Topic: new rim / tyre combo for 550?

[PeWe]

One of the links had CB500 discussion too. It was one chart for CB400 so the tire and rim sizes must cover narrower tires than the CB750 use as minimum.

The Tower's charts contains wheel diameters which is really useful to be aware of when compare the tire sizes.

The tire sizes have hardly changed. New or old tire must fulfill its markings.
That chart made me to see the light from an era to use widest possible tire for look only.

 I ordered a new front tire today in 90/90-19 size since it has a height close to stock 3.25-19, a little wider. I have used 100/90-19 before and it is too fat for 1.85 rim, too tight to fender too when it is much higher.
Handling not better, I have photo where a worn 100 tire is really flat. The handling not good.
In the 80's 3.25 and 3.50 only.

That chart also made me to understand why bike did not reach top speed as in the 80's.

A 100/90 tire is higher and make wheel to rotate slower, speedo too.

I'm sure there are more tire discussions to dig up on this forum for our 40-50 years old bikes to whom the tire makers start to reproduce their old tires for. Tire designs from 2010 are relatively new! Still old style diagonal

Dunlop K81 (TT100) still produced too. Hopefully better now.
Avon Roadrunner not back yet?

I think my stock K2 will get old style Metzeler ME11, ME77 when its Heidenau tires are done. 2022 as earliest.

ME11 and ME77 were too old and out of business in the mid 80's when my bike got ME33 and ME99!

Now the old are still in business with improved rubber compound.

[Flyin900]

I just sent an email to Avon in England about the new Avon Roadrider MK11 which is a newer tire than the earlier Roadrider model.

As noted they do have a correct 325-19 size for the front so that is not an issue. Other brands also have a correct front tire size of 325-19, so no real issue there. The problem is the rear rim width of 1.85-18 where nothing is correct it seems. The Roadrider MK11 has a 100-90-18 tire in the series plus a 100-80-18 that can be mounted on front or rear applications depending on how the tire is mounted on the rim.

From Towers spreadsheet this size (100-90-18) is slightly narrower than a 400-18 that a number of manufacturers also make, yet not good for my narrow rear rim. I will see what the manufacturer says on this as an option for the narrower 1:85 rear rim sizing.

If it is a good choice then I will post the results, so others may use the info in the future. Since this is a rear tire there should be no issues with fender clearance or fork clearance. It just comes down to how well this will fit a narrow rim without too much pinching and a spec close to the original tire.

[Bankerdanny]

I ran a 110/90 on my 77 550K and didn't notice any adverse wear or handling

[flatlander]

pewe dug up some good threads from the past. putting it here for easy access.


source: http://forums.sohc4.net/index.php/topic,19346.msg274511.html#msg274511


source: http://forums.sohc4.net/index.php/topic,56494.msg609309.html#msg609309

two posts from tower about effect of different tyre size on the same rim width:

• http://forums.sohc4.net/index.php/topic,19346.msg255231.html#msg255231
• http://forums.sohc4.net/index.php/topic,19346.msg274041.html#msg274041

this is really useful. unfortunately, tower doesn't share his calculations and the reasoning behind what pinch angle he deems acceptable, but assuming his numbers are right it's really helpful information.

and here's a guy who tried both corresponding metric and inch sizes on the same rim. on a 550F so i guess the rim was 1.85:
http://forums.sohc4.net/index.php/topic,111400.msg1249955.html#msg1249955

[flatlander]

Seems most of these recommendations are now for a 2:15 width CB 750 rear rim and the CB 550 rear is a 1:85 width.

Yes, but Flatlander is considering buying new rims and would most likely get a 2.15". 
I have considered this as well for my 550.

exactly. from most things i've seen so far, 1.85 is very much at the lower limit of what is recommended even for the stock front tyre at 3.25-19.

so i'm leaning now towards 2.15 front, and either 2.15 or even 2.50 rear.

that would support the stock inch sizes (or the 4.00-18 for the rear as 3.75 you can't get any more), and open up options for metric sizes as alternatives without pinching them too much.

[PeWe]

There are other threads by the racing guys that use wider rims, 18" front. CB750 and CB500 by wellknown racing forum members. More tire and rim experience to find!

When I read one of them I felt the need to use 18" front too. But the rim will then hit the caliper bracket as I mentioned earlier. If doing this, different fork.... So I could stop myself. It's just a street bike.

2.15" front and 2.50-3.0" rear seems to be a better choice when using the wider tires.
Honda should have used those from the very beginning, right?

Time to investigate the market for these rims and follow the tire and rim width recommendations. Honda used  narrow rims according to earlier posted rim and tyre chart, post 39 by Flatlander.
Chromed DID rim style.
2.15 19" front (3.25, 3.50, 90/90 tire)
2.50- 2.75 18" rear  (4.0 -110-120/90 tire)

Here how my Dunlop Streetsmart  100/90-19 looked like when I replaced it with a 3.25-19 1 year ago.

100/90-19 in need of wider rim.



 New 3.25-19 tire on 1.85" rim

[flatlander]

i saw those posts from the racers but indeed, those choices would be too wide for me, with my stock fenders etc.
racers have stripped down bikes with more severe modifications than what i want to do for street use. also, i don't think there is any need on the street for such wide tyres.

"2.15" front and 2.50-3.0" rear seems to be a better choice when using the wider tires.Honda should have used those from the very beginning, right?"
that's what i'm thinking, too. and now that i'm getting new rims there's no reason to stick with the skinny old sizes.

[PeWe]

I would like to find same model of rims as used on CB5X0/750 but wider.
D.I.D chromed. Difficult to find wider except for Akront aluminium.

[Flyin900]

My only experience in using a wider tire on a stock rim was a front tire on a 1000cc metric bike, where I changed from the stock 110-90-19 size to a 120-90-19 on the recommendation of a poster on another forum years ago. The tire fit yet it was close on fender and fork clearance on the front end.
 
I regretted the change immediately, since the bike was much heavier steering wise than the stock tire, plus riding on roads I was very familiar with the front tire seems to amplify every bump more than the stock tire did on those roads.

As Sean pointed out way back in this thread his experience with using metric tires where originally inch sizes were the correct stock units wasn't positive. His being a CB500 I believe, he reported it definitely changed the way the CB500 handled in both steering and overall performance vs the stock inch sized tires.

I realize that your talking about a CB750 here and that is a difference for sure, yet as the old saying goes " everything affects everything"

In my case I am trying to find the best compromise, as close to stock as possible. To keep the bike as neutral in handling/riding as compared to what Honda originally designed into the overall frame and tire geometry.

I do really appreciate all the responses, as it has been a learning experience and forced me to really dig a little deeper. The OCD also helps too.

[PeWe]

CB500 or CB750 does not matter when matching rim width with tire size. These bikes can have same rims If I have understood the rim sellers adds correct.

Use a too wide tire on a rim will not help the handling nor tire  milage.
The rim vs tire size is not bike related, tire only.

The tire size however, is bike related. Rim to match.

Front and rear to match too as the angles Tower' charts show.

[seanbarney41]

PeWe, if you have not ridden a cb500/550, you do not have a clue comparing it to a cb750.  Although the 2 seem to be very similar designs, the handling characteristics are a world apart.  In my opinion, in stock form, the cb550 is nearly as perfect as a vintage bike gets.  The cb750 feels like a big fat wallowing pig in comparison.  The cb550 frame and forks are just rigid enough for the amount of grip it generates and it's weight, so seemingly insignificant changes can be surprisingly detrimental unless approached in a balanced fashion.


You may wonder why, I am more of a "750 guy" then.  Well?...the answer to that is where I live in the mostly straight roads of Michigan, there are certain other factors to cconsider.

[Stev-o]

  Although the 2 seem to be very similar designs, the handling characteristics are a world apart.  In my opinion, in stock form, the cb550 is nearly as perfect as a vintage bike gets.)

I agree with Sean [except the wallowing pig reference!]

The 550 is a wonderful handling bike.  The 550F was my first SOHC many moons ago, sold it to buy my K4 as I thought it was not a good highway bike, too light weight.  Big trucks would move me around with their "wake".  I really missed throwing it around the hills here and I soon bought another [and another and another]
I very much enjoy riding both bikes, everyone should have both.

[seanbarney41]

OK, well, maybe over exaggerated to make a point...

[flatlander]

guys, before any flaming starts: i wasn't looking to change tyre dimensions for the 550. there's a reason why i chose this bike and why i'll try to keep it on the road for as long as it makes sense.

my aim is to find the right rims to support those tyres available today, that are the most ideal meaning closest to original dimensions. and based on the available data i came to believe that the stock 1.85" rims are too skinny for that.

even at the front i think a bit wider would help. if you think that's wrong then please talk me out of it now before i sink a few hundred euros into this 

[seanbarney41]

guys, before any flaming starts: i wasn't looking to change tyre dimensions for the 550. there's a reason why i chose this bike and why i'll try to keep it on the road for as long as it makes sense.

my aim is to find the right rims to support those tyres available today, that are the most ideal meaning closest to original dimensions. and based on the available data i came to believe that the stock 1.85" rims are too skinny for that.

even at the front i think a bit wider would help. if you think that's wrong then please talk me out of it now before i sink a few hundred euros into this 

I think a few long time posters, who know each other well internet-wise, are having fun and learning stuff...if anyone feels flamed, my apologies and I will stop.

flatlander, as said before, if you want to go wider, it will not ruin your bike, but I do not believe you will find an improvement in steering feel.

[Stev-o]

guys, before any flaming starts...

I think a few long time posters, who know each other well internet-wise, are having fun and learning stuff...

Absolutely!

[flatlander]

sorry, wrong choice of words.
as long as we don't descend into oil thread territory call the 750 whatever you want as long as it's clear that the 550 is superior 

i'd like to keep the steering behaviour of the 550. don't think it needs improvement, and don't want to make it worse.
so i'm not looking for a wider tyre, but it seems to me from all i've read that a slightly wider rim (2.15") would support the standard 3.25-19 tyre with a correct "pinch angle" (whatever that is - haven't seen an explanation of what the correct range is) and, if needed, would do so also for a 90/90 or even 100/90.
that would probably make the contact patch of the 3.25-19 a bit larger than with the 1.85" rim but would it be enough so to turn the bike into a pig?

and if honda wanted to stay really small upfront, then why did they not use a narrower tyre (say 3.00-19) that would perfectly fit that 1.85" rim according to general guidelines?

[seanbarney41]

Go look at the 3.25 front on your 1.85 rim now.   Does that look adversely pinched? 

[flatlander]

no it doesn't.
but it should also work as it's within the recommended spec from tyre manufacturers and other sources. but it's at the low end of the range. the ideal or recommended rim width for a 3.25 tyre is usually mentioned to be 2.15".

see here for example: https://www.avontyres.com/en-gb/tyres/roadrider-mkii?cartype=motorcycle
and that chart i posted earlier.

a 2.15 rim will weigh a bit more than a 1.85 one. maybe the tyre's profile is shaped to be a little bit wider - but that i don't know and as this width is indicated as ideal for 3.25" tyres, i assume it would be the shape that the manufacturer intended.
am i missing anything that would speak against using a 2.15 rim upfront?

[robvangulik]

and if honda wanted to stay really small upfront, then why did they not use a narrower tyre (say 3.00-19) that would perfectly fit that 1.85" rim according to general guidelines?

Like the 400Four you mean?
Did you ever ride one? That can run circles around the 550......

[flatlander]

yes i did ride my neighbour's 400 a few times before she sold it. she didn't use it much just told me to take it out whenever i wanted. 
circles it can run as long as you stay in a circle - but once you pull away from the circle the 550 will leave it in the dust 
honestly, nice bike for the smaller roads!

[low-side]

I think 2.15 / 2.50 is a good combo that will let you run (near) stock tire sizes with room for metric options.  I'd run a 90/90-19 and 110/90-18 myself.  Should handle really well.

[grcamna2]

pewe dug up some good threads from the past. putting it here for easy access.


source: http://forums.sohc4.net/index.php/topic,19346.msg274511.html#msg274511


source: http://forums.sohc4.net/index.php/topic,56494.msg609309.html#msg609309

two posts from tower about effect of different tyre size on the same rim width:

• http://forums.sohc4.net/index.php/topic,19346.msg255231.html#msg255231
• http://forums.sohc4.net/index.php/topic,19346.msg274041.html#msg274041

this is really useful. unfortunately, tower doesn't share his calculations and the reasoning behind what pinch angle he deems acceptable, but assuming his numbers are right it's really helpful information.

and here's a guy who tried both corresponding metric and inch sizes on the same rim. on a 550F so i guess the rim was 1.85:
http://forums.sohc4.net/index.php/topic,111400.msg1249955.html#msg1249955

This is a nice tire chart flatlander 

[flatlander]

i can't take credit for them. they were made by an old member called tower.

[PeWe]

Rims only from the very beginning. Based on rim vs tire dimension charts. Nothing else.
Read again and everything will be obvious.