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opus
Senior Member
66 Posts |
 Posted - 03/28/2017 : 2:03:38 PM
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New tires, new shocks, alignment is good, rear engine bus. Outside and inside 1" feels like it wants to scallop.
Seeing the front end is so light, the tire looks over inflated, yet its not. What do you run for pressure to get the best wear? Our roads here suck so I can see thats an issue too. |
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dferrell
Senior Member
102 Posts |
Posted - 03/28/2017 : 3:34:35 PM
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| We have all rear engine buses with 12R22.5 tires. We run 120psi - same as what the ID plate in the bus recommends. We get decent even wear for the most part. |
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opus
Senior Member
66 Posts |
Posted - 03/28/2017 : 7:40:35 PM
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| Really....interesting. My plate says 115. 12r22.5?? |
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RonF
Top Member
867 Posts |
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bwest
Administrator
United States
3820 Posts |
Posted - 03/29/2017 : 05:35:49 AM
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quote:
Originally posted by RonF
Try this chart from Firestone. Find your tire size, then take your front axle weight, divide it by 2 and go to the top of the chart and that is your pressure. For the rears divide your axle weight by 4. I've been using this for years and have gotten much better tire wear. You will find that with 11R22.5 tires on most conventional buses you will run 85 psi all the way around.
http://commercial.firestone.com/content/dam/bcs-sites/firestone/TBR/load-inflation-tables/mar2015/FS_TBR_load-inflation-tables_web_2014.pdf
Was just about to post this link. I still have people tell me there's no way you can run only 85 psi in a 22.5 tire. lol |
Bryan |
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torque
Advanced Member
Canada
358 Posts |
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RonF
Top Member
867 Posts |
Posted - 03/29/2017 : 07:36:27 AM
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Michelin's on Page 7 run right in line with FireStone, 85 psi for most of my applications.
When I first took over this system and dropped all the pressures to the charts I had many drivers ask me what I did to smooth out the ride. |
US Army retired CMBT |
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opus
Senior Member
66 Posts |
Posted - 03/30/2017 : 10:21:16 AM
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| Found my weight scale, 9000# front 16000# rear. So you were pretty close, 75-80# is whats suggested for my tire. Then, you have to account for ambient temperatures, if you are going to do it right. |
Edited by - opus on 03/30/2017 11:12:26 AM |
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ICBUS07-30
Senior Member
USA
59 Posts |
Posted - 03/30/2017 : 2:59:20 PM
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| The company I work for tells us 100 psi in the front and 85 psi in the rear. |
Formally ICBUS0730
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bwest
Administrator
United States
3820 Posts |
Posted - 03/31/2017 : 04:49:36 AM
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quote:
Originally posted by opus
Found my weight scale, 9000# front 16000# rear. So you were pretty close, 75-80# is whats suggested for my tire. Then, you have to account for ambient temperatures, if you are going to do it right.
My buses weight anywhere from 15k to 20k empty. Add kids and that's another 4k to 7k. Mine are all conventional. |
Bryan |
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RonF
Top Member
867 Posts |
Posted - 03/31/2017 : 05:18:35 AM
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My buses weight anywhere from 15k to 20k empty. Add kids and that's another 4k to 7k. Mine are all conventional.
Bryan
That's why Gross Axle weight rating is used, them maximum amount that axle is designed to carry. That tire pressure with that weight rating takes in account a full load. |
US Army retired CMBT |
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bwest
Administrator
United States
3820 Posts |
Posted - 03/31/2017 : 07:23:36 AM
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quote:
Originally posted by RonF
My buses weight anywhere from 15k to 20k empty. Add kids and that's another 4k to 7k. Mine are all conventional.
Bryan
That's why Gross Axle weight rating is used, them maximum amount that axle is designed to carry. That tire pressure with that weight rating takes in account a full load.
So, what is your GVW? |
Bryan |
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opus
Senior Member
66 Posts |
Posted - 03/31/2017 : 07:40:31 AM
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| 36,000#. Its not a school bus any longer. My weight fully loaded is 25,000# |
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eddo
Advanced Member
USA
311 Posts |
Posted - 03/31/2017 : 10:46:04 AM
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our AZ highway roads used to be complete crap. To help combat front tire wear, I ran a tire with a "coupling groove" on the inner and outer edge. Basically, a real thin extra tread that would take the abuse off the real treads. at least that is what the tire guy told me, lol.
It worked wonders for our front tire wear. Highways are better around here now, so I don't have to worry about it as much. |
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Fastback
Top Member
1500 Posts |
Posted - 03/31/2017 : 11:14:01 AM
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In rural Iowa, I avoid steer tires with the "decoupling grooves" around the outer edges of the tread, they pick up a lot of rocks on the gravel roads then fly out once you get up to highway speeds.
We run 90 lbs in all our 22.5s except for steer axles on front engine transits, 105 in those. |
Why yes, the ORIGinal CHARGER is a Fastback |
Edited by - Fastback on 04/03/2017 04:58:13 AM |
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BigPapa
Advanced Member
215 Posts |
Posted - 04/03/2017 : 11:55:51 AM
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So, are we supposed to use axle rating or actual weight with the chart?
I checked a couple of ours thinking this may be a solution to a couple of issues and the buses I checked showed I need to run 120 front and 80 rear on our buses with 11R22.5's and we have quite a few buses running 255/70R22.5's and according to the chart they won't meet the weight rating for the axles. The buses came from Thomas with this size tire on them. |
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RonF
Top Member
867 Posts |
Posted - 04/03/2017 : 12:44:03 PM
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Axle rating. What bus are you running and what is your axle rates?
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US Army retired CMBT |
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muddywater
Senior Member
USA
50 Posts |
Posted - 04/03/2017 : 4:19:19 PM
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| We've always had one Type D 65 passenger bus here for the twenty years I've been here. 85 psi in front, 90 psi in rear. Used to have lots of cupping problems until I started rotating tires on every annual inspection. |
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BigPapa
Advanced Member
215 Posts |
Posted - 04/04/2017 : 06:09:50 AM
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quote:
Originally posted by RonF
Axle rating. What bus are you running and what is your axle rates?
From what I can find all the front axles are 13,200. Most are Thomas transit FE's with 11R22.5's but we do have some buses, mostly with lifts, running the 255/70R22.5's. |
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RonF
Top Member
867 Posts |
Posted - 04/04/2017 : 06:53:16 AM
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"From what I can find all the front axles are 13,200. Most are Thomas transit FE's with 11R22.5's but we do have some buses, mostly with lifts, running the 255/70R22.5's."
From what I'm reading on the Firestone chart, the 225 tire is the wrong tire for the front of your buses. It's under weight rated. |
US Army retired CMBT |
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BigPapa
Advanced Member
215 Posts |
Posted - 04/04/2017 : 08:28:47 AM
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quote:
Originally posted by RonF
From what I'm reading on the Firestone chart, the 225 tire is the wrong tire for the front of your buses. It's under weight rated.
That's what I was saying, but these buses came from Thomas with those tires on them. Surely, they wouldn't have shipped a bus with under-rated tires. Maybe when they were ordered, way before me, our buyer wanted to stay with the 13,200 axle so all our buses would be the same and the axle is just overkill for that application??? |
Edited by - BigPapa on 04/04/2017 08:30:06 AM |
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bwest
Administrator
United States
3820 Posts |
Posted - 04/04/2017 : 09:54:28 AM
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| My opinion is that you use your actual weight to figure your pressure (actual being what it weighs empty plus students you are hauling). Further, my opinion is that on a 71 passenger conventional you'll never be over 10k "payload". Most days on a regular route you'll be in the 4k to 6k range on "payload". |
Bryan |
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Front Tire Wear
