Using a rear tire on the MC with a width of 140, 145, or 550. I realize max width is determined by the swingarm (and such) but how narrow can I go. I also believe that narrower (less contact patch) will provide less resistance thus gain on mpg and getup and go. Am I wrong in that assumption? Is there a point where too narrow will cause stability problems? I also know that Avon makes a Sidecar Triple Duty tire (3.5” wide) that can be used for all 3 spots (front and rear of MC, sidecar). So it stands to reason that someone is using at least 3.5” narrow rear tire somewhere.
Now you are in the right place
Ron, that's a matter of in interpretation.
General size comparisons
3.5" = 100mm
4.00" =110mm
Tire height will have a far greater effect on mpg and performance then width. Generally taller = better mpg and slower performance.
I find that the narrow (4x18) rear I run on my r100rt rig can actually help its handling when riding agressively. For hard cornering most rigs need to drift their rear tire/sidecar tire. To do this safely*, you need to have enough excess horsepower to use up rear tire traction from the traction pie with acceleration so that there is less traction available for cornering and the tires drift sideways. If you have too much rear tire/sidecar tire traction available for cornering the rig will roll over rather then slide. On a hp rig with lots of horses and a low center of gravity the cornering traction can be very high before this is an issue. On a tall rig like mine it does not take as much traction to create a roll over rather then a drift, it there is limited excess horespower to use up rear traction with acceleration.
When braking, a wider higher traction tire will nearly always be an advantage, if the rest of your brake system is capable of using the traction.
An issue smaller tires may bring to the table is a load rating less the the weight of the rig. With a sidecar tire like the avon triple duty or metzler k block this should not be an issue. Also check out the avon sm, it is a nearly square heavy duty bias rear tire that also comes in narrow tall sizes that work well on 18" and 19" sidecar wheels and front wheels.
My understanding of the avon 3.5 x 19 is that it was developed for early british rigs that ran on 19" rubber and the metzler k-block was designed for bmw /2 rigs that used 18" wheels all around. So i've been told.
* disclaimer - some would consider it never safe to intend to break your rear end free.
Originally written by akathetroll on 3/17/2007 6:45 PM
Ron, that's a matter of in interpretation.
Well if it ain't here and ain't SCT you are definatley beginning to narrow down you choices...LOL.
Thanks for the feedback tkpinsc. I need to think about this but lean toward braking has high concern.
Keep in mind the maximum width tire that can be squeezed into most airhead swingarms is a 120/90
