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I have a spare front rotor I'd like to try out on my rear wheel. Does anyone know if it will fit? I have an 88 GL1500.
 

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They are different numbers in the Honda parts fiche and EBC brake parts. Did you measure them and line them up Jack?
 

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Not yet Stu. I'm about to remove the rear wheel now. The diameters are about the same at just over 11 5/8 inches. I haven't checked the hole positions yet to see if they line up. But if the holes match, anyone see a problem with mounting it on the rear wheel?
 

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Check thicknesses along with diameter and bolt holes bro.
 

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Okay, I checked the holes and they do line up. Good point on thickness Stu. The front has a minimum thickness of 5 mm but the rear has a min thickness of 6 mm. The rotor I wanted to use came in at just under 6 mm (5.91 mm). Bummer.
 

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The rear pads are the thickest FA69(3)so you can't use it. Are you needing a rotor?
 

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Yea I do. I bought a used rear rotor on ebay but the diameter of that rotor is too big for my 88. Still, using the 5.91 mm front rotor with new rear brake pads might work while I wait on a new one to arrive. Hmmm.
 

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Jack - the rear rotor for '88 and '89 was 296mm diameter, in 90-up they went to a 316mm diameter. SOunds like you've got the 90-up rotor there with ya.

Just a thought, you can change the rear caliper mounting bracket and run the 90-up rotor on your bike for a little increased rear braking, and it may save you a few bucks too as the caliper bracket is typically less expensive than the 88-89 rear rotor...
 

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satan wrote:
Jack - the rear rotor for '88 and '89 was 296mm diameter, in 90-up they went to a 316mm diameter. SOunds like you've got the 90-up rotor there with ya.

Just a thought, you can change the rear caliper mounting bracket and run the 90-up rotor on your bike for a little increased rear braking, and it may save you a few bucks too as the caliper bracket is typically less expensive than the 88-89 rear rotor...
Good call.
Jack
I know a local guy here that might have 1 if you don't have a local supply
 

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A later year bracket might be the way to go. I just checked the rear rotor I bought on ebay. The guy advertised it as an 89 rotor from a running 89 GL1500. The po of that bike must have changed out his stock rotor for a later model as this one is clearly bigger than my 88 stock rotor.

Satan...does a larger rotor equate to better braking power? Wouldn't the pad surface area on the rotor be the same with the smaller rotor? Maybe the combination of the increased height of the bracket and the bigger rotor provided better stopping power. Don't know.

Stu, I'll send you a pm if the new bracket doesn't work out. Thanks for the help guys.
 

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JackfromCT wrote:
...does a larger rotor equate to better braking power? Wouldn't the pad surface area on the rotor be the same with the smaller rotor? Maybe the combination of the increased height of the bracket and the bigger rotor provided better stopping power. Don't know...
> Yes, larger roter = larger braking power.

Think of it this way... A Longer Wrench = More Torque (on a bolt)

The analogy being, the brake pads upon the rotor are the "Wrench"... and the distance from the pads to the axle is the "Handle". So then, as the rotor diameter get's larger, the Torque (eg Braking) provided by the pads Increases.
 

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Alex
I wish I could articulate words that well
 

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Like Alex posted... the "radius" = length of wrench ...

The pressures and pads are the same, bigger diameter will get you a little more radius and a touch more stopping for the same amount of heat (~7% more).

There may be some advantages for better air cooling (outer edge is moving faster for same gound speed, but the radiant loss to the wheel is reduced from the longer travel length...) -- I'm thining it's all pretty much a wash for the heating.

I changed rotor material when I did the swap on mine, so I can't offer an objective/subjective apples-to-apples braking change. I can say that the price to change was less than the price of OEM replacement.
 

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satan wrote:
I changed rotor material when I did the swap on mine, so I can't offer an objective/subjective apples-to-apples braking change. I can say that the price to change was less than the price of OEM replacement.
Ok, so what did you change to?????? Inquiring mind(s) want to know.....
 

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Discussion Starter #15
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Got the correct bracket from a 1990 model today. Fits perfectly just like you guys said it would. It was a lot cheaper than getting a new rotor. Thanks.
 

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sweet... I love it when a plan (or HACK) comes together... let us know what you think of the braking (or if you can even tell the difference) now that you're running the larger diameter rotor on the older bike...
 

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Rear braking has improved with the bigger rotor. Not a huge difference, but definitely better. I put in new pads at the same time. One of those items is responsible for the improvement. I'm leaning toward the rotor since the old pads were still in great shape.

I'm just happy the old girl is complete again with absolutely no mechanical issues. Thanks for helping me get her back into fighting shape.
 
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