What a beauty Jerry. Hey what size Spitfires are you running? I just sent this over to Mark (Hondaman), but have not heard back yet! What do you think??
So specifically I said to him relative to my desire once the bike is setup: "So as a VJMC member my intent would be to ride it on short weekend rides, not a commuter bike, and not a touring bike, I have my ’05 Goldwing for that. I would like it to be a nice responsive fast rider. I do like high speed sweepers and would like to accelerate quickly from the stop light."
1st, this was the response he had given me regarding other stuff (jets, needles, front sprocket, etc., not included herein) but specifically tire sizes:
"So, about the tires: if yours has the 17" rear wheel, you probably would like the widest front tire you can fit as the rear tire will likely be a 130 profile. If, for example, the front is a 100/90x19 and the rear is 130/90x17, the roll-over roundness profiles will be bigger on the rear than on the front. When in fast corners, this makes the bike feel like it wants to roll down more into the turn as you increase power, because the rear tire accelerates ever so slightly as the bike is heeled over, relative to the front tire. This means the rear feels like it is trying to "slide out" (as is often the description) when power is applied while heeled over. As the round side profiles begin to match each other closer, this begins to neutralize this sensation. Some of it can be controlled with tire pressures: for example, I run:
38-40 front and 36-38 rear when using 100/90x19 front and 110/90x18 rear (or 3.25x19 front with 4.00x18 rear), or
36-38 front and 34-36 rear when using 110/90x19 front and 120/90x18 rear (or 4.10x19 front with 4.50x18 rear, in TT100 profiles of old).
So, when picking out your tires, go to shop where the tires are, and pull out both sizes. Set then in line with each other, then lean them over and watch their centerlines as you do: this will explain in a second what I am trying to describe. The rear tire (wider, heavier load) simply rolls over at a different radius from the front (narrower, lighter load), and it's up to you to figure out which profile and tire pressures will neutralize this for that smooth sweeper. This was 50% of road-race handling issues when I did it."
My questions back to him:
"I have an 18" rear (4.00"X18") & 3.25"X19" front, I think stock on the '75F for sure and probably the '76F as well, not sure about the '77/'78F's. In reading your book again (Suspension and Handling) and alluding to what you said below (now above), I had been thinking about the larger front tire 3.50 verses 3.25. Specifically I was thinking the Bridgestone Spitfires (S11). So my options in the S11 would be 90/90X19, 100/90X19 or 110/90X19 in the front and 110/90X18 or 120/90X18 in the rear. They also offer a 130/90X18 for the rear.
So I'm a little confused on the tire size issue and going back and forth between metric and std. it would appear the closest std today to stock would be a 90/90X19 on the front (3.25") and the 110/90X18 on the rear (4.00"). Your book recommends a 100/90X19 front (3.50") or 110/90X19 (4.10", TT) and a 5.10" TT in the rear or what I'm thinking would be the 130/90X18 S11. So I'm thinking the best choice for me would be the 110/90X19 in the front and the 130/90X18 in the rear. Do you think those S11's would fit, front and rear, or should I just stick with the 110/90X19 in the front and 120/90X18 in the rear? Do you have any concerns with the Spitfires or do you have a better preference?"
