Author Topic: 19" Wheel on Rear of CB 550 (Read 3547 times)

Nestcraft · « **on:** December 16, 2015, 07:00:34 PM »

Hey guys,
Does anyone here have any experience with running a 19" wheel on the rear of a CB 550?

I picked up a new stock 19" front rim after a initial conversation with Buchanan's about custom spokes. Now they are wondering if the hole angle of the stock rim is going to work since we are moving from the stock front hub up to the larger stock rear hub with the same rim. Granted this is just speculation on their part since they don't have the parts in front of them. I don't want to sink a ton of money into two new rims from them if at all possible.

So my question is has anyone laced up a stock front 19" rim to a stock CB 550 rear hub?

Thanks in advance!

goldarrow · « **Reply #1 on:** December 16, 2015, 07:04:29 PM »

Why would you?

Stock 19" front rim is narrower, even if you can fit it on the hub, may be clearance issues with swing arm?

Nestcraft · « **Reply #2 on:** December 16, 2015, 07:07:57 PM »

I want the look of two thin 19" wheels, the swing arm is being extended 3", longer shocks, etc, both front and rear would run Avon 100/90 - 19 Roadriders. This is not a "performance" thing just an aesthetic one.

Nestcraft · « **Reply #3 on:** December 16, 2015, 07:11:32 PM »

It is the width of the front disc hub vs. the rear drum that may be the issue, not the diameter. Apparently.

bwaller · « **Reply #4 on:** December 16, 2015, 07:46:31 PM »

You may need to change hole angles., not sure. I know someone in the early 70's that raced a 750 with a 19" rear for a while. The result is similar (helping turn in) to lowering the front 1/2" with an 18" front. We had 4:10x19 K81's then at least. Otherwise it's a bit goofy.

seanbarney41 · « **Reply #5 on:** December 16, 2015, 08:05:47 PM »

could possibly run flat track race rubber?...gonna be expensive and NOT last long

jonda500 · « **Reply #6 on:** December 16, 2015, 08:09:38 PM »

Quote from: goldarrow on December 16, 2015, 07:04:29 PM

Why would you?

Stock 19" front rim is narrower, even if you can fit it on the hub, may be clearance issues with swing arm?

In Australia cb400/500/550's have 2 1/2 inch rims front and rear (measured inside where the tyre sits against)
John

Nestcraft · « **Reply #7 on:** December 16, 2015, 08:10:57 PM »

Right now I am running an Avon Roadrider 100/90 - 19 on the front and a 100/90 - 18 on the rear.I put about 2,000 miles on this set up this summer and it was great, no handling issues what so ever. These are dual direction tires so if I can get the rear rim laced up I would just run another 100/90 - 19 on the rear.

I think the Buchanan's tech was just giving me a head's up to a potential issue, surely they have crossed this bridge before there.

greenjeans · « **Reply #8 on:** December 16, 2015, 09:21:37 PM »

I would think it's the angle of the spoke at the rim that would be the issue. The diameter of a front hub is much smaller than that of a rear hub. Long story short, the holes on the 19 rim are drilled with less of an angle - they are closer to being perpendicular with the rim that that of your 18" rim. However, the rear hub is actually skinner than the front, which will help out a little - the spokes won't bind on the hub. It would result in a weaker wheel than the original.
Can it be laced up? Yes. However, you will find that the nipple will want to bind at the hole in the rim. One side of nipple will have more pressure on it than the other side. It will be noticeable. That might make it a bit more difficult to true, and I'd think it would try to bend the spoke a little there.

Since it sounds like this bike is more for aesthetics, you can probably get away with it. But I'd definitely keep an eye on it if you decide to give it go.

Nestcraft · « **Reply #9 on:** December 17, 2015, 06:50:58 AM »

Thanks Greenjeans,
I believe you summed up what the Buchanan's tech was explaining perfectly. Don't get me wrong, the 19" rear is for visual symmetry but this is basically my fair weather daily rider so I do need some longevity out of the setup.

Do you think there is anyway to know if this will hold up until I try it? It seems like it would be hard to test until you have the actual spoke set.

Powderman · « **Reply #10 on:** December 17, 2015, 07:38:29 AM »

Quote from: Nestcraft on December 16, 2015, 07:11:32 PM

It is the width of the front disc hub vs. the rear drum that may be the issue, not the diameter. Apparently.

There will be no issue with the width if you plan on running a rear hub in the rear. It does't care what diameter rim is on it for mounting in the swing arm. But, as mentioned, the larger diameter of the wheel/tire may create clearance issues at the front of the swing arm and the tire. Granted you're only gaining a 1/2", but it only takes slight contact for it to become critical issue.
When a wheel is laced it seldom has the nipple at an angle that it is binding on one point. There is room to rotate it, if you will, to accommodate variances in angle. Going from an 18 to 19 and the rear hub will require a shorter spoke but the angles shouldn't change by so much it would cause binding on every spoke. I think your plan will work without any issues or concerns. I wouldn't do it, but that's just me.

greenjeans · « **Reply #11 on:** December 17, 2015, 07:46:34 AM »

Steel rims and thick steel spokes are pretty hard to break. Although it would would be weaker than a stock set up, I don't think it would break anything. A bunch of bikes ran 19" rear wheels back in the day. I laced a drum brake to a 19" rim (the bike in my avatar) back in 2006. I didn't notice until I was 99% done tensioning the spokes that something just looked a bit off. It wasn't too noticeable - the my spokes were bending ever so slightly at the hole. Nobody noticed it but me. It turned out that I had mistakenly sent the wrong rim to the powder coater. I had a front rim drilled for a drum and a front rim drilled for a disc. I laced the drum to the rim that was drilled for the disc. It took some head scratching before I figured out what I had done. Although I don't own that bike anymore, I do see it from time to time.

For what it's worth, none of the spokes have cracked or broken. Wheel still spins as true as the day I laced it up.

Nestcraft · « **Reply #12 on:** December 17, 2015, 07:56:04 AM »

That is great info greenjeans and powderman, thank you! I am going to give it a shot. I am planning on getting new Sun rims down the road, so this may just be a somewhat temporary set up.

754 · « **Reply #13 on:** December 17, 2015, 10:09:58 AM »

You can tweak the holes slightly if need be but first off ...
Simply draw it out..
Diameter of rim where nipples enter...minus....diameter of hub on spoke drilling circle. Divide by 2. And now width of flange where spokes exit.. Draw it like a V on paper ..for both hubs ..
Now compare the angles..

A crude example rim dia is 18, drum is 10.. Width is 2.5
Gives you 4inches of length, 2.5 width of short end of triangle.

Camrector · « **Reply #14 on:** December 17, 2015, 07:27:41 PM »

Going for that 10 speed look!

Nestcraft · « **Reply #15 on:** December 18, 2015, 05:03:07 AM »

More of a board track, also really tired of people using oversized tires on small bikes.

Retro Rocket · « **Reply #16 on:** December 18, 2015, 05:36:13 AM »

Quote from: Nestcraft on December 18, 2015, 05:03:07 AM

More of a board track, also really tired of people using oversized tires on small bikes.

Its only "oversized" if its on the wrong rim, you mean bigger than the stock combination, i'm sure. I'm not sure why you'd be tired of bigger wheels and tires on small bikes, huge ones yes , but most, if not all smaller bikes bikes these days, have bigger wheel tire combinations , its not done for looks, technonogy has come a long way since the 70's, if I can make my bike handle better with better rim and tire combinations then i'm all for it, all the period Honda race bikes i've seen wear bigger wheel and tire combinations, I have a set of old wheels that were common on 70's Honda race bikes, they are a DID 3.5 inch rear and a DID 2.15 front set, better tire selection is also another reason this is done. I will agree that, most {definitely not all}"cafe racers" i've seen with big wheels and tires are done because it "looks cool", very few are done right..

Nestcraft · « **Reply #17 on:** December 18, 2015, 06:39:06 AM »

Agreed, I didn't mean that to sound as negative as it did. I just prefer the look of thin tires and wheels on a cafe bike that is stripped down, I think it visually reinforces the lightness and streamlined quality of the bike. We spend so much time cleaning up and removing what is not needed on these bikes and then sticking huge tires on them just seems to fight it aesthetically.

Here is a photo of the 550 engine I rebuilt for this project.

Nestcraft · « **Reply #18 on:** December 18, 2015, 06:41:39 AM »

Also, I had a final conversation with Buchanan's and the tech assured me that I will have a usable wheel. The spokes will be very slightly bowed, which is not ideal but the wheel will be fine.

Camrector · « **Reply #19 on:** December 18, 2015, 06:52:13 AM »

I think you have been looking at the wrong cafe bikes.
That engine is beautifully btw! Great work!

Nestcraft · « **Reply #20 on:** December 18, 2015, 07:13:00 AM »

Here is a photo of the bike in its rough state this summer.

754 · « **Reply #21 on:** December 18, 2015, 08:46:50 AM »

Boardtrack ? Then you want 21 or 23,s...

Nestcraft · « **Reply #22 on:** December 18, 2015, 08:48:47 AM »

No need to go that big! Might look cool though.

Camrector · « **Reply #23 on:** December 18, 2015, 09:43:59 AM »

Personally I think you should focus on performance. That is a beaut as is.
Update suspension/nicer seat would be where I would invest.

Nestcraft · « **Reply #24 on:** December 18, 2015, 09:45:25 AM »

That seat is hand carved cherry.

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Author Topic: 19" Wheel on Rear of CB 550 (Read 3547 times)