Shinko I'm using is the 712, which may be a bit different than the 230
I could get up to 90-95 mph on the stock IRC, might hit 80-85 on the shinko
Of course there's a bit of speedo correction involved, but not, I think, a full 10 mph
as far as traction, it's a non issue on a bike as light and low powered as a Savage, the stock 140 / 80 (in a decent tire) has more traction than this bike really needs, and so does a 130 / 90, in a decent tire (no, IRCs are not decent tires

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I've gotten used to the bike "humming' along at 70 since I moved out of town, so that's not an issue (I didn't see much of a change anyway)
Of course you went from a wore out IRC to the 230, so near anything is an improvement

I might try the 230 next time, on your recomendation, if I don't go Pirelli MT66 (also budget priced and highly recommended, but not available in 140/90 I don't think)
stability has never been an issue for me on the Savage (except the crappy IRC tracking grooves like a slot car) I came off a Ninja 500, and before that a Rebel, neither as stable as the savage (wish I'd kept the Ninja, I could use it for a commuter and just use the Savage for easy ridin)
that bit of extra resistance in the steering puts me off a lot, though, and I'm slow in the tight stuff as it is (Captain Slow I am

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