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Author Topic: Tire question...I'll probably get hammered!!!  (Read 711 times)

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Offline rtnoble

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Tire question...I'll probably get hammered!!!
« on: March 09, 2012, 01:15:45 PM »
Howdy,
Bought '80 CB650 new...still have it.  Original rear tire was 4.50H17-4PR.  I have a 4.50/85 H17 on it now.

Everyone seems to cross this to a 120/90-17. 

Question:  where did they get the 90% aspect ratio?  Does anyone out there know the actual height of the original tire so I can calculate the original ratio?  I can't find it anywhere.

Dunka!

Russell in B'ham 
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Russell in B'ham
1980 CB650 bought new
Unmolested, sans 650C pipes

Offline TwoTired

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Re: Tire question...I'll probably get hammered!!!
« Reply #1 on: March 09, 2012, 02:22:16 PM »
Inch sized tires were 95 to 100% aspect ratio.

The largest metric standard (I think) is 90%.  So, they cross what they have to what they want you to fit onto the bike.

Weren't the cross charts made by salesmen?
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline rtnoble

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Re: Tire question...I'll probably get hammered!!!
« Reply #2 on: March 10, 2012, 05:04:11 PM »
Dude,
That is the first bonified statement I have heard about the aspect ratio of the tire. 

I'll go with it,

Love you man!

Russell in B'ham
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Russell in B'ham
1980 CB650 bought new
Unmolested, sans 650C pipes
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