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Thread: Clincher tyre tubes and pressures

  1. #11

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    This is an update to what I posted the other day...

    I found the OEM specs for 28x3 tires... the factory book says 45 PSI. While it seems low (to my eyes), I figure they factory ran these for enough time to know what the recommended safe pressure was... so I would go with what the book says (eg 45 PSI) and learn from this one not to take "rules of thumb" too seriously when the factory already gave me the "ISaySo" on it!

    -S-

  2. Default

    45psi sounds good, but for what size tire, and under what load? Which factory book are you referring to? Excelsior recommended 45psi for it's circa 1917 bikes that ran 28x3's, but I haven't seen any factory literature for the earlier and smaller sizes. I've listed several sources from the 19teens and earlier in the article (linked above) that show various pressures for various tire sizes and various loads. 45 should be fine, especially for 28x3 with a heavy rider and passenger. But I wouldn't run more than that, and would use less with smaller tires, lighter bikes and lighter loads. For 24" and 26" tires, 30-40psi works well.

    By the way, I had the rear tube pop the other day on my 1913 Veloce. It was the loudest pop that I've heard other than a firecracker or a gun. I wasn't on the bike, it was parked at the time, but I was planning to ride it in about 10 minutes. Close inspection showed a slight crease to the tube, where it must have folded slightly on a portion of the tire bead.

    I'll repeat my advice: run what pressure you like, but check the pressures often, and do a good job during installation. And have fun out there!

  3. #13

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    Quote Originally Posted by pete @ occhiolungo View Post
    45psi sounds good, but for what size tire, and under what load? Which factory book are you referring to?
    Sorry about that - 28x3, under a Harley JD/FD, from their 1920-21 owners handbook... so between 300-400 lbs or thereabouts (likely the same as the henderson, as bikes then were thereabouts the same weight). Figuring a 9 sq. inch patch on the ground x 2 (I know its less, but that's what I was told to go by on autos, tho that's x4) 45 PSI x 9 Sq. inches x 2 tires... in theory it should handle 810 lbs total weight. I know there are other factors involved, but that would cover the bike and 2 riders, so maybe it's pretty close...

    I had the scary experience of having a 30x3 1/2 tire let go near where I was standing - sounded like a gunshot!! It was also because of a pinched tube... I had a similar tire on a similar car (Ford T) that had been underinflated to 30 PSI (make that grossly underinflated by clincher standards) by the former owner (who ran it at that for a while, according to him) and it spun the tire, taking off the valve stem... What I noticed was the sidewalls (Older NZ Non-skids, IIRC from the 70's?) were severely damaged as well... like had the thing not gone flat from unstemmage (How's that for new terminology? ) and he then put the correct pressure in the tire (which is 60-70 PSI) the sidewall would have likely come apart...

    It's also interesting to think that sidewall blowouts were apparently in the day not uncommon, and they sold shoes to fit over blown tires to get them to whereever... or home... or down the road. I also complain about the poor wearing quality of modern manufacture clinchers (from a certain southeast asian country) until I read the ads and realize high mileage then was 7500-10000 miles... so maybe it's not all that much different...

  4. Default

    yeah, I hear complaints about the quality of tires from Asia, and just as many complaints about the tires made by a certain US company too. But the Dunlops in the UK are made well, and are very tough. Not as sticky as the Cheng Shin type, but they last longer. Expensive, and hard to find too, but I don't have much choice on that. I use the ones that fit the rims the best. And that varies rim by rim, bike by bike, unfortunately. There were something like 27 different tire sizes in the old days, each with its own rim dimensions. But now we have to use what we can find. fun fun fun.

  5. #15
    Join Date
    Apr 2003
    Location
    Seaford, NY
    Posts
    374

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    I was just looking at the 1929 Harley riders manual. The recommended tire pressure back then was 16 lbs front, 20lbs rear for a solo machine! This is for 3.85X20 tires. My 27' Jd feels better to ride with 30lbs than with 45 lbs. I do worry however, that the tires will fly off.

  6. #16
    Join Date
    May 2006
    Location
    Southeast WI
    Posts
    179

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    Just for comparison...Anyone know what pressures the riders handbook gave for the VL's drop center rims??? I'm running
    those on my 28J. .thanks Rod

  7. #17
    Join Date
    Apr 2003
    Location
    Seaford, NY
    Posts
    374

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    My 1936 riders hand book states 18lbs front, 20lbs rear for VL with 4.00 tires.

  8. #18
    Join Date
    Apr 2012
    Location
    Canyon Lake, Tx
    Posts
    543

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    My VL Rider's Hand Book sez: Solo service
    4.00 in tires (standard equipment) Front 18 lbs. Rear 20 lbs.
    4.50 in tires (Special equipment) Front 16 lbs. Rear 18 lbs.
    Supposed to be for an "average rider of 150 lbs."
    Rich

  9. #19
    Join Date
    May 2006
    Location
    Southeast WI
    Posts
    179

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    Thanks guys....18 and 20 lbs. I'll just add a couple more lbs. I'm not in the 150 lb class anymore......Rod

  10. #20
    Join Date
    Aug 2013
    Location
    1 mile east of the Rocky Mountains.
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    873

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    i realize this thread has been dormant for 5+ years, but it is still a good one. i am running 40psi in my 3.85x20 clincher Coker tires with a Malcolm Smith motocross tube on brand new Al McCormick rims.

    Reading the stories of blowouts in the thread and the fine article, the one thing that is not mentioned is the condition of rims in the cases where blow outs occurred. Does anyone know of cases where blowouts occurred on new rims withe the heavy duty 4 mm motocross tube was fitted?

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