Maximum Rear Tire size

[Red_250X]

Anyone have any experience with a rear tire larger than 110/100-18? I want the largest tire possible.

[yamaman1]

I got a 110/100-19. So i guess thats a little bigger. Check outIRC they make unusual tires mayeb they have what you want.

[smoker]

I personally do see the point in going any larger than a 110/100-18. I still run the stock size 100/100-18. The larger the tire the greater drag on the motor. Going larger you are hindering the bikes performance. So, why do you want a larger tire?

[kelstr]

that is so true, the larger tire is going to kill your motor, it is going to make the chassis react very different in turns it is just not a good idea----the wheel size is not optumum for that width of tire -------its the same thing with the bozo that gets the new truck and puts a lift on it and puts the wrong offset wheels and way to large of tire on it -----he just ruined a good truck, is no longer safe and is just plain stupid. the manufacture spent millions of dollars on design, testing set up ,wheel spin ,braking ,structural engineering design and they know what to put on it and list the sizes you can run in the manuel. ------and why do you think you want a larger tire on the poor little thing ??

[mcnut]

I put a 4.5 x 18 Pirelli MT16 on my X for Colorado trails. It ever-so-slightly rubs on the coolant catch can under full rear suspension compression.

[jchantzWR400F]

The biggest/most wide tire is a 140 that I have seen. For the guys asking why, I would say bigger foot print, more traction in soft terrain.

[Red_250X]

I can't imagine anyone thinking that a wider tire would actually slow the bike down significantly. This bike has power to spare!!! I've always run large tires on my bikes. I had a 120/100-18 on my XR250 and it worked great.

As for the reasoning, I ride on a lot of different types of terrain. I need additional traction on mud, snow and sand.

[smoker]

Some of us actually have had discussions w/ engine builders, and understand loads that are placed on motors. There are always positive and negative affects to modifications.

[Red_250X]

Some of us are actually engineers and understand the laws of physics and how they apply to engines, the drivetrain, and tires. Any engine builder that believes what you're telling us, isn't worth his weight in salt.

Let me explain this so even you can understand.

A taller tire will "gear up" (less power, more speed) a vehicle. Here we are talking about a 1" maximum difference on a 26" tire. That equates to a 3.7% change in gearing...very minimal...and that's the MAXIMUM difference.

Now, a wider tire. If we assume that a wider tire is heavier (it may or may not be depending on the construction), we are talking about a maximum difference of about 4% (maybe 6 oz).

Now, since the overwhelming majority of the load in placed on the engine by it's attempt to move the weight of the bike (245 lbs, with a few aftermarket add-ons) plus the weight of the rider (200 lbs) which equals 445 lbs, the effects of a 3.7% gear change and/or a difference of 6 oz on the tire is VERY minimal.

Now, we could get into torque, rotational velocity, centrifugal force, gyroscope effect, etc., but none of this is significant with the types of changes that I'm talking about, and you probably wouldn't understand it anyway.

As far as how the bike handles, you will tell more difference due to the construction of different tires (4 ply vs 6 ply, sidewall stiffness, rubber compound, tread design, etc.) than you will the difference in size unless you go to extremes.

Now, here's where you may have a point. The larger tire will have a larger contact area, therefore better traction, therefore the tire will "hook up" better and spin less, therefore loading the engine more, therefore improving the acceleration of the motorcycle and rider, WHICH IS EXACTLY WHAT I WANT!!!!!

There would be less of a load change on the engine in going to a larger tire, than there would be in the change from a 190 lb rider to a 200 lb rider, or even in having significant amounts of mud stuck to the bike.

The analogy of the big truck tires that are 300% to 500% larger than stock is a poor comparison. We're talking small changes here!!!

Please, if you want to show your ignorance, that's one thing, but don't mislead these people who may not know that YOU don't know what you're talking about.

[FGR01]

You really won't get a larger contact patch when switching to a wider tire unless you also put a wider rim on. When you place a wider tire on the stock rim it is forced to squeeze down to the skinny rim and gets a more "rounded" profile and less footprint. You really should switch to a 2.15 or 2.50 rim if you want to run a 110 or 120 width tire. ?

[Tuner]

At what air pressure? Contact area changes with the pressure used as well.

[Optik]

You really won't get a larger contact patch when switching to a wider tire unless you also put a wider rim on. When you place a wider tire on the stock rim it is forced to squeeze down to the skinny rim and gets a more "rounded" profile and less footprint. You really should switch to a 2.15 or 2.50 rim if you want to run a 110 or 120 width tire. ?

I know that holds true for sportbikes since they run fairly high tire pressures and run on ashphalt which has very little give.

On dirtbikes, we run pretty low tire pressure so I think the tire would flatten out and most of the tread would be on the ground. If you live where the dirt is softer, your tire might sink into the dirt a little allowing the entire contact patch to touch the ground. I'm not sure on any of that, just guessing.

On another note, I always ran a 130 Michelin (110 other brands) on my 250f because for some odd reason the knobs on the 120 s12 are WAY smaller than the knobs on the 130 s12. I found that the 120 would wear out much quicker as a result. If I used another brand of tires, I would buy the correct size.

[Danceswithtrees]

On another note, I always ran a 130 Michelin (110 other brands) on my 250f because for some odd reason the knobs on the 120 s12 are WAY smaller than the knobs on the 130 s12. I found that the 120 would wear out much quicker as a result. If I used another brand of tires, I would buy the correct size.

This is very true. The bigger S12 works way better, even on a 250f.

[Red_250X]

You're exactly right Optik. If you don't believe me, mount one and see...I've done it many times. The outside knobs don't move that much with different rim sizes. Take a new tire (not mounted) and sqeeze the inside to various width's to simulate different rim sizes. Even though it will be a little different when inflated, the difference is very similar.