Honda Insight Forum banner

1 - 20 of 55 Posts

·
Registered
Joined
·
93 Posts
Discussion Starter #1
Every month for work I have to drive about 1500 miles in a few days. It is LOTS of stop and go around town, with about about 700 miles of freeway. I dont try to get super high milage on these trips because I am in a big hurry, usually driving between 75 and 80 on the freeway.

Normally on these trips I run 45 PSI and get 50-52 MPG. This month because of the rain I ran 35 psi and only got 47-48 mpg. I just thought I would share some real world comparison of MPG vs tire pressure.
 

·
Premium Member
Joined
·
743 Posts
Tyres filled with nitrogen rather than air are much more stable to tire pressure during a trip and loosing air pressure over time. They also keep the tires cooler than with natural air. The bikes hate it but Michelin is developing a fuel saver tire that is cool when driven straith and only get warmer/grippy in turns.
 

·
Premium Member
Joined
·
4,948 Posts
Sorry to pop the Nitrogen bubble but,

Honda has addressed this recently in a Service News article.

_Except_ for _slightly_ lower permeability (smaller loss over time) the difference in a passenger car is zero. And except for a high quality fill (air purged out to less than 1%) which cannot be done by merely adding "pure" nitrogen at the valve stem, even this one "advantage" will be reduced. It does not eliminate the need for a semi annual 2-4 psi topping off of the tire pressure.

Now a in a NASCAR where the pit crew isn't merely wearing gloves for appearance (those tires fresh off a 200 MPH lap will burn you) a pure nitrogen fill makes the all the difference in the world. You'd either have to start off so underinflated to allow for the pressure increase as the tires heated that even a first lap at 100MPH would be difficult. Or risk (and expereince) many tire failures as a result of the overinflation that would result if starting "cold" with sufficient air pressure for a full speed run around the track. Nitrogen "solves" those issues.

Nitrogen better in a passenger car at speeds under 100 MPH? Only if its free. Else you've paid for more than you got.


HTH! :)
 

·
Premium Member
Joined
·
941 Posts
because of the rain I ran 35 psi
Uh, think about that for a minute. Why put more tire surface down and increase your chance of hydroplaning? More pressure reduces the risk of hydroplaning not less. What gets you on top of the water easier, a boogie board or a slalom ski?

Atmospheric air is already 78% nitrogen. Use in passenger tires is a waste of money.
 

·
Registered
Joined
·
232 Posts
While more surface increases the risk of hydroplaning, it will improve grip. Most of the time in rain grip is the issue in teh Insight, not hydroplaning. Depends on road type/condition obviously.
 

·
Premium Member
Joined
·
743 Posts
Uh, think about that for a minute. Why put more tire surface down and increase your chance of hydroplaning? More pressure reduces the risk of hydroplaning not less. What gets you on top of the water easier, a boogie board or a slalom ski?

Atmospheric air is already 78% nitrogen. Use in passenger tires is a waste of money.
The insight tires are already very slim that hydroplaning is not an issue. In rain, less pressure resulting more grip is a good trade-off.

The problem with nitrogen fillings is that the air has to be sucked out first which my dealer didn't. But I could feel that the tire pressure was much more stable with cold tires compared to hot tires and the tire lost much slower air pressure over time which doens't mean you don't have to check it from time to time. :)

More stable air pressure means that you can put more pressure in cold tires to get the desired air pressure with warm tires. This should reduce the roll resistance. The critical question is how long do the tires take to get warm? On a highway, they soon get hot but around town? Maybe the relation of miles running with cold and those running with warm tires is very low. Therefore the whole effect could not be measured and it would be right to say it's a waste of money. :cool:
 

·
Premium Member
Joined
·
941 Posts
If the OP is driving 80mph the last thing they want to do is lower their tire pressure. Sidewall flexing from low pressure and speed are what overheat tires. Higher pressure also enhances handling. At 35psi the tire is going to want to roll over on it's sidewall in cornering or emergency maneuvers and lose grip. You make my argument nayrhyno, if the tread doesn't reach the pavement through the water there is no grip. At 70-80mph hydroplaning does become an issue with any tire. Motorcycle hydroplanes over water#
 

·
Premium Member
Joined
·
1,632 Posts
If the OP is driving 80mph the last thing they want to do is lower their tire pressure. Sidewall flexing from low pressure and speed are what overheat tires. Higher pressure also enhances handling. At 35psi the tire is going to want to roll over on it's sidewall in cornering or emergency maneuvers and lose grip.
35 psi is not low pressure for auto passenger tires. What people have been using for pressures in the Insight for higher fuel economy reasons is considered high pressure. An Insight tire @ 50 psi has less rubber contact with the road compared to a tire @ 35 psi.

A picture is worth a thousand words....Check out the contact area of a properly inflated tire vs the other two options:



JoeCVT = Just your average CVT owner
 

·
Premium Member
Joined
·
941 Posts
That's not a picture, it's an exaggerated illustration. This is just an example of the propaganda the auto manufacturers and tire companies put out to get you to feel you haven't left your living room couch driving down the road and to sell more rubber by having you wear your tires out quicker.
Here is a realworld example, my left front tire with nearly 22K:


The sidewalls on my tires bulge more with less air than with more. Those illustrations are a bunch of hooey. That or they are from the days of bias-ply tires. The steel belts on modern tires don't allow the tire to bulge in the center of the tread. Judging by the track left on my garage floor when my tires are wet they lay down a full tread pattern.
My experience has been very good with 60#, sun, rain, snow and ice. I have more resistance to hydroplaning, better handling, cooler running at high speeds, more even and longer wear, and to top it off lower rolling resistance and thus better gas mileage.

And more realworld experience, (save the we're not driving fully loaded police car arguments, much of this applies to any car): Driving Under Pressure (full article) - CleanMPG Forums
 

·
Registered
Joined
·
642 Posts
Tyres need some flex to generate grip, it seems sensible to run lower when its raining and friction coefficients are better. At 40psi my insight feels like it has very little grip and Ive lost the back end a few times at low speed when its wet.

Tread depth will effect hydroplaning resistance far more than tyre pressure.
 

·
Premium Member
Joined
·
1,632 Posts
That's not a picture, it's an exaggerated illustration. This is just an example of the propaganda the auto manufacturers and tire companies put out to get you to feel you haven't left your living room couch driving down the road and to sell more rubber by having you wear your tires out quicker.
Yep....not an actual picture of a tire....I was just using a common phrase. I used the image as a visual method to convey what I was writing about. I am talking about the contact patch area (the actual area that rubber meets the road)....It only makes sense that the more pressure you put in the tire, the less of a flat spot (contact patch area) you have. Your picture only shows that your tires are wearing evenly and that according to your judgment, the entire width of the tire is in contact with the pavement. However, looking at wet tire marks on pavement does not and can not determine the actual contact patch area.

My experience has been very good with 60#, sun, rain, snow and ice. I have more resistance to hydroplaning, better handling, cooler running at high speeds, more even and longer wear, and to top it off lower rolling resistance and thus better gas mileage.
Why stop at 60 psi then?

That link you gave also claims that tires won't be forced off of the rim with higher pressures but I know that some people in this forum had that happen to them using higher pressure in the OEM Insight tire.

Look I am not opposed to running higher psi than Honda recomendations. In fact, I run at 48 psi on my tires. I am just saying that there are plus and minus factors with any tire pressure but it only makes sense that the higher the pressure, the less of a contact patch area and that can lead to loss of vehicle control.

JoeCVT = Just your average CVT owner
 

·
Premium Member
Joined
·
941 Posts
If you increase the contact patch you lower the weight to contact patch ratio and increase the tendency to float/hydroplane in wet conditions. No?

I agree tread depth will affect hydroplaning resistance as will a tread configuration's ability to raise the weight to contact patch ratio.

Perhaps my near total highway driving miles hasn't led me to push the cornering envelope. I don't disbelieve other owner's experience with the Insight breaking loose it's rearend. I'm certainly having second thoughts about 60# the more pot holes I've run across lately.;)
 

·
Registered
Joined
·
29 Posts
Tyres need some flex to generate grip, it seems sensible to run lower when its raining and friction coefficients are better. At 40psi my insight feels like it has very little grip and Ive lost the back end a few times at low speed when its wet.

Tread depth will effect hydroplaning resistance far more than tyre pressure.
Boy, what you've said is no joke. Is rained in Vegas last week and I was spinning tires away from lights and having the tail sliding quite often. Traction is pretty OK when dry, not so much when wet.
 

·
Premium Member
Joined
·
941 Posts


Thought I'd show that same tire at 32K, getting replaced with some Michelin Energy saver AS this week. If it was summer I might push these a little longer, though I wouldn't feel safe in much rain. Middle of winter, new shoes.
Looks like I might have a little positive camber with that wear on the outside. Wanted to show that 60# does not wear the center of the tread.
 

·
Premium Member
Joined
·
941 Posts
And quirky as they are I'm getting these new Michelins yanked off and going back to the OEM Bridgestones. Worst gas mileage I've ever got in the Insight! Plus I got to experience what a Summer touring tire feels like on snow last night. Between the mileage and the misrepresentation as a all-season tire they are going to take them back or risk my ire. :mad:
 
1 - 20 of 55 Posts
About this Discussion
54 Replies
20 Participants
met-head
Honda Insight Forum
We’re the ultimate Honda Insight forum to talk about Honda’s hybrid car and its fuel economy and specs!
Full Forum Listing
Top