Moving to narrower rim?
 

I'm thinking of getting some tubeless rims for my bike. The stock rear rim is 4.25x18". They also offer narrower sizes (3.00x18" and 2.5x18"). The 3.00x18" is advertised as more for 50/50 on/off-road and it seems a better compromise than the stock. What are the pros and cons of moving to a narrower rim? Any negatives (or positives) I should be aware of? Or in real times, will it make little or no difference?
Cheers.

I don`t know really but by logical thinking I say:

- a narrower rim will change the relation between width and height of tyre.
- this will affect the contact surface to the ground
- the handling of the motorcycle will be different
- it changes the carry capacity
- it will offer less comfort riding on roads because of the relation between width and height
- much smaller than usual fitting of the tyres into rim will restrict the choice of tyres generally
- it will get much more difficult to find a tyre on your trip if you use a special or unusual size

Tyre sizes
 

If we talk about tyre sizes, not rim sizes.

I have some experince as a chopper bulider.

And I have also changed a 16" wheel to a 18" as front on my WL 750....

This is a rule of tumb

5.00*16"
4.10*18"
3.50*21"

Have more or less the same other diameter.

So when I changed from 5.00*16 to 4.10*18 wheel.
I kept the outside diameter of the tyre.

Oposite on old school chopper.
Replace a 4*18 with a 5*16 kept the outside diamter of the tyre.
(And for the estetics. It is good if front and rear had the same outside diameter)

If you just change to a narrower rim, you will also reduce the diameter of the wheel (If we keep standard ratio high/width)

So you really need to know what you are doing,if you do things like this.
If you change outside diameter of the tyres, you impact the handling of the bike. (e.g trail)

So I would recomend to stay with original sizes.

What it boils down to is finding out the manufacture supplied diameter or circumference of your stock tyre and your proposed new tyre and ensuring that they are as close as possible. As to the width of the tyre as opposed to the width of the new rim, you shouldn't have a rear narrower than the front.
In my opinion.

Thanks for the responses. I'll stick with the oem rim widths.
bier

Tyres
 

You can put a slightly narrower tyre on the original rim.
And at the same time increase the height to width ratio


Example

If standard is 150/70
You can use a 140/80


70% of 150 = 105 mm
80% of 140 = 112 mm
=> you will add 7 mm to the height. OK

or 130/80, if the rim allows that
80% of 130 is 104 mm. Spot on