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Swapping to 365/70-22.5 on Steer
So we have this different bus now. And I went to the truck stop here to weigh on their CAT scales. I knew it would be bad, 2 slides, 6 8d’s bay 2 right, 20 kw gen bay 2 left:
steer 17240, drive 20820, tag 12160.
I have to run 125psi in steer = bumpy ride
Researched posts from 2010 on a different forum on the subject swap. My takeaway: 1) not enough fender clearance on XL
2) fits on XLII but a little rubbing of the foam on the front of fender well
3) also swap the tag for a spare
4) must change studs and nuts to hub piloted ( current Prevost quote $225 all in both sides)
5) total for wheels, tires, and hardware above, about $3500 ( axle covers extra)
Tire pressure can drop to about 105, allowing for more range flexibility.
With respect to the tag, don’t plan to change it because the 315/80 has a diameter of 42.3” while the 365/70 is 42.5”. So in an emergency I would drive with that much difference. Further, the tag has to skid sideways in a turn, and adding 4” of patch on that axle would increase stress.
Would like comments from those that have done this. And those that chose not to.
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14 Replies
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Oops, I would have a stud piloted to hub piloted problem.
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Dan,
Others may disgree but here is my opinion. First, let’s disregard the current issue of some 365 tires with a splitting ot separation problem between the tread and sidewall.
When you install the 365 tires, jumping through all the hoops required to make the switch you are going to trade some harshness for noise. The bumps that feel harsh now as you go over cracks, expansion joints and bad pavement are going to be loud. I don’t know why but my 315 equipped previous bus went over those road conditions quietly compared to the noise lever the 365 tires make.
Then the bigger issue is not clearances or rubbing but dealing with replacement tires if you have an issue on the road.
First, you will have to replace a 365 with a tire that is available. A 365 wheel is beyond the size listed as acceptable for a 315, but so far if a 365 tire has to be replaced and none are available while traveling the acceptable short term solution has been to take a good 365 off the tag and mount a 315 on the 365 wheel that was on the steer. You won’t be able to do that unless you do steers and tags. You won’t be able to mount a 315 wheel on the steer because you say those are stud piloted.
But even if you do resolve the issue, mount 4 365 tires you still have an overloaded front end unless it is rated for the weight. That means while you solve a tire issue you remain with an issue on air bags, brakes, bearings, etc.
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Thanks Jon, I thought road noise would increase with wider tires. The 911 reminds us of this. The Prevost spec front axle weight rating is 16,500. So we are about 1,000 over. But don’t know what to do about it. Converter placement of the house batteries and generator aggravate this. And we have the less durable independent front suspension. Since these issues would remain, may not mess with tires. Also I haven’t been able to get the front to go up to full height yet. Back no problem. Need to look into valving and air bag size (Mae West).
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Hmm, Dan, our previous four coaches all had 315’s all around.
CC XLI 2 HWH slides
Marathon XLII 1 slide
Marathon H3-45 no slide
Prevost Beaver Xl 40
Our current coach you saw at the Eclipse Rally is a 2000 Marathon XL 40 that the previous owner had converted steer and tag to 365’s
our front axle weighs in at 15,240 lbs We run 96 psi we disagree with the noise issue mentioned above. We pretty much ride like we are driving a marshmallow on a cotton ball, and the noise level is less than our previous coaches but that may also be contributed to Marathons superior insulating installation 😉
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OK, forget the noise.
Let’s talk about availability and how to get back on the road after a tire failure.
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Both my H Marathons are noisier with 365’s vs 315’s. I had the same issue as Dan, had to run 125 lbs in the steers with 315’s and that’s why I changed to 365’s.
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From your experience Tom, which set up do you prefer?
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Boy Jon, didn’t much of a rise out of you. Anyhow, our XDN Grip 2’s on the drive axle drowned out other noises.
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But those XDN’s sure do have traction. We used them on our trucks for a few years and they were fantastic in snow and slop!
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FWIW, The whole 365 conversion is overrated as far as ride & noise. Over the last 18 years , 3 Coaches , 300,000 mi. 4 Sets of Michelin 365 Fronts, Prevost 3 Axle alignments . The only reason to be running 365’s is for the weight ratings. I’ve yet to get close to wearing a set out without the shoulder /edge wearing early . I’ve always run 115 -120 psi attempting to get decent tread wear. I know what my axle weights are. Front axle regularly runs 18,800 – 19,000 … 2 Slide H-345.
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Previously I said the front axle gross weight rating was 16,500. That was taken from the Prevost Owners Manual. Just looked at the data plate riveted to the left wall drivers position. Numbers there are: steer 17,200 125psi, Drive 22,500 90psi, tag 14,000 100psi. So we are still a little over on steer by not so much.
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If I wasn’t heavy on the front Dan I prefer the 315’s, especially in case of a tire problem on the road.
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Thanks for everyone’s input, exactly what I was looking for. Based on it, think I’ll run the 315’s until my own experience convinces me I need to change. The challenge will be micro managing the acceptable pressure range of 125 for the weight but not over 130 per Michelin’s limit. Example: Leave Chicago at Christmas at, say 0 degrees, arrive Naples two days later at 50 degrees plus the heat generated by rolling resistance and I’m over 130. We have all the air pressure we need on board, so why doesn’t some entreprenurial type come up with a hummer inflation system adapted to our rigs? Barb would be an outstanding micro manager. 🙂
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Dan,
All of our tires vary in pressure depending on how much heat they get while we are driving. If you start out at 125 in the cold and get to warmer temps which drive pressures up to 135 (not likely but let’s pretend), you will be returning to the colder temps so it makes no sense to bleed and add air as needed during various segments of a trip.
I would suggest contacting Michelin and get their opinion on this but I suspect you will not be expected to readjust pressures every day.
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