[katanarider]

Ok, did a test of the transmission with the bike up on a stand and engine running 3000rpm.
Important note: Before I posted that the 100mm pushrod worked with the cable clutch, NOT. That's too long and slips the clutch.
I slowly shortened the push rod till I got it right: 98mm seems just right.
The clutch is very sensitive to just a few mm, 95mm is way too short.

98mm then...very nice details Sir !

[buffalobill]

About rear wheels, seems like a waste of money to get a 5.5 wheel just for a 170/60. That's not much wider than a 160, because you can only use one side at a time.
Makes more sense to spend the money on the best tire @160/60.
For a track/street bike that means a Michelin Power One or equal.
I was looking at 3.5" front wheel possibilities for my pre, and a Kat 98-02 bolts in but they want over $200 for them on ebay.
Again, it makes more sense to use the 3" wheel I got with a 110/70.

[katanarider]

I noticed I have slower turn in/more effort with the post 98 front rim and wider tire.
I think I would keep the pre front rim, but it may be harder to find good track tires... I don't know
You mentioned getting a more expensive name brand set of tires, but did you consider Shinkos race slicks ? I've wanted a pair for a long time, just haven't had the spare cash. Since they wouldn't pass state safety inspection for the street, I would have to get another set of tires just for inspection then swap...just more trouble than I can handle at the moment.

[buffalobill]

Well, for the track you gotta use tire warmers for slicks or only ride in July. More work and fu$$ spoils the fun.
The best street tires warm up real fast on the track, plus they're great rain tires too. So no work, no fuss, more fun.
Shinkos will be fine on the track, and I rode my old GS1100G on the track with them, but that was my 1st track day and the only bike I had.

Thanks for telling me about the slower turn in with the wider rim.
I spent much of yesterday researching tires and rims.
Right now I have 120/60s on my 3" rim, because that's what the Slingshot had, but they're supposed to be on 3.5 rims.
I haven't had any grip issues with them on the track, and I was riding real bad, trail braking most of the way to the apex and my weight up front.
The one problem I do have with them is: air leaking, about 4lb psi in the 1st 24 hours.
I think I'll try 110/70 next time, Michelin, Bridgestone and Shinko have sport radials that size.

[Kreylyn]

Tire profiles make a larger difference in turn in than the rim width. Every tire out there will have a different profile for the design and is the most common direct effect on how the bike feels and handles.

Speaking specifically about profiles in this manner, a simplification is to say it's one of the largest differences between "touring" and "sport" tires from the same manufacturer. Touring tires will have a "flatter" profile (slower turn but steadier on long rides), and sportier tires will have a "taller" profile.

The rim width can "tweak" that profile so the tire responds differently than it's designed too. An example of this would be to put an over sized tire on a rim. This pinches in the sides, pushes the center out.

The #1 most commonly used tire on the front of a kat right now is the 120/70. That's over sized for the Pre kats 3" rim. That means the tire is pinched in on the sides, pushed out in the center... makes all have a more agressive turn profile... with smaller contact patch, than the tire was really designed to do.

Here is a big thing with that though... it's also a very uneven profile. It has several difference transitions. Quick drop off the point (so turn in starts fast) then it flattens out a bit then it drops off real quick again near the edges. This makes taking turns rather sporadic, and you will get different bike feedback at different lean angles. It's not something I would recommend on a track when your trying to get every 10th of a second out of a lap.

The results might be a quicker turn in to start, but you end up with what I refer to as a "weeble wobble" through the turns. The bike dips in quick, almost too much... and instead of getting a nice smooth curve through the turn... it almost weaves as the bike keeps wanting to drop (you counter) drop (you counter).... so on.

The 3.5" rim is the correct size for the 120/70 tires. A good sport brand tire will have the profile for quick turns, and give you a smooth transition. You get steady constant feedback from the bike, and over all it's a much better feeling. Definitely would build confidence.

The original tire for the front of the pre kat with a 3" wheel was a 110/80. That's the widest tire you will be able to use and keep the proper profile.

Just to clarify... (because I'm sure someone will say how they run a 120 and never had problems... yes... the wheel still turn round and round, yes yes... I run 120s on my pre too!)... I'm not talking about working vs not working. I'm talking about minute details of performance in a track setting. Situations where 1 click adjustments on he rear shock = .01 second savings on your lap times.

Not things that make a huge effect necessarily on every day riding.

Krey

[buffalobill]

Thanks Krey, riding track days we're not worried about 1/10th of a sec either.
PS: I've had visions of how I could cut some tire room, and weld on reinforcement of the swing arms.

[katanarider]

I'm not making judgment or giving advice here, just sharing my experience...I had a 110 tire on my pre rim when I first bought my bike. From what I remember it handled better than any 120 tire I've ever put on my post98 rim. Tires I've used on my post rim are Michelin (not the Pilots, Dunlop Qualifier ( I thought it looked cool) and my current Shinko Apex. Out of those 120 tires, the Shinko has made me happiest. However, like Kreylyn was saying, I believe the Apexes sport profile is different as my Shinko Advance rear tire which is made for touring. They feel like they fight against each other on the sharpest/low angle turn ins, and will even bind up/skip on those sharpest of angles only.
EDIT: I guess if I had to draw conclusion and I was in your situation, I would say make sure you get matching name brand/style tires for front-back and choose a company that also offers the same exact tire in a 110 too...so 3 matching tires, a 110, a 120 and what ever rear tire/rim combo you decide on.

[steves]

You can still get modern rubber in the 160/60 size, so I wouldn't sweat it.

[buffalobill]

Fitment of a wider wheel

Ok Kreylyn,
I have a wider wheel from a 750 GSXR 88-92, and I'm reading your sticky, but no pics.
It looks like the 5.5 wheel will be 8-9mm left of center in a pre 750 swingarm.
This means that only one swing arm needs cutting?
How bad is that for handling? Seems like left-right turns will be different.
Thanks.

Kreylyn wrote:
" Lets move on to other wheels... like say, off a RF600 4.5" (curved spoke like the pre styled wheels) or the 1992 GSXR 600 5.5" (straight spoked like the Post). Both of these wheels were designed to be used with 20mm axles... and both have the same hub diam. of 5.5"

The difference is 1/2" that has to be made up. This will offset your wheel by half that much... but 1/4" that isn't really that much of an issue to be honest. You could still flex out the end of the swinger to compensate. Several people have already posted about getting bikes where someone forgot to put the sprocket side spacer back on before torquing down the axle, and permenantly flexing the swinger in by 1/4+".

See picture here.. GSXR axle, all spacers correctly in and spaced for the chain side... the difference is shown here...

[picture here]

It's not so much the axle point that you have to worry about. Pick the right wheel.. you can easily fit 3.5-5.5" rims in. The problem comes in when you look at the tire clearance.

So.... lets look at that.

The following are pictures of a GSXR 600 5.5 Straight spoke wheel with a Post Kat swingarm, a 190/50/17 tire is mounted on the rim. The sprocket carrier is the same for a Kat, the RF6, or the GSXR 6 for these model wheels. No difference there. Only differences then are going to be the size of the wheel hub, and the tire total width.

The difference in tire width between a 180/55 conti road attack mounted on a 5.5" (185mm wide) vs the 190/50 race tire (192mm wide) is 7mm total. Not that much of a difference. (anything over 180 a 5.5" rim will pull in, decreasing it's size... for example, a 200/50 tire is only 197mm wide on a 5.5 rim, but due to this the profile is way messed up.)

Sprocket side... appropriate clearance, with the wheel in correct alignment.

[picture here]

Other side though... shows the problem.. with the wider hub, pushing things to the other side offsetting the wheel, if it's lined up right you get this...

[picture here]"

[katanarider]

Ok Kreylyn,
I have a wider wheel from a 750 GSXR 88-92, and I'm reading your sticky, but no pics.
It looks like the 5.5 wheel will be 8-9mm left of center in a pre 750 swingarm.
This means that only one swing arm needs cutting?
How bad is that for handling? Seems like left-right turns will be different.

I hope your not thinking about racing around a track with a off center wheel. I can tell you now that its not going to balance the 500lb weight of the bike worth a damn. On top of that you've got your body weight shifting around as you transition left to right...not good in any way!!! Think of it like this, your tires have a weight limit of a few hundred pounds each, but combined they hold the 500+lbs of the Kat. With off set wheels, the weight transfer will be increased on one tire or the other which could lead to a blow out. Plus, the leverage difference front to back is going to most likely twist the bike around in a 360 spiral spin.

[92xjunker]

That doesn't sound quite right.

[katanarider]

Ever pulled on a wrench from the center vs the outside outer edge and feel the leverage/torque difference ? You'll notice the nut breaks free/spins easier, same principle in reguards to the front,back wheels and center mass of the bike.
EDIT: The wrench thing maybe not the best example, but its going to cause un-balance front to back and spin easier during a lean which is the point I'm trying to make.
Then there is the profile issue which has already been discussed.
2nd EDIT: I can't really explain it , so I guess I don't know.

[buffalobill]

First I think had the sprocket hub on the wrong side when I looked at this, (sorry), so the offset will be to the brake disc side - the right? Because the hub is wider.

Well katanarider, Front to back is perpendicular to the offset.
Geometrically the offset will affect a different rotational axis than it was designed to have, not ideal.

The bike will dip lower on left turns, than right. That will be frustrating to the rider>me.
Having a 4>1 exhaust changes the balance too.

[katanarider]

Well katanarider, Front to back is perpendicular to the offset.
Geometrically the offset will affect a different rotational axis than it was designed to have, not ideal.
The bike will dip lower on left turns, than right. That will be frustrating to the rider>me.
Having a 4>1 exhaust changes the balance too.

You said it best !
Axis, thats the word I was looking for. I thought about saying that but I got tired of editing my reply. I tend to speak with out putting much thought into my words...Sorry everyone

[buffalobill]

I been waiting for somebody to chime in who rides with a 5.5 wheel, let us know how much of a difference it makes from their experience.
I'm just talking theory here, I haven't yet taken the time to mount my 5.5 wheel with it's 190 tire for a look see and measurement. Will probably do that soon.