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**Steve** · 07-31-2013, 09:53 AM

I think this is one of your "oh $#!T scenarios" mentioned in your signature.

I think you are measuring your rims incorrectly. They should be measured INSIDE the rim, not the outside. If you look on the rim, probably near the valve stem, you will see the rim size cast in. Your front is going to be a 19" diameter (not 20") and is likely to be 1.85" or 2.15" wide, but WE HAVE NO IDEA WHAT BIKE YOU ARE TALKING ABOUT.

If you have a 2.15" rim, you might get away with a 110/90-19 tire, but it will really mess up the handling of the bike.

This comment is very confusing:

As of now my bike has a 100/90-19 up front and a 130/90-17 out back. rear rim measures 18 inches.. So im hoping an 18" will work because thats all i can get.. Front is 20" but i can get a 19" tire like before. Not sure if it will work?!

You are saying in that statement that you have a 19" tire on a 20" rim up front and a 17" tire on an 18" rim. Sorry, that just does not compute. Stock rim sizes are 19" on the front and 17" on the rear. You already have the proper sizes on the bike, that is what you need to get if you are going to replace them.

If you want a bike with the fat-tired look, get one that is designed around the look. If you want a bike that handles, keep the stock sizes on your GS.

.

**Nessism** · 07-31-2013, 09:56 AM

EDIT: Steve posted while I was typing so (sorry) my message makes some of the same points as his.

For one thing, you don't mention what kind of bike.

Most GS bikes use a 1.85" wide front wheel. Widest safe tire size is 110, but a 100 is the proper size.

Most GS's with a 17" rear wheel are 2.5" wide but not sure about your particular bike. Some people that don't care about performance squeeze on a 140 but it's a very poor fit and may even rub on various parts. A 130 is the proper size.

You can NOT install an 18" tire on a 17" wheel.

Remember, safety first. Appearance comes second. The modder crowd often get this order backwards. And mistakes can cost you your life.

**boingk** · 07-31-2013, 10:15 AM

Don't try and mess with this unless you get a new front wheel.

You will not want to run the tyre sizes you mention because they will a) not fit and b) cause your bike to handle unsafely if they do go on and inflate.

If you are wanting to do this you'll need a rear wheel that you can modify to fit to the front, and then fit 120/90's to both it and the rear.

- boingk

**Tamara** · 07-31-2013, 10:27 AM

Based on your original tire sizes, Bridgestone Battlaxs should fit fine. I agree with Steve & Nessism about not messing around with tires. The wrong size could turn you into roadkill.

**Steve** · 07-31-2013, 10:31 AM

I just noticed something else in the post.

Originally posted by 08rangerdan View Post

I plan to use a 400-19. (4.25" x 27.59) up front and a 450-18 (4.84 x 27.4) out back

If you do the math, 4.25" is 107.95mm and 4.84" is 122.94mm.

In other words, YOU ALREADY HAVE THE SIZES THAT YOU WANT.

In fact, you will have to reduce your rear tire from a 130 to a 120.

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**08rangerdan** · 07-31-2013, 11:47 AM

Yes i see the stamps on the actual rim now. I always though rim size was width and height diameters. Outside measurement

Bike is an 82 gs850

Mainly i want the front tire to match the back for size. Doesnt need to be super fat but scale to the look im trying to achieve. Im not building a great handeling machine.. For sure. But im trying to get something bigger then a 4" tire on the front. But in limited for options. I pulled those sizes of a website who reccomended those sizes.. Ill look into them because something does seem funny with those numbers

**Steve** · 07-31-2013, 11:53 AM

If you want a "fat" look, you are going to have to go to 5" (130mm) or more.
I don't think that will fit with stock forks, but CERTAINLY not with the stock rim.

The only practical way you are going to get your front to match the rear is to reduce the size of the rear.

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