Cushman Speedometer Information Page

There have been many requests for information on the Cushman speedometer and the use of after market motorcycle speedometers. The following information is provided to assist you in choosing the speedometer that is right for you and selecting the proper gearing for it.

There were two different primary gears used on the wheel hub over the years. The first is a 12 tooth which is used on all 1950-1954 Eagles, 1959-up Eagles, and 1958-up Highlanders that use the larger hubs. The second is a 10 tooth which is used on 1955 to 1958 Eagles, 1957 and 1958 Road King and Pacemaker, and all 1958-up Highlanders using the small hubs. The secondary gears currently available are 12, 14 and 15 tooth. The 14 tooth secondary is standard for the 12 tooth primary and the 12 tooth is standard for the 10 tooth primary. The 15 tooth secondary gear is believed to have been used on some Trucksters.

Increasing or decreasing the number of secondary gear teeth by one will change the speedometer reading by about 7 percent using the 12 tooth hub or about 9 percent using the 10 tooth hub. Increasing the number of teeth will lower the indicated speed, decreasing the number of teeth will increase the indicated speed. As an example, the chart below shows that on a bike using 58 inch circumference tires, a 12 tooth primary gear and a 14 tooth secondary gear, the speedometer reads low by over 6 percent. If a 13 tooth secondary gear were available it would reduce the error to less than one percent. Perhaps with the number of larger wheels in use today someone can tool up and make us some secondary gears to match.

A word about accuracy. Most Cushman speedometers are notoriously inaccurate, usually reading too high. Notice on the chart below that even if the speedometer head was perfect it would indicate 2 MPH too high at 60. I am only using 60 as a reference here as there is no standard Cushman that will go 60. On the last restoration I did the original Cushman speedometer indicated about 7 MPH too fast. The substitution of a 15 tooth secondary gear for the original 14 tooth made it read very close. Show me someone that boasts that his standard Cushman will run way over 50 MPH and I will show you someone that does not have a clue about speedometers.

The chart below shows the best matches currently available with the gear choices we have. Stock Cushman tires measure around 52.5 inches in circumference. To measure the circumference of your tire use a square and chalk a vertical line on the tire and extend it down to the floor. Roll the bike until the chalk mark is at the bottom again and make a second mark on the floor and measure between the marks..

1 Tire Rotation in Inches	Tire Rotation Per Mile	Wheel Gear Teeth	Cable Gear Teeth	Gear Ratio	Speedo Shaft RPM	Speedo Indicated Speed	Percent Error
52.5	1206.86	12	14	.857	1034.45	62.07	3.44
52.5	1206.86	12	15	.800	965.49	57.93	-3.45
53.0	1195.47	12	14	.857	1024.69	61.48	2.47
53.5	1184.30	12	14	.857	1015.11	60.91	1.51
54	1173.33	12	14	.857	1005.71	60.34	.57
55	1152.00	12	14	.857	987.43	59.25	-1.26
56	1131.43	12	14	.857	969.80	58.19	-3.02
57	1111.58	12	14	.857	952.78	57.17	-4.74
58	1092.41	12	14	.857	936.35	56.18	-6.36
59	1073.90	12	12	1.00	1073.90	64.43	7.39
60	1056.00	12	12	1.00	1056.00	63.36	5.6
61	1038.69	12	12	1.00	1038.69	62.32	3.87
62	1021.94	12	12	1.00	1021.94	61.32	2.19

1 Tire Rotation in Inches	Tire Rotation per Mile	Wheel Gear Teeth	Cable Gear Teeth	Gear Ratio	Speedo Shaft RPM	Speedo Indicated Speed	Percent Error
52.5	1206.86	10	12	.833	1005.71	60.34	0.57
53	1195.47.	10	12	.833	996.23	59.77	-0.38
53.5	1184.30	10	12	.833	986.92	59.21	-1.31
54	1173.33	10	12	.833	977.78	58.67	-2.22
55	1152.00	10	12	.833	960.00	57.60	-4.00
56	1131.43	10	12	.833	942.86	56.57	-5.71
57	1111.58	10	12	.833	926.32	55.58	-7.37
58	1092.41	10	12	.833	910.34	54.62	-8.97
59	1073.90	10	12	.833	894.92	53.69	-10.51
60	1056.00	10	12	.833	880.00	52.80	-12.00
61	1038.69	10	12	.833	865.57	51.93	-13.44
62	1021.94	10	12	.833	851.61	51.10	-14.84

Several manufacturers make speedometers for motorcycles that will work fine on a Cushman. My choice is the miniature speedometer sold by Chrome Specialties as their part number 310411 for about $50.00. It is a 1:1 unit which means that it indicates 60 MPH when the cable rotates at 1000 RPM. It is very accurate, even at the lower speeds. It is designed to fit in a 2.390 inch hole which is smaller than the 2.690 hole in the Cushman dash plate. The choices are to fill and re-drill the dash plate or use an adaptor ring. The adaptor is by far the best way to go. I mill them out of billet aluminum and polish them and they look nice. The silver colored Eagle in the Vanguard Center uses one. The speedometer has a socket for a 9MM cable. A screw-on adaptor is available which will allow the use of the standard Cushman cable 5/8 inch cable end with absolutely no modifications. To secure the speedometer in the dash plate you will have to either fabricate a simple "U" bracket or make two separate little brackets, fasten each one with one of the speedometer screw holes, and clamp the brackets to the speedometer with a gear type clamp. To order an aluminum adaptor ring click HERE

Pictured below is the Chrome Specialties speedometer. It has an adaptor ring installed on it. A loose adaptor ring is also pictured.

UPDATE 9/15/03

Chrome Specialties has merged with Custom Chrome and apparently the speedometer pictured above is no longer available. I suggest using the Drag Specialties part number DS-244130 which is an almost identical 140 mph speedometer. The 12 mm adaptor is Drag Specialties part number DS-243953. If you cannot find a local Drag Specialties dealer you may order one from Jim at Discount Motorcycle Parts in Lakeland, Florida. His telephone number is 863-667-1866. Jim does not stock this 1:1 unit, but he can get it for you in 3 to 5 days. You can also order a similar speedometer from J&P Cycles as their part number 27-800 (catalog) or 730-147 (web site) www.jpcycles.com. If you order one from J&P verify that the case will fit in the 2.290 inch inside diameter adaptor ring.