another tire question

[CDonaldson]

I recently purchased a used 5er, nice shape for it's age, but needs new tires. It is a lightweight trailer, only 21. 5 ft.



I am trying to understand the tire numbers, and want to make sure I am on the right track with what I think I understand about them.



The current tires are 205 - 75 - 15's. Am I correct in assuming the 205 has to do with tire height/diameter, 75 has to do with tire width, and of course the 15 is the rim diameter (no-brainer there).



So, can I go to a 215 or a 225, and will that only affect tire height/diameter?

Anotherwords can I replace this tire with a 215-75-15 or a 225-75-15 tire?



I am thinking that a little more tire height would be better, I do have the clearance between the axles/tires for an increase of an inch per tire. I have yet to research the weight loads of tires. I am alo thinking that the taller tire might also have a greater weight load capability? Also, does it make a difference when looking at trailer tires vrs passenger tires vrs LT tires? All this tire stuff that I have been reading is getting a little jumbled.



A couple years ago I replaced my horse trailer tires with TOYO Light Truck 16" tires. They wear like steel. I was thinking about going to the TOYO's for my trailer. Any thoughts or suggestions would be greatly appreciated. Thanks.



CD

 

[LandShark]

First thing to do is weigh your trailer. Don't go by the sticker. They lie! Get it weighed. Let us know what you find out. We'll have lots of advice for you.



The load capability on the tire is stamped on the side of the tire: both a letter (B,C, D, or E) and a actual weight (2200 pounds, 3042 pounds, etc... ).



I would find a tire that has at least 25% extra capacity, if possible. Many trailers run at close to 100% of rated tire capacity and that is why so many have blow outs.



You can go to any of the tire manufacturers sites to learn more on tire ratings.

 

[EricBu12]

the numbers on the side are the size. 205/75-15



205 is the distance from bead to tread. the 75 is the height aspect. like a lot of those hot rod cars that have a 20" rim and 40 series tire and are very lo profile.



So a 215 or 225 will be bigger but also wider across the tread resulting in more drag. if there is a tire out there like a 205/85-15 then you will be bigger diameter but the same width.



So first thing is to weigh it and find the best tire for the weight. a "trailer service" tire is supposed to be able to dissapate heat better so look for those. a tire called Roadmaster are made by goodyear in canada and for my heavy 5th they do good. but get the weight and the right size tire for it.

 

[CDonaldson]

Thanks guys for the heads up about the weight, that WOULD also shed some light about what would be the right tire. I read and re-read the explinations about how to de-code the tire info. As I understood it the P205 was the width in mm's sidewall to sidewall. The 75 is called an aspect ratio - ratio % of the tread width (P205) that equals sdiewall height. So, going to a 205/85 would make more sense to just get tire height/larger diameter.



Now to find someplace to get the weight check done. Not an easy task living out in the middle of nowhereville!



CD

 

[opjohnny]

Take the 205 part change it to inches take the 75 part change it to % ( it would be . 75). 0. 75 times 205 /25. 4, double that number(you have 2 side walls) plus diameter gives you a rough tire height for that size. Tires very a little from make to make but this will be close. Hope this is understandable.

 

[AKaiser]

Thanks guys for the heads up about the weight, that WOULD also shed some light about what would be the right tire. I read and re-read the explinations about how to de-code the tire info. As I understood it the P205 was the width in mm's sidewall to sidewall. The 75 is called an aspect ratio - ratio % of the tread width (P205) that equals sdiewall height. So, going to a 205/85 would make more sense to just get tire height/larger diameter.



Now to find someplace to get the weight check done. Not an easy task living out in the middle of nowhereville!



CD

P indicates a passenger tire. 205 is the tread width in milimeters.



tire ht = sidewall height (tire width x (2x aspect ratio))+rim dia.



So, to get tire ht in inches from a metric tire (1 inch =25. 4 mm)



tire ht (in) = ((tire width (mm) / (25. 4mm/inch)) x (2x aspect ratio))+rim dia. (in)



Therefore an LT 275/70 R 18 would calculate as follows:



((tire width (275mm) / 25. 4mm) x (2 x . 70))+rim dia. (18 in)= 33. 157 inches



((tire width (275mm) / 25. 4mm= 10. 827 in) x (2 x . 70 = 1. 4))+rim dia. (18 in)= 33. 157 inches



(10. 827 in x 1. 4 = 15. 5) + rim dia. (18 in) = 33. 157 inches



(15. 15 in (tire sidewall ht) + rim dia. (18 in)= 33. 157 inches



Are you thoroughly confused yet?

 

[CDonaldson]

Let's see how confusing the TOYO mfr specs are, easier to just look them up.



current tire is 205/75 R15 = 27. 2 dia / load rated 1598



215/75 R15 = 27. 6 dia / load 1753 - 10mm wider tread (aprox 3/8")

225/75 R15 = 28. 4 dia / load 1874 - 20 mm wider tread (aprox 3/4")



I guess I will also have to take a look at the rims and make sure the rim width is OK with the tread width. The manufacturers handbook/manual actually says that any of these size tires are acceptable, comes standard with the 205's.



CD

 

[WestTN]

You can usually go one size larger on a rim without too much of a problem. If you go further, the center of the tread no longer sits flat on the road and you get excessive wear in the middle. This crowning isn't controlled by air pressure as it was on bias ply tires.

 

[J&LRam]

your present tires are probably ST [special trailer] which are 65 mph max rated. Folks with heavy trailer [8000 + lbs] and travel at interstate speeds avoid these tire and use a LT rated tire that the tire manufactor recommends for a heavy trailer. Your light trailer can use a ST but a LT works better as the ST is 65 mph rated only. If your just an weekender on occasion the STs may work for you. If your hittin' the interstates often and lots of trips a LT 225/75-15 D [65 psi 8 ply rated tire] load range would make a really bullet proof tire for that type of use. Also a LT215/75 or LT 225/75 in a C load range [6 ply rated at 50 psi] will work on that small trailer. Most bad tire problem stories are from folks with a 8000-12000 + lb trailer with 15" ST tires and hittin' the interstate. Most folks in those situations go with a 16" LT235/85-16 E 10 ply rated tires at 80 psi which would be way way overkill in your situation.

JIM

 

[CDonaldson]

Thanks Jim for the info about the ST vrs LT. I went out and checked the tires again they are a P (passenger) radial tire. Their weight rating is 1598lbs.



So, I'm thinking I will look more strongly at the LT215/75 in a C or D load range, that's one size up from stock size that's on there now. I put the TOYO AT's on my horse trailer, believe that was a D weight, could have been an E, have to look. They really have been a good-wearing tire, I have a good 30K on them and they still look like new. My rim is a 5-lug, I have been unable to find a 16" with the small pattern, so I guess I will just get new 15" tires and call it quits. I also have to find a place to buy a spare rim as there is no spare. I find it interesting that someone would drive around without a spare, no wonder you see so many trailers alongside the road standing on a jack, different mentality sometimes.



Thanks for all your info guys.



CD

 

[Grizzly]

First thing to do is weigh your trailer. Don't go by the sticker. They lie! Get it weighed. Let us know what you find out. We'll have lots of advice for you.

The load capability on the tire is stamped on the side of the tire: both a letter (B,C, D, or E) and a actual weight (2200 pounds, 3042 pounds, etc... ).











When you weigh your trailer, weigh it like you are going on a trip, full of water, propane, food and all your other supplies. Get "D" or better load range.



Good thread!

 

[Foil Freak 1211]

a tire called Roadmaster are made by goodyear in canada and for my heavy 5th they do good. but get the weight and the right size tire for it.

I think that Roadmaster's are made by Cooper. That is what my 5er came with. I had two blowouts (on two separate occasions) when they were properly inflated, not at their max weight, and only 3 years old. I replaced the other two tires after my second blow-out. I would not buy Roadmaster's again.



http://www.coopertire.com/html/products/tires_commercial. aspx?page=roadmaster_rm275