3.5x18 rim, 140/70 or 150/70 better? front & rear performance tire sizing

[Chuck78]

I have a DID 3.50"x18" rim laced into a GS hub to swap onto my bike when I start modding it. I'm looking for the best tire size setup I can get to make for great handling in the twisties.

If you read my other posts, you will see that I was pretty sold on either the awesome budget Shinko's ($77 SR741 140/70/18 rear and 230 Tourmaster front @ 5000/10000 miles tread ft/rr) or possibly the Avon AM26 Roadriders for almost twice the treadlife at 55%-65% more cost (cost per mile is almost equal though).

Then I started to think of doing long road trips on a sticky 5000 mile tire, lots of highway time, lotsa center tread wear... The Avon in the 140/70 is $151 (ouch), but the Avon in a 150/70 is much cheaper, $115. Here's what the manufacturers say on the specs for rim width:

Avon AM26 RoadRider rears:
$151 140/70/18 5.6" wide 26.2" diam (3.5-4.5" rim, 3.75 is best)
$115 150/70/18 6.1" wide 25.9" diam (3.5-4.5" rim, 4.25 is best)

Shinko SR741 rear
$77 140/70/18 5.47" wide and 25.7" diam (recommended 3.75" rim)

[Chuck78]

I have read RapidRay and a few others with GS1150's or 3.5" wide wheel swaps say that a 150 is awesome. Ray, are you mostly doing drag racing and city riding on the 150+3.50" rim setup? I'm trying trying to figure out if the 140 is a better fit for the 3.50" rim as far as pushing the limits in cornering. The recommended rim widths from Avon and Shinko seem to dictate that, but I was hoping for some real world experienced opinions, as the sticky Shinko's short tread life in the event I'd ever do a several day road trip is bothering me a little, and a 6" wide rear would look pretty killer!

Also trying to decide if I want to go 530 chain or get a 520 for extra clearance for the possiblity of the 6" wide 150/70/18, so if the 140 is a better bet, then I'll just stick with the wider/cheaper/more durable 530 chain.

It seems that GS Resources members seem to say stay away from a 120 front tire, stick with a 100-110. I was considering ditching the 1.85"x19" stock steel front rim for a 2.50"x18" alloy Excel/Moose/DID rim. I wonder if that would change the negative outlook on a 120, or even with a 2.50" front rim if I should still stick with a quality sticky 110 in the front for faster turn-in time and better handling???

Also, it was seeming to me like the wider tires leading to slower and sluggish turn-in time was more relevant to the front tire, am I right? Would a 6" wide 150/70 rear slow my turn in time a lot more than a 140? Maybe 140 is best? I think modern sport bikes run a 120 front and up to 180 in the rear (in radials), so maybe the rear is not too relevant with slowing the turn-in ability much, and worth it for the extra drive wheel traction????

[John Kat]

This is what a 140/80*17 tire looks like on my GS 1000 ST.
It's a BT 21 from Bridgestone.

[Big T]

By the chart, even the 140 is a bit large

The 150 looks like it would be ballooned up, ruining the handling

[gearhead13]

I have a 150/70/17 on my 3.5" rim and its fine with no pinch.

[blowerbike]

750 katana's...
maybe 89 to whatever..................
3.5x17 rear.
guess what size suzuki put on those bikes?????
yeah a 150/70/17
any more questions

[rapidray]

I LOVE the 150 Michelin Pilot on my 1150! It turns in easily & as quickly as any other tire I've used on it, 140 or other. Ray.

[rapidray]

By the chart, even the 140 is a bit large

The 150 looks like it would be ballooned up, ruining the handling

Not even close! Ray.

[Smokinapankake]

750 katana's...
maybe 89 to whatever..................
3.5x17 rear.
guess what size suzuki put on those bikes?????
yeah a 150/70/17
any more questions

These are the wheels I'm in process of installing on my 82 Kat. I'm a little concerned about chain clearance with a 150 tire, however. Having a fellow at work make up some spacers as we speak. I'll be converting to 530 chain (probably, rather than a 520) which is no narrower than a 630chain, so it will be interesting to see how it all shakes down...

[speedyandypandy]

530 chain for road, 520 for racing
530 lasts longer

wider rear tyre = great acceleration, slower turn in
thinner rear tyre = slower acceleration, faster turn in

but profile and hard/medium/soft rubber makes alot of difference,
higher profile = more rubber contact area at full lean
I don't have a normal gs on the road, but I guess side covers touches down before you run out of tyre grip, or exhaust, or side stand, or footpegs......

The thing most people neglect is to check and adjust tyre pressure atleast every week.
Just my $0.50

[Chuck78]

I was a slight bit worried about increasing the turn-in time too much, and am still contemplating the Shinko's in a 140/70/18 vs the Avon AM26 RoadRider in 150/70/18.

I'm worried about treadwear - if I have 3000 miles on my tire, and I want to do a 5 day road trip to West Virginia/Skyline Drive/Blue Ridge Parkway/Tail of the Dragon, that I would be down to nothing in no time... This is where the Avon's have the advantage.

The reason I was posting was to justify to anyone who is quick to shoot down non-stock tire sizes on our bikes,
from a review on the new "retro CB1100F":

The 110 front and 140 rear instead make low speed handling something of a revelation. Know how 10mph, 90-degree city corners are a bit of a hassle on a modern superbike? You won’t realize how natural they can be until you hop back on something with narrow rubber.