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Old 01-19-2015, 01:04 PM   #1
Scubadvr OP
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Now I'm the second type of rider.

After 40 years and hundreds of thousands of miles of riding, last Thursday I went down on the street for the first time. I always expected it might one day happen, but didn't expect it to be for something as stupid as this.

For the TLDR folks, it was a combination of excess salt on the road, cold tires, and air pressure in my rear tire. My fault completely.

I ride year-round, which means riding a lot in sub-freezing temps during the winter. When commuting, I check my tire pressure a couple of times a week, and it rarely needs adjustment, unless there's an unusually big swing in temps.

Which is exactly what happened last Thursday.

On Tuesday, I added about 1 psi to the front tire and 1.5 to the rear to bring them up to my standard street pressures of 36 front/38 rear. The ambient air temp was 12 degrees F. Tires are OEM Metzeler Tourance EXPs with 1500 miles on them. Drove to work, no problem, although I always take it pretty easy because of the loss of traction in those cold temps.

Along comes Thursday, and I'm champing at the bit to get going, running a little late, and didn't bother to check the air pressure in the tires, since I'd filled them just two days earlier.

I also hadn't checked the weather report that morning, although the night before the local meteorologists said it would be a nice warming trend. Well, the temps were about 25 degrees warmer than the previous day. As I was leaving my subdivision, still taking it easy because the tires were cold, I was taking the same left-hand turn out of my subdivision that I've taken for the last 16 years without incident. Our subdivision road ends at a secondary cross street, so you must turn left or right; there's no continuation straight ahead.

I was right at the apex of the turn, going about 15mph, and the rear tire washed out with the bike lowsiding out from under me. It happened so fast, I didn't even have time to think, "WTF?" I apparently landed on my left elbow and hip, then slid about 5 feet (like sliding foot-first into 3rd base), and the bike slid about 10 feet.

Since this is a busy intersection, with two lanes in each direction, I immediately got the bike upright and wheeled it over by the curb. My left elbow hurt a bit, but otherwise I was feeling nothing else. I put the kickstand down, then stepped on the sidewalk to do a quick self-assessment. My entire left side was covered in salt residue.

The elbow of my jacket was worn through, all the way down to the armor. Had I not been wearing armor, I would have likely shattered my elbow, instead of getting a slight bruise.



My hip armor also did its job, but my pants didn't wear through, other than where the pocket zipper was underneath. There's also a slight scratch on the ankle armor of my left boot. I didn't hit my helmet.



I looked back at the intersection, and there was salt everywhere. No chunks, just a total salt glaze. I was looking for glare ice, but everything seemed dry as a bone. At the time, I thought it must be the coating of salt, and maybe a little moisture had been absorbed from the air. That salt has been there for two weeks since the last bit of freezing rain went through, and I had rolled over the same track for the previous two weeks, so it didn't really make sense to me.

I decided to continue on to work, since the damage to the bike seemed cosmetic (more on that later). About a half-mile further on, I bagan slowing for my next left-hand turn, and as I smoothly braked, the rear felt really greasy, like it was sliding on Crisco. The rear started to slide out to the right. This time, I had time to think, "WTF?" because I wasn't leaned over in a turn, I was simply slowing for the next turn. There was no traffic around me, so I made a command decision and let off the brakes, aborted the turn, went through the intersection, then dabbed a 180 in the middle of the street, spooked as all get-out by now, because I don't understand what the frack is going on.

Then it dawned on me.

I got out my air gauge, and my rear tire (max PSI 42) is at 46psi, and my front is at 42. Crikey! I was lucky the front hadn't washed out, too!

I released a surprising amount of air to get the rear tire back down to 38psi, and also brought the front down to its requisite 36. I made it to work without any further incident. I of course know that air pressure increases as temperature increases, but I never even thought about it that morning, and quite frankly, I was surprised the delta in pressure was so much from when I'd topped up the tires two days previously at 12 degrees F. Lesson learned.

Damage to the bike:

Left-rear pannier took the brunt of the damage:



Left-side engine bars did their job:



Left side light cover likely saved the tupperware:



Left hand guard scraped:



So, after 40 years of surviving the street (I've eaten plenty of dirt over the years, I'm not going to count off-road spills), I added some road patina to my new Triumph. I never thought my first kiss of the pavement would be something so stupid; always figured I'd screw up in a hot corner on some rural decreasing-radius turn. Go figure.
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Old 01-19-2015, 01:21 PM   #2
jdbalt
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Ouch

Well let me be first to say. ATGATT wins! I am glad you are OK. And the trusty steed has some added character. I live in the north and ride year round as well. Tire temps and pressure do suck this time of year. I think you just hit some slick stuff and down you went. It isn't if you will drop it, but when. Welcome to the second type of rider.
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Old 01-19-2015, 02:37 PM   #3
UtahK
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Glad you're OK. I'm surprised that your tire pressure was that far off. The rule of thumb that I use is tire pressure will change 2% for every 10 degrees Fahrenheit temperature change.
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Old 01-19-2015, 05:22 PM   #4
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I wonder...when you inflated your tires last time, were they in shade? If so...were they in sun before you rode this time?
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Old 01-19-2015, 07:19 PM   #5
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TLDR?

Glad you're okay and thanks for sharing. I didn't know over inflation could make that much of a difference. Yet another thing I learned from these forums.
Cheers,
Brent
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Old 01-19-2015, 07:30 PM   #6
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One of the biggest problems with tire pressures changing like that is the moisture content inside the tire. The dryer the air inside the tire, the less change of pressure versus temperature, the wetter the air inside the tire, the much greater change of pressure versus temperature.
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Old 01-19-2015, 08:22 PM   #7
74C5
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Glad you didn't break anything and that no one ran over you!

12F to 37F and 36 psi to 46 psi don't go that well together from a physics standpoint. Your final pressure has a bunch of road heat added.

472/36 should equal 497/46. You have to use Rankine temperature BTW. I would have expected only a 2ish psi rise from air temperature. A bit rusty but, I think I got that calc right.

It is entirely possible you also have a wonky pressure gauge.
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Old 01-19-2015, 08:49 PM   #8
Scubadvr OP
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74cs, I thought about that possibility, too, especially since the gauge I use to fill the tires is integrated with the filler I use with my compressor. It is digital, and I usually keep it inside during the winter, but it has been in the garage all winter. Not sure if it was reading lower than normal when it was so cold on Tuesday, but it checks out fine with two other digital gauges.

Jarlaxle, the bike was in the garage when I filled the tires, and I rode right from the garage the day I lost it, as well.
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Scubadvr screwed with this post 01-19-2015 at 08:55 PM
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Old 01-19-2015, 08:57 PM   #9
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Tread55, TLDR = "Too long, didn't read."
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Old 01-19-2015, 08:59 PM   #10
brownricer
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Salt- the underrated winter menace.
I was noticing today how even fine and well-spread salt is a lot like sand, on a dry, cold-hardened area of asphalt. I'm glad you went down OK with no complications.
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Old 01-19-2015, 09:37 PM   #11
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Quote:
Originally Posted by Scubadvr View Post
Tread55, TLDR = "Too long, didn't read."
And the learning never stops Thanks for the clarification!
Cheers,
Brent
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Old 01-20-2015, 07:24 AM   #12
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Thanks for the post. Good story about how too much air can be worse than too little air from a contact patch standpoint.

Here in NW Arkansas we get wide swings in temperature on a daily basis.

Like today, this morning it was 32, this after noon it will be 50, yesterday afternoon , I think it was like 67 .

I have a nice pressure gage , the kind with a flexible hose, circular analog dial, pressure relief valve. So I checked my tires, back needed a few, which seemed reasonable, front was down too by 8, which seemed odd. hooked up the old crappy 12 volt air pump, started to air up, then noticed the crappy gage on the air pump read way high,, WTF?,, stopped, and remeasured,, tire was up above 47 !!

I know I had a good seal with the high dollar gage, but it is a mechanical device, maybe it just stuck or something, dunno
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Old 01-20-2015, 07:36 AM   #13
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This is why I love having the tire pressure monitor from BMW on my bike. Every morning, I cycle through the info and verify that I'm close to where I need to be. Yes, I have checked to make sure the readout on the bike is the same as a gauge and it is pretty close. I find very little handling difference between 36-42 but have never tried anything like the 47 in the cold as reported here.
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Old 01-20-2015, 08:53 AM   #14
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Liquid de-icer?

Do they use the Liquid de-icer where you are? I have noticed a huge difference in slip here in extreme cold and just above freezing temperatures. That salt residue on your gear. Maybe?
That stuff is like Lichens on rock, it holds a just a bit of moisture and gets slick.

I'm sure pressure was the issue, but this could have been the catalyst
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Old 01-20-2015, 06:17 PM   #15
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Quote:
Originally Posted by cliffy109 View Post
This is why I love having the tire pressure monitor from BMW on my bike. Every morning, I cycle through the info and verify that I'm close to where I need to be. Yes, I have checked to make sure the readout on the bike is the same as a gauge and it is pretty close. I find very little handling difference between 36-42 but have never tried anything like the 47 in the cold as reported here.
There is not that much difference... Given the really ice like traction he was reported, this was definitely NOT air pressure. If the description of the second event is anywhere close to accurate, something was on the street. No way, no how, is increasing the pressure just over 10 % going to result in that.

I am surprised no one caught onto this earlier...

Mike
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