Topic: wider rear rim and tire for 78 cb750f

[samm_j2]

Hey guys,

I have been looking over this topic for a week or so and read a whole bunch on it, but I am wondering if anyone can help me consolidate some stuff...

The bike is a 78 cb750f as stated and I want to put a larger tire on the back, nothing crazy but shooting for a 140-160. I think this will just give me more tire options since I have a CBR front end. Am I able to go that wide with the stock swing arm?

Yes I plan to run a wider rim as going wider on the stock rim makes no sense.

So what I am wondering is if anyone has a suggestion on which rim to use? I would like to stick with the 20mm rear axle. I get that I will possibly need to offset the front sprocket and that is fine. But is there a rim that works better than others?

any help would be much appreciated!

Thanks!

[JWB]

I have seen a number of people use this kit for a wider rear wheel for 750s and 550s.  Not cheap, but has all the items needed and is well tested.
https://cognitomoto.com/products/wide-rear-wheel-kit-cb750?variant=8109390401

[samm_j2]

Thanks for the reply JWB

I was hoping to find a mag wheel off a bike. I can't help but feel if I put a spoke wheel on the rear I would want the front to match. doing all of that is a little more than I want to spend.

thanks again though!

[gschuld]

Well, you have the wider longer late swingarm on your bike.  I assume you are planning on a 17” wheel up front, but haven’t decided yet.

Ideally budget wise you would use a matching used set from a sport bike that both matched the aesthetic look you wanted and was readily adaptable.  With an offset rear sprocket on the output shaft, you can accommodate a 180 series tire and clear the chain, but I’d think you would run into clearance issues from the tire to swingarm, even on the late arm.  150 easy, 160, likely, 180 not so sure.

A 4.25 x17 rear wheel will certainly fit in there, maybe a 5.5x17 too.

Keep in mind your need to adapt the sprocket to work and rear brake.  Custom axle spacers/caliper brackets/sprocket/etc will likely be in order.  Nothing “drop in” exists of course.

But if carefully selected, you might be able to minimize out of pocket costs and complicated machining.

George

[Shtonecb500]

If you are talking about mags and not using spokes then i dont think the rim is your problem. Its going to be spacers, offset sprockets space inside the swing arm. Honda VFR wheels have the same axle as our hondas. I think you should choose your rim of choice and then figure out the best way to make it work. Or do what I would do and have a custom swing arm made that will fit your wheel of choice.

a member on here used a cb900 swing arm and fit his gsxr wheel to that.
http://forums.sohc4.net/index.php/topic,168796.0.html


the bike below looks like a stock 750 swing arm, he must have cut out where the wheel would rub and welded in some curved supports.

[754]

A 140 should not rub at all..

[CB750R]

Hey, I run an 18” FZR600 rear wheel, I had a 160mm on the rim for the last 10 years, I’m about to put a 140mm on it as I had less than a 1/4” of clearance.  The FZR wheel spacing is more narrow than the old com star wheels and is a smaller axle diameter, so I have spacers that take up both differences. I don’t pile a tone of mileage on my CB, but that wheel has seen high speed, rain, rough pavement, lots of twisties etc... I was contemplating a more modern fork/wheel swap as I did my conversion back in 2005, but I’m happy how my bike rides so leaving well enough alone for now.

This is super anecdotal but when I did my swap the only info I could find was “someone” had done a cbr600 (f2 or f3) and I believe did front and rear... but that’s REALLY OLD info.

[samm_j2]

Wow, thanks for the reply's everyone!
CB750R, 754, Shtonecb500, and gschuld, I really appreciate it!

School has gotten the best of me and I have not been around to check this post.

The bike already has a 17 inch up front so I am wondering what 17in rear in the back I could work with. Hoping to run the stock axle but I have access to a lath so cutting my own spacers would not be a problem and fabbing up a bracket for the caliper is something I can definitely do at home.

I am not caring to go super wide like a 180 or anything. just want better tire options. would be more than happy with 140-160

it has the stock 78 cb750f swingarm, I do not know how this compares to a k model swingarm.

Does any one know of a 4 inch-ish (4-4.5) width 17in rim with a 20mm axle?

of course worst case scenario is get any 4inch-ish 17 inch rim and custom make an axle to fit whatever axle the wheel takes and then mod the swing arm to make it work.

Thanks!