Topic: CB550 tires

[Untold]

So I've been thinking about getting some new tires for my 1976 CB550k.  The tires on the bike now, that were on it when I bought it, are both the same size, front and rear.  This is my first motorcycle, and in reading up about tires, I realized that normally the rear gets a bigger tire.

So, if I get new tires, should I stick with the size that is on there now? Or should I be shopping for different sizes for the front and rear?  Since this is the only bike I've ever ridden, I don't know if it has affected the way the bike handles at all.

Long story short, is it ok to have the same size on the front and rear?  Or should I go back to stock sizes?

[Bru-tom]

being a noob myself, i have read a ton on just about everything.

i refer to something i read that "TwoWired" wrote, if you want it to hand as good as it should, use the same tyre sizes as the manufacturer recommends. he also mentioned that he uses the same on both his 550 and 750.

front: 325 19
rear: 400 18

hope this helps

[CafeDawg]

IF bike is running stock rims the larger is on the front and as Bru-tom noted the correct size stock for your bike are 18 rear and 19 front.  I would start looking in the FAQ section for Tires and Rim info and then google search(it's your best friend) for threads in the forum as this topic has been covered before.  Looks like you've got some reading to do in order to make an informed decision.  I have same bike and am running 100 19 front and 110 18 rear.
 Metric    Alpha    Inch
80/90       MH90    2.50/2.75
90/90       MJ90    2.75/3.00
100/90    MM90    3.25/3.50
110/90    MN90    3.75/4.00
120/80    ----    4.25/4.50
120/90    MR90    4.25/4.50
130/90    MT90    5.00/5.10
Welcome and good luck.
Respect
CD

[Untold]

Thanks guys.  I've been reading up, and they all mention running different sizes for front and rear.  Since I have the same size on the front and rear now, it made me question it.  I believe the rim sizes are stock.  I actually kind of prefer the look of having the same tires on the front and rear, though.

[Bru-tom]

please be specific now, are you wanting for example, 18" front and rear? like a bicycle?

[Untold]

Well, I'm just saying what I have.  What I want is two new, good tires in whatever size makes the most sense. 
I don't have the bike in front of me, but I believe the tires on it now are Spitfire or something like that.  And they both appear to be the same size and width.  So yes, like a bicycle I suppose.

[Bru-tom]

thats the first iv seen like that. normally the rear tyre is a lil wider than the front, the rim diameter is normally larger in front too. stick to what was mentioned, get stock tyre sizes if possible as mentioned above. see size chart posted and take it from there

[fmctm1sw]

i refer to something i read that "TwoWired" wrote, if you want it to hand as good as it should, use the same tyre sizes as the manufacturer recommends.

Sounds like something Lloyd would say.  Did he change his handle?   

[Bru-tom]

hahahaha, was supposed to be handle

was not quoting though merely referring hehehe

[cabrala]

Thanks guys.  I've been reading up, and they all mention running different sizes for front and rear.  Since I have the same size on the front and rear now, it made me question it.  I believe the rim sizes are stock.  I actually kind of prefer the look of having the same tires on the front and rear, though.

It's so incredibly easy to read all of the information and suggestions when trying to make a decision, only to end up confused as f@*#.

With that said, there are plenty of threads that will tell you sizes, brands and bang-for-your-buck by you need to read on the "science" behind the manufacturers dimensions. Running the same size front will cause uneven wear and potentially poor(er) handling. While it looks good, it might not be what you want when it comes to rideability.

Personally, I just picked up Dunlops in the proper spec listed above by Bru-Tom.

[TwoTired]

Tires same front and rear not stock.  I suspect "looks" or economy was involved in the abnormality.

Originals were 3.25 x19 front and 3.75 x 18 rear.  You can't put a 19 inch tall tire on an 18 inch rim and vice versa.
 A 4.00 rear tire was stock on the CB750's 18 inch rear rim and also works well on the CB550.  These are still available to purchase (from Metzeler for one).  I don't know if a 3.75 x 18 tire is available from any mfg.

You didn't actually list the tire sizes you currently have.  But, if they are indeed the same size front and rear, its a field modification, and I'd be wary of some rather odd handling behavior, relative the the 550 nice neutral, well balanced, easy behavior they have in stock form, Stock sizes also maintain characteristics during their tread life. 

FYI: None of the metrics come in 98-100% aspect ratio, so they will all be a compromise, from what was originally intended, though they will still "work" for some value of "work".