Thunderbird 900 Sport ‘04 Tires!

I would fit a Michelin Anakee III in the OEM size. The manufacturers test size and profiles pretty exhaustively. I assume you intend to stray onto loose surfaces.

 

I'm also a proud owner of a TBS.
However, I'm only a few years into biking and have no experience of a different tyre profile than the manufacturers recommended size.
I have Avon storm 3D XM on mine, again I'm not experiencing enough to compare them with much else.
Hope that helps

 

When it comes to handling what you would be concerned with would be radius not overall diameter. As I figure it, an aspect ratio difference of 10% [from 70 to a 60] would only mean a decrease in radius of 16mm. I am running a 160/60X17 on my Legend [a very similar chassis] and it handles fine. If you really needed to, you could slide your front fork up 16mm to make up the difference. I don't think you would notice it that much in handling. You might notice a bit of change in engine RPM. It won't be much, but you engine will spin a bit faster per a given speed than it did before. One positive in this would be you would lower your C.G. in the process. You pay your money, and take your choice....J.D.

 

Going thinner on the back wheel by that tiny amount as @Wire-Wheels calculated , would sharpen, speed up the bikes turning in , that would be my thoughts !
I put one size wider on both front and rear on my Laverda many years ago , the wider front caused two things to happen. Slower turn in response and slight under steer ! But that was possibly lessened by a wider rear !

 

The tire is not thinner. Both are 160 section width. A 160/70X17 has a side wall that is 70% of the section width. A 160/60X17 is not thinner. It is however shorter. It's sidewall is only 60% of the 160mm section width. ...J.D.

 

Carbon
Welcome to the family.
Do hit the upload a file button bottom right corner and show the inmates your beast.
Regards & Ride Safe
Joe

 

When I say to move the fork up, I mean slide it up in it's mountings. By so doing, you are brings the bike down. This is measured by the distance the fork tube sticks out of the top clamp. You need to increase that value. If I were doing the setup myself I would measure the old tire/wheel assembly and the new one to make sure of the amount of change needed. Don't just use my estimated numbers. If you are really serious about handling, you may also need to fine tune this adjustment. When you get in this deep, you are re-engineering things. You have to be the engineer yourself at that point. ..J.D.

 

I would like to read what happens. It is one thing to have a conversation and quite another when you get in and do it. You always run in to those "unintended consequences" that keep the workshop lights on late. ...J.D.

 

@Carbon.
What tiers did you finally decide on and how is your experience so far riding the bike this summer?