Shaft drive model speedometer info

[Guest]

I installed a 140 MPH speedometer on my 1981 1000G (specifically a GX) to replace the factory 85 MPH unit. My front tire is a 100/90-19, so it is approximately correct for the stock 3.50-19 as far as I can tell (a metric replacement occasionally mentioned is a 90/90-19, which crosses over to a 2.75/3.00-19). If the speedometer is 100% accurate with a factory tire, a larger (taller) tire slows the speedometer, making it read slower than you are going. A shorter tire works in reverse- it makes the speedometer read fast. I have not worked out the math for the several tire sizes, and diameters vary from make to make.

My speedometer is 5 MPH fast at 70 MPH according to my GPS.

This prompted me to look at the various speedometers and drive gears from the various parts books that I found on BassCliff's site in a huge zip file. Not all models are listed there. Some model years (GG) are suppositions on my part. Here is a breakdown:

Model / Speedometer (34110-xxxxx) / Drive gear (54600-xxxxx)
GS650GT= 1980, GX=1981, GZ= 1982
650GT & GX: 47330 / 18401
650GZ: 34580 / 18401

GS850GT=1980, GX=1981, GZ=1982, GD=1983, GE=1984, GF=1985, GG=1986?
850 (generic): 45130 / 18401
850GE & GF & GG: 49430 / 18401
850GT & GX: 45132 / 18401
850GLT: 45330 / 49100 (oddball)
850GZ & GD: 49430 / 18401

1000GT= 1980, GX=1981
1000 GT & GX: 45132 / 18401 (2008 manual I found showed 18402 replacing 18401)

1100GZ=1982, GE=1984
1100GE & GZ: 49430 / 18401


Summary:
The speedometers break down as follows when translated to year & model:
34580: 1982 650G
45130: 850 (generic)
45132: 1980-81 850 & 1000G (known to be 85 MPH unit)
45330: 1980 850GL (suspect 85 MPH unit)
47330: 1980 & 81 650G (suspect 85 MPH unit)
49430: 1983-86 850 & 1100G; 1982 1100G (suspect 140 MPH unit)

As an observation, I think the "3" as the next to last digit might mean MPH & kilo scale.


The drive gear 18401 was universal for everything except the 1980 GLT, which used a 49100. I suspect the other "L" models may have used this same drive gear, but there are no other parts manuals I have found. This answers the question about changing your drive gear when you put a 140 MPH speedometer on- you don't have to change the gear. From what I've read here, a 5 MPH fast error at 70 is not bad at all, so my experience bears this out.

My speedometer came in a Suzuki parts box with a parts label of 45132 and it had 7/10 of a mile on the dial. Someone had handwritten 45150 below it. It bolted right in & was obviously made for the bike. My 85 MPH speedometer did not have any numbers on it that related to the above. I did a Google search on 34110-45150 and ended up here. When I put it in the part number box, it crossed over to 45132, an obsolete part.

If you have one of these models and can post here as to the OEM MPH (no kilometer units please, as they are a different part #) of the speedometer, I'll update the list.

Thanks & hope this helps.

[GS1000G Shopper]

Wheel & tire data-
It looks like most of the 650/850/1000 models used a 1.85" wide 19" diameter wheel according to the parts books. Most listed a 3.25 tire, but the 1000 listed a 3.50. The 1100 models as well as the later 850 models listed a 2.15" wheel and a 3.50 tire.

The GL listed the 1.85 wheel and 3.50 tire.

Looking at some specs I found for the Dunlop D404 front tire, it comes in 100/90 and 110/90 sizes.

The 100/90 diameter is 25.82" and recommended rim width is 2.15.
The 110/90 diameter is 26.56" and rim width is 2.50.

I found data for the Maxxis 6011 front tire:
90/90: 25.7", 2.15 rim width
100/90: 26.4", 2.50 rim width
110/90: 26.8, 2.50 rim width

Bridgestone Spitfire S11F front (this is what is on there now):
90/90: 25.5 rim width 1.85~2.5
100/90: 26.2 width 2.15~2.75
110/90: 27.0 width 2.15~3.00

According to all of this, my 1.85 rim is undersized for the 100/90 tire now on it.

EDIT
I went back to the books and looked at the various bearings, spacers, dust seals, etc. for the 1100GE and my 1000GT. Looks like the only different parts needed to swap the wider wheel in are as follows:
Spacer on disk side, 54741-49300 (1000 used 49000), about $11
09159-12011 12mm nut (1000 used 12004), about $2

Looks like a good time to replace the bearings "while I'm at it."

I measured my existing wheel bead to bead with a caliper and got about 2.6".

I'm going to either find a place that calculates bike tire diameter to speedometers or figure out the formula, so I can see about what a difference the 110/90 would make.

EDIT 2
Found a tire calc here that will allow narrow (100) tires, but not 90 aspect ratios- max is 85. Adjusting the width 5mm and using a 105/85-19 and a 115/85-19 (26.03 diameter to 26.7 for a difference of .67"), I get a speedometer difference of only 1.67 MPH at 65 MPH. The actual difference would be less, since the Maxxis data above is 26.4 to 26.8, a difference of .4".

I also played around using impossible sizes to get as close to the exact Spitfire numbers above, 26.2 and 27.0. I got 26.16 and 27.03. The speedometer error at 65 MPH was 2.16 MPH. It would be slightly higher at 70, about 2.3 MPH or almost half the error I'm seeing. According to the tire calc, I'd have to run an almost 28" tall tire to correct the speedometer error.

Conclusion-
It is not cost effective to try & correct the speedometer error with a wider wheel and taller tire. Probably wouldn't hurt to have the correct width wheel for the tire that's on the bike though.

[posplayr]

Wheel & tire data-
It looks like most of the 650/850/1000 models used a 1.85" wide 19" diameter wheel according to the parts books. Most listed a 3.25 tire, but the 1000 listed a 3.50. The 1100 models as well as the later 850 models listed a 2.15" wheel and a 3.50 tire.

The GL listed the 1.85 wheel and 3.50 tire.

Looking at some specs I found for the Dunlop D404 front tire, it comes in 100/90 and 110/90 sizes.

The 100/90 diameter is 25.82" and recommended rim width is 2.15.
The 110/90 diameter is 26.56" and rim width is 2.50.

I found data for the Maxxis 6011 front tire:
90/90: 25.7", 2.15 rim width
100/90: 26.4", 2.50 rim width
110/90: 26.8, 2.50 rim width

Bridgestone Spitfire S11F front (this is what is on there now):
90/90: 25.5 rim width 1.85~2.5
100/90: 26.2 width 2.15~2.75
110/90: 27.0 width 2.15~3.00

According to all of this, my 1.85 rim is undersized for the 100/90 tire now on it.

EDIT
I went back to the books and looked at the various bearings, spacers, dust seals, etc. for the 1100GE and my 1000GT. Looks like the only different parts needed to swap the wider wheel in are as follows:
Spacer on disk side, 54741-49300 (1000 used 49000), about $11
09159-12011 12mm nut (1000 used 12004), about $2

Looks like a good time to replace the bearings "while I'm at it."

I measured my existing wheel bead to bead with a caliper and got about 2.6".

I'm going to either find a place that calculates bike tire diameter to speedometers or figure out the formula, so I can see about what a difference the 110/90 would make.

EDIT 2
Found a tire calc here that will allow narrow (100) tires, but not 90 aspect ratios- max is 85. Adjusting the width 5mm and using a 105/85-19 and a 115/85-19 (26.03 diameter to 26.7 for a difference of .67"), I get a speedometer difference of only 1.67 MPH at 65 MPH. The actual difference would be less, since the Maxxis data above is 26.4 to 26.8, a difference of .4".

I also played around using impossible sizes to get as close to the exact Spitfire numbers above, 26.2 and 27.0. I got 26.16 and 27.03. The speedometer error at 65 MPH was 2.16 MPH. It would be slightly higher at 70, about 2.3 MPH or almost half the error I'm seeing. According to the tire calc, I'd have to run an almost 28" tall tire to correct the speedometer error.

Conclusion-
It is not cost effective to try & correct the speedometer error with a wider wheel and taller tire. Probably wouldn't hurt to have the correct width wheel for the tire that's on the bike though.

Linky giving me an error

[GS1000G Shopper]

You can't put in 90 as the aspect ratio. I used the maximum of 85, and then changed the first number to get the diameter I wanted, i.e. 107/85-19 gives you 26.16 diameter.

If you know the brand & size of the tire you have and the one you are considering, you can look up the specs like I did and then plug in the diameters via the above process to see the difference.