Small bike tire selection

[suprf1y]

I'm building a 125 4 stroke to run at Maxton.
I will be using 110 70 17 on the front, and can use either a 130 70 17 on the rear or the same 110 70 17.

Is it worth running the lighter, narrower tire (diameter can be easily corrected by gearing), considering the low hp, or would it make little to no difference?

[Seldom Seen Slim]

I expect there'd be a bit more rolling resistance with the wider tire, maybe, but then -- maybe the wider one wouldn't deflect as much so there'd be less power loss to bend the rubber back and forth.  I would feel safe in generalizing -- it won't make much difference.  

If you use the same tire front and back -- make sure the thing isn't labeled "Front tire use only", 'cause I've been known to give an entrant a bad time in inspection for using a steer tire as a drive tire.  There are those that are labeled with directional requirements -- "This way 'round for front, that way (the other direction) for rear tire".  Those are okay for either location, obviously.

[suprf1y]

Thanks for the reply
Normally I'd have a feeling for something like this, but it's not coming to me, and there's not a lot of room for mistakes when you're only making 15 hp.
The tires are not marked front, or rear, but are directional, so I assume I'd run them according to marked direction. I bought just a 110 to make sure everything is legit.
It's a 14 hr drive. Not making it through tech is not an option

[Seldom Seen Slim]

Downtown Ontario -- or out in the suburbs, like Trillium and Jody?  As for only a 14-hour trip -- does the engine even get fully warmed up?  Nancy and I have a 1,200-mile each way ride to Maxton -- so you're getting off easy.  Whatever the distance, though -- it's worth it to be able to spend some personal time with the greatest bunch of folks and racers you'll meet.  We look forward to seeing you there in a few more months.

[suprf1y]

SW Ontario, across the lake from Erie Pa.

[wobblywalrus]

There is less internal friction within a smaller tire this helps performance.  There is less frontal area, too.  These small differences are important on a little bike.

[dr j]

I'm building a 125 4 stroke to run at Maxton.
I will be using 110 70 17 on the front, and can use either a 130 70 17 on the rear or the same 110 70 17.

Is it worth running the lighter, narrower tire (diameter can be easily corrected by gearing), considering the low hp, or would it make little to no difference?

I agree with wobbly.  Pick the smaller tire.  Less rolling friction and less drag.  You don't need the advantage of the larger tire's better traction for cornering at Maxton, nor the better traction for accelerating with a 125cc 4stroke.
Welcome to the Maxton small bike club.  Look us up in the pits next to Eric (Racer X of Dark Horse Racing).

[suprf1y]

Thanks guys.

I look forward to meeting everybody this year. I haven't been to Maxton since 2004 when I was there with Tom Bruch.