Clincher Tires / Beaded Edge Tyres. Pressures and Installation Tips
Not very many people today are riding old bikes with the early style tires. They were called ‘clinchers’ in the US and ‘beaded edge’ in the UK, and both were replaced by drop center tires in the period of 1928-1930. The were replaced for good reasons, the main one being that drop center tires stay in place better on their rims. But the subtitle for this website is “Fun Stuff From 100 Years Ago” so I’ll write a bit about the early tires instead of the drop center type.
The big question among today’s enthusiasts is about tire pressures, and rightfully so. The shape of the bead is such that the pressure from the inner tube forces the tire bead under the edge of the wheel rim. This pressure then holds the tire on the rim. So many people think that more pressure is better. Which sounds good. But more pressure also means more stress on that thin rubber inner tube. This reminds me of a clown’s rubber balloon from a kid’s birthday party. Blow it up just a little, and you can poke it with a stick and it will just bend and flex. Blow it up to a higher pressure, and it will pop at the slightest touch against Madonna’s pointy sweater.
Looking back at the information that was available in the old days, the tire pressures that were recommended were not extremely high. Typically they were about 10psi higher than pressures that were recommended for drop center tires of the same size, with the same weight of bike. Here is a snip from Victor Page’s book c1913:
Those recommended pressures of 32-40psi are about half of what some guys are currently using. But when they hit a rock, or a pothole in the road, then there is a loud noise, the tube pops, then the tire comes off the rim and the bike goes down. Running a lower pressure seems to give less popped tubes, but too low is also a problem. When my friend James crashed his 1920’s Sunbeam and sadly lost his life, the tire came off the rim, wrapped around the front forks and he fell down. But the tube was not popped. It was still holding air. However the pressure was too low to hold the tire bead in the rim. To get another reference, I checked Radco’s book, and found this table. It gives very similar numbers to the Goodyear information from Victor Page, and Radco didn’t name his source, so it might be the same.
Note that for a typical single cylinder bike, the 26×2.5” tire would be run at 30 psi, give or take a few psi depending on your weight. For a big American twin with 28×3” tires, it would be around the same. The table doesn’t even list pressures above 36 psi, except for 3” tires with extremely heavy loads (440 pounds loaded onto each tire of a circa 1913 bike? wow.)
An important aspect of these tire pressures is the weight of the vehicle, rider and luggage. For a light vehicle (motorbike), less tire pressure is recommended. For a heavy vehicle (car), more pressure is recommended. The two sources shown above both deal with motorcycle tire pressures. However, there are a lot more old and new books existing that recommend tire pressures for cars. These seem to vary from 35-80 psi, depending on the car weight. I wonder if the current practice of using such pressures on bikes is from those books? (and possibly even from well meaning tire vendors who deal with car customers almost all of the time?).
Here is a similar table from the Veteran Car Owner’s Manual by Ernest F. Carter. Motorcycle tires are about 65-75mm section, which gives a recommended pressure of 35-60psi for a car, while the same tire size gets 30-35psi for a voiturette (a very tiny car, analogous to our motorbikes).
Thinking about this mathematically, we can calculate the force that the tube puts onto the tire to hold it against the rim. If the tire is 21”diameter at the bead, and say that the bead is 1/4” tall, that is an area of 16.3 square inches on each bead. At 30 psi, there is 490 pounds of force on each tire bead. A very interesting thought is that a drop center tire has about the same area and the same force, yet it doesn’t fall off the wheel nearly as easily…
That force is applied to force the tire under the “hook” of the rim. Which leads us to a short discussion of the tire design. Beaded edge tires have a thick bead of rubber to fit under the edge of the wheel rim, Here is a view of the UK style Westwood rims. The US style didn’t have the slight “V” at the center:
In order for the tire to be installed on the rim, the beads are somewhat flexible. Now if we compare that to the later drop center design, we’ll see the difference:
source for the image is here.
The drop center, or wired on tire has a metal wire around the lower portion of the sidewall, instead of a hooked bead. An interesting side note is that the rims are called “drop center” due to the indentation of the rim at the center. This was only needed because the metal wire of the tires was so strong and stiff. It required that the tire be dropped down into the rim center during installation, otherwise the bead on the diametrically opposite side couldn’t be stretched enough to be forced over the rim. (stay with me on this, we are getting somewhere).
Recall that the hook of the beaded tire was forced under the hook of the rim, and yet those tires are famous for falling off the rim. Yet they have about the same pressures and the same areas, therefore about the same forces forcing the tire to the rim. If anything, that hook should make the beaded edge / clincher tires stay in place BETTER THAN THE DROP CENTER TIRES. Yet we know that they don’t. And the simple difference is that little bit of metal wire. It has a huge circumferential strength that resists stretching, hence is was hard to fit them over the rim. And the strength and stiffness keep that tire on the rim too.
Taking this back to that big question among today’s riders of 100 year old machines; “What tire pressure should we run?” It must be more than the pressures for drop center/ wired on tires. The reasoning behind the standard answer is now understood. But how much more? That is a harder question to answer. Personally, I use 42 psi. 35-45 would be find I think, but 42 is an easy number to remember. Lots of other guys that I’ve polled use similar pressures. And 30 psi might be ok, based on the old books. Some guys like 65 psi, but that scares me due to the party balloon analogy. I’ve developed a few flats on early tires, and none of them were catastrophic in any way. The tire went down slowly, the bike handled poorly, and I stopped to investigate why. No blow outs yet, but I’ll keep my fingers crossed. It does happen though, unfortunately our friends can tell us bad stories about subsequent crashes. One friend runs higher pressures, and his tire blew with a spectacularly loud bang in the parking lot. The bike wasn’t being ridden, in fact it was parked 20 feet from the nearest person when it popped without warning or provocation.
This could be the spot in the article for a speech about being safe, and fitting modern rims to old bikes. Or the counterpoint that all old bikes are inherently unsafe, and that we should leave them stock and ride them with due caution. But I’ll leave that alone. However if you choose to run early tires on your early machine, here are a few tips.
- Check the air pressure often. Know if you tube is developing a slow leak.
- Don’t bother with tire irons when fitting and removing clincher tires. If they won’t go on using just your hands, then you should investigate why not. Possibly the tires are not made well, or for your rim size. There were a lot of different sizes in the old days, at least 39 different sizes!
- Use some French chalk (aka talc or talcum powder) when sliding the tire on if you have to. It is a dry lubricant that will make the rubber slide over the rim easier. I try not use anything to decrease the friction, as I want that tire to stay stuck to the rim when I’m done. Using some talc on the tube to decrease chafing on the tire is recommended by many old books, but I’m not sure how to keep it off the beads.
- Warm the tire in the sunshine for a couple of hours before you fit it onto the rim. It will soften the rubber a bit, and makes it easier to stretch into place.
- If you do use tire levers, they will bang up the rims, which were often painted in the old days. You can protect the rims with plastic, cardboard, or try the neat Rim Protectors from Motion Pro.
- You don’t need a rubber rim strip with clincher tires, the tire itself fits down between the tube and the spoke nipples. But you do need to trim a small half-circle into the two tire flaps for the Schrader valve stem to fit through. Just use a box cutting knife, make the circles about 1/2” radius or less and make sure that you install one bead of the tire so that the circles are lined up with the hole in the rim before you put the tube in.
- Try using an adhesive if you like. I’ve been putting belt dressing on one side of the Rudge tires with their funky rims and Dunlop tires. It is a spray compound made to make rubber belts stick to steel pulleys, which seems appropriate for rubber tires and steel rims. Putting it on the right bead, I can still remove the tube via the left bead. When I need to replace the tire, a few good hits to the right tire sidewall with a big hammer loosens the belt dressing. One 18 oz. can lasts a decade or more for $10.
Update Nov 9th, 2012: Anton Dee sent in a link via the OcchioLungo page on Facebook. (check it out if you’re on FB! lots of different stuff that isn’t on this website). It shows the testing of a new clincher tire from a factory, with tests on a stand, and with the tire fitted to some old cars. They wanted to really work the tire to see when it would fall off the rim, so they fitted it to a new Nissan pickup truck! As they lowered the air pressure, and continued testing, they found that the tire would stay in place at lower and lower pressures, until they got to about 20-25psi. Then the tire would come off the rim. Very interesting. Here is the link to Vintage Tires.
Update Nov, 6th, 2012: Bevars sent in this note, which I thought covered some really good points:
Hi Pete – there have been many discussions on this topic over the years! And yet lots of people still believe that you need high pressures.
I have been riding early bikes with Beaded Edge tyres for the last 40 years. At first I listened to the guys who said that you had to have 60 psi or higher. That was until I had a rear tyre blow off the rim with a sound like a rifle shot. Not sure my heart has ever recovered.
So I investigated and found that it was way too high for the weight being carried. Nowdays I run 30 – 35 psi front and 35 – 40 psi rear. On the Baby Triumph (24 * 2 1/4 inch BE) I am at the lower end, and on the Power Plus (28 * 3 inch) at the higher end. I use modern motocross or heavy duty tubes that have thicker walls than the standard rubbish (2.75 * 21 tubes in 26 * 2 1/4 BE tyres, 2.75 * 19 in 28 * 3). If I ride the bike a lot I replace them each year as a precaution. If these tubes get a puncture they go down slowly. The cheaper tubes split when they get a puncture and deflate instantly. What the guys on the English “Red Dwarf” TV program used to call a “Brown Alert” – one worse than a red alert.
I leave the valve lock nut loose and keep an eye on the valve stem each time I stop. If it has developed a lean it means that the tyre has shifted. I let the tyre down, re-centre the valve stem and pump it up again – but I gotta say it don’t move often! To put this in perspective I weigh over 20 stone so my bikes are carrying a fair old load. As I have to lose some weight for a hip replacement they will get an easier time in the future
The one thing you mention but don’t really emphasis is the importance of having a good fit – the right tyre on the right rim. As you say – originally there were many very similar size tyres, both imperial and metric sizes. Today we have only a few standard sized tyres available. We also have some oriental rims made for rickshaws which are slightly off size. If the fit is not good then the tyres will move. Higher pressures may help stop it revolving with respect to the rim, but that is fixing the symptom, not the problem. New good quality correct size rims is the only answer.
Most of the blow outs I have seen on BE tyres have the valve ripped clean out of the tube which suggests that the tyre rotated until it tore the valve out.