Tires

Topic: Tires (Read 9729 times) previous topic - next topic

Re: Tires

Reply #150 – April 13, 2017, 11:56:47 am

You know our tires are speed-limited to 75mph, right? I'd hate to think you were damaging your tires right off the bat.

Re: Tires

Reply #151 – April 13, 2017, 12:41:33 pm

Tires have a huge safety factor built in and 75 mph rating also covers tire company liability. Big rigs abuse the 75 mph rating all the time but the drivers are professional and are much better able to handle an emergency. Naturally, a blowout at 80 is a lot different than 55. Good video of what can happen to a RV in less than two seconds on YouTube: https://www.youtube.com/watch?v=9LkLeljt4t0

While the tire may not be damaged going 80, a road gator may give you a bite anytime. The guy above was going a lot faster than 55 and pretty typical of what would happen to the majority of RVs at that speed with a blowout.

Pierce

Re: Tires

Reply #152 – April 13, 2017, 08:28:37 pm

The speed limit here is 70mph and I only took the coach to 80 briefly to check for how well balanced the tires feel. I have been a professional racer most of my life, and have over 2 million safe driving miles with Trucks hauling heavy equipment, cranes etc. I know what my limitations are barring a mechanical failure. Pierce is right, big safety margins are built into these tires as well as most equipment. Crawler cranes are rated at 75 percent with a 25 percent margin tipping and structural. I do not advocate exceeding ones own skill set!

Re: Tires

Reply #153 – April 14, 2017, 07:50:48 am

Yikes! Sobering video. Looking at it I wonder if having the toad was a positive or negative factor. It seemed like it was initially working to keep the wheels in line right up to the point when the front end tucked under.

Re: Tires

Reply #154 – April 14, 2017, 08:36:57 am

" Looking at it I wonder if having the toad was a positive or negative factor. "

That is entirely dependent on how the braking system functions on the toad relative to the coach. The toad could be used as an anchor to help keep coach in a straight line, however, in most cases the weight of the toad just adds to a loss of complete equilibrium, not good. Most of the time in racing, there is an old saying, when in doubt gas it for good reason although, counter intuitive to most.

Re: Tires

Reply #155 – April 14, 2017, 10:42:26 am

Count the tenths of a second in the slow motion of the tire failure. One second later, it's way too late to keep it on the highway. He had to turn the wheel hard to the right in several hundreds of a second and at 80 mph, he was light years too slow.

I had the exact same blowout years ago southbound on I-5 in California's Central Valley. The tires were only a month old. It made a funny noise each rotation for about a half second and then a huge bang right below me. I was in the fast lane at about 65 mph and it instantly headed toward the center divider. It really only moved a couple of feet before I had a lot of correction in the wheel. Just lots of tire noise after that. I got it stopped pretty quickly on the shoulder but the tire was in small pieces after that.

In case anyone is wondering, there is no time to even contemplate using the brakes. It's steering input that happens way before anything else. The nice truck blowout video on the straight and level highway is wishful thinking. Blowouts can happen on off ramps, turns, mountain roads with downhill turns. Each case is unique. One Foreforum member bought a coach that had a blowout on a curve and went down the side of a hill. After getting pulled out, he put a back tire on the front and drove across Mexico with only one tire on one side in the back. Tires DO have a pretty good safety margin to have survived this. Why would you do this???

Pierce

Re: Tires

Reply #156 – April 14, 2017, 11:08:57 am

I had the front right blow out on the '81 on HWY. 14 in Mojave. It was not so much counter steer as hold my line when it popped. Until getting slowed down, I didn't use the brakes. I was towing my Grand Cherokee with the brake buddy.

Re: Tires

Reply #157 – April 14, 2017, 12:14:23 pm

Quote from: craneman – April 14, 2017, 11:08:57 am

I had the front right blow out

We had the same thing happen. It was so noisy, I thought something had let go in the whole front end! Same deal, no brakes, just found a (sorta o.k.) place to pull over. I was sticking out in the lane a little, called for assistance and put the markers out. Cop pulled behind, looked at the trashed tire, and said, "you are one lucky driver."

Re: Tires

Reply #158 – April 14, 2017, 12:38:45 pm

Quote from: John and Stacey – April 12, 2017, 12:07:21 pm

John,
The Toyo's I put on mine were Toyo M177's, 295 75 22.5 H rated. Paid $400.00/tire in Sealy TX. Have not been on a real trip yet. Going to Kerrville Sunday for a week. Will give an update when we return.

John

Hi John,
just got new TOYO's all round (Same size) as well. From Lampasas Tire to the house they road nice. May make a trip to Port A in May so will have a better idea about their performance. Interested to hear how your Kerrville trip goes.
Safe travels,
Chuck

Re: Tires

Reply #159 – April 21, 2017, 10:03:07 pm

Replaced the 7 year old Michelins today, With toyos , initial impression is that they are quieter and definitely less "float " on steering , I can only assume this is due to stiffer sidewall .
Thanks to everyone for their input

Re: Tires

Reply #160 – April 21, 2017, 10:53:22 pm

On my recent trip to NAC and back I weighed my 2001, U320 coach and Toad at a nice new scale in Casper, WY for $9. I came up with a front axle weight of 12,860lb and the rear (no Tag) 19940. That is a fully equipped coach on the road with full fuel and ready to go on a voyage. The Toad (Daihatsu Rocky) was 3020lbs.
I run Michelin 275/80 22.5, LRH tires. With those weights I should run the front at 105psi and the rear at 90psi according to the FT chart.
I had been running 100psi cold on the front and 95psi cold on the rear. NOT CORRECT as I did not take into consideration the heat build-up while running. My fronts were showing 120psi on the TPMS and if you look at the Alcoa rims they are rated only for 120psi so I was on the upper limit.
So the answer is to have a cold pressure that gives me 105psi Front and 90psi Rear, for my weights, on the road. My cold pressure is about 82psi. on the front and 80psi on the rear.
Others may disagree and with different tires there will be a variation, as will different weights of course. But I am a lot closer than I was before and it steers a bit better.
Next challenge is to check to alignment?? That is next weeks job.
Speedbird 1

Re: Tires

Reply #161 – April 21, 2017, 11:00:32 pm

Quote from: speedbird1 – April 21, 2017, 10:53:22 pm

On my recent trip to NAC and back I weighed my 2001, U320 coach and Toad at a nice new scale in Casper, WY for $9. I came up with a front axle weight of 12,860lb and the rear (no Tag) 19940. That is a fully equipped coach on the road with full fuel and ready to go on a voyage. The Toad (Daihatsu Rocky) was 3020lbs.
I run Michelin 275/80 22.5, LRH tires. With those weights I should run the front at 105psi and the rear at 90psi according to the FT chart.
I had been running 100psi cold on the front and 95psi cold on the rear. NOT CORRECT as I did not take into consideration the heat build-up while running. My fronts were showing 120psi on the TPMS and if you look at the Alcoa rims they are rated only for 120psi so I was on the upper limit.
So the answer is to have a cold pressure that gives me 105psi Front and 90psi Rear, for my weights, on the road. My cold pressure is about 82psi. on the front and 80psi on the rear.
Others may disagree and with different tires there will be a variation, as will different weights of course. But I am a lot closer than I was before and it steers a bit better.
Next challenge is to check to alignment?? That is next weeks job.
Speedbird 1

Tire pressures are supposed to be set cold. They will always read high when hot. Fronts on my crane cold are 110 I get over 130 0n a very hot day.
Page 24 says do not exceed cold pressures marked on the wheel

https://www.arconic.com/alcoawheels/catalog/pdf/2017_service_manual_english.pdf

Re: Tires

Reply #162 – April 21, 2017, 11:15:54 pm

Quote from: cubesphere – April 14, 2017, 08:36:57 am

" Looking at it I wonder if having the toad was a positive or negative factor. "

That is entirely dependent on how the braking system functions on the toad relative to the coach. The toad could be used as an anchor to help keep coach in a straight line, however, in most cases the weight of the toad just adds to a loss of complete equilibrium, not good. Most of the time in racing, there is an old saying, when in doubt gas it for good reason although, counter intuitive to most.

Funny you should say that, on a motorcycle say the same "when in doubt, power out" not quite sure how that works on a rear heavy coach with heavy rear brake bias. One thing for sure experience isn't in textbooks, and unfortunately only one way to get it.

Re: Tires

Reply #163 – April 22, 2017, 12:47:00 am

Quote from: speedbird1 – April 21, 2017, 10:53:22 pm

On my recent trip to NAC and back I weighed my 2001, U320 coach and Toad at a nice new scale in Casper, WY for $9. I came up with a front axle weight of 12,860lb and the rear (no Tag) 19940. That is a fully equipped coach on the road with full fuel and ready to go on a voyage. The Toad (Daihatsu Rocky) was 3020lbs.
I run Michelin 275/80 22.5, LRH tires. With those weights I should run the front at 105psi and the rear at 90psi according to the FT chart.
I had been running 100psi cold on the front and 95psi cold on the rear. NOT CORRECT as I did not take into consideration the heat build-up while running. My fronts were showing 120psi on the TPMS and if you look at the Alcoa rims they are rated only for 120psi so I was on the upper limit.
So the answer is to have a cold pressure that gives me 105psi Front and 90psi Rear, for my weights, on the road. My cold pressure is about 82psi. on the front and 80psi on the rear.
Others may disagree and with different tires there will be a variation, as will different weights of course. But I am a lot closer than I was before and it steers a bit better.
Next challenge is to check to alignment?? That is next weeks job.
Speedbird 1

All the tire charts are for cold tire pressure, not for hot after driving.

Re: Tires

Reply #164 – April 22, 2017, 02:31:42 am

My point was not to state the obvious (for some) but to show the numbers from a basic level as related to any similar FT coach of about the same weight.
From the forum it has been fairly clear to me that few have any idea of the weight of their coach so my numbers were to give some idea and to start at the beginning!!!
Speedbird1.

Re: Tires

Reply #165 – April 22, 2017, 07:46:16 am

Quote from: speedbird1 – April 21, 2017, 10:53:22 pm

I run Michelin 275/80 22.5, LRH tires. With those weights I should run the front at 105psi and the rear at 90psi according to the FT chart.

So the answer is to have a cold pressure that gives me 105psi Front and 90psi Rear, for my weights, on the road. My cold pressure is about 82psi. on the front and 80psi on the rear.

Others may disagree

"Others" include the tire manufacturers, RV Safety, Escapees' Smart Weigh, etc.

As others have stated, your cold pressures in the second paragraph are way too low (20% or more if you are only inflating to 80 psi!). Follow the tire manufacturer's recommendation. You are otherwise risking serious sidewall damage and a blowout.

BTW, the Foretravel chart is for the OEM tires that were installed on your coach, which are no longer made. Be sure to use the most current inflation tables for your tire size and load range. They are slighly different.

Re: Tires

Reply #166 – April 22, 2017, 08:48:56 am

And, if you have a 20 PSI pressure rise (unless you had an extreme ambient temperature swing), it is quite likely you are running insufficient pressure.

An underinflated tire flexes more, which creates HEAT which makes for a larger PSI change.

And, as all have stated, 100% of the tire manufacturer's inflation tables are for COLD PSI. Cold is defined at "before driving" at whatever ambient temperature is.

Re: Tires

Reply #167 – April 22, 2017, 09:03:52 am

Quote from: speedbird1 – April 21, 2017, 10:53:22 pm

............... "With those weights I should run the front at 105psi and the rear at 90psi according to the FT chart"...

***Yes, correct - that is the COLD tire pressure to use according to the tire industry, every major coach builder, car manufacturer, trucking industry, etc. ***

....................."I had been running 100psi cold on the front and 95psi cold on the rear. So the answer is to have a cold pressure that gives me 105psi Front and 90psi Rear, for my weights, on the road...........My cold pressure is about 82psi. on the front and 80psi on the rear"......

***Incorrect. That is the wrong answer according to tire industry experts across the board, and all vehicles manufacturers***

Speedbird 1

Just like with cars and over the road trucking, tire pressures are ALWAYS set cold -- to the recommended charts and/or manufacturer guideline.

Yes, the pressure does increase substantially running down the road. That was already taken into consideration by the tire manufacturer, the wheel manufacturer, the coach builder, and every other type motorized vehicle running down the road manufacturer.

You are substantially and dangerously under inflated.

Looking at your weight versus pressure, with your load range H tires, you need 105 front and 85 rear COLD pressures (minimum, another 5 psi for margin is what many of us do).
See bottom link for newest chart of weight/pressure.

https://www.michelinb2b.com/wps/b2bcontent/PDF/RV_Tires_Brochure.pdf

http://www.rvtirepressure.com/assets/images/extrapages/Michelin_Rv_Load_Inflation.pdf

Re: Tires

Reply #168 – April 22, 2017, 09:27:06 am

Thank you 7880,

That chart is much different from the one that I was given by FT and my pressures will be adjusted to reflect the difference.
Again the value of this forum. Thank you all.
Speedbird 1.

Re: Tires

Reply #169 – April 22, 2017, 11:02:54 am

RV and tire companies list pressures that will give a comfortable yet safe ride. The last thing they want is a competitor that offers a softer ride.

Pierce

Re: Tires

Reply #170 – April 23, 2017, 09:16:58 am

Speedbird....sorry mised you in Nac, glad went well.

Nothing to add to this thread but to reassure you....my weights are very similar to yours so we same. For tires I start cold at 108/90 psi. Not unusual I use 110/90.

Perhaps you have seen variation in the inside and outside duals at times. I recall a thread says it can happen due to heating differences during the day. Not much different but enough my gauge could show it.

By the way, Brian, i was having some trouble getting to the 110 at times. The air chuck was the problem...got a straight in chuck rather than angled and airing up front became easier.

Cheers, safe travel to the last best place

Re: Tires

Reply #171 – April 23, 2017, 09:42:24 am

Quote from: craneman – April 21, 2017, 11:00:32 pm

Tire pressures are supposed to be set cold. They will always read high when hot. Fronts on my crane cold are 110 I get over 130 0n a very hot day.
Page 24 says do not exceed cold pressures marked on the wheel

https://www.arconic.com/alcoawheels/catalog/pdf/2017_service_manual_english.pdf

Yup

Re: Tires

Reply #172 – April 23, 2017, 11:20:48 am

Quote from: Michael & Jackie – April 23, 2017, 09:16:58 am

got a straight in chuck rather than angled and airing up front became easier.

Where did you get it?

Thanks,

Trent

Re: Tires

Reply #173 – April 23, 2017, 11:33:44 am

Quote from: craneman – April 21, 2017, 11:00:32 pm

Tire pressures are supposed to be set cold. They will always read high when hot. Fronts on my crane cold are 110 I get over 130 0n a very hot day.
Page 24 says do not exceed cold pressures marked on the wheel

The Alcoa wheels are forged aluminum and very tough. The maximum pressure is stamped on the wheel and has a huge margin of safety. Forged wheels don't chunk off like cast wheels and just bend. Our U300 Alcoas are stamped 120 psi cold. This is higher than any maximum recommended cold tire pressure for our sized tires I have seen. Bottom line is to check and adjust pressures cold and don't worry about the pressure later in the day no matter how hot the road or weather is.

Heat is the enemy of tires and the more the tire flexes, the hotter it gets. Dropping pressures on a hot day will cause the tire to heat up more and make it more susceptible to damage or failure.

Pierce

Re: Tires

Reply #174 – April 23, 2017, 02:36:59 pm

Trent, I got it from Kelly Truck Stop, a supply parts outfit out of Nac. But they seem available too at NAPA for I have now gotten a straight in gauge as well and find both work better for me. The chuck was the best find for the higher pressure versus the auto tire chuck. Had wondered why Herman Power could more easily get their chuck to fill the tire, they showed me the straight in version they use but did not sell them.

mike

Affiliate Notice