Author Topic: Tire Size on stock CB550 rim  (Read 11245 times)

0 Members and 3 Guests are viewing this topic.

Offline jmtuccini

  • Full Member
  • *
  • Posts: 29
Tire Size on stock CB550 rim
« on: September 18, 2012, 10:19:57 AM »
I have a 78 CB550k. It has a 4.0 width tire on the rear stock rim. It looks a bit skinny and weak to me.

What is the max width tire I could use on the rear? I've heard even just a 120 width could have issues due to "pinch angle"

Any thoughts please.

Offline chickenman_26

  • Hot Shot
  • ***
  • Posts: 598
    • Motorcycle Consumer News
Re: Tire Size on stock CB550 rim
« Reply #1 on: September 18, 2012, 12:26:37 PM »
It may look skinny and weak compared to what you see on the chopper builder TV shows. But given the weight and power of your bike, it's actually overkill. The original tire was a 3.75-18. Many bigger bikes with twice the horsepower were equipped with 4.00-18. Just because some is good, more isn't necessarily better. You'll negatively affect the ride and handling, if nothing else.

Stu
MCN DTF

Offline CoachDoc

  • Hot Shot
  • ***
  • Posts: 615
  • 1974 CB550, 2005 GL1800, 1997 Valkyrie Standard
Re: Tire Size on stock CB550 rim
« Reply #2 on: September 18, 2012, 01:04:28 PM »
Chickenman is right..... the 4.00 tire you have is already oversized (but acceptably) over the stock 3.75 tire. I don't think going any larger will be wise unless you go to oversize rims. I have 4.00x18 on the rear of my 550, and both handling and cornering are exellent. Fret not, and stick with what you have.

Offline jmtuccini

  • Full Member
  • *
  • Posts: 29
Re: Tire Size on stock CB550 rim
« Reply #3 on: September 18, 2012, 01:15:17 PM »
I will follow good advice, thanks. I just have a thing for big tires.

Offline mono

  • Definitely no
  • Expert
  • ****
  • Posts: 1,271
  • 1975 Honda CB550, 1978 CB750K (in progress)
Re: Tire Size on stock CB550 rim
« Reply #4 on: September 18, 2012, 01:35:01 PM »
yup, +1 on stock sizes working just fine.   i can get pretty low on my stock-sized Avons.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: Tire Size on stock CB550 rim
« Reply #5 on: September 18, 2012, 01:52:38 PM »
I can tell you that a 120 is WAY too big and pinches a whole lot.

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Tire Size on stock CB550 rim
« Reply #6 on: September 18, 2012, 02:03:30 PM »
A 120 rear tire will work fine when new with higher tire pressure (to bolster sidewall support) and the original tread crown profile.  But, it won't wear evenly, with more wear in the middle of tread.  This will "square" the tire and make handling worse, particularly during the last half of the tread life.

I was talked into oversize tires for years.  The result being very frequent replacement.  Tire manufacturers and salesmen like this reoccurring sales.

Stock rims need stock tire sizes for a good riding experience.  If it's for show rather than riding, then do whatever you want.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline jmtuccini

  • Full Member
  • *
  • Posts: 29
Re: Tire Size on stock CB550 rim
« Reply #7 on: September 18, 2012, 03:26:58 PM »
What about a 110? I can't tell exactly what the conversion is.

Offline IndyFour

  • Hot Shot
  • ***
  • Posts: 601
Re: Tire Size on stock CB550 rim
« Reply #8 on: September 18, 2012, 04:35:06 PM »
I've been running a 100/90-19 front and 110/90-18 rear for a few years now.  The tires seem to be wearing evenly and I have no complaints with how they handle.  FWIW, they are Dunlop D404.
1974 CB550K
2000 VFR800FIY
__________________
Indianapolis, Indiana

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Tire Size on stock CB550 rim
« Reply #9 on: September 18, 2012, 04:37:40 PM »
What about a 110? I can't tell exactly what the conversion is.
Why Convert?
Excellent tires are available in inch sizes.  Metzeler, as one example.
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: Tire Size on stock CB550 rim
« Reply #10 on: September 18, 2012, 07:12:02 PM »
Also, 110 in the front is WAY too big. Ask me how I know.

TT: I read in a different thread in which HondaMan recommended 3.25 front and 4.00 rear (converts to just a hair over and 80 and 100) RoadRiders because the profile works well together. I wasn't exactly sure if he was referring to 550s or 750s though. Care to shed some light?


Offline singedebile

  • Hot Shot
  • ***
  • Posts: 583
Re: Tire Size on stock CB550 rim
« Reply #11 on: September 18, 2012, 07:16:34 PM »
The Avons are available in 90/90-19 front and 100/90-18 rear which is darn near the stock sizes. They are excellent gripping all weather tires with good mileage as well. Of course you can step up the tires from there if you so choose. Though it is a good idea to keep the tires proportional to one another. For instance no 90/90-19 front and 120/90-18 rear.
1975 cb550f super sport, 1976 Yamaha IT400, 1974 Suzuki T500

Offline brooze72

  • Talk to my friends here at SOHC4 if you need an
  • Expert
  • ****
  • Posts: 1,308
Re: Tire Size on stock CB550 rim
« Reply #12 on: September 18, 2012, 08:14:41 PM »
Tire sizing sure is confusing & converting sizes to metric seems to be far from simple.  Be aware of available "low profile" inch tires also, known I belive as "trigonometric" as the sizing/ratio is different again from stock.  I ordered some TT100 tires, (also known as K81) in these sizes for my 500K1.  4.10H19 front (82% aspect ratio) and 4.25/85H18 rear (85% aspect ratio.)  The front tire barely fits in the fender & looks pretty "fat", I have a buddy with the exact same tires on a Commando.  I would recommend looking at Hondaman's excellent explanation of tires & how they can affect handling, for educational purposes. There is some good cross reference info on the Dennis Kirk site too.

 http://www.sohc4.net/index.php/hondaman05/

2011, 2012 & 2013 Godzilla Relay Rally Rider
"Hold on loosely...don't let go
 If you cling too tightly...you're gonna lose control"
1972 CB500K1 - restored rider
1981 CB650C - new project

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Tire Size on stock CB550 rim
« Reply #13 on: September 18, 2012, 10:50:11 PM »
Also, 110 in the front is WAY too big. Ask me how I know.

TT: I read in a different thread in which HondaMan recommended 3.25 front and 4.00 rear (converts to just a hair over and 80 and 100) RoadRiders because the profile works well together. I wasn't exactly sure if he was referring to 550s or 750s though. Care to shed some light?
The 550s and the 750s used very nearly the same tire sizes, until the K model changed to 17 " rears in 77.  I use the 3.25 front and 4.00 rear on both my 550s and 750s.  They will scrape pegs before breaking traction.

Remember the profile for inch size tires was 95-100% but profile height wasn't in any public specification until metrics became popular.

3.25W/ 3.25H tire would convert to 82.55 x 82.25 in metric.    90/90 metric would covert to 3.54 x 3.16 in an inch size for a direct conversion.  But, tire makers would recommend this substitution rather than make a tire that was originally intended for the 1.85 inch rim width.

4.00/4.00 inch size would convert to 101.6/101.6 in metric.   A metric spec 100/90 would convert to 3.94/3.55 in inch sizes, and a 110/90 would convert to 4.33/3.9 in inches.

I'll note that some have measured their metric tires and didn't come up with the true metric measurements marked on the tire.  So apparently, the metric numbers are advisory rather than actual, at least from some manufacturers.

None of the metrics are direct substitutions for the inch sizes originally specified.  The tire salesmen don't care if you pound a square peg into a round hole as long as you pay their commission.

After years of accepting tire "upgrades" offered by tire salesmen, I finally went with manufacturers that make tires in inch sizes for these 70 bike's.  They work well.  And work better over their operating life than the metric ones that are "close enough", imo.  All new metric tires fitted work better than what was replaced for the short term.  Then you gradually get used to strange wear patterns while riding and adapt your riding habits.  Next time a tire replacement happens, you are so impressed with the new ones, that you think they must be *that* much better than those replaced, until wear happens. 

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: Tire Size on stock CB550 rim
« Reply #14 on: September 18, 2012, 10:58:15 PM »
Thanks for info TT. And you're totally right. I have a 110 and 120, and they felt AMAZING. For the first month or so. Now when I'm cornering it feels a bit sluggish, and when I start the lean, it feels a bit more abrupt because of the pronounced squaring off.

Definitely going to try out the 3.25 and 4.00 AM26s when it comes time for new tires.

Offline brewsky

  • Expert
  • ****
  • Posts: 1,110
Re: Tire Size on stock CB550 rim
« Reply #15 on: September 19, 2012, 01:22:54 AM »
+1 on the 3.25F / 4.00R combo for the 550

I just replaced a set of metrics with K70's and love the difference in handling, not to mention the vintage look.

I would put them on my 750 if I could (k8)

AND....if people quit buying them......they will quite making them and then we will not have a choice.
« Last Edit: September 19, 2012, 01:24:30 AM by brewsky »
66 CA77
78 550K
78 CB750K
02 FZ1
09 GL 1800

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: Tire Size on stock CB550 rim
« Reply #16 on: September 19, 2012, 02:23:39 AM »
Hehehe... People WON'T stop buying them :P