Topic: 1978 CB750F Tube or Tubeless? Size?

[736cc]

Just picked-up a 1978 CB750F and it needs a rear tire. Do the comstars run tubeless?  And whats the oem rear tire size (4.00x18? 110/90-18?)

[ZanVooden]

Stock is 4.00-18 (which i do believe translates to a 110) and yes it still is a tube type tire with the comstar wheels.

Very nice looking bike!

[TwoTired]

They are Tube Type rims.  I put 4.00x18 Metzelers, on mine.  They work well.

[cavi]

I am installing a 130/80/18 tomorrow, I currently have a 120/90/18 and it is too tall in my opinion, and it looks like there is clearance for the 130, I will let you all know for sure tomorrow afternoon.

[TwoTired]

A 130/80 tire on a 2.15 rim is not an intelligent choice, imo.

What manufacturer recommends using that large a tire on 2.15 rim?

Take a look at the change in sidewall pinch angle!

Because you can put it on doesn't mean you should.

[ZanVooden]

A 130 on a stock 78F Comstar rim?! I can imagine that being a good idea... Im not ever sure there's room with the caliper brace on F.

Although I could be getting my bikes confused as far as the caliper brace goes...
But I dont know anyone who'd recommend a 130mm tire on a stock F rear rim.

[cavi]

rear comstar on my 78 is 2.5, not 2.15, the front is 2.15

[scondon]

rear comstar on my 78 is 2.5, not 2.15, the front is 2.15

Must have a Comstar rim from a another model Honda. Would explain why you are fitting wider tires on rear than people with the stock 2.15 rim.

[cavi]

could be....

[TwoTired]

My comstars have the size stamped on the right side of the rim.  1.85 front and 2.15 rear.

[DWS]

My comstars are staped on side off rim also that sides front 1.85*19 and rear 2.15 * 18
so the best tires to get are 3.25 H19 front and 4.00H18 rear?
is that right or is there a better one and what brand?
Thanks
Duane

[TwoTired]

My comstars are staped on side off rim also that sides front 1.85*19 and rear 2.15 * 18
so the best tires to get are 3.25 H19 front and 4.00H18 rear?

"Best" is subjective and disregards intended purpose.

I put Metzelers in those sizes on my 77 Cb750F  I like them and haven't crashed yet.  Of course, I have haven't tried or tested every other tire available in the marketplace.  But, I've tried a few popular brands since 1975 and like these better than any others I've tried.

[DWS]

Thank you for your time
Duane

[Indiz_Inc]

Just to piggy back on this. I have a 78 750F and it has comstar 1.85 in the front 100/90 and 2.15 110/90 in the back. I am thinking of bumping both up a size. Front to 110/90 and rear to 120/90. Bad idea? Or limited drop offs? Also, if i get tubeless tires, should i get the tube. I see my old ones run a tube.

Thanks!

[Powderman]

A 130 on a stock 78F Comstar rim?! I can imagine that being a good idea... Im not ever sure there's room with the caliper brace on F.

Although I could be getting my bikes confused as far as the caliper brace goes...
But I dont know anyone who'd recommend a 130mm tire on a stock F rear rim.

You can?

[Powderman]

Just to piggy back on this. I have a 78 750F and it has comstar 1.85 in the front 100/90 and 2.15 110/90 in the back. I am thinking of bumping both up a size. Front to 110/90 and rear to 120/90. Bad idea? Or limited drop offs? Also, if i get tubeless tires, should i get the tube. I see my old ones run a tube.

Thanks!

Usually  one size bigger is not a bad idea. Any bigger and you start dealing with modern rubber adhesion on a 40 year old frame, may cause stress issues with other parts when you do that. Plus the bigger the tire you put on the smaller rim cause crown shape difference that will dramatically effect handling. Tire were designed to be used on specific size rims.

[Pat_at_APE]

I put a 120 rear on my 77F and it negatively impacted the corner feel.  Went back to 110 rear and will stay there.   Makes the bike feel more nimble. 

Pat at APE