GL1500 tire v. speedometer


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jenagle
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Joined: Tue May 13, 2014 9:56 pm
Location: Adrian, MO
Motorcycle: 1981 Goldwing 1100
1989 Goldwing 1500

GL1500 tire v. speedometer

Postby jenagle » Tue Sep 16, 2014 9:31 am



My GL1100 is spot on the money where the speedometer is concerned, so I was very surprised when my new (to me) '89 GL1500 reads about 5% fast (i.e. it reads 74 mph when actually doing 70). Doing a little research, I found that the E3 bias tire on the bike is 25.15" in diameter (front where the speedo is driven). To get the proper speed I need to increase the diameter to 26.4" (25.15 x 1.05). This happens to be the exact diameter for the MR90-18 Dunlop E3. Since the tires on the bike are new, I'm going to wait until they need replacement, and then go to the MR90. Does anyone have pros or cons about the MR90 Dunlop?

P.S. I like the Dunlop tires that I have now, so I'm not considering changing brands. I also don't have any problems with going to radials v. bias ply tires, so long as I do both front and rear with the same type.

Thanks in advance.



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cbx4evr
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Re: GL1500 tire v. speedometer

Postby cbx4evr » Tue Sep 16, 2014 10:32 am

Speedo error is common with Goldwings and motorcycles in general.

My 1500 must be a freak as the speedo is near spot on with my GPS. I've run the bias E3's and now running Avon tires with the same result.
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

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WingAdmin
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Re: GL1500 tire v. speedometer

Postby WingAdmin » Tue Sep 16, 2014 10:38 am

My GL1500 (also with Avon tires) is very close to my GPS. It generally reads about 1-2 mph higher than my GPS, at highway speeds.

My GL1100 (again with Avon tires) always read exactly the same as my GPS, at all speeds.

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jenagle
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1989 Goldwing 1500

Re: GL1500 tire v. speedometer

Postby jenagle » Tue Sep 16, 2014 10:59 am

Thanks for the reply's. According to Avon, the AM42 is 26.1" diameter, which would bring it much closer than the E3 bias. I'd still like to know if anyone has had experience with the Dunlop MR90's.

Again, thanks.

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robb
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Re: GL1500 tire v. speedometer

Postby robb » Tue Sep 16, 2014 11:10 am

Just replaced the E3 on front of my 89, was as much as 3.6 mph off at highway speeds. New tire is a BT45 rear on front, not much better. Not a real problem until the cruise is set at 75 and GPS shows 71. I went with a taller tire on rear that lowered rpm by 400. Mow cruise will set and hold at 81 mph.

I tried swapping 4th and 5th gear wires but then cruise would not hold at 50 mph in 4th gear for rpm being too high. Last 400 mile trip was good for 49 mpg. I'm so happy that I sold my Vstar 1100.

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jenagle
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1989 Goldwing 1500

Re: GL1500 tire v. speedometer

Postby jenagle » Tue Sep 16, 2014 11:17 am

So with the speedometer difference, you're actually getting a little over 46 mpg. Still great.

Since the speedometer on a 1500 is driven by the front wheel, doing anything to the back tire won't make any changes to the speedo.

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robb
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Re: GL1500 tire v. speedometer

Postby robb » Tue Sep 16, 2014 7:53 pm

By the gps I got 49 mpg. By the bike it has been average of 44 mpg for years running stock tire sizes.

I never said the rear had anything to do with the speedo. I put on a taller rear tire that lowered the rpm by 400. But I did add a sensor to read drive shaft rotation, added a Electronic to Mechanical Speedometer Box that allows the speedo to be calibrated to the speed of GPS. No matter what size car tire chosen to run on rear, the speedo can be calibrated to match. Totally abandoned the front speedo gear.

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jenagle
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1989 Goldwing 1500

Re: GL1500 tire v. speedometer

Postby jenagle » Wed Sep 17, 2014 4:26 am

Sorry for my error. What kind of speedometer box did you use, and where did you get it. Would be interested to see how that works.

Thanks for the reply.
John

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robb
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Re: GL1500 tire v. speedometer

Postby robb » Wed Sep 17, 2014 8:41 am

This is simple to use with an input from rear. I'm reading the shaft but was told it is possible to read a point on the rotor. Swingarm was drilled and shaft was fit with a 1/4" magnet, this was the tough part.

http://www.highperformancepontiac.com/t ... converter/

This is what I tried first, but really needed about a 5% offset that it did not deliver. Was thinking of triking the 89 and using a rake kit that would allow the use of a 20" tires, front and rear. Speedo is ready, now to save enough money for trike.

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jenagle
Posts: 79
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Motorcycle: 1981 Goldwing 1100
1989 Goldwing 1500

Re: GL1500 tire v. speedometer

Postby jenagle » Wed Sep 17, 2014 8:57 am

How big is the motor box, and where did you mount it? Looks real slick.

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robb
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Re: GL1500 tire v. speedometer

Postby robb » Wed Sep 17, 2014 7:32 pm

Think it was 6 x 6 x 2 and it is tywraped between forks under fairing.

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jenagle
Posts: 79
Joined: Tue May 13, 2014 9:56 pm
Location: Adrian, MO
Motorcycle: 1981 Goldwing 1100
1989 Goldwing 1500

Re: GL1500 tire v. speedometer

Postby jenagle » Wed Sep 17, 2014 8:37 pm

Thanks for the info. I'll be checking it out as a project.
John




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