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79 ironhead sportster, tire pressure

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  #1  
Old 26th February 2021
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ThenCameHarry ThenCameHarry is offline
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Default Tire Pressure 1979 XLH

I am just about finished with the restoration of one of my two 1979 Ironheads.

Both bikes have cast wheels.

A few years ago I had installed the following brand new tires:

Front:
Dunlop RS-310F tubeless 100/90-19, max load is 507 lbs
@ 41 PSI cold.

Rear:
Dunlop RS-310R tubeless 120/90-18, max load is 632 lbs
@ 41 PSI cold.

The manual calls for pressures of 26 PSI front and 32 PSI rear.

Of course that was for the tires used back then which, I seem to recall were Goodyear.

Given the above data should I use the factory recommended tire pressures 26F/32R or should I go somewhat higher like 30F/36R

I will ride without a passenger, not loaded and I weigh around 180 pounds.

I realize that I could just use a certain pressure and wait for a while to see how they wear.

Well I will be definitely doing that. But I’d like to start off with the best guess possible.

Thanks for your thoughts on this.

Harry.

Last edited by ThenCameHarry; 26th February 2021 at 23:26.. Reason: Correction of load number
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  #2  
Old 27th February 2021
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I've always kept 35psi front and rear. No issues.
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  #3  
Old 27th February 2021
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Quote:
Originally Posted by doodah man View Post
I've always kept 35psi front and rear. No issues.
Thanks much for your feedback.
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  #4  
Old 27th February 2021
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more than comfort and wear is here. a lot depends upon the tire and rim. being cast, i think there is no concern. but the tire profile does make a diff. i hate the so called sport or mushroom tires and they do call for more pressure if you are into the twisties. but that comes at a cost, the 2" contact patch down the middle will wear quickly. i have smoked them in under 4k miles. i like the flat profile like the commander tire with 4" contact patch. yep, more road feel and effort needed for the twisties but predictable, not the fall off the center feel. on the sport tire, i can break traction at 70mph. i think mr. doo suggestion is right, middle of the road approach. personally, i ride what the tire calls for but i ride diff than most.
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  #5  
Old 27th February 2021
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Manual air pressure figures are for GoodYear Tires from back then. Use the manufacturers recommended pressures. Tires work in a "heat range" and that will depend greatly on inflation pressure which affects sidewall flex.
Too cold or too hot, either way reduces grip.
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  #6  
Old 27th February 2021
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Modern Sporties with modern tires run 30F/36R. Ironheads being a tad lighter can go down a smidge, but I run mine at that and they do fine (Shinko 777, 100/90-19 front and 130/90-16 rear) when checked while hot.

You want to run the cold psi so that when you get it hot after riding you see about a 10% increase. If it didn't increase enough, the cold pressure is too high. If it increases too much, the cold psi is too low.
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  #7  
Old 28th February 2021
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Scuba10jdl,
Thanks for the substantial information on the different tires and pressures.
Much appreciated.
Harry
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  #8  
Old 28th February 2021
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Quote:
Originally Posted by Ferrous Head View Post
Manual air pressure figures are for GoodYear Tires from back then. Use the manufacturers recommended pressures. Tires work in a "heat range" and that will depend greatly on inflation pressure which affects sidewall flex.
Too cold or too hot, either way reduces grip.
Thanks so much for your reply.
What you are saying makes perfectly sense and agrees with what I seem to recall about tires on Ironheads of that era. But since it’s been over 35 years that I rode my last Ironhead, I just wanted to make sure.
The tires I have now are 41 psi cold front and rear. With that in mind it sounds like I should just run them from around 35 psi.
Thanks again.
Harry.
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  #9  
Old 28th February 2021
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Modern tyres do seem to run higher pressures. I have Avon Roadriders on my 76 and use 40psi rear, 30 psi front. Simply because the guy at the bike tyre place who fitted them suggested it and it seems fine so I stick with that.
Paul
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  #10  
Old 28th February 2021
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Ya got modern tires on an old bike. On my 77, 30 front & 36 rear.
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