A tale of the lowly 235/75R15 tire... (1 Viewer)

[ozarkmud]

I feel like it's easy to forget the negative impacts a larger tire has. Sure, there are many, many cases where you want something larger, but it's not without consequence.

The original FJ80 came with 235/75R15 or 31x10.5R15. The FZJ80 came with 275/70R16 and wider fender flares as a result.

We happen to have a FJ80 with 31x10.5R15s and a FZJ80 with 265/75R16s (which are pretty close to the stock size.) It's been interesting how much better the FJ80 rides. It could be mostly down to be different tires (BFGoodrich K02 vs Firestone Destination X/T) and different load ratings (C vs E.)

On the FZJ80 I swapped the 265/75R16s for 265/70R16 winter tires. The ride and handing improved tremendously. Even still with ample tread, they are a little bit hydroplaning prone.

I have a domestic truck with 235/75R15s, XL rated. They are fairly old, but weren't used very much. 7-9/32nds of tread left. Just a mild A/T tire.

I drove the truck home in the rain last night, and through plenty of snowy slush. It was much less hydroplaning prone than the FZJ80 (been a while since I drove the FJ80, so I can't comment much there) and it steers better in the snow than the Landcruiser when I have it in rear wheel drive. The narrow tires just cut better through the snow.

Even being older, not even mountain snowpeak rated, they were pretty impressive. They used to be standard issue on numerous vehicles.

I imagine this is part of the reason pizza cutter tires are popular.

Has anyone else found the allure of the 235/75R15?

 

[JoeCova]

Nope. Pizza cutters suck which is why they are practically dead.

Tire compound and tread design are more important on ice and snow. Tire construction and psi will impact comfort and should be adjusted based on tire load rating tables. As an example an XL tire psi will not be the same as an LT of the same size.

 

[ozarkmud]

Nope. Pizza cutters suck which is why they are practically dead.

Tire compound and tread design are more important on ice and snow. Tire construction and psi will impact comfort and should be adjusted based on tire load rating tables. As an example an XL tire psi will not be the same as an LT of the same size.

Pretty sure that the higher the load rating, the lower the comfort. Every time.

In this case I'm comparing an older all-terrain XL 235/75R15 with a modern (unrated?) studless winter tire in 265/70R16 and find that the narrower tire steers better in the snow. Different type of vehicle, but still seems like the snow tire should be better with rain/snow/slush than the all-terrain.

Unless it's more RWD vs AWD?

 

[JoeCova]

Pretty sure that the higher the load rating, the lower the comfort. Every time.

In this case I'm comparing an older all-terrain XL 235/75R15 with a modern (unrated?) studless winter tire in 265/70R16 and find that the narrower tire steers better in the snow. Different type of vehicle, but still seems like the snow tire should be better with rain/snow/slush than the all-terrain.

Unless it's more RWD vs AWD?

Ya thats often due to overinflation when converting tires. As an example our cruisers are rated for a standard P-Metric tire at 32 psi, converting to an SL/XL LT requires different psi. Most people just inflate it to 32 or higher and is too much. I run 80 psi in my F350 to meet load requirements and it ride slike ass but I need to because of the load, reducing it to say 50-60psi would make it significantly more comfortable, same concept with our cruisers.

As far as your comparison, a true winter tire is designed (siping) and manufactured (silica) for ice/snow and freezing temperatures. True winter tires are not built to eject water and slush and instead designed the opposite to pack snow for grip which is why they will perform worse in some cases of rain and slush than an all-terrain which has channels for ejection. If you aren't driving a winter tire directly on snow or ice then their potential is being wasted. The performance is attributed to design and manufacturing characteristics and less about size.

 

[AirheadNut]

I am firmly in the pizza cutter camp. I have always run studded winter tires on my FWD cars (VW Jettas) and AT tires year round on my LandCruisers. A 185 section tire on my Jetta far outperformed the 205 section tires on my parent's Jetta (both studded snows). The 235/85R16 load range E tires on my 70-series (Cooper ST Maxx) perform excellently in almost all conditions except pure ice, whereas the 275 section tires on my brother's 80-series have a tendency to skate around more in slush. The only downside I've found to narrow tires is when snow wheeling they want to cut through the snow and dig rather than float, even at low pressures. The stiffer sidewall of the E rated tire is less comfortable, but gives better road handling and is far tougher and less likely to allow damage to rims when wheeling rocks.

 

[greentruck]

I am firmly in the pizza cutter camp.

Same here. Changing the PSI to suit conditions alters the tread length significantly making them the Swiss Army knife of tires. I'll be going back to my long standard BFG KM3 skinnies once the Corsas that came with this truck reach the end of their service. They also have a slight MPG advantage over wider tires.

 

[SteveH]

Anyone who has ever driven anything (foreign or domestic) with 33x12.50x15s on it will come running to the pizza-cutter camp. My FJ40 has 33x9.5x15 Kendas and I love them and I ran BFGs in that size beforehand. I ran 235-75-15s for years, as they were cheap and readily available. My FJ62 has 31x10.5s, which are pretty close to pizza-cutter material.

 

[ikarus]

I love pizza cutters, all the height and a good contact patch when aired down and less weight. I haven't tried that specific size but I've run pizza cutters on a couple of Tacomas in the past and loved them - 235/85r16 and 255/85r16. Biggest downside is they look funny on certain vehicles. But they do look great on more utilitarian vehicles like 70 Series and 80s with no flares.

 

[ChaseTruck]

The potential upsides of skinny tires notwithstanding, praising the virtues of an old, nearly bald tire where the rubber is by now probably hard as a rock somehow rubs me the wrong way...

 

[greentruck]

Even with flares, I always liked the looks of the 255/85 R16 BFG KMs under my old 80.

They do give a bit of visual height enhancement.

 

[Devils Paw 80]

Has anyone else found the allure of the 235/75R15?

For starters you've got to have a fairly old truck to be running 15 inch wheels. Not many FJ80 owners are likely to keep 235's, if originally equipped, because they don't look very macho.

I have them on my '95 Nissan 4x4 pickup because that was the OEM tire size. Of course they are better for MPG than larger tires, say 31x 10.5., yet I'm tempted to upsize in the future because on the rough roads to my place in Hawaii a larger, wider tire would probably afford a less bumpy ride. The truck is brutal, and of course there's little hope for a decent ride with a short wheel base truck that has stiff leaf springs in the rear so I probably won't.
Truck rides WAY better with a heavy load in the back. On pavement I have no complaints.