So… I had been riding with Travis at Carnegie and I lowered my tire pressure down to 20 psi while we were there. I hadn’t pumped it back up when I got home. Fast forward to the other night when I was leaving Calicraft after a few beers. There’s a couple of speed bumps in the parking lot and well, I may have pulled a small wheelie as I hit one of them.
MILEAGE
28,538
The front wheel came up just as it touched the leading edge of the speed bump and I applied a good amount of throttle as the rear tire hit the bump. As I hit the bump I felt the rear tire slip a bit. I thought maybe I had just slipped in a wet or greasy spot.
LISTEN:
As I left the parking lot I knew it wasn’t just a slip. I had a flat tire! I limped the bike home (1 mile) and took it apart in the morning. It turns out that the slip was actually the tire spinning on the rim and when it did that, it also took the inner tube with it – ripping the valve stem from the tube.
The combination of low tire pressure, throttle, weight transfer, and the extra pressure from the speed bump all contributed to the malfunction.
Easy fix.
I went online to order a new tube. I run a Michelin Ultra Heavy Butyl Rubber 4mm Tube. My first look was at my favorite retailer Rocky Mountain and a quick search for them came up empty! They had Bib Mousse and the standard 2.5 mm tubes but nothing in 4 mm.
Cycle Gear did have the Tube but not in stock locally. I bought the tube and picked it up 2 days later in the store. They aren’t cheap but they are the best. Look at almost any pro racer running tubes in the desert and they’ll be running these Michelins.
For the install I decided to use my existing tire, it has about 50% tread left, but also I wanted to install a Rim Lock. I had not been running a Rim Lock so this was an added security so this same thing didn’t happen again.
I had a set of Aluminum Motion Pro Rim Locks in spare parts and the rim was already drilled for it so it’s an easy add. I would have preferred the Motion Pro Plastic version for the savings of weight but maybe next time. The Aluminum version weighed in at 103 grams or 3.6 ounces.
That’s a lot of weight to add to a spinning object.
Speaking of weight, the new tube clocked in at 2,098 grams or a whopping 4.6 Pounds!
Natural Rubber vs Butyl Rubber
Let’s take a moment to talk about the different types of rubber you can get for an inner tube.
Natural Rubber is a renewable, elastic hydrocarbon polymer derived from the milky sap (latex) of the Hevea brasiliensis tree. It is prized for high tensile strength, elasticity, and tear resistance.
Butyl Rubber (Isobutylene-isoprene rubber) is a synthetic, highly impermeable elastomer known for excellent gas/moisture resistance, thermal stability (from -75f to +250f) and chemical resistance.
They sound very similar and you can find inner tubes made from either substance. When it comes to inner tubes each variation has it’s better attributes.
Natural Rubber Tubes are generally softer which gives the ride a slightly softer feel. Because they are more pliable some people believe they are less prone to pinch flats. If I was a Hard Enduro, MX or Trials guy this would be the tube for me.
Butyl Rubber Tubes are generally stiffer and give a slightly harsher ride. But, because they are less pliable some people believe they are more resistant to punctures.
Natural Rubber is molecularity more open and so it tends to leak air naturally over time.
Butyl Rubber is just about a virtual seal and does not allow air to leak through it.
Knowing the difference between the two, here’s my thinking on my choice of Butyl.
I don’t want to have to check my air pressure every morning before riding while on a trip. At the start of the ride? Yes of course. Just not in the middle. Obviously, I would like to minimize both the pinch flats and the punctures, but I’m simply not as worried about the Pinch Flat issue. The heavier and thicker 4mm version is going to help with both of those to a certain extent but I am also going to go back to Jimmy Lewis Air Pressure as a general rule and that should make a pinch flat a very low percentage item.
What is Jimmy Lewis Air Pressure?
I’m glad you asked. Years ago, Jimmy happened to say in some podcast somewhere that he ran all his bikes at 27psi front and rear. Off road and on road. Small little dirt bikes (125 cc MX weapons) and huge ADV behemoths (KTM 1190 Adventure). I tried it on my KTM 950 Adventure and ran as hard as I could in the gnarleyest places and never got a pinch flat. I picked up a puncture once but that was a nail on the freeway. If you ask Ai about it you get this:
I might still “air down” for the deep sand of LAB2V but I’ll do better riding 27 psi on a daily basis.
When I do air down, I’ll have the Rim Lock doing it’s job keeping that tire from spinning on the rim.
The Install:
I had already taken the wheel and tire off and cleaned it all. It was going to be a nice sunny 70 degree day. I started in the morning by putting the tire in the sun. I blew some air into the new tube and let it sit in the sun for a while too.
I used silicone lubricant for the tire lube and put the first lip over the top of the rim pretty easily.
Next, I tried to get the Rim Lock up in the tire and thread the bolt portion through the new rim strip and rim. Picture the same idea as getting the tube up in the tire and threaded through the valve hole. Not a chance!
I then tried to go at it from the outside and that worked better. I used a tire iron to push the tire out of the way (as if I was taking it off again) and managed to thread the Rim Lock in that way. I them managed to move the tire bead over the Rim Lock to it’s proper side and then pushed the Rim Lock up into the tire so that it would properly come down on the bead. I would have shot some great pictures of all of this but I needed all my hands and could have used a few more.
Next up it was wrestling the inner tube. This thing is so thick and heavy it’s more like an Inner Tire! I had the valve core out but it was still inflated naturally and had a hard time getting it to tuck into the tire. Travis happened to be over at the time and so we both squished as much air out as we could.
I dusted the tube and inside tire with a fair amount of baby powder and gradually got it to fit in. The last section to get in was the valve. I use one of these guys. I carry one on the road too. Not sure what it’s called or who makes it but they are invaluable in getting the valve through the hole with a 4 mm tube.
You simply thread it through the hole in the rim, then screw it into the valve stem core and by pulling on the T end you can guide it to the hole and through. I did it once and then realized I had accidentally dropped the conical washer from the tube and had to do it all over again.
Oh, and then that brings up the two valve stem nuts. Does one go on the inside of the rim, one on the outside? Or do both go on the outside?
Right on the box Michelin answers this with a simple graphic. It should be Tube, Conical Washer, Rim, then the two Lock Washers, then Dust Cap. So, no nut on the inside. Got it! You might miss it if you didn’t know it was there.
But wait… I just saw this.
Rocky Mtn and Randy Richardson
He’s even wearing a Michelin shirt and a quick Google search suggests he works(ed) for Michelin!
Next I inflated it to 40 psi and checked for leaks (yeah right), and to make sure the bead was set all around on both sides of the rim. I then tightened the Rim Lock down. Motion Pro specifies 14 lb/ft.
I dropped the pressure to 27 psi, installed the rubber cushies and my nice clean sprocket and carrier and mounted it up on my wheel balancer. With the added weight of the Rim Lock it took a lot of weight to a good balance. Four of the 27 gram spoke weights later I was happy enough to mount it on the bike and take it for a spin.
“Why don’t they put the Rim Lock on the opposite side of the rim so it balances easier?” you might be asking yourself. Then you realize it needs to be close to the Valve because that’s the part it’s trying to protect. If it was on the other side of the rim the tire might still spin a little on the rim in the weakest part and that would then be the valve stem section.
New Tech from Nuetech
I am so close to running a PROLOCK 360 by Nuetech. A couple of years ago I spent an hour on the phone with the engineer / owner of Nuetech, Jeff – talking about why his Tubliss system might or might not work on my 690 rear wheel. At the time he mentioned that he had a new product in design and it would work for all sorts of bikes. It was leaked by Cody Webb recently and is now available. It’s like a 360 degree Rim Lock that makes your wheel like a tubless tire. It should be available to public any day now.
https://slavensracing.com/shop/prolock-360-by-nuetech/
2 1/2 pounds, No new rim strips, no tubes, run any tire you like at almost any tire pressure you like.
Wow!
He's an avid hockey fan, rides a mountain bike, sometimes rides a road bike, has a few motorcycles (he had a really fast one, had a big cool orange one, rode a really slow one, and is currently building a perfect "BDR Weapon"). If that isn't enough, he makes cheese and sourdough bread, loves strong beer and good red wine, and poorly plays the Mandolin.
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