Katana (GSX600F, GSX750F)
Tire Advice, Tire Tips, Tire Warnings

SPECIAL NOTE:
 
   There is a general "Understanding tire technology" webpage on our site here: How to understand Motorcycle Tires: Sizes, speed & weight ratings, belt technologies, arc-design, etc.... The page you are currently at has additional advice specific to tire concerns for Katana (GSX-F) motorcycles, although it may well apply to certain other similar motorcycles (Bandit GSF, and SV650 come to mind). Most of these items were collected from various tire-related posts by myself (The CyberPoet) at KatRiders.com to tie them into a single webpage for future reference by other riders.
 

98+ Rim Sizes and Acceptible Rear Tire Sizes:
 
   The rear rim on the 98+ is built to take a 150/70ZR17. Normally you can go up one size by decreasing the sidewall height 10% (160/60ZR17), which gives you an advantage in straight-line dry grip, but increases tendency to hydroplane (more surface contact, same weight = less loading per square inch) and will force the tire to deform slightly in response (normally making run a bit hotter than the stock sized tire, thus last a shorter number of miles). The wider tire will also reduce the handling sharpness of the bike compared to a narrower tire with the same tread composite, arc design and tread design (can't compare a 150 Macadam to a 160 Pirelli or a 150 Metzeler -- the Pirelli and Metzeler are just head & shoulders above and have both better tread composites and triple-arc radius designs). Finally, a larger width tire will also weigh more, which penalizes handling, braking and acceleration some as well.
 
   Once you go past that one step-up, you are traditionally setting the angle of the mounting lip on the tire at hard enough of an angle that it can provide stress issues at the first bend above the mounting flange of the rim. The tire also has to distort to compensate for being pulled so tightly at the center, so the arc deforms to compensate, resulting in elevated heat at the carcass. Both of these issue can lead to premature and unexpected failure, although it tends to be infrequent. Only one company produces a 170 width tire specifically designed to mount to a 4.5" mounting flange size (the size of the 98+ kats' rear wheel) with all the other required specifications (i.e. - weight/speed ratings, etc): Avon Cooper.
 

1988-1997 Katana Rim Sizes and Acceptible Rear Tire Sizes:
 
   The 3.5" rear rim on the earliest 88-97 Kats was built to take a 140/80VB17; that tire was later replaced in the line-up with a radial Z-rated replacement. Normally you can go up one size by decreasing the sidewall height 10% (150/70ZR17). Because no manufacturer has been putting any new tire research into 140/80V17 tires for over 8 years now, I specifically recommend moving any pre-98 to a 150/70ZR17 tire, which will provide you a benefit in both safety (because it is a radial, not a bias tire), as well allowing you access to the most modern tire compounds and designs from many manufacturers.
 
Do not attempt to mount a 160 width or wider tire on a stock (4") rear wheel of a pre-98!
 
The 98+ Rear 4.5" rim can be swapped into a pre-98 Kat to permit running up to a 160/60ZR17; 88-90 Kats may have fitment issues with this swap -- check katriders.com for advice before starting the mod.
 

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Some Tire Manufacturers' Fitment Charts are Wrong!
   Some manufacturers have the wrong weight requirement for the pre-98 front tire in their fitment databases & printed materials, so their tire recommendations are dangerously wrong. I have contacted Metzeler and Pirelli about these issues already. The correct weight ratings for the Katana tires are listed below, as well as at my Katana Family Tree Webpage: Specifications, measurements, standards. The weight requirement for a pre-98 front tire is weight code 57, which translates into 507 lbs (230 Kg) -- some fitment cross-references have it incorrectly listed as 54, which is about 40 lb lighter!

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Katana Original Tire Specifications:
 

• 1988 - 1997 Katana 600 - FRONT: OEM was a 110/80V17 (57V). We recommend moving to a 120/70ZR17 (58W).
• 1988 - 1997.5 Katana 600 - REAR: OEM was a 140/80VB17 (69V). We recommend moving to a 150/70ZR17 (69W).
• 1997.5 - 2006 Katana 600 - REAR: OEM was a 150/70ZR17 (69W). We recommend sticking to a 150/70ZR17 (69W)
   
• 1988 - 1997 Katana 750 - FRONT: OEM was a 110/80V17 (57V). We recommend moving to a 120/70ZR17 (58W).
• 1988 - 1997 Katana 750 - REAR: OEM was a 150/70VB17 (69V). We recommend moving to a 150/70ZR17 (69W)
   
• 1998 - 2006 Katana 600 & 750 - FRONT: OEM was a 120/70ZR17 (58W). We recommend sticking to a 120/70ZR17 (58W).
• 1988 - 2006 Katana 600 & 750 - REAR: OEM was a 150/70ZR17 (69W). We recommend sticking to a 150/70ZR17 (69W), although a 160/60ZR17 can be safely used.
   

Where the R&D Dollars are going in terms of tire sizes
 
   All of the major MC tire manufacturers are concentrating all their R&D on 120/70 front tires, thus buying a 120/60 (or a 110/80, etc) means that you are effectively buying older technology, according to MC tire insider Bryn Phillips of Bridgestone (includes Q&A session with a former tire rep: see UK Buell Enthousiasts Group - Thread: Tyres).
 
   You'll find the 70 profile is also where virtually all the R&D in sports-touring tires goes for rears (because most sports-tourers & many sport-bikes use 70 profile tires as spec).
 

Why to NEVER run Bias-tires on a Kat if you don't have to...
(i.e. - why to use radials)
 
   Bias motorcycle tires contain plastic belts of some sort (nylon is common, polyester, dacron and others less commonly). Although a distinct improvement over prior tires (those built with cotton and other naturally occuring threads or no threads at all -- pre 1940's), bias tires do not compare well to modern metal-belted radial tires.
Although it can be said that radial belts can be made of plastics (and that bias belting can be made with metals), to the best of my knowledge, all currently offered radial motorcycle tires have metal belts of some form (steel, kevlar, etc) and all bias motorcycle tires utilize plastic-based belting.
 
   Bias tires offer some serious draw-backs compared to metal-belted radials (and these are the reasons virtually every non-cruiser bike now sold spec's radial tires as stock fitment, as do many of the cruisers):

1. Shape retention at rapid depressurization.
   THIS IS THE CRITICAL ONE.
      Plastic threads have good tensile strength, but very little compression strength or form memory. When your tire gets seriously punctured at speed and loses pressure very quickly, bias tires tend to result in very nasty spills because the tire deforms immediately. Metal belted radials transfer the load into the metal belts and retain their shape normally long enough to come to a full and complete stop, even with very major damages, which can be a serious lifesaver.
      A specific example from one of our own at KR/KP (told as exactingly as I can remember): one of our members was running at high speed through the Eiffel forest (lies at the eastern border of Germany and what is now the public road used to be used as a race track) when, while pitched over hard, his tire hit a large piece of jagged metal debris from a truck at speeds of about 85 mph. The hole the debris cut was about 3/4" across and about 6" in length, across the edge of the tread area and well into the sidewall area. If I recall correctly, he was two-up at the time as well. Because of the steel belting, his tire held up well enough to slow, clear the turn and come to a complete stop safely. If he had been on the bias tires he had been running just three weeks earlier (before I told him never to run bias tires and why), he and his passenger would almost assuredly be dead.
    
2. Weight, and handling/braking prowess
      Although nylon and polyester weigh less than steel, the ability to use far thinner steel threads to acheive the same strength normally represents a total weight savings in the tire construction, which improves handling, braking and acceleration.
    
3. Heat distribution.
      The contact patch of the tire generates heat as it comes past the road and deflects upon contact, then again when it bends back to it's original shape. Plastic threading is a poor carrier of heat, while metal is good carrier by comparison. Thus, metal-belted tires warm up quicker, and run cooler over-all because the heat generated spreads through the carcass much more evenly, while bias tires will create localized heat build-up that can lead to earlier failures, accelerated wear and even delamination in cases of being under-pressurized.
    
4. OEM Spec in the sizes you want to run
      Because the OEM specifications for most years Katana's is specifically radials, and Suzuki specifically warns against using bias tires on those bikes (I believe bias tires shipped stock through '95, at which time the entire line-up was changed to radials -- though I'm not sure of the year break for it). The fact that the earlier Kats can run radials is just a boon for them -- make the switch, gain the benefits.
    
5. Better Grip at High Speeds
      Because radials excert a better grip factor at speed (if using identical tread compounds and shapes) due to the rotational outward pressure of the metal belting. This also makes for a smoother ride and better contact patch rentention over slightly uneven surfaces (better at sucking up minor irregularities such as 1/16th to 1/8th inch imperfections at the road surface) at speeds above about 60 mph, as welll as providing less kick-back under heavy braking. Bias tires do tend to provide smoother rides at lower speeds.
    
6. Better Straight Line Stability
      Radials provide better straight-line stability at high speeds due to the directional nature of the belt windings.
    
7. Better Fuel MileageBecause radials provide slightly improved fuel mileage (due primarily to being able to transmit more contact to the road while minimizing rolling resistance).
    
8. No Z-Rated Bias Tires exist
      No one makes Z-rated bias motorcycle tires (as far as I know), which is the speed rating called for on the Katana due to a combination of load weights and heat build-up. Generally, most bias tires cap off at H ratings, although some manufacturers do now make V rated bias tires for smaller-sized (generally 500cc and smaller) bikes.
    
9. Where the R&D Dollars Go
      And finally, because no major tire manufacturer is putting any serious research into bias tires at our tire sizes, concentrating their R&D efforts on radials in specific sizes which represent the direction of the market and racing efforts about the globe. Thus, in general, bias tires are old-technology, not benefiting from the newest R&D, unlike the better radials on the market.
    
    

Macadams = Crap-a-damns
tire apex design and
selling your Macadams right away
 
   The stock Michelin Macadam has an gradual arc shape (single apex) that is very poor for handling. Suzuki uses it for a couple reasons -- it's cheap for them in bulk, and it discourages young bucks who have this as their first bike from pushing it beyond their limits (as evidenced by those of you saying you felt as if the back end would give out). This has zero to do with the fact that it's a 150/70ZR17, and everything to do with the fact that it's a Macadam (commonly called Crap-a-damns around here).
 
   Moving to a Metzeler Z6 all around (120/70ZR17 front, 150/70ZR17 rear) will fix this issue, as will switching out to Pirelli Diablos Stradas (120/70ZR17 front, 150/70ZR17 rear), or straight Pirelli Diablos (where you have to use a 160/60ZR17 rear because it's not offered in a 150/70ZR17 -- not a safe move for a pre-98 with the stock rear rim). A pair of Z6's will run you right around $185 - $220 mail order; you may be able to find a local price in that ballpark after you factor in mounting costs (many dealers mount tires they sell cheaper than they mount tires from elsewhere, since they've made their money on the tire as well).
   If you feel the stock tires aren't up to snuff (OEM tires: they aren't), replace them and sell the existing ones on eBay to help offset the cost -- someone will want them. I've posted eBay item descriptions with the eBay-acceptible html text already embedded here:
 
Used Michelin Macadam 150/70ZR17 eBay write-up (html as a text file)
and
Used Michelin Macadam 120/70ZR17 eBay write-up (html as a text file).
 
   Modify those two files as necessary to disclose the truth of the plug, wear levels and embed your own pics. Order yourself a set of Metzeler Z6's, list up the Macadams when the replacements arrive, and when the tires get changed, you'll already have a buyer for the used ones ;)
 

Why Not to Use Mismatched Tires:
 
   As for running mismatched tires -- don't do it. There are several reasons, including: the front tire "sweeps" for the rear's tread pattern. Mismatched tread patterns will not permit correct sweeping and may cost you a loss of rear traction on water, sand, etc.
   The arc design between the tires is designed to work together, so that as the bike leans, both tires are offering the same surface to the ground in unison rather than exerting stress through the frame due to an imbalance in angles (which again can cause loss of traction).
 

CyberPoet's Specific Tire Recommendations:
 
   Here's my tire recommendations, based on actual back-to-back tire swaps on 98+ katana's (one brand-new set a week, a few hundred miles inbetween):
 
1. If you primarily rail your bike hard (knee-down cayon riding), live in a dry area (think desert, etc) and wet-grip isn't critical (but dry-grip is), get yourself a set of Pirelli Diablos (not Diablo Stradas) or a set of the Metzeler SportTecs. Best dry surface grip and great triple-apex design. For street/track use on a 98+, go 160/60ZR17. Neither is available in a 150/70ZR17, and the 150/60ZR17 isn't weight-rated appropriately to the Kats, so these tires are only available to 98+ rear rims for safe mounting.
Expect 3k - 5k miles out of a set on a stock Kat.
 
2. If you primarily commute, tour, engage in all-weather riding or high-speed highway mile eating, with some railing involved, get yourself a set of Metzeler Z6 Roadtecs or Pirelli Diablo Stradas. They have a good triple-apex design, about 90% of the dry-weather grip of the straight diablo's, about 140 - 200% of the wet-weather grip, and about three times lifespan in them. Go 150/70ZR17 rear for best handling. The Pirelli Diable Stradas appear to be exactly the same tire in terms of design (Metzeler builds Pirelli's motorcycle tires for them), with the exception that the Stradas have only 4 rain-grooves for every 5 that the Z6's have.
Expect 10k - 14k miles out of a set on a stock Kat.
 
3. If you for some reason insist on having the biggest, widest damn tires you can squeeze in (which negatively impacts handling, but it seems to be bling-bling right now), Avon, a Cooper Tire subsidiary (which in turn is owned by Continental, aka Conti) makes a 170 that will fit the stock rear rim of the 98+ Kats. They also have a limited road-hazard warrantee in Canada & the UK & the USA (covers the tire, not the labor, valid for the first 3.5mm of tread depth wear). This tire is about 5 years old now, so it doesn't benefit from the latest compound and tread-design research the way the other tires I recommended above do, but they do work.
Expect 6k - 9k miles out of a set on a stock Kat.
 
4. Or, if you have the $$ and time to try it, do what I did and simply order yourself a whole variety of suitable tires (you can get quantity discounts this way, both from the vendor and from the local shop that will install them each week if you don't install them yourself). Compare them back-to-back and sell the barely used ones on eBay -- if you shop wisely, you'll make back every penny you spent on tires when you resell them (at least I did). Keep the ones you like the best. I compared: stock Macadam 90x's, Dunlop 205's & 207's, Metzeler Z4's & Z6's, Pirelli's Diablo's, Chen-Shins (never again!), plus rode other people's Avons and Bridgestones during that same timeframe. You can pick your own tires for your own comparo...
 
Tire Test Notes from my back-to-back tire tests:

• Chen-Shins, aka Barracuda's, aka JC Whitney no-name house-brand, aka Maxxums: the crappiest, cheapest tires ever. Use only if you are showing threads and are in starving college student mode; expect no handling or stopping capabilities. Worst tire I've ever tried on the Kat, these tires are really designed for 400cc and under super-light-weight/low-power bikes used in the early 80's and in third-world countries.
• Michelin Macadam 90x/100X: Broad, single apex design makes for wallowy, slow handling but decent braking performance. Ran into scalloping, uneven tire wear. I suspect high road-surface temps in Florida, combined with my highspeed (100 mph+, hard lean-angles) style of riding played into the tire tread wearing unevenly.
• Dunlop 205's & 207's (not 207RR): Dual-apex design, better than the Macadams, but advantages wore away within 1200 miles. Same type of uneven tire wear as the Macadams, although it took longer to develop. I suspect high road-surface temps in Florida, combined with my highspeed (100 mph+, big lean angles) style of riding played into the tire tread wearing unevenly.
• Pirelli Diablos (not Diablo Stradas): Triple-apex design, superb dry-weather grip, unfortunately grip nose-dives on wet surfaces, especially at first mist and in torrential downpours.
• Metzeler Z4's: My original tire of choice; went through 3 sets of them so far (almost 30k miles) between two late model Kat 600's. Triple-apex design, more grip than a stock Kat 600/750 can break loose railing as hard as possible; hyper-reliable grip in the rain (which we get a ton of in Florida). I liked the fact that when locked, the rear bunny-hops a couple times before sliding out... Now outdated and out of production, replaced by the Metzeler Z6 RoadTecs (see next entry). Do not buy any Z4's as they are (now) inevitably very-old-stock that's been sitting on a shelf for who-knows-how-long.
• Metzeler Z6's: What I run these days as my tire of preference on the Katanas. Metzeler's engineers tell me that they are basically the Z4's with a smaller initial bead compound (10% more grip in the dry, 18% more in the wet, and 8% longer lifespan) and a modified tread-pattern for supposedly better heat & water dissipation. I'm on my second set now, and the first set outlasted my Z4's by about 3k miles under the same duty-cycle (putting in 14k miles total before hitting 1mm tread-groove depth). These are the bomb in the rain, and I've railed the Dragon many times on them. A stock Katana engine will not over-power these, even knee-down in a tight apex. The only thing I'm not thrilled by is the oscillating center groove in the front tire -- the Z4's didn't have any center groove at all.
  KNOW THIS: a stock 150/70ZR17 Metzeler Z6 is actually 159/61ZR17 when mounted on a 4.5" Kat rear rim.
• Avons: Used to be the Canadian tire of choice. Not sure why, but I suspect that road-hazard warrantee plays into it. I liked them, but they still weren't quite up to the spec of the Pirelli's and Metzelers, plus I got an uneasy feeling about the belt construction (can't recall the exact why's anymore -- perhaps bias tires?)...
• Bridgestones: Longlasting, single and double-apex designs, but took quite a while to warm up and never were as grippy as the Pirelli's and Metzeler's.
   

Q: I've got a 160/60 rear tire on my pre98, and i've read this is bad, why is that?
 
   The reason it's normally considered "bad" is really to say it's "not perfectly safe" because the width of the tire on the stock pre-98 rear rim causes a less than ideal mating between the rim flanges and the tire bead lip, and exerts excess stresses onto the junction between the tire bead reinforcement and the sidewall (as well as deforming the actual arc radius of the tire, causing it to run hotter than intended). Most riders who try it may like it, but are missing the fact that the squeeze is making the tire act more like a 150/70 than a 160/60. Switching rear rims to a 98+ Kat rim will set everything right again, since the 98+ rim is wide enough to take a 160 safely without too much distortion.
 

Comparing Online and Catalog Tire Prices:
 
   When shopping for tires online, always include shipping costs into your calculations. Many firms low-ball tires and then make it up on shipping. I've bought my tires mail-order from:
AmericanMotoTire.com,
RonAyers.com,
DennisKirk.com among others. Always shop around, and ask around KR for which companies are trust-worthy (some have bad reputations -- all of the above have good reps).
 

Comparing Online and Catalog Tire Prices - PART 2:
 
   Be cautious: depending on where you live, local dealers & shops may not be willing to mount tires acquired from elsewhere (shops in rural WV were like that), or may charge an arm & a leg to mount tires they didn't sell you. Shop around for mounting prices before you buy the tires, so you can find out if you are going to be overly penalized by buying your tires mail-order.
 

New Tires = New Tire Pressures!
 
   Double-check with the manufacturer's site on recommended tire pressures on your bike with a specific tire. Not all tires are supposed to run at the same pressures as the OEM Macadams or Dunlops that originally came with your Katana (the Metzlers and Pirelli's for example run 34 - 36 PSI front, 37 - 39 PSI rear rather than the 32/36 recommended by Suzuki for the OEM Macadams & OEM Dunlops).
 

Hey, what's up with Pirelli and Metzeler?
 
KNOW THIS: Pirelli motorcycle tires are built in Metzeler's factories. In some cases, the division is even smaller, with the Pirelli Diablo Strada tires being produced two tire-press machines over from where Metzeler's Z6 roadtecs are made (information came from decoding the DOT required tire production facility information on a front Z6 and a front Stradas).
 
   Metzeler is the only motorcycle-only tire manufacturer in the world. In a weird bit of stock and control swapping, the two companies own interests in each other.
 

Balancing is Critical!
 
   Balancing is critical. Always get the tires balanced at time of install, and again later if they start acting up.
Also insist the tire's valve is replaced at time of tire replacement for your own safety -- unless you are using my specialty lifetime aluminum 82 degree tire valves (which are good for the life of the bike -- you can still replace the valve core if you want)...

Click here to buy a set of our specialty valves now!
 

Chain and sprockets at time of tire swap is cheaper!
 
   If you have your local motorcycle garage or dealer do your tire mounting, getting a new chain and sprockets installed at the same time can save you the majority of what they would charge to install them separately. You may have to haggle a little with some shops (pointing out that they'll already have the wheel off the bike) to get the discount, but any good shop will cut you a significant break on the labor pricing...
 

Cheaper Tire Mounting (Part 1)
 
   Tire mounting prices vary very very widely, from as cheap as $10 a wheel (off the bike) to the highest I've seen being around $85 a wheel (on the bike). Let your fingers do the walking to price tire mountings before you drive to your local dealer and get a shock. You may also want to call some car tire places -- with a $20 bit of adaptor hardware, they can mount and balance motorcycle tires and usually charge dirt-cheap prices if they are set-up to do it.
 

Cheaper Tire Mounting (Part 2)
 
   Most dealerships & shops will charge you half-rate or less if you bring them the wheels already off the bike (saves their mechanic's time). Ask about it when pricing mounting...
 

Cheaper Tire Mounting (Part 3)
 
   If you have the space to house a tire mounting rig (say 4' x 4' worth of floor space), you can get a tire changing rig from HarborFreight for around $100, plus the other stuff you'll need for another $40 (tire levers, etc). Compare that to some shops charging as much as $70 a wheel to mount tires, and it makes sense to learn to mount your own if you can. There are some good write-ups online with details, tips and tricks.
 

The Biggest-is-Best Tire Myth Clarified
 
   Now it would seem the latest rage is to shoe-horn the widest tire possible onto the bike, because this is what is happening on the R6/R1/GSXR600/GSXR1k/etc. The fact of the matter is that these bike's handling is designed around this fact (or in-spite of it, with extremely aggressive headstock angles to compensate). They would still handle better with narrower tires, but then the motorcycle manufacturers would open themselves up to a ton of lawsuits from street riders who lost the rear-end traction by getting on the gas while coming out of a dry corner. Thus, it's a trade off between sharper handling and the ability to sucessfully transmit power to the ground without loosing the traction in the rear excessively.
 
   On a bike like the typical Kat 600 or 750, there simply isn't the horsepower or torque levels to overwhelm the stock tire sizes coming out of the corner with a good compound on there (this may well change you've changed gearing radically, or dropped in a bigger engine like a Bandit 1200 motor, or used a wise-co over-bore kit).
 
   When you look at race bikes, they use the narrowest tire they can readily get away with, because narrower tires handle better -- they weigh less (so they brake easier, accelerate faster, and change direction quicker), and their arc shapes are sharper (making it easier to drop the bike into the turn). MotoGP bikes almost all use 16.5" front wheels at this point for just this reason...
 
   Thus, wider tires are strictly BLING on a Kat, and actually have serious draw-backs in handle prowess for the bike.
 

I got a Flat Tire, what do I do?
 
   Depends on where you are and how desperately you need to be able to ride. Although Z-rated radials should never be patched/plugged according to every manufacturer (except Dunlop USA, who says you can plug certain Dunlop Z-rated rear tires once, but the max speed rating drops to 70 MPH from that instant forward), AND it's serious enough of an issue that it's even illegal to plug/patch a Z-rated motorcycle radial in the UK, the reality is that you don't want to be stuck in podunk or the middle of nowhere. So you go to the auto parts store and get a tire plug kit (or hopefully you'll already have one under your seat), pull out whatever punctured the tire, and following the direction from the plug kit, plug the hole. Pump up the tire and ride on after whatever the cure time is, ordering a replacement tire as soon as you can, like as soon as you get home.
 
   To help offset the cost of the replacement tire, list up the plugged tire on eBay (disclosing the repair!) -- someone will want it even though it's plugged, either as a stunt tire for a single weekend's use (or burn-out tire), or because their bike doesn't get riden over 70 MPH... If you time it right, you can have your replacement tire arrive from mail order at the same time as the old tire sells on eBay, so you can immediately mail off the old tire (may also save you a tire recycling charge, depending on your location).
 
   This is also a great excuse to replace a set of poor handling tires with something that handles much, much better, like a set of Metzeler Z6's.
 
   Remember, your tires are the single most critical factor in your safety on a motorcycle: a blow-out at speed can easily spell your untimely demise, and being penny-wise and dollar-foolish is just stupid when it comes down to tires on a 500+ lb motorcycle!
 

Using Tires to Lower the Bike:
 
   If your inseam is particularly short and you have problems getting your feet on the ground, aside from all the other tricks to get the bike shorter, moving to a 60 profile tire in the same width instead of a 70 profile tire can trim another 1/2" off the total height of the bike -- although it will also trim off 1/2" of ground clearance.
 
   CAUTION: Make sure that the shorter-sidewalled tire is still weight rated appropriately for your Kat! Many manufacturer's 150/60ZR17 and 120/60ZR17 tires have significantly lower weight ratings than their 150/70ZR17 and 120/70ZR17 tires!
 

I accidentally bought a Metzeler Z6 in a 110/70ZR17, what do I do?
 
   First, you contact Metzeler & the seller and see if either will swap it for a 120/70ZR17 (58W) Z6 tire at no charge, since Metzeler's fitment catalog and fitment database is wrong (or was as of 10 Nov 2006 [still is as of Jan 08]) -- their 110/70 is rated at a weight rating of 54, and all the 1988-2006 Kats call for a weight rating of 57 (pre-98) or 58 (98+).
 
   If that doesn't get you the satisfaction you need, download this text file to sell the tire on eBay (the file already contains the correct cross-referenced bikes and marketing information -- all you need to do is change the condition statements for the tire and insert your own pictures):
Metzeler Z6 110/70ZR17 eBay text file.
 
CAUTION: DO NOT RUN A 54 WEIGHT-RATED TIRE ON ANY KAT BUILD BETWEEN 1988 AND 2007! It could result in spontaneous failure and your premature demise.
 

Additional readings:

• CyberPoet's "How to understand Motorcycle Tires: Sizes, speed & weight ratings, belt technologies, arc-design, etc...".
• Sport Rider: "The Rubber Plant", a visit to a Michilen Tire factory
• Dunlop Motorcycle Tires - FAQ & Tire Tips
• Wheel weight issues and handling results