Off road tires for a Subaru CrossTrek.2018 what needs to be done to get a good 75 height tire?

Question

I just bought a 2018 Crosstrek. It has OEM tires on 18 inch wheels. I will be doing a lot of desert travel so I want a quality tire that I can safely deflate for extended miles. I have been doing some research and to get the right kind of tire I need smaller wheels. There is a number on any tire that describes the sidewall height as a percentage of the width of the tire. The stock tires are 55, The off road tires are a 75.

So my understanding is one needs smaller wheels to accommodate the higher sidewall, else there will be rubbing issues as the tire will be to big to fit in the wheel well.

I see wheels online 17" 17.5" 16.5" etc. What size wheel do I need? If the answer is depends, what does it depend on?

Tire suggestions appreciated.

Also Am I going to need to get speedometer recalibrated? And if you have done this have you ran into any major problems? The vehicle will be lifted if that makes a difference.

Update:

So I bought Wheels from Method, A rallitek 2' lift, after market coil springs and General AT 215/75 R15.

A little problem with the tires, while they are fine, they went out of production just months after purchase, I wasted one and the replacement is now the spare.

I got a little lucky at the tire store, one of the clerks was a Subaru owner and fan, and was aware of clearance issues. He was able to get the sales guy and installer on the right track, with the right wheels.

The total lift on the vehicle might be 3 inches. The heavier coils are supposed to add an inch. However at the shop the installer was not sure, or did not think so, although on the web site the coils are advertised to give a 1 inch lift.

Anyway, everything is great. The ride is very solid on highway, and lovely on dirt. I have had no clearance issues and I feel very comfortable with the setup.

The difference between stock and these modifications is night and day. For those of you in southern Nevada I made it over Wheeler pass, with only slight damage to the skid plate, Easy sledge hammer repair. The gas mileage suffered, about 3-4 MPG.

Answer 1

So my understanding is one needs smaller wheels to accommodate the higher sidewall, else there will be rubbing issues as the tire will be to big to fit in the wheel well.

Your understanding is correct. Typically you can deviate from the stock tire size by one size, up or down, in width or aspect ratio. From what I'm seeing, the stock size is a 225/55R18, nominally 225 mm wide, with the sidewall being 55% of the width. There are sites, such as https://tiresize.com, that will show you a list of tires that are of equivalent or comparable size.

A tire in the size of 215/70R16 or 215/75R15 would be the same diameter, so you would not lose any power, and you would not need to recalibrate your speedometer. (There are few, if any off road tire options in the 225 width, and a 235 width would most likely work, but a wider tire has a higher chance of rubbing, though if you keep to the stock diameter you should be fine.) Off road tires usually have higher rolling resistance, so your gas mileage will probably get worse. You would of course need new 15 or 16" wheels, and they would have to be aftermarket, as OEM Subaru wheels from another car will most likely not fit over your brakes. There are many companies that sell wheels in the 5x100 bolt pattern you would need, but it's worth giving them a call to verify their wheels will fit over your calipers.

There are plenty of All Terrain and Mud Terrain tires in both of the sizes mentioned previously. You probably do not want Mud Terrains, as they will be much heavier than the stock tires, loud on the highway, and pretty terrible in snow. I run a set of General Grabber AT2s on my lifted 2006 Forester and I've been very happy with their performance. They've been phased out now and replaced with the ATX. People also seem to like the Toyo AT3s. The Cooper AT3 4S, Yokohama Geolandar AT GO15, Falken AT Trail are all a milder AT tire that will be more road oriented. The BF Goodrich K02 is an excellent tire, but almost certainly too heavy. It is worth trying to keep the wheel and tire package weight close to the OEM wheel and tire package weight to keep performance relatively good.

If you follow this advice, you should have no issues fitting off road tires on a stock Crosstrek. If you lift it, the company that made your lift will most likely have a chart showing what tires fit without rubbing. Often you can go up two sizes with a 2" lift, but the lift supplier will know. Larger tires will impact your speedometer, but tiresize.com has a calculator for that to see if you need to be concerned. You will also lose some engine power, but when I went up one size (215/60R16 to 215/65R16) I didn't notice a change.

And finally, I haven't had any problems at all. With AWD and AT tires, I haven't been able to get it stuck yet.

Answer 2

"A lot of desert travel" has quite a bit of wiggle room but if you are going to be doing extended drives aired down, I'd assume you are going to be on bad dirt roads or larger/sharp gravel roads or even sand, so you probably want a more aggressive tread. You'll sacrifice noise and a bit of mileage on the highway, but something more like an MT will be worth it when you need them. Make sure you get something with appropriate sidewalls and sidewall tread to handle airing down.

If you want to keep the same overall diameter tire but change the aspect ratio and run on a smaller rim that is usually doable. @Alaska Man mentioned brake caliper clearance as an issue but that also applies for other front end parts like A-arms, tie-rods etc.

If you are having issues fitting a smaller diameter rim, you can usually order the rim with a larger degree of offset that will move the centerline of the rim outward relative to the hub, and away from any parts that might not clear because they usually sit within the wheel rim on the inside. If you can't find the rim you want with the right offset you can also achieve the same effect with wheel spacers. Be aware with an offset rim you may need to install some fender skirts because the wheels will sit a little outside the stock fenders, and that's not legal in most places.

If you want to actually size up your tire you're going to have to deal with a lot of clearance issues. I know they do make some aftermarket lift kits for those types of Subarus, so look into that. You won't be getting a massive improvement over stock though. This won't give you a monster truck.

As some overall advice, try and keep alterations like this minimal. A little improvement can go a long way, so change only what you need to. Things to consider:

• A 75 tire is significantly wider than a 55. While this gives you more traction, it's also going to make for a "heavier" ride and the vehicle won't be quite as nimble due to the larger contact patch it's working against.
• While a smaller rim allows you to run a tire with more cushion or ability to air down, changing your aspect ratio will definitely affect the handling. Your ride is going to feel "softer" and probably less responsive.
• Don't go crazy with wheel offset or spacers. A wider stance can fix your clearance issues but it may be putting unnecessary new stresses on your suspension and front-end components.
• Installing a lift will almost always mess with the geometry of the car, so be prepared for that to affect the handling. It may also introduce extra stress so pay attention to wear on drive-shafts, axles, and universal joints.
• At minimum you will need to do an alignment job after any kind of lift but you still may see permanent changes in the way it drives.
• Try and make sure your lift keeps the vehicle as level as possible. Any relative difference in front-to-back height can dramatically change the way a car drives.