Topic: new tires for my 78 CB750F with comstar wheels

[garyS-NJ]

I have stock tires on my bike and need new rubber.  I'd like to fatten the rear as much as possible  but also keep the bike as low as possible and go for a sideways look that is asthetic.  With a 19 in front and an 18" in rear, the factory chose a narrow 3.25" square front tire and a 4" square rear tire resulting in a ration of diameters at 1.05 rear to front.  that 1.05 kept asthetics and also made for a level ride with the stock shocks and front end...

I've heard the 78 has "the wider" swingarm and will easily take a 140mm tire or maybe a 150 tire.  Ton-up carpy recommends a 1309016 or 18 for the rear but I saw a post of his stating the 140 tire was OK (and I think all his advice was for the earlier CB750's with narrow swingarm).  I know I can measure my swingarm and shock width but then I need to account for flex in turns and also tire buldge from putting a fat tire on a narrow rim (I want to keep my comstars for now).  This is where experience is the only solution.  can anyone talk to these points??  below is my wheel selection spreadsheet and I have not yet been able to find the comstar wheel widths but heard they might be stamped in my bike (I'll look at rim to stock as a ratio and rim to new tire as a new ratio and create a "
buldge factor".  can I fit that 5.9" wide by 4.13 inch tall 150 70 18 tire in back with the 110 80 19 up front?


   front            rear      
   tire   width (inch)   height (inch)      tire   width (inch)   height (inch)
                     
stock   3.25H19   3.25   3.25      4.00H18   4.00   4.00
choice 1   110 80 19   4.3   3.44      140 80 18   5.51   4.408
choice 2   110 80 19   4.3   3.44      150 70 18   5.9   4.13

[garyS-NJ]

went with the BT45's because they speced a slightly wider tire for my rim width,,,  rides good.

      height   
      front   rear
avon roadrider   909019 & 1109018   25.5   26.1
      delta inches   0.6
      delta %   2.352941176
         
avon roadrider   1009019 & 1209018   26.4   26.6
      delta inches   0.2
      delta %   0.757575758

[katmol]

went with the BT45's because they speced a slightly wider tire for my rim width,,,  rides good.

      height   
      front   rear
avon roadrider   909019 & 1109018   25.5   26.1
      delta inches   0.6
      delta %   2.352941176
         
avon roadrider   1009019 & 1209018   26.4   26.6
      delta inches   0.2
      delta %   0.757575758

So what is the size of the tires, front and rear? 110/90 front and 140/80 rear?