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Author Topic:   Changing Tire Size

floater88 posted 08-04-2015 06:41 AM ET (US)
I'm finding it difficult to find the same size tires and rims for my trailer. I currently have 215-75R14 Load Range C tires. I'm noticing squishing of the side walls when towing. Air pressure is set to just under maximum. I'd like to get some new tires as I am planning on some highway trips and these tires are from 1996. What other size of tires could I get? I have about two-inches of room under the fenders with this size.
Jefecinco posted 08-04-2015 08:40 AM ET (US)
Tire Rack: Goodyear Marathons $85.58 for your exact replacement tire. Try a Bing search for several others.
Butch
jimh posted 08-04-2015 09:47 AM ET (US)
While not an expert, I believe the tire size notation is as follows. For the example
215 75R14
the interpretation is
215 = width of tire
75 = profile of tire
R = radial
14 = wheel size
You can find fatter or thinner tires, such as
205 75R14
225 75R14
Or tires with a different profile, such as
205 70R14
215 70R14
225 70R14
Or tires with bias belts instead of radial belts
215 75D14
The size you presently have seems to be a very common size in boat trailer tires. My experience is that trailer tires are not kept in stock at local stores and often have to be ordered from a regional distributor by the local store.
contender posted 08-04-2015 01:13 PM ET (US)
jim is correct about the tire sizing, 215 width, 75 height, 14 rim size...If you want a taller tire try to fine something like a 225 80/85 R14...letters on the tires tell you that they aree a radial and look at the smaller letter for the load. I think trailer tires should be a c or d load....
Marko888 posted 08-04-2015 02:13 PM ET (US)
I bought the Goodyear Marathons in 215/75 R14 C in 2013 and would suggest trying a different brand as I'm not that happy with them. They're made in China, run quite hot (in the PNW) and even when inflated to 50 psi there is a lot of sidewall flex and bounce. I've weighed my Outrage 18 and trailer and the total axle weight was 2750 pounds.
They are cheap, but I got what I paid for. I will try a different brand next and will also go for load range D.
Jefecinco posted 08-04-2015 04:50 PM ET (US)
Due to their construction radial tires by design have more sidewall flex than do bias tires. Some think this is a good thing as it provides a softer ride to the load. I agree this can be a good thing as long as the tire rating is not exceeded.
Goodyear Marathons tend to get mixed reviews.
I personally change to radial LT (light truck) tires as soon as the first replacement set is due if my size requirement is available. My reasoning is that LT tires are superior in almost every respect to trailer tires.
Butch
Ridge Runner posted 08-04-2015 11:21 PM ET (US)
I have had excellent results towing long distances (NJ to FL - 4 times a year) with Kumho Radial 875's. The are one of the only D load rated and 99 MHP speed rated tire.

Kumho does not use the publish conventional profile sizing so you would have to measure the sidewall of your current tires.
Here is the spec -
Tire Size - 205R14C
Ply Rating / Load Range - 8/D
Rim STD (inch) - 5.50
Rim APP (inch) – 6.50
Overall Dia (inch) – 27.0
Section Width (inch) – 8.2
Static Load Radius – 12.5
Max Load (lbs.) @ Cold Inflation Pressure (psi) Single – 2,271lbs @65 psi
RPM - 774
Tire Weight – 27lbs
The D load rating will have stiffer sidewalls.
You can purchase them from tirerack.com at ~$129.00 per tire.

floater88 posted 08-05-2015 12:28 AM ET (US)
Great info. I was thinking of going with truck tires as an upgrade because my trailer has only one axle and the Revenge 20 wt, with all my salmon tackle onboard including a 15 hp kicker and two batteies, adds up the weight. Thanks
EJO posted 08-07-2015 01:55 PM ET (US)
There are I think two good trailer parts and tire supply companies on the net that can fill your request from stock. An LT type will do fine. Radials have more side wall flex. Do you need the wall height and profile of 75? A lower profile height will automatically give you less flex. Most performance car tires don't have 75 profiles but more likely 60 or less. If you have not bought any tires, look at http://www.easternmarine.com/Heavy-Duty-LT-Truck-Trailer-Tires-Only/ or http://recstuff.com/14-Inch-Trailer-Tires.aspx
Good luck.
deepwater posted 08-08-2015 01:09 AM ET (US)
What do you have on the trailer?
jimh posted 08-08-2015 07:29 AM ET (US)
I think my trailer has 14-inch radial tires. I can't recall the width and profile.
mb159 posted 08-14-2015 02:52 PM ET (US)
X 2 on the Goodyear Marathons.. just had to replace older tire that shredded a fender when it blew. Marathon is a steel belted tire that actually runs cooler than bias ply. VERY happy with them
Don SSDD posted 08-16-2015 07:59 AM ET (US)
215 is the width in MM
75 is the height of the rubber as a percentage of the width.
14 is the rim size in inches.
Using those numbers, you can calculate the height of the tire by converting the 215 MM to inches= 8.46 x 0.75=6.345 inches (X2 for the tire height twice)= 12.69 inches + rim size 14= 26.69 inches.
You can easily calculate the height of any tire using this math. You can set it up in excel and quickly calculate tire sizes for comparison purposes.
Tire Height RIM Tread Width Aspect
26.696825 14 215 75
This is the excel formula where A is the solution, B rim, c tread width, and d the aspect ratio.
=B2+(2*((C2*0.03937)*(D2*0.01)))
I find 14 inch tires are getting very hard to find, you might be better going to a 15 inch rim and even raising the fenders a bit if you can do that. Since 14 inch tires are getting hard to find, you may also be buying a "new" tire that was made a couple of years ago. Buy from a high volume place, more likely to get a fresh tire. There is a date code on the sidewall of all tires, just google decoding those numbers.
I would say more sidewall is good, more rubber to dissipate heat? More rubber to squirm when turning or cornering. Take a look at highway tractors and trailers, nice tall rubber and fairly narrow.
With stiff sidewalls and high tire pressures, the LT tires would be good. I don't think the boat trailer tyre tires are very high quality.
Don
n1ywb posted 08-16-2015 09:58 AM ET (US)
It's important for any pneumatic tire to flex somewhat so there is a "contact patch" between the road and the tire. If the tire didn't flex at all, then the only contact would be along an infinitely thin line and traction would be very low. Also shock absorption is one of the main reasons why pneumatic tries are so widely used. So it's normal to see a bit of a bulge
EJO posted 08-18-2015 01:13 PM ET (US)
Don made a point about buying new old tires. Read this article http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11 and familiarize yourself with the code so you won't be taken.

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Author	Topic: Changing Tire Size
floater88	posted 08-04-2015 06:41 AM ET (US) I'm finding it difficult to find the same size tires and rims for my trailer. I currently have 215-75R14 Load Range C tires. I'm noticing squishing of the side walls when towing. Air pressure is set to just under maximum. I'd like to get some new tires as I am planning on some highway trips and these tires are from 1996. What other size of tires could I get? I have about two-inches of room under the fenders with this size.
Jefecinco	posted 08-04-2015 08:40 AM ET (US) Tire Rack: Goodyear Marathons $85.58 for your exact replacement tire. Try a Bing search for several others. Butch
jimh	posted 08-04-2015 09:47 AM ET (US) While not an expert, I believe the tire size notation is as follows. For the example 215 75R14 the interpretation is 215 = width of tire 75 = profile of tire R = radial 14 = wheel size You can find fatter or thinner tires, such as 205 75R14 225 75R14 Or tires with a different profile, such as 205 70R14 215 70R14 225 70R14 Or tires with bias belts instead of radial belts 215 75D14 The size you presently have seems to be a very common size in boat trailer tires. My experience is that trailer tires are not kept in stock at local stores and often have to be ordered from a regional distributor by the local store.
contender	posted 08-04-2015 01:13 PM ET (US) jim is correct about the tire sizing, 215 width, 75 height, 14 rim size...If you want a taller tire try to fine something like a 225 80/85 R14...letters on the tires tell you that they aree a radial and look at the smaller letter for the load. I think trailer tires should be a c or d load....
Marko888	posted 08-04-2015 02:13 PM ET (US) I bought the Goodyear Marathons in 215/75 R14 C in 2013 and would suggest trying a different brand as I'm not that happy with them. They're made in China, run quite hot (in the PNW) and even when inflated to 50 psi there is a lot of sidewall flex and bounce. I've weighed my Outrage 18 and trailer and the total axle weight was 2750 pounds. They are cheap, but I got what I paid for. I will try a different brand next and will also go for load range D.
Jefecinco	posted 08-04-2015 04:50 PM ET (US) Due to their construction radial tires by design have more sidewall flex than do bias tires. Some think this is a good thing as it provides a softer ride to the load. I agree this can be a good thing as long as the tire rating is not exceeded. Goodyear Marathons tend to get mixed reviews. I personally change to radial LT (light truck) tires as soon as the first replacement set is due if my size requirement is available. My reasoning is that LT tires are superior in almost every respect to trailer tires. Butch
Ridge Runner	posted 08-04-2015 11:21 PM ET (US) I have had excellent results towing long distances (NJ to FL - 4 times a year) with Kumho Radial 875's. The are one of the only D load rated and 99 MHP speed rated tire. Kumho does not use the publish conventional profile sizing so you would have to measure the sidewall of your current tires. Here is the spec - Tire Size - 205R14C Ply Rating / Load Range - 8/D Rim STD (inch) - 5.50 Rim APP (inch) – 6.50 Overall Dia (inch) – 27.0 Section Width (inch) – 8.2 Static Load Radius – 12.5 Max Load (lbs.) @ Cold Inflation Pressure (psi) Single – 2,271lbs @65 psi RPM - 774 Tire Weight – 27lbs The D load rating will have stiffer sidewalls. You can purchase them from tirerack.com at ~$129.00 per tire.
floater88	posted 08-05-2015 12:28 AM ET (US) Great info. I was thinking of going with truck tires as an upgrade because my trailer has only one axle and the Revenge 20 wt, with all my salmon tackle onboard including a 15 hp kicker and two batteies, adds up the weight. Thanks
EJO	posted 08-07-2015 01:55 PM ET (US) There are I think two good trailer parts and tire supply companies on the net that can fill your request from stock. An LT type will do fine. Radials have more side wall flex. Do you need the wall height and profile of 75? A lower profile height will automatically give you less flex. Most performance car tires don't have 75 profiles but more likely 60 or less. If you have not bought any tires, look at http://www.easternmarine.com/Heavy-Duty-LT-Truck-Trailer-Tires-Only/ or http://recstuff.com/14-Inch-Trailer-Tires.aspx Good luck.
deepwater	posted 08-08-2015 01:09 AM ET (US) What do you have on the trailer?
jimh	posted 08-08-2015 07:29 AM ET (US) I think my trailer has 14-inch radial tires. I can't recall the width and profile.
mb159	posted 08-14-2015 02:52 PM ET (US) X 2 on the Goodyear Marathons.. just had to replace older tire that shredded a fender when it blew. Marathon is a steel belted tire that actually runs cooler than bias ply. VERY happy with them
Don SSDD	posted 08-16-2015 07:59 AM ET (US) 215 is the width in MM 75 is the height of the rubber as a percentage of the width. 14 is the rim size in inches. Using those numbers, you can calculate the height of the tire by converting the 215 MM to inches= 8.46 x 0.75=6.345 inches (X2 for the tire height twice)= 12.69 inches + rim size 14= 26.69 inches. You can easily calculate the height of any tire using this math. You can set it up in excel and quickly calculate tire sizes for comparison purposes. Tire Height RIM Tread Width Aspect 26.696825 14 215 75 This is the excel formula where A is the solution, B rim, c tread width, and d the aspect ratio. =B2+(2((C20.03937)(D20.01))) I find 14 inch tires are getting very hard to find, you might be better going to a 15 inch rim and even raising the fenders a bit if you can do that. Since 14 inch tires are getting hard to find, you may also be buying a "new" tire that was made a couple of years ago. Buy from a high volume place, more likely to get a fresh tire. There is a date code on the sidewall of all tires, just google decoding those numbers. I would say more sidewall is good, more rubber to dissipate heat? More rubber to squirm when turning or cornering. Take a look at highway tractors and trailers, nice tall rubber and fairly narrow. With stiff sidewalls and high tire pressures, the LT tires would be good. I don't think the boat trailer tyre tires are very high quality. Don
n1ywb	posted 08-16-2015 09:58 AM ET (US) It's important for any pneumatic tire to flex somewhat so there is a "contact patch" between the road and the tire. If the tire didn't flex at all, then the only contact would be along an infinitely thin line and traction would be very low. Also shock absorption is one of the main reasons why pneumatic tries are so widely used. So it's normal to see a bit of a bulge
EJO	posted 08-18-2015 01:13 PM ET (US) Don made a point about buying new old tires. Read this article http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11 and familiarize yourself with the code so you won't be taken.