| Author |
Message |
Peter E (Sdibaja) (67.117.218.28)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 03, 2004 - 1:06 pm: | |
Getting ready to hit the road for Las Vegas, decided to check the web and find the propper MINIMUM tire pressure for the Bus, a 4905 with 12R22.5 Bridgestone rib tires.
http://www.trucktires.com/us_eng/technical/loadinfl/table04.asp
according to this...
with 9060 pounds on my front axle (9060/2=4530 each) 4940 max for singles is 70 PSI
with 15180 pounds on my rear axle (15180/4=3795 each) 4780 max for duals is 70 PSI
I can bleed all the air pressure down to 70 pounds!
Man, I am going to be riding on Silk!
even at Max load I should not need more than 75 PSI on the rear and 95 PSI on the front...
Pays to read up...
Peter |
Gary Carter (68.25.50.209)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 03, 2004 - 1:28 pm: | |
And added benifit to correct tire pressure is much better handling. |
Tom Caffrey (Pvcces) (65.74.65.65)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 03, 2004 - 10:35 pm: | |
We tried lowering tire pressures to 90 fronts and 80 rears on our 4106 because we were encouraged to do that by several people. While we noticed a softer ride, we also noticed a drop of slightly over 1 mpg from near 10 to the high 8 range.
We increased the pressures up to 110 fronts and 100 rears and are getting near 10 again. We chose to continue with the higher pressures. Our coach runs 9300 fronts and 17300 rears and we are running Goodyear Unisteel II 12R22.5 tires.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
Larry (208.18.102.8)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 04, 2004 - 9:58 am: | |
Tom,
Did you notice any improvement as to drive-ability, such as tracking, wondering with those higher pressures ? |
DonTX/KS (66.82.9.59)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 04, 2004 - 1:57 pm: | |
Ya gotta be careful with them charts. Some have a little footnote of adding say 10% to the pressures for speeds over 60mph, etc.
Also, different manufacturers have different pressures for their tires, one pressure don't always fit all. |
Tom Caffrey (Pvcces) (65.74.65.65)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 04, 2004 - 10:07 pm: | |
Larry, there was no improvement that I noticed, but it's entirely possible that there was some improvement. We didn't make any effort to objectively gauge handling.
To me, the fact that I didn't notice the difference tells me that these coaches are engineered to accommodate the softer ride without messing up the handling.
One of the reasons that I want the higher pressures is for the greater margin between the intended and the unsafe pressures. I feel that it improves my odds of catching a tire losing air before I lose the tire.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
DonTX/KS (66.82.9.44)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 04, 2004 - 10:57 pm: | |
That sounds like condeming the inflation charts and just "doing it my way". Surely you don't advocate everyone ignoring the inflation/load tables for tires, do you? |
Tom Caffrey (Pvcces) (65.74.65.65)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 04, 2004 - 11:48 pm: | |
Don, we're well within the maximum cold inflation pressures marked on the tires. Also, Les Schwab tire people favor the higher pressures for safety.
We tried to consider all the information available so that we would make a good choice. Our choice of pressures was made by looking at both the sidewall markings and the charts.
We are not condeming the charts at all.
Tom Caffrey PD4106-2576
Suncatcher |
DonTX/KS (66.82.9.68)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 05, 2004 - 9:34 am: | |
I was unable to find a single Les Schwab person that would admit to "favor(ing)higher pressures for safety"
They assured me that the sidewall pressures are ONLY for maximum loading as it states on the tire, and that each tire manufacturer recommends the proper inflation based on load, and that they indorse those charts.
Do you have a name or number of that "Les Schwab tire person" that made such recommendations? |
Tom Caffrey (Pvcces) (65.74.65.65)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 05, 2004 - 8:03 pm: | |
Don, I can't tell you the name of the person that I talked to, but it was the Burlington, WA store about a year ago. I'm uncertain, but I seem to recall some comments along the same line in either the Walla Walla or the Dalles store.
I gather that you are saying that removing some load from an operating tire with all other conditions remaining the same will somehow render it less safe or increase its wear.
I haven't seen anything that would make me believe that, yet. I'll try to keep an open mind on the subject, however. I have been watching for some sign of tread wear, but haven't seen anything, yet.
I figured that there was at least a possibility that the recommendations might favor increased replacements of the tires. Certainly, if there is any looseness in the suspension, soft tires will tend to mask it.
How about something a little more clearcut than the tire makers' charts, such as a warning not to exceed the recommended pressures by some value or percentage?
Tom Caffrey PD4106-2576
Suncatcher |
DonTX/KS (66.82.9.67)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 05, 2004 - 8:37 pm: | |
"I gather that you are saying that removing some load from an operating tire with all other conditions remaining the same will somehow render it less safe or increase its wear.
I haven't seen anything that would make me believe that, yet. I'll try to keep an open mind on the subject, however. I have been watching for some sign of tread wear, but haven't seen anything, yet."
Well, I agree the charts and the manufacturers don't actually SAY that in those words, but of course there would be no reason to put the work into the charts if they intended to just run the sidewall pressures. Obviously a tire inflated to more than the load and speed indicated as "correct", would have to be considered "overinflated" by any reader. There are warnings about overinflation, causing wear (and blowouts), but as you say, they are vague about just how much over the load inflation becomes officially overinflated.
The easy way to solve the problem is as I did, just build the darned thing so overweight that sidewall pressure is barely enough! |
Tom Caffrey (Pvcces) (65.74.65.65)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 06, 2004 - 6:00 pm: | |
Then who would I get to pay the fuel bill? -grin-
I have to admit that your solution has simplicity going for it!
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
dougthebonifiedbusnut (24.62.99.43)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 06, 2004 - 9:23 pm: | |
Hey All,
couldnt agree with Peter more. One of the things I think people are forgetting is the fact that at over 100 psi those tires are hard as a rock and the pounding that the suspension is taking is tremendous. With the reduced pressure, the shock that the suspension is recieving is greately reduced, by far a more faverable condition.
Also if im reading Tom correctly he opted for the higher pressure to gain 1 mile per gallon. |
Johnny (4.174.112.38)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 07, 2004 - 9:45 pm: | |
Looked at another way, he raised the pressure for an increase in fuel mileage of about 10-15%. |
Peter E (Sdibaja) (67.117.218.28)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 10, 2004 - 6:59 pm: | |
well, this caused quite a stir!
I don't plan to ever run them rock hard again (I used to run at 110). Just got back... ran 80 fronts, 75 rears (5 psi over chart pressures).
One week on the road, about 1200 miles, some warm weather (85) some cool (45) mostly interstates, some secondary... an hour ot two of rain.
it rode a bit smoother, not much.
handeling, mileage, road noise, etc. no difference.
the tires did not get warmer than usual either.
Peter |
Jerry Liebler (165.121.33.47)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 17, 2004 - 8:56 pm: | |
I'd like to see the experiment that justifies the statement 'over inflation increases the risk of blow-outs' where the sidewall rating is not exceeded. The risk of blowouts must be less at reduced load regardless of pressure, heat is the enemy. A bit more wear on the center of the tread is the only negative to modest over inflation & if this gives better fuel economy go for it. Who has worn out a set of tires on a bus conversion anyway, they always die of old age instead. Regarding the comment about suspension wear the only wear item is the shocks and I still think the economics strongly favor the overinflation for fuel economy. If it handels well enough I'd wager inflation to the sidewall rating is the most economical way to go.
Regards
Jerry 4107-1120 |
DonTX/KS (66.82.9.68)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 17, 2004 - 9:56 pm: | |
Don't blame me! I did not do the "experiment", I only copied what the tire manufacturers said, they all may well be wrong and you may well be right. Until you finish your experiment, I will go with the manufacturer. |