Replacement tires: confused after reading tire forum threads

[uncle_bob]

Originally Posted by Scott S

Tires whose size starts with "ST" were specifically designed to be used on Trailers. Before ST's were made, LT's were used. Either will work but ST's were designed for our usage. Will other tires work? Yes, but perhaps not quite as well, thus the practice of discounting the load rating.

Hi

..... errrr ..... ST's go back a *long* ways. The use of LT's on trailers is a new thing.

Bob

[Tom_T]

Originally Posted by wonderlust87

I have a 1988 airstream excella with a dry weight of 5100 lbs and loaded weight 6400lbs. The current tires I have from the previous owner are:

MCHLN P235/75R15 108T

I know from reading that P (passenger is not recommended) and that LT (light truck) is recommended. I understand that weight plays a role in tire selection and pressure needed.

The 2 tire recs I see the most on the forums are:
1. Goodyear endurance: which do not come in the 15in diameter with the 235 width (and I don’t want to have to buy new wheels to go up to the 16). The dealership told me not to go down in diameter but that’s all that’s offered…
2. the Michelin defender 235/75R/15 XTRA which is an LTX (and not a P, LT, or ST) which makes me concerned because I don’t understand it.

I travel by myself and am just starting to feel more confident towing so I want to make sure I make an educated decision on tires and was having trouble decipher tire lingo as a newbie! Note I WILL be getting a tire pressure monitoring system. Not sure which one, but I’ll do that once I get some safe tires on. Thanks in advance for your input!

wonderlust87 -

You don't say which length & floorplan/layout of `88 Excella you have, nor whether it is single or tandem axle.

I'm guessing that at 5100 lbs dry & your stated 6400 lbs wet/loaded - that your `88 Excella is the 25' with tandem axles - in order to carry the weight of 5100 lbs + 1700 payload (see AS link below) for a max 6800 lbs GTWR - in order to safely divide that between 4 tires.

However, if it's a single axle with that 6800 GTWR - then you may have to go back to what may have originally been 275/75R16 tires & 16" wheels (see the 1988-89 owners manual link below at pgs 264-265).

You should first check in your owners manual for the AS recommended tire size(s), & if you don't have one - you may be able to download one from the AS website like the one below, or by googling for one for sale online.

https://www.airstream.com/wp-content...-manual-75.pdf

>> PS - When I did the AS website documents look-up at the link below - it skips 1987 to 1989 - with 1988 missing - but the above linked scanned manual is copyright dated 1988. So I assume it is the correct one for 1988 as well.

https://www.airstream.com/owners/manuals/product/tt/


You can also use this AS Specs Chart to determine your trailer's weights, or the tag with the larger maximum GTWR - & confirm that it is that 6400 lbs you stated (vs. how much you have it loaded & wet now).

https://www.airstream.com/wp-content...ts-guide-7.pdf


You'll want to size your tires to carry the full rated max GTWR (base + payload) total allowed load with enough rating for either 2 or 4 tires.

You don't have to necessarily size them to that 235 width - because the prior owner probably had to use them in order to get them in the load weight rating in those passenger tires. Either 215 or 225 in ST XXX/75R15 in either D or E load rating are probably adequate - per the load weight rating required.

Passenger tires are generally unsuitable and too light duty for trailer use, & should be avoid using P tires on both trailers & on SUVs & Light Trucks. I would recommend that you change out your P235/75R15 passenger tires ASAP, & replace them with proper ST trailer tires.

(That said for full disclosure - due to the unavailability of ST145R10 trailer tires here in the USA - I've had to use the classic size Mini Cooper tires in P145/80R10 tires for our little 1,000 lbs GTWR 1970 Eriba Puck with it's stock 10" wheels.)

ST tires are specifically designed & made for trailer use with lower rolling friction & stiffer sidewalls to perform best in trailer use, & be easier to tow without the traction of car or truck tires, & the associated heat build up - which while not overheating tires too much, may still cause earlier aging & wear.

Some folks prefer LT tires which are light truck tires with relatively stiff sidewalls, but they still have more rolling resistance (i.e.: traction) because car & truck tires need traction to grip the road & transfer power to move the vehicle.

FYI - Here are some good articles on the ST trailer tires:

https://www.rv.com/archive/rolling-a...-a-tire-guide/

https://www.tirerack.com/tires/tiret...jsp?techid=309


We were recommended the Maxxis M8008 ST Tires for our 1960 Avion T20 by a guy who restores & customizes all sorts of Airstream & other trailers (Uwe Salwender at Area 64 Productions), & they've performed great on our Avion, & for many others with their Airstreams, Silver Streaks, etc.

You can check for the size you need as D or E Load Rating & weight ratings in 15" tires in their chart at the link below. They're sold at America's Tires or Discount Tires (depending on which in your area - both same overall company) & some other tire shops.

https://www.maxxis.com/us/tire/m8008-plus-st-radial/


I also use the Maxxis LT205/70R14 tires for our `88 VW Westfalia CamperGL van, which have proven to be superior rated & better running than the original Michelins which came new with our Westy (we're original owners).

So if you must go to the "LT Darkside" - which I don't recommend - they also have 15" or 16" sizes with adequate weight per tire load ratings for your `88 Excella.

https://www.maxxis.com/us/tire/bravo-series-ue-168/


>> PSS - I'm not a fan of Michelin tires being the holy Grail of any tires - & we own an `88 VW Vanagon Westy, an `85 BMW E30 325e Coupe (both since new), & a `73 Porsche 914-2.0 (2nd owner since 1975) with many sets of Michelin & many other makers' tires on them all over those decades of ownership. Some are good & some are bad tires.

The last 2 sets of factory spec Michelins on our `88 Westy van were crappy & 3 of 4 had tread separations & 1 blow-out within 2000-5000 miles - & the tall narrow track Vanagons are known for higher side stresses, which those Michelins for which they were supposed to be specifically designed.

So I take all of the Michelin worship on here & other car forums with a grain of salt.

IMHO you'll be best off with the Maxxis M8008+ ST tires on your Excella. Also note that most AS dealers do not know anything about the Maxxis ST tires, so they're just recommending what they sell &/or what AS is recommending today.

Another great ST tire option is the Carlisle tires, which are specified by Pete Brock for his Aerovault auto trailers (he designed & raced many top race cars). They are as or more pricey than Maxxis & Michelin, but great tires from what I've heard.

https://www.carlislebrandtires.com/o...dial-trail-hd/

https://www.bre2.net/aerovault.info/


Hopefully the linked articles & documents will be helpful to you in sorting out your trailer tires question.

Good Luck!
Tom
///////

[wonderlust87]

Originally Posted by Tom_T

wonderlust87 -



You don't say which length & floorplan/layout of `88 Excella you have, nor whether it is single or tandem axle.



I'm guessing that at 5100 lbs dry & your stated 6400 lbs wet/loaded - that your `88 Excella is the 25' with tandem axles - in order to carry the weight of 5100 lbs + 1700 payload (see AS link below) for a max 6800 lbs GTWR - in order to safely divide that between 4 tires.



However, if it's a single axle with that 6800 GTWR - then you may have to go back to what may have originally been 275/75R16 tires & 16" wheels (see the 1988-89 owners manual link below at pgs 264-265).



You should first check in your owners manual for the AS recommended tire size(s), & if you don't have one - you may be able to download one from the AS website like the one below, or by googling for one for sale online.



https://www.airstream.com/wp-content...-manual-75.pdf





You can also use this AS Specs Chart to determine your trailer's weights, or the tag with the larger maximum GTWR - & confirm that it is that 6400 lbs you stated (vs. how much you have it loaded & wet now).



https://www.airstream.com/wp-content...ts-guide-7.pdf





You'll want to size your tires to carry the full rated max GTWR (base + payload) total allowed load with enough rating for either 2 or 4 tires.



You don't have to necessarily size them to that 235 width - because the prior owner probably had to use them in order to get them in the load weight rating in those passenger tires. Either 215 or 225 in ST XXX/75R15 in either D or E load rating are probably adequate - per the load weight rating required.



Passenger tires are generally unsuitable and too light duty for trailer use, & should be avoid using P tires on both trailers & on SUVs & Light Trucks. I would recommend that you change out your P235/75R15 passenger tires ASAP, & replace them with proper ST trailer tires.



(That said for full disclosure - due to the unavailability of ST145R10 trailer tires here in the USA - I've had to use the classic size Mini Cooper tires in P145/80R10 tires for our little 1,000 lbs GTWR 1970 Eriba Puck with it's stock 10" wheels.)



ST tires are specifically designed & made for trailer use with lower rolling friction & stiffer sidewalls to perform best in trailer use, & be easier to tow without the traction of car or truck tires, & the associated heat build up - which while not overheating tires too much, may still cause earlier aging & wear.



Some folks prefer LT tires which are light truck tires with relatively stiff sidewalls, but they still have more rolling resistance (i.e.: traction) because car & truck tires need traction to grip the road & transfer power to move the vehicle.



FYI - Here are some good articles on the ST trailer tires:



https://www.rv.com/archive/rolling-a...-a-tire-guide/



https://www.tirerack.com/tires/tiret...jsp?techid=309





We were recommended the Maxxis M8008 ST Tires for our 1960 Avion T20 by a guy who restores & customizes all sorts of Airstream & other trailers (Uwe Salwender at Area 64 Productions), & they've performed great on our Avion, & for many others with their Airstreams, Silver Streaks, etc.



You can check for the size you need as D or E Load Rating & weight ratings in 15" tires in their chart at the link below. They're sold at America's Tires or Discount Tires (depending on which in your area - both same overall company) & some other tire shops.



https://www.maxxis.com/us/tire/m8008-plus-st-radial/





I also use the Maxxis LT205/70R14 tires for our `88 VW Westfalia CamperGL van, which have proven to be superior rated & better running than the original Michelins which came new with our Westy (we're original owners).



So if you must go to the "LT Darkside" - which I don't recommend [emoji41] - they also have 15" or 16" sizes with adequate weight per tire load ratings for your `88 Excella.



https://www.maxxis.com/us/tire/bravo-series-ue-168/





Hopefully the linked articles & documents will be helpful to you in sorting out your trailer tires question.



Good Luck!

Tom

///////

Hi Tom,
I’ve got tandem axles, 4 wheels, 5100dry weight for my 1988 excella. In my manual that came with the RV my only indication on Tires is that you inflate to 50psi and that the number next to tire on the purchase sheet is 0098. The wheels that came from the previous owner are 15ins. I’ll check out the links provided - thank you

[Tom_T]

Originally Posted by wonderlust87

Hi Tom,
I’ve got tandem axles, 4 wheels, 5100dry weight for my 1988 excella. In my manual that came with the RV my only indication on Tires is that you inflate to 50psi and that the number next to tire on the purchase sheet is 0098. The wheels that came from the previous owner are 15ins. I’ll check out the links provided - thank you

You're welcome.

It sounds like you can use either the D or E rated ST225/75R15 - but don't get E rated for your 4 + a spare if you don't need the weight rating, since the 1989 AS Owners manual that I linked at pgs. 274-275 for the 50 psi lists mostly D rated, & 6800 lbs GTWR divided by 4 is only 1700 lbs each tire - but you want some cushion with tandem so that you can still drive/tow with 3 good tires to a safe place or shop to fix or change tires.

Ours being single axle - we run the two #TL00096800 D rated ST225/75R15 rated at 2450 lbs each (+ spare) which we use on our 1960 Avion T20 21'-6" L & only 3000-3500 lbs wet/loaded (no GTWR listed in those days), but we could use the next down "C" rated by weight, but the original Bias Ply Tires back then were 8 Ply - & the D Maxxis are 8 Ply Rated.

So that's another thing that you can look for any Ply Ratings - in a deeper look into the AS 1989 Manual's many pages (index at back lists 2 sections on tires).

If that linked manual covers your Excella, then I'd recommend that you download the full PDF file & print it out on a ream of 3-hole pre-punched copy paper, & put it into a 3-ring binder to keep with your Excella (or have Staples, Kinkos, Office Depot print it for you) - so you have a full manual with you.

We had to download & print our 1960 Avion manual, because ours didn't have it's original one either.

Happy Reading!
Tom
///////

[Bill M.]

My 1988 25’ trailer came with bias ply tires with a load range C rating so knowing the original is not going to help much when purchasing tires now.

[AlbertF]

Originally Posted by uncle_bob

Hi



..... errrr ..... ST's go back a *long* ways. The use of LT's on trailers is a new thing.



Bob

Our 1975 Airstream, according to the label in the trailer, came from the factory with LT 7.00x15 tires.

225/75/15s are similar in overall diameter, but wider. The originals had a 92% aspect ratio.

[richard5933]

Originally Posted by AlbertF

Our 1975 Airstream, according to the label in the trailer, came from the factory with LT 7.00x15 tires.

225/75/15s are similar in overall diameter, but wider. The originals had a 92% aspect ratio.

Did they have ST tires in 1975?

I've tried to find the info online regarding when the ST first appeared on the market, but haven't yet.

I see it included in the Airstream manuals by 1980, but not before.

[lemley]

I’m guessing I have the same trailer. 1988 29 foot Excella. 5700 pounds dry, 6300 wet.

I run Carlisle Radial Trail, ST225/75R15, load range E. I’m quite happy with them.

I just added the TST507 TPMS. Don’t know why I waited so long.

One other word… how old are your axles? This is my second 1988. One of the high priority updates on each was a new set of axles.

[wonderlust87]

Originally Posted by lemley

I’m guessing I have the same trailer. 1988 29 foot Excella. 5700 pounds dry, 6300 wet.

I run Carlisle Radial Trail, ST225/75R15, load range E. I’m quite happy with them.

I just added the TST507 TPMS. Don’t know why I waited so long.

One other word… how old are your axles? This is my second 1988. One of the high priority updates on each was a new set of axles.

I ordered the GY endurance ST225/75R15 the other day based on the combined wisdom of the group.

I didn’t even think about the axles. Thanks for mentioning it. I’m not sure if they’ve been replaced or not. Is there something to look for to see if they need replacement?

I notice that most folks get the tire pressure monitoring system and it looks like all metal valve stems are recommended. Other than asking for all metal stems at discount tire, is there anything else I need to specify about the stems when I get the tires replaced Friday?

[waninae39]

we has been using the the Michelin Defenders E rated LT's for 3 years now
we went from 15" to 16" at the same time. it only raised the As by 1/2 "

[Fungus]

Originally Posted by wonderlust87

I ordered the GY endurance ST225/75R15 the other day based on the combined wisdom of the group.

I didn’t even think about the axles. Thanks for mentioning it. I’m not sure if they’ve been replaced or not. Is there something to look for to see if they need replacement?

I notice that most folks get the tire pressure monitoring system and it looks like all metal valve stems are recommended. Other than asking for all metal stems at discount tire, is there anything else I need to specify about the stems when I get the tires replaced Friday?

Get the tires balanced with the new stems and TPMS on the tire. Ask ahead of time. My DT lost two sensors. Made good though by paying me cash for replacement sensors and comping me a tire all in.

Don’t take your eyes off your trailer when they jack it up. Jack points are critical. Better yet, remove them at home two at a time. Take ‘em in. Bring ‘em back home. Repeat.

[LNBright]

If you have your tire monitors in-hand, they can install them at the time. If not, you can have them installed later. As an AS is a bit big for a garage, the shop had me pull up outside the bay and rolled a jack out, and were fine with me showing them the jack points underneath.

[wonderlust87]

Originally Posted by Fungus

Get the tires balanced with the new stems and TPMS on the tire. Ask ahead of time. My DT lost two sensors. Made good though by paying me cash for replacement sensors and comping me a tire all in.



Don’t take your eyes off your trailer when they jack it up. Jack points are critical. Better yet, remove them at home two at a time. Take ‘em in. Bring ‘em back home. Repeat.

Thanks. I’ll get them balanced. I haven’t ordered the TPMS yet, but decided on the TST 507 this evening, so I’ll have to get that done another time.

I’ll watch them with the trailer and make sure they use the correct jack points. Unfortunately I don’t think my tires are currently good enough to do the 2 trip bit. Should I give them any instruction on the lug nuts? I’ve read up on here that they often aren’t tightened enough..

[uncle_bob]

Originally Posted by lemley

I’m guessing I have the same trailer. 1988 29 foot Excella. 5700 pounds dry, 6300 wet.

I run Carlisle Radial Trail, ST225/75R15, load range E. I’m quite happy with them.

I just added the TST507 TPMS. Don’t know why I waited so long.

One other word… how old are your axles? This is my second 1988. One of the high priority updates on each was a new set of axles.

Hi

The Carlisle tire plant has been "replanted" in town houses. They are now a "who knows who makes them" brand. What you got two years ago may not be what you get today. Do a search for "China bombs" and see what comes up. They are something you want to avoid ....

Bob

[gypsydad]

4th AS over the years; Found the Goodyear Endurance 225-15 ST's to be excellent tires for our AS's. Made in USA. Michelin does not make 15' LT tires anymore which is why you see folks changing wheels to 16', if they want to run with the Micheline LT's; that said, the Goodyear Endurance are less expensive, and they are made for trailer towing; stiffer sidewalls then the LT tires, because a trailer puts more stress on the sidewalls.

Several years ago, I tried to replace my 15" Michelin LT' tires installed on my 25'FC; all I could find were Michelin passenger tires; Michelin had stopped making the 15" LT's. The Defender LTX 15" tires (confusing I know) were not LT rated; I argued with the dealer that the LTX should still work, since I was under the capacity. He reluctantly installed the P rated LTX tires; I could tell the difference immediately on my trip back thru the mountains home in MT...the AS felt mushy in turns; unlike the earlier LT's I had used previously. I am sure the reason was the sidewalls in the P rated tires. My experience...I ended up selling the 25' 4 months later; the new owner was happy with the tires he told me later. I know I could tell the difference. The New 25' FC I had purchased (2014) next, had the GY Marathons...I immediately replaced with GY Endurance as they had just came out...never looked back! I am on my 2nd set of GY E's now with our 28' and very happy.

[CapriRacer]

Originally Posted by uncle_bob

Hi

..... errrr ..... ST's go back a *long* ways. The use of LT's on trailers is a new thing.

Bob

Ah ..... Mmmm .... Not exactly. There is a very complex story here.

First, I have seen ST tires in tire yearbooks from the 1970's. What was unusual was that the sizing of ST tires was in the format of the previous generation passenger car tire sizing. For example: AlphaNumeric (G78-15) I suspect that is because the tire manufacturers wanted to save money using old passenger car tire molds. (Molds are expensive!)

Prior to that, it was common for travel trailers to use the same tires as pickup trucks.

And here is where it gets complex:

P metric tires and LT tires were also introduced in the 1970's. So ST tires and LT tires came into existence at about the same time - but - the ST tires weren't sized like they are today. Part of what happened in that time frame was the realization that folks were getting confused about tire sizing and they introduced that letters to help clear that up.

Now let's talk about the modern era: Since the 1980's it was common for travel trailers (and other trailers) to use ST tires because they were inexpensive compared to what was used on pickup trucks (LT tires). Besides, ST tires had more load carrying capacity compared to their dimensions than LT tires. It wasn't until people started noticing that ST tires had a disproportional amount of failures that people sought out alternatives like LT tires. If that had not happened, we wouldn't be talking about LT tires on trailers.

[suncoasteng]

Originally Posted by uncle_bob

Hi

The Carlisle tire plant has been "replanted" in town houses. They are now a "who knows who makes them" brand. What you got two years ago may not be what you get today. Do a search for "China bombs" and see what comes up. They are something you want to avoid ....

Bob

I have had no problems with any older or newer Carlisle ST tires. I have them on my ski boat trailer, my tri-axle boat trailer and my RV. In fact, of the several thousand miles I put on my trailers each year, the only recurring problem has been roofing nails!

[lemley]

Without knowing the age of the axles a good way to check is by raising the trailer and seeing how much the axles drop.

3” is considered the minimum.

Before replacement mine only dropped about an inch when the trailer was raised.

You may be able to check that when they raise the trailer to replace the tires.

[djarrett]

I have a similar situation as I have a 1968 26 foot with a current tire that is an ST 205/90 R15. I'm only finding "trailer" tires - mostly at farm stores in Nashville, but I want to put an LT All Terrain on. A tire comparison chart recomments 275/35 R15s but I loose an inch and a half of lift and not certain the General Tire AT or BFG All Terrain will fit. Any experience with this "old school" ST 205 tire size? The tire rack chat guy was like ... what? Ha!

[tjdonahoe]

Originally Posted by uncle_bob

Hi

..... errrr ..... ST's go back a *long* ways. The use of LT's on trailers is a new thing.

Bob

Our 1973 25’ avion came with G78 x 15 tires…car tires..….they lasted over 15 years…