Topic: wider rear tire

[friedfish80]

77 CB750K motor in a 76 F model frame.

Ok im kicking around the idea of going with a wider tire on the back of my bike. I have already done the search and got a good idea in the direction that i need to get going as far as lining up the chain and all. Im just curious on how wide can one go on the back of a stock swing arm? Can swapping out to a DOHC swing arm give me more room to go wider? (i only ask that cause its my understanding the DOHC arm is longer. possibly wider?)

[bistromath]

search the archives.

[friedfish80]

I did.

I guess i dident go far enough into it

[TwoTired]

Topic has been discused ad neausea.

Isn't the stock rim only 1.85 inches wide?   Modern wide tires simply don't fit on such a narrow rim properly.

If you dig some, the manufacturers will specify the rim width required for the tires they have designed.  Dealers aren't smart enough to figure this out.  And, they would rather sell you the most expensive tire you will buy, as the that gives them the highest profit margin.  Bigger tires make more profit.

For a 1.85 rim, a 120 metric is too wide, giving excessive center wear because you have to over-inflate the tire in order to make the sidewall rigid.
As the tire "squares off", you have to fight the bars in turns to hold your line.
Works great new, as it wears out (enevenly) the bike becomes more of a pig.

The stock rims were designed for tires made well before the industry added metric sizes or tubeless into their product lines.

But, if you like ketchup in your coffee....

[754]

Maybe he wants to go fast mostly in a straight line..

 Maybe he has a big wide rim waiting...

 Maybe we dont all have the same riding styles/desires expectations..

 So i will try to help with the question;

 You can get at least a 150 in it, and get a better 60 ft than a Busa if you do it right.., hope tht helps.

 Yes going wide on STOCK, rim is not ideal..

[BVCB650]

Topic has been discused ad neausea.

Isn't the stock rim only 1.85 inches wide?   Modern wide tires simply don't fit on such a narrow rim properly.

If you dig some, the manufacturers will specify the rim width required for the tires they have designed.  Dealers aren't smart enough to figure this out.  And, they would rather sell you the most expensive tire you will buy, as the that gives them the highest profit margin.  Bigger tires make more profit.

For a 1.85 rim, a 120 metric is too wide, giving excessive center wear because you have to over-inflate the tire in order to make the sidewall rigid.
As the tire "squares off", you have to fight the bars in turns to hold your line.
Works great new, as it wears out (enevenly) the bike becomes more of a pig.

The stock rims were designed for tires made well before the industry added metric sizes or tubeless into their product lines.

But, if you like ketchup in your coffee....

Well, my original 4.50H17 rear tire size converts to a 120/90/17.  It isn't an exact crossover however. The 4.5 inches equals 114.3mm. I doubt the 5.7mm is going to matter that much. I mean it's less than 1/4 inch, So it is less than 1/8 inch on each side of the rim. Hardly noticable if at all.

[cb650]

You can go 1 size bigger on stock rims but thats about it.

[BVCB650]

If you do, you are approaching no mans land like what tootired was trying to say.

[cb650]

Ok a ? was asked so lets argue about it.   I have just about always run 1 size bigger on my bikes.  No I wouldnt go 2 on the stock rim.  If you want to bring in the slide rulers and engineers that are safety cautious so be it.  I have no probs with doing it. You gave sizes for your 79 right?  I am running a 79 rear on my 80 with a 130.  No problems.  I have a 110/90 18 on the back of my 360 and stock is a 100.  And my chicken strips have gotten the smallest they have ever been this summer. 

[bigsherm]

I have a 180/18 on the back of my 78 CB750K, in the stock swingarm.  Even with trimming the rib on the right side of the swingarm and making my own offset sprokets, it barely, BARELY fit.  I used a 5.5 x 18 inch rim from Buchanan's on the stock hub.

I don't know if my 78 K has the same swinger as your 76 F, though.

Sherm

[BVCB650]

Ok a ? was asked so lets argue about it.   I have just about always run 1 size bigger on my bikes.  No I wouldnt go 2 on the stock rim.  If you want to bring in the slide rulers and engineers that are safety cautious so be it.  I have no probs with doing it. You gave sizes for your 79 right?  I am running a 79 rear on my 80 with a 130.  No problems.  I have a 110/90 18 on the back of my 360 and stock is a 100.  And my chicken strips have gotten the smallest they have ever been this summer. 

The stock size I quoted was on my 79 650 as well as the OP's 77 750.

[Hush]

It's a hard one this, you need to measure the widest part of your swing arm near the pivot point.
My 650 came with a 100 on it which the bike shop guys told me was well under shod, the 110 didn't look much wider so I ended up with a 120, would have liked a 130 and when this tire runs out I may check out if one will fit.
The more modern 81/82 650 bikes fit 130's easy, probably the bobber boys on here would have a good idea what a 750 will take without getting radical.

[BVCB650]

Clearance is one issue, but on a stock rimm, imaging what your side walls look like with a too wide of tire? Do you really want to lay it down in a turn on gummy worm tire walls?

[Hush]

I'm pretty sure the Comstar mags will take a 130, the spoked wheels maybe not.

[cb650]

4.50H17 rear tire size converts to a 120/90/17           From your post BV.
I stated I have a 130/90 17 on the same wheel.    All I'm saying is 1 size isnt going to make a diff.  
Hush the stock size for the 16 custom wheels is a 130.  I have run a 140 on them no problems.
Still would but they cost too much anymore. 

[TwoTired]

Perhaps the original poster could state the rim width of wheel he wants to mount a tire on?

[friedfish80]

Ahh the issues of working night shift and not being able to properly add my $0.02.

Im sorry, i should have stated that if i do go this way im most likely going to be laceing a 4 inch wide rim on the honda hub. this way im not trying to squeese a huge hunk of rubber on a thin wheel.

Out of bordom today i decided to hardtail my bike by making a pair of struts for the swing arm. I actualy kind alike the ride. (seems about the same to me) Ill most likely will do the weld on hard tail this winter. and thats a whole other search topic i need to look up.

[BVCB650]

Using a wider rim for a wider tire makes serious sense. Thanks for enlightening us.

[friedfish80]

Ya know posting questions when your mostly asleep is not a good idea. Nore is going back to bed once a question has been posted on this board.

Ok so wider rim in stock swingarm or weld on hardtail. 

Dose the fact that it's got a rear disk brake change things?

I'll be up around noon central time. At the latest 3. More answers at then.

Thanks guys you all rock.

[Hush]

Can't see rear disc making any diff, it will still sit in same position and even if you hard tail it just tilt the master cylinder so it's level.