Does tyre size matter that much?

[yeadon_m]

Folks,
Obviously, a stupid question. I have always put the stock tyre sizes on all my bikes.

But, I was having my GT380B's annual inspection recently, and in their workshop was a GT380B (not as amazingly coincidental as it sounds, it was Suzuki Robinsons, pretty famous for old GT bits here in UK).

That bike was wearing tyres the sizes that are fitted to a GT750!

Front 3.25 x 19 and rear 4.00 x 18. They did look nice and chunky, granted.

Stock for a 380 is front 3.00 x 19 and rear 3.50 x 18. I will fit some new tyres this winter, so size is relevant to choice time soon.

I asked the mechanics wouldn't the oversized tyres upset the handling and they said nope.

I'm not so sure, so I'm asking you lot!

Whaddya think?

Cheers,
Mike

[Craig380]

I had a 3.25x19 (i.e. a 100/90) on the front of my 380 and I thought it was OK .... until I put a 90/90 Avon Roadrider on it. Steering is now faster and grip is miles better.

Wider tyres on narrow rims means the tyre's profile isn't ideal, I think

[markush]

Hi!

A few years ago I mounted Bridgestone BT45, 3,25x19 front, rear 4.00x18 and thus drove a completely different bike, much better than the previous (Continental 3,25x19 f., 3,50x18 r.) driven tires. Since then I go over again with these tires and I am fully satisfied.

The tire sizes front 3,25x19, rear 4.00x18 are approved by Suzuki-Germany especially for the GT380.

Calculations indicate that 90/90x19 wider than the 3,25x19
(3,25x25,4mm = 82,55mm)
But the actual tire widths never correspond exactly to the nominal dimensions.
The currently mounted BT45 4.00x18, calculated width 102mm, is 119 mm!

bye
Markus

[Vintageman]

Not a stupid question ->

Wider tire just waste power. Some guys liked to put the wider and heavier 250 mx tire on rear of 125 mx bikes and just loose quickness due to added inertia and then unsprang weight. I went the other direction. But, Suppose that's not how we run our gt380's though . I still respect the fact a lighter tire is more response. I never run wider then OEM and like lower profile tires on lighter bikes.