Kawasaki Sportsbike Riders Club - Australia - Online Forum

This is more of a general interest thing (and lack of knowledge thing):

What are the widest profile tyres I could fit on my ZX2R? Will having wider tyres affect the handling positively or negatively? I've noticed that a lot of the Aprilia 250s seem to have really fat tyres in comparison to my little ones, so to speak

Also, I've read that a lot of people swear by the Pilot Power brand - how many k's should I expect to get out of them mainly from commuting with the occasional weekly blat through the hills?

As I said, this is just out of interest - I've got some pretty much brand new Bridgestones on the bike at the moment (not sure of model).

I'm no expert on this by any means, but I've seen this topic come up again and again on 250cc boards. Usually some kid who really wants to be riding an R1 but who's stuck with a GPX250 complains that the bike looks wimpy because of its rear tyre.

The consensus seems to be that the skinny tyres that 250s come with as standard are one of the reasons they can corner so well. I don't know how to describe the physics involved, but the decreased curvature (in cross section) of the fatter tyres doesn't do a lot to help their ability to lean into corners.

The bigger tyres on the bigger bikes are there to put their much greater power down on the bitumen. If you don't have that greater power, there's not a lot of benefit in having the big tyres. The RS250 probably does something like 55 or 60hp at the rear wheel, whereas your ZX2R is probably more like 35-40hp?

How this would work out with a larger tyre but the same profile (ie something with bigger overall diameter) I don't know, but I reckon you're then starting to run into probs with clearance.

I've seen sites that tell you the largest tyres that can squeeze onto a GPX250 or ZZR250, but can't help you with the ZX2C sorry

I believe your rear would be a 140?? or 170???.. the safest youcan legally go is ten up which would be a 150 but not sure if they make them if its a 170 you can go to a 180

Shaman wrote:What are the widest profile tyres I could fit on my ZX2R? Will having wider tyres affect the handling positively or negatively? I've noticed that a lot of the Aprilia 250s seem to have really fat tyres in comparison to my little ones, so to speak

The RS250 has a wider rear rim than the ZXR250. Stock-fit rear tyre size on them is a 160/60-17.

The widest rear that will fit inside a ZXR250's swingarm is a 150/60-18.

Keep in mind the ZXR has the wider-diameter 18" rear wheel compared to the otherwise almost-universal 17". That makes the tyre look more slender.

Also, I've read that a lot of people swear by the Pilot Power brand - how many k's should I expect to get out of them mainly from commuting with the occasional weekly blat through the hills?

Out of a rear, about 340,000,000... because Pilot Powers don't come in a size to fit an 18" rear wheel, you won't be able to fit the tyre you buy to your bike; thus, you won't be able to ride on it, thus you won't be able to wear it out.

Annoyingly, though, they come in a 110/70-17 front and 150/60-17 rear. That means they make them to fit almost every other sporty 250...

I see - thanks for the advice. I wasn't sure if having a wider tyre would actually be beneficial or not - I'm yet to get a knee down on it, but I'm a little timid because I feel like I just don't have enough rear tyre to play with as compared with the bigger bikes. If it's purely for putting the power down, then that makes sense.

So I shouldn't be worried I'm going to be running out of tyre (hence grip) when in a big lean?

BT014's come in 18's and are a far cry from GPR70's which were the tyres to get for many years

Shaman wrote:I see - thanks for the advice. I wasn't sure if having a wider tyre would actually be beneficial or not

On a short, low, squidgily-suspended 250, turn-in speed is never going to be a problem. Mid-corner stability, on the other hand... no harm in trading off some of the overkill turn-in for some much-needed stability.

My own ZXR250 felt considerably better with a 150-section rear tyre on it than a stock 140-section.

Shaman wrote:So I shouldn't be worried I'm going to be running out of tyre (hence grip) when in a big lean?

Once again I'm speaking with not a great deal of expertise to back me up (lucky then that I-K at least knows what he's talking about!) but I think you'll probably find your ZX2R will happily lean to the point of scraping the pegs before it lets go.

A GPX or ZZR is not even intended to be a race bike, but they'll lean to the point of scraping the centrestand, and can lean over harder once the centrestand is removed. All of this with skinny little 140 rear tyres. And I reckon whatever 18" rubber you're running on your ZX2R is going to be far more performance oriented than the stock Dunlop K275s the ZZR250 comes with.

I'm not brave enough to lean mine that far yet, but I'm pretty sure that the tyres are no impediment to doing so. It's more my comfort level and my skill level, and my chickenstrips are slowly but surely thinning out.

Johnnie5 wrote:BT014's come in 18's and are a far cry from GPR70's which were the tyres to get for many years

I can sure vouch for the GPR70's - had a 140/70 x 18 fitted to the back of the Z for racing, it was just fantastic for 'sprint' races ( 5-6 laps).

A couple of tyre mechs told me it would be *shithouse* and *too soft* for a 220kg z1000 (as it was designed for a 400 class racing), but for my purposes it was ideal.....

BT014's are the go for your bike - but don't put a huge tyre on the rear, it will just *push* the front because the contact patches are further *out-of-line* at big lean angles......this will make you run wide.....

Skinny tyres are OK, hells bells, I run a 130/80 x 18 Conti on the back of the Zed these days, and it corners just fine, don't you worry about that

Shaman - like many i'm no expert, but it sounds like whatever tyre you have on at the moment is 'good enough' and you need to keep building up the confidence with the bike tilted over.

If you are leant over, on the gas a bit, and the rear steps out - then that's your limit

Your rims are the same size as my 91 fzr6 champ. I have done half a dozen track days on a pilot power front110/17 & BT014 150/18 rear It aint no R6 but has passed a couple at morgan park raceway.
Get the best that will fit & save up for the insurance premium on your first BIG Ar$ed Rear Tyre bike.
My first track day a certain Brisvegan ksrc memeber name "Major Strap on" (Gnome) passed Barrabob 6r, fab 12r. kev 12r. yappa 6r & myself fzr6 on a ZZR250 shod with Dunlop road buttercutters.
hth.
Cheers Brett

Once again I'm speaking with not a great deal of expertise to back me up (lucky then that I-K at least knows what he's talking about!) but I think you'll probably find your ZX2R will happily lean to the point of scraping the pegs before it lets go.

i can assure you about this as i leaned and scrapped the my toe in a left hand corner at 70kph

So if i was going to buy a new tyre for my ZX2R (a), and i wanted it to be fat and juicy, what brand and model would you say? Also whats the price for a good tyre for a ZX2R? I've never had to buy one until now.

Cheers guys...

<<<<--- The new guy !

for commuting/twisties but riding everyday bt45 bridgestones for twisties and trackdays weekends only gpr70s.

Barrabob wrote:for commuting/twisties but riding everyday bt45 bridgestones for twisties and trackdays weekends only gpr70s.

Or a Bt014 for the best of both worlds. should be $200 - $250 fitted & insist on steel valve stems if it doesn't already have one.

hth.
cheers Brett