see if you can find a used 1100RT drive unit (the whole shebang) on E-Bay. Maybe at one time someone put a RT-P drive/driven unit in your bike.

 

 

[Red]

New data.

Borrowed the neighbors hand held gps and the spousal unit took notes.

Speed Indicated GPS

35 28.8

45 37.6

55 46.3

65 54.6

75 64.3

85 71.2

95 79.6

105 87.4

115 97.2

[Red]

Took my bike to local dealer this week. They put in a new speed/odo drive unit down at the axle under warranty. Reads much better. They explained that there are actually 3 different drive ratios available for the 11xx rt. Only one part # shows on the A&S schematic. BUT, if you are a dealer and have BMW parts software, 3 options (gear ratios) pop up for that one part #. You have to pick the right one AND you need to inspect the part prior to installation as the drive ratio is stamped into the part.

Mystery solved. I have to say both dealerships, Sierra BMW and Big Twin BMW were very good to deal with on this. Now my speedo/odo is only off by 5 mph or so. At 65 mph by gps indicated on speedo is 70 plus or minus 1.