Clincher tyre tubes and pressures

[Steve Slocombe]

Dear All, a customer just made it 300 yards down the road before both tubes blew out on his newly restored 1927 Harley J model, running 3.85 x 20 clinchers. What tubes and pressures should he have been using?

[23JDCA 808]

87090 28X3 TR-4 MS CYCLE TUBE $12.95
89200 17" - 22" RIMSTRIP $2.99
From Coker. I run at 35psi.

[exeric]

Those are good questions Steve. I ran 50 p.s.i. in my Series 20 Excelsior with 3.85 x 20 Clinchers with no problems. As for inner tubes. I ride a bicycle every day and have had at least 40 flat tires in the past 5 years. Without sounding xenophobic, all I can find are Chinese inner tubes and they are junk. I've looked on-line and cannot find quality tubes. For what it's worth, I now slit old tubes and wrap them around the new tubes to give some more protection.

[gharper]

35 PSI sounds low to me. I run my 28X3's at 50 psi, never had a problem. The whole design of the clincher relies on high pressure to keep the tire on the rim.

Gene Harper

[Tom Lovejoy]

Agree with Eric and Gene, been told the Chinese tubes are not any good at all. Try for Japan or Europe for tubes, that's what Rotten Richard told me, good luck.

[John Mertens]

Hi guys. i race at davenport every year and what the race guys do is to take electrical tape and tape the inside of your rim around the area were the spokes are. in other words the center of the rim. use a good tape and go around it several times at lease 8 to 10 times.. next use the correct tube for the tire . 28/3 clincher. or what ever tire size it is for. i know that some of the guys use the harley tube for a 21/3 tube. i guess that works just fine.. and they use about 50 pounds of air. if your useing a tube from a china or elsware you will want to put at lease 50to 60 pounds of air. most important is that you clean the rim and tire with a good soap and water . and make sure that you dry it well. this works very well for us on the race track.i hope this helps you out. thanks John Mertens . board track racer #24 #21 #23.Mertens race team.

[LouieMCman]

Imagine going into a sweeping curve at about 40-50 MPH and having your tire come off your rim....It's never happened to me but I think about it alot when riding a clincher rimmed bike. I would not run any thing under 50 psi.

[Rod K]

http://occhiolungo.wordpress.com/201...allation-tips/

I'm not an expert on clinchers, but ran across this article by Pete Young on the Occhiolungo web site. I found it interesting, hope you do too....Rod

[pete @ occhiolungo]

I'm not an expert either, but I'll never run super high pressures. I've seen too many clincher tubes pop like a balloon at high pressures. The books in the old days recommended medium pressures, like 5-10 psi more than drop center tire pressures. It depends on the size of the tire and the weight of the bike/rider/passenger. But mine work ok at 42psi. I've had a few go flat, but it was a gradual loss of air, not a sudden pop! Some old timers run less psi around 35-38, even though they are bigger guys. The most important thing is to check them often. And to install them well. And to prep the spoke heads. I guess that's three important things.

Regards,
Pete

http://occhiolungo.wordpress.com/201...allation-tips/

I'm not an expert on clinchers, but ran across this article by Pete Young on the Occhiolungo web site. I found it interesting, hope you do too....Rod

[Susanne]

This is a HUGE safety issue - so pardon me for going on for a sec...

Clincher tires use - and are DESIGNED - for high pressure to hold the tire on the rim, and keep it from slipping on the rim. If you run low pressure, you will likely blow one out from rimcutting and/or valve shear... The rule of thumb is 20 PSI for every inch of width... so for a 28x3, the "proper inflation" is 60 PSI.

Remember, we're talking about *clincher* tires... Saying that - normally, "balloon" tires end not in a fraction (27x3 1/2, 28x3, 31x4 1/2 etc) but in a decimal (20x4.25, 22x3.875, etc.) - they are not clinchers the rim, if you took a slice out of it, would look like the letter "C") but either drop centers or on cars splitrims (looks like a "U")... and they run slightly lower pressures... saying that, they considered lower pressures 45 PSI in the day, something to think on... It's why racing bikes run rim locks - to keep those tires from spinning themselves flat.

If you are running 28x3's and only have 30-35 PSI in them, you're riding on pure luck. When those tires go flat at speed, they are really likely to come apart quite quickly and not in a nice way... In an old car, I've seen them wrap an axle in lickety split time, locking up a wheel and doing some van-dammage to the car. (and yes, it's because the driver was running 32 PSI on a 3 1/2" wide tire - which specs 70 PSI...)... on a bike, they'll rap the rider on the road. The Van-dammage would be somewhat greater...)

Think of it as a technological thing. Just like you wouldn't put modern 0w20 oil in your pocketvalve motor...(or 60 wt in your Subaru Forester)... Clinchers are a different technology, and work differently, than "modern" tires.

[Susanne]

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-

[pete @ occhiolungo]

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!

[Susanne]

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...

[pete @ occhiolungo]

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.

[harleytoprock]

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.