Hello all,
New CBR here, 91 F2, pretty stock. It came with some old Dunlop touring rubber in the 160-60 ZR size at the rear. Looks pretty skinny to me. Can I put a 170 on that rim? I recall my Honda Hawk had F-2 wheels with a 170 rear and it seemed OK.

I tried looking through the Search function but I must have done it wrong and didn't find an answer..Sorry this has probably been asked and answered hundreds of times, but ....

Also, different subject...the fork preload is all the way stiff and it still sags and dives too much for comfort. Normal? New springs (for now)?

Thanks, love the little scoot after a brief interlude on a VFR...ugg, lot of work that one...OK but heavy and BIG!

Don Hanson

 

Don, you definitely can do it, whether or not it's safe, is up for debate - some say it's very dangerous, others say they've ridden on track and even raced with one size up, and not had a problem...they will definitely fit, though. The profile will without a doubt be somewhat deformed.
Best recommendation would be to acquire an F3 rear rim, which is what's on my F2 - the stock size for this rim (5", whereas F2 rim is 4.5") is the 170/60.
With the F3 rim, you can fit a 180 even, which, if I remember correctly might require a little trimming of the fender/tire hugger, if present, but once again, this is recommended/not recommended by seemingly equal numbers of people - I myself have not run a tire size that is not optimal for the rim, whether on street or track, so I cannot speak from experience on whether or not it is dangerous...some of it really depends on what kind of riding your doing.

 

Thanks, I did ride my 70+hp race Hawk with the skinny rim and the 170 rear as primarily a track bike. I will look for an F3 rim then. This bike is (ostensibly) my S.O.s and she is not a fast rider...but I get to take it to the track, too...so I want to at least take the older touring rubber off before I get out there. I love the way this handles compared to my big VFR....but I have to say, the V4 torque of that one makes up for it's "stately" demeanor when flogging it.

I am currently looking for another 600.

Don Hanson

 

The stock size on F3 rim was still the 160. Some of the older 600's came with 5.5 in rear wheel and they came stock with 170. Then they started going with the 180. I got a stack of old Sport Rider Magazines I've been reading at work. When the F4 came out it had 5.5 wheel with 180 but the Kaw had the same size wheel with the 170. What the hell?

 

But, lets think about this for a second. 160/170 is 10mm difference. F2 wheel/F3 wheel is half inch difference. 10mm is almost .400. A half inch is .500. So I would think the 170 would be perfectly fine on the F3 wheel. I would run a 170 on the F3 wheel no problem. But I would also think a 180 on the F3 wheel would be no problem even on the track. But most people say dont do it. But if you do the math it dont seem like that big of a deal. But they all say "slow handling, distorted tire profile, stick with manufacture recomendations. blah blah blah. One more thing any of you watch the Harley XR1200 road racing series. They are using the wrong size rear tire. Why? Because its the compound they need? Because its a spec tire series? Hmm.......interesting.

 

Without a doubt, the 170/60 is perfectly safe on the 5" rim...I'm surprised though, that you say the 160/70 was also the stock size for the F3 with the 5" rim as well as the F2, not because I think you're wrong, but because a lot of F3 guys have said their bike came stock with the 170 - I have never owned or ridden an F3, so I have no real knowledge of it, other than what I've been told. At any rate, the 170 works well on the F3 rim, though the wider rim could make better use of the 160 than the 4.5" F2 rim.
I do keep up with the current AMA stuff, and watch the Vance & Hines XR1200 series when I can (don't have Speed2 through ***, in KS )... Frank, what rim width and tire sizes are the running on those HDs?

 

Too many numbers

 

...and too early in the morning for said numbers

 

Any magazine I've ever seen where they were testing new F3's had the 160 rear. I'm not saying some came stock with 170's I'm just saying what I seen in old magazines when those F2's, F3's, and F4's were new. Oh yeh, I still got most of those magazines. I'm just saying.

 

It works well with no issues at all. I like the feel of the bike and the larger profile looks more proportional to the bike...I thought the 160 looked kind of small. I mounted Dunlop Q 2s and they do stick! The bike did a track school (Pridmore's Class) last weekend at Oregon Raceway Park, a tight and technical track. The temps were in the 90s. With my wife riding the F2 (she is still learning sport riding) the tires were hardly stressed at all. The general wisdom for air pressure was 29lbs, which I put in and they worked well at that.

It was hard to listen to my almost newbie-rider S.O. going down the front straight shifting at 5000 rpm, to watch her learning, but she came away a much more confident rider. The F2 was the hit of the day in the paddock...."Wow, that thing is a classic!? or "I had one just like that back in the 90s"
Don Hanson