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Discussion Starter · #1 ·
I know this has been discussed before, but the more I read, the more confused I become. I bought a 79 cm400t a couple years ago, put a 120/90/16 on the rear and left a nearly new 3.00 x 18 on the front. It's now time to buy a set of new tires and I find the selection for this bike limited, so I've researched possible sizes, and effect on bike handling. I know most folks say the proper size is the 120/90 for the rear and 100/90 for the front, but my front rim of 1.85 inches is really more suited to a 90/90 or 90/100 which is much closer to the 3.5 inch tire the bike calls for and wider than what I'm running now. How will going to the wider tire affect my handling and why should I go with the 100/90? Also, how is the 120/90 different from the 4.6 x 16 the bike calls for, which is available in a couple tire brands? I know I'd have more choices with the 130/90's, but don't really want to modify the chain guard which is almost rubbing the 120. My current tire brands are Duro up front and Kendra Challenger in the rear and neither seemed to last very long, less than 3000 miles. I ride a lot of curvy mountain roads, but the wear is mostly in the center of the tire, I suppose from accelerating and braking. Probably ran a bit too much air pressure 30-32 front and rear, which I'll lower for the new set to what the manual calls for. I'd like to hear your recommendations on tires that I might use considering the above comments. Thanks in advance for your help. I'm also getting ready to change chain and sprockets and will be going to a 17 tooth front sprocket, if that makes a difference in your recommendations.
 

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100/90 is probably closest to stock size for a 1.85 rim. What width rim is on the rear?
 

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Discussion Starter · #3 ·
The back rim is 2.5 x 16 inches. When I divide a 100mm width tire by 25.4mm/inch, I get 3.94 inches which is much wider than the 3.5 that came on the bike. 90mm tires would be 3.54 inches wide. Is this not correct? The charts I've looked at show a 2.15 or larger rim size for a 100mm tire.
 

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My CB450 has 1.85 rims front and back and I put 100/90's on it. CX500 has 2.15 and 2.5 rims and I have 100/90 on front and 130/90 on the rear. All the 100/90 tires seem to fit just fine on the 1.85 and 2.15 rims.
 

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I have the road riders on my CB, probably would have got the Shinko Tourmasters if they had been available in the correct sizes.
 

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Discussion Starter · #7 ·
Thanks for your input. I like the look and reviews of the Shinko and have looked at all of them, but fear they would be a stretch for my bike too. 130 on the rear would likely require some mods to the hub/brake stablizer and the chain guard. The 120 Kenda is already very close to both. It seems all these tires are a little wider than the metric sizes suggest. I really want to go with something more narrow, maybe a 90 up front and a 120 or even a 110 on the rear. Pinching the tires with a narrow rim just seems to change the shape of the tire and result in less rubber on the road. Most older bikes came with 3 to 4 inch tires and the cm's apparently pushed the limit with their tire sizes to look like a cruiser, but didn't go up in rim sizes so even the 3.5 and 4.6 tires are at the limit for what these rims were designed for.
 

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I'm going to keep an eye on this thread because I'm probably going to be dealing with this same situation this upcoming season or the next. I'm finding some of the conversion charts a little vague or sometimes contradictory. Owners manual for my '81 CM400T says front is 3.50 S18 4PR and rear is 4.60 S16 4PR. I don't want to alter anything I don't have to and I figure Honda had a reason to suggest those sizes, so I'm planning on going with 100/90-18 in the front and 110/90-16 in the rear, as that seems to be the closest match. A pair of Shinkos in those sizes look to be about $110 from Amazon. Interestingly, the front is a Shinko 712, but the only rear in the size I'm looking for is a SR735 which they say can be mounted front or rear.

I'd be curious to hear any further thoughts on this, for my sake and the OP's. Thanks.
 

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Don, when a thread is this old with no further activity, it's likely not to get any new posts. You can post the question in a new thread or just Google search "tires for CM400T Honda Twins" and you'll probably find many posts. The search feature here isn't nearly as effective as Google searching the subject while adding Honda Twins at the end. When you find some posts to read, look for posts that longdistancerider provided answers in... he's as good as it gets on the 400 series around here
 

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Oops. Thanks. Funny thing is, I thought of that before posting, but figured six months wasn't that old, especially since it gets bumped up when a new post is added. Hell, I think I've been guilty of posting to even older threads in the few months since I've been here. And I did search (using the forum), which is how i found this thread and why I decided to add my question to it. Anyway, thanks for the suggestion and I'll try to be more mindful of that.

-edit-

And man, you were right. searching that way via google brought up several threads with very helpful info. Thanks again.
 
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I’ve had several 130/90-16 rear tires. Not all of them are made the same width. I had a Shinko 777 and had to put a washer under both chain guard bolts and flip the rear brake stay around. Now my last tire a pirelli route 66 tire was narrower but still a 130 size. So I undid the mods and it fit fine. I have a duro 130/90 rear tire on now and it was no wider than the rt66.

For the front I’m just running a 100/90-18.
 

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the more i research the more confused i get, most of the brands i want only have a tire that will fit either the front or rear haha...I was hoping to get Shinko 712 for both, but they only fit front...
 

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Theres Shinko 712 (or 711?) sets specifically for Cm400t bikes on EBay, but they don’t say the sizes. They say they’ve saved us the guesswork and other info but no size info. I checked and there’s no 120/90-16 tire that Shinko even makes. So what would that rear tire that they’re saying fits cm400’s be?
(I have the Shinko 100/90-18 on the front and it’s time for a rear tire. Wanted to get a rear tire to match.)
I wrote and asked them, no response.

They do make a 120/80-16 and a 130/90-16. Would 120/80-16 be really awkward on the rear? Anyone use that size?
 

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Theres Shinko 712 (or 711?) sets specifically for Cm400t bikes on EBay, but they don’t say the sizes. They say they’ve saved us the guesswork and other info but no size info. I checked and there’s no 120/90-16 tire that Shinko even makes. So what would that rear tire that they’re saying fits cm400’s be?
(I have the Shinko 100/90-18 on the front and it’s time for a rear tire. Wanted to get a rear tire to match.)
I wrote and asked them, no response.

They do make a 120/80-16 and a 130/90-16. Would 120/80-16 be really awkward on the rear? Anyone use that size?
Since this is your first post here, you should begin with this -
Critical - READ BEFORE YOUR FIRST POST
 

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According to Shinko they don't make a 120/90/16 rear tire 712 Tire
They do make a 120/80/16 Front tire which doesn't count.
So these people have to be selling a 130/90/16 which will fit once you change the rear brake stay front mounting to outboard it's bracket with a spacer to fill where the stay used to sit.
 

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According to Shinko they don't make a 120/90/16 rear tire 712 Tire
They do make a 120/80/16 Front tire which doesn't count.
So these people have to be selling a 130/90/16 which will fit once you change the rear brake stay front mounting to outboard it's bracket with a spacer to fill where the stay used to sit.
Thank you so much for that info, and they just barely replied with the sizes and you’re right.
 

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There's nothing wrong with running the 130 rear tire unless you're wanting to maintain the stock sizing, appearance and handling. I've been running that size for years now.
 
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