BMW Luxury Touring Community banner

1 - 12 of 12 Posts

·
Registered
Joined
·
1,080 Posts
Discussion Starter #1
I bet that like many of you, we use our LT as transportation for work.

Well I had a trip I scheduled from Orlando to Columbia SC over to ATL and then home to Orlando. Airfare was over $1000 for the trip so a quick approval from the boss ,(1100 miles X .45 = $495 and $600+ savings for the company)

Well Sunday came around the Hurricane Debby was sending bad vibes my way. Lots of rain but not too much wind.

So I sucked it up, geared up, manned up, grew a pair and got on the bike with two suits in the panniers and off I went.

The whole time, Billy Joel singing in my head

Even rode my motorcycle in the rain
And you told me not to drive
But I made it home alive
So you said that only proves that I'm insane

So now the real questions.

1. Should the tire pressure be the same for long distance riding in the rain?
I would think that less pressure would provide a bigger contact patch.

2. Other tips LT specific for rain riding?

Thanks
 

·
Registered
Joined
·
338 Posts
I would think that a bit less tire pressure would result in better road grip. ( as recomended for driving in the snow also ,)
 

·
Enjoy The Ride
Joined
·
3,994 Posts
Other than good rain gear the only tips I have is a pinlock no fog shield & plenty of tread depth. After the first few minutes ( enough to wash the road off ) I very seldom slow down for rain no matter how hard it is raining. Another tip is when crossing a RR track at an angle when the road is wet hang on to the bars tight it can rip the bars loose from your hands
 

·
Premium Member
Joined
·
7,650 Posts
No need to change air pressure. If anything, you would want to increase the pressure. The speed at which hydroplaning occurs is proportional to pressure with higher pressure increasing the speed at which hydroplaning commences.
 

·
Registered
Joined
·
372 Posts
Rode through tropical storm lee last Sept with the standard pressure. Not a problem that I noticed. Am in the middle of a coast to coast ride now and it looks like I will get mixed up in Debby before I get back to the house.

I am running 46 in the back and 40 in the front on the me880s.
 

·
Premium Member
Joined
·
4,886 Posts
My main concern in a semi tropical storm would be wind gusts. I can adjust to riding in a stead wind, but when a heavy gust comes by, it will move the bike. That and other motorist are my concern. For some strange reason, others seem to get closer to me when it is raining!

Given the choice, I would have either taken my SUV or an airplane. It is just too easy to get into an accident in bad weather.
 

·
Registered
Joined
·
1,080 Posts
Discussion Starter #7
as far as the tire pressure, I was just stabbing in the dark.

@Dave, once I was on 95N and outside of Daytona, I just kept here at 70MPH and hung on for the ride...
 

·
Super Moderator
Joined
·
1,409 Posts
Rode many times in rain from the light stuff to frog drowners - kept the tire pressure at
42/48. The bike never hydro planed up to 80 to 85 mph - the contact patch is small and
the pressure is high due to the weight of the LT. I also only run Bridgestones - in my
opinion a better gripping compound when dry and a better tread when the road is wet.

Only issues I have in the rain are:

- tar snakes
- painted road stripes
- rubber cross overs at railroad tracks
- metal expansion joints on over bridges that run parallel to the direction of travel

The other big issue when I drive in the rain is the total concentration it takes - very tiring
and fatiguing . . .
 

·
Premium Member
Joined
·
7,650 Posts
dfinazzo said:
Rode many times in rain from the light stuff to frog drowners - kept the tire pressure at
42/48. The bike never hydro planed up to 80 to 85 mph - the contact patch is small and
the pressure is high due to the weight of the LT.
The contact patch pressure has nothing to do with the weight of the bike and nearly everything to do with the air pressure in the tire. That is why higher tire pressure is generally better in the rain as it raises the pressure of the contact patch.
 

·
Super Moderator
Joined
·
1,409 Posts
Voyager said:
The contact patch pressure has nothing to do with the weight of the bike
and nearly everything to do with the air pressure in the tire. That is why higher tire pressure
is generally better in the rain as it raises the pressure of the contact patch.
"Nothing to do with weight . . . .???"

I believe what I typed was "the contact patch is small and the pressure is high due to the
weight". Pressure = Weight / Area . . . under most conditions the higher the tire pressure,
as you mentioned" you would get a smaller the contact patch thus the higher the pressure on
the contact patch for a given weight. There are several articles on the net that show that this
is not always true.

If the bike was 1/2 the weight of the LT with the same contact patch the pressure would be
less and the ability to run thru water at high rates of speed in a stable fashion is reduced.

Here is an article that proves your point and mine as well - the motorcycle pressure goes up
rather dramatically with a small change in weight but with tire pressure as well . . .



My 2¢ . . .
 

·
Registered
Joined
·
62 Posts
You must have proper inflation for the tread to work properly at dissipating water.
 

·
Premium Member
Joined
·
7,650 Posts
dfinazzo said:
"Nothing to do with weight . . . .???"

I believe what I typed was "the contact patch is small and the pressure is high due to the
weight". Pressure = Weight / Area . . . under most conditions the higher the tire pressure,
as you mentioned" you would get a smaller the contact patch thus the higher the pressure on
the contact patch for a given weight. There are several articles on the net that show that this
is not always true.

If the bike was 1/2 the weight of the LT with the same contact patch the pressure would be
less and the ability to run thru water at high rates of speed in a stable fashion is reduced.

Here is an article that proves your point and mine as well - the motorcycle pressure goes up
rather dramatically with a small change in weight but with tire pressure as well . . .
Yes, nothing to do with weight as I said.

I agree that tires are not perfect diaphrams (a balloon comes close), especially narrow motorcycle tires with stiff sidewalls. However, even so the air pressure is typically the primary factor that determines the pressure exerted on the road, even though the sidewalls do carry a substantial part of the load and thus contribute to the pressure on the road.

For a bike 1/2 the weight of an LT to have the same contact area would require that the tire have about half of the air pressure as that of the LT. So, as I said, the key difference is the air pressure in the tire. If you want to compare apples to apples, you need to keep the air pressure in the tires the same for both the LT and the 1/2 LT. If you do this, then the pressure exerted on the road will be roughly the same as the contact patch of the 1/2 LT will be about 1/2 that of the LT.

The article you posted does not address the weight of the bike at all as near as I can tell. It addresses the ratio of contact pressure to tire pressure. And it shows that narrow tires have a greater percentage of the contact pressure due to the load carried by the tire itself rather than the air in the tire. However, it doesn't matter much how the load is transferred to the contact patch. The fact remains that all else being equal (tire pressure and tire stiffness), the contact patch pressure is not a function of the weight of the bike. If you double the bike's weight, you will also double the contact patch area and thus the pressure will remain about the same.
 
1 - 12 of 12 Posts
Top