Topic: tire dimensions

[cb500-1972]

Hello

im planning to order new dunlop bt45 to my cb500

i see that the original dimension is front 3.25 x 19 rear 3.50 x 18

is it possible to mount wider tires? will wider tires give a better ride or is it the same?

[flybox1]

honda engineers put those tires on there for a reason.

[johnrdupree]

Tires are designed for a specific rim width.  Fitting a tire to a rim that is smaller than is intended will bring the beads closer together and distort the shape of the tread.  This could lead to all manner of ills: reduced grip, less stability, bizarre handling, shortened tire life, etc.  Your best bet is to stick to the stock tire sizes.

[Kong]

honda engineers put those tires on there for a reason.

The reason being that is all that was available 30 years ago.  Today times are better and you have more choices.

[cb500-1972]

thanks for the pointers. my local tiredealership suggests 4.0 on the backtire, but this will be too wide?

[Kong]

For a moment forget whatever the guy at the tire shop told you.  For the most part those guys have more experience with flipping quarter-pounders than they do with tires.

Go to this site and look at the charts on the bottom of the page first:
http://www.bridgestone.com/products/motorcycle_tires/products/battlax/bt45.html

Now you have the tire manufacture's recommendations of rim size for the tires you are interested in.  Your bike, like all CB500s, has rims on it that are 1.85" wide, both front and rear.

First take a look at the column that gives the "Recommended Rim Width, in inches, for every size of the BT-45 tires.  

Notice that there are lists for both H and V rated tires, first the H rated:  Notice that there is not one BT-45 tire that has a recommended rim as narrow as the rims you have - not one.

Of the H Speed rated Front tires there are 8 sizes which can be used with your narrow rims.  Pick one.  Notice that there is no H rated rear tires that is suited to your rim width.  Tough luck.

If you were to go to the V Speed rated BT-45 tires you would have two choices in a front tire (100/90-18 and 100/90-19).  Your stock wheel is 19" so you really only have one choice, the 100/90-19 for the front in the V Rating.

Now the Back in V Speed Rating, you see there are, once again, no tires that the factory recommends may be used with your skinny rim.  So, what are you going to do?  The closest tire for the rear is one of the H rated ones with a designated minimum of 2.15"  Do you want to chance it? 

The point is that the information you need to chose tires is available from more trustworthy sources than a guy behind a counter.  Arm yourself with the information.

[TwoTired]

honda engineers put those tires on there for a reason.

Yes, and to expand on that, Honda sized the rim to work with the available tires.  Modern tires have changed, and usually (always?) require different rims.  Modern Honda rims/wheels work with Modern tires.  Not all tires work well with the stock CB550 rim width.  Manufacturers, know this.  And yes, it limits what you can properly select for you vintage bike wheels.  

Tire salesmen are more concerned with you forking over larger quantities of money.  They get more money selling larger tires.
20% of $50 is $10.   20% of $100 is $20.  Which item do you think the salesman will guide you toward?

Then there is the store stock issue, which they would rather sell now, than ordering the correct tire for your bike for future income.

You're a consumer.  Places that sell don't play fair very often.  

Cheers,

[faux fiddy]

honda engineers put those tires on there for a reason.

Yes, and to expand on that, Honda sized the rim to work with the available tires.  Modern tires have changed, and usually (always?) require different rims.  Modern Honda rims/wheels work with Modern tires.  Not all tires work well with the stock CB550 rim width.  Manufacturers, know this.  And yes, it limits what you can properly select for you vintage bike wheels.  

Tire salesmen are more concerned with you forking over larger quantities of money.  They get more money selling larger tires.
20% of $50 is $10.   20% of $100 is $20.  Which item do you think the salesman will guide you toward?

Then there is the store stock issue, which they would rather sell now, than ordering the correct tire for your bike for future income.

You're a consumer.  Places that sell don't play fair very often.  

Cheers,

You should combine all the times you discuss wider/taller/larger tires into a single cut and paste treatise that appears in every thread like this.