Author Topic: 350f fatter rear tire. (Read 7406 times)

taymoor · « **on:** April 21, 2009, 08:05:24 PM »

My cb350f has a rear tire size of 3.5 x 18. I'd like to get a fatter rear

tire for the looks of the bike. I know nothing of tires and wheels. would I need a different rim?

what size rim, what size tire? ???would a fatter tire affect the ride?

would it get in the way of the chain?

HELP!

P.S. I've noticed that all of my posts are asking for help. As soon as my rebuild is complete, I'll be able to help others though, I promise.

markjenn · « **Reply #1 on:** April 21, 2009, 09:03:33 PM »

The rims aren't wide enough to mount wider rubber properly. You might be able to upsize to a 4.00 and not rub, but the profile of the tire will be incorrect (the tire will be "pinched" in at the sidewall), and the bike will probably not handle as well.

If you want proper handling with a wider tire, you need to fit a wider rim. A good wheel shop will lace a wider rim to your hub but it won't be cheap. And you will have to bird dog the interference issues.

All in all, you're talking a lot of trouble and expense to get a better "look". And if your bike is otherwise stock, you'd be decreasing its value. To my eye, these old bikes look "proper" with their narrow rubber and attempting to make them look like more modern bikes with wider rubber is a little like lipstick on a 7-yo.

- Mark

taymoor · « **Reply #2 on:** April 21, 2009, 09:38:29 PM »

I don't mean to pervert the look of the bike, but I'm making a cafe racer, and I think a fat tire would look good with it. I don't think welding wheel extensions is my cup of tea. What is the size of the wheel I'd have to buy for a fatter tire? would it be 4 x 18?

rude · « **Reply #3 on:** April 21, 2009, 09:56:51 PM »

taymoore
I've put Michelin 4.00x18 rear, 3.50x18 front on my 350F, fit is no problem, once she is back on the road I'll be able to comment on the handling characteristics as described by markjenn, the tyre dealer did not indicate any problems. Like you I wanted the fatter look, see pics

cheers

taymoor · « **Reply #4 on:** April 21, 2009, 10:12:35 PM »

I like what I see. Do you remember where you got the wheel? and is there quite a distance between the tire and the chain?

rude · « **Reply #5 on:** April 21, 2009, 10:25:20 PM »

michelin M45, as we know 18 inch tyres are getting hard to find, there is no problem with clearance, standard chain guard mounting still used.
I'm in Oz, got these from a dealer in Canberra Australia,
cheers

taymoor · « **Reply #6 on:** April 21, 2009, 10:26:54 PM »

so you're just using the stock wheel with a bigger tire? Thats great. saves me money!

markjenn · « **Reply #7 on:** April 21, 2009, 10:27:23 PM »

Not sure what you're talking about with wheels and wheel extensions.

Each tire width has a recommended rim width that will give the tire the proper profile. Rim widths are measured from bead seat to beat seat and are not the same as tire widths. Stock, I believe a CB350F has a very narrow 1.85" wide rim. According to the book, you shouldn't mount a tire wider than 3.50", but people routinely go a bit larger than stock size and live with the non-optimal profile. But if you go really crazy, you may have trouble with the tire not seating properly in the bead with the possibility of a blowout.

I doubt there are any aftermarket wheels to fit the 350F, so if you want a wider rim, you have to have a wheel shop relace the wheel with a new/wider rim and new spokes. This is pretty pricey, probably $300 or so.

A 4.00 inch tire should have a 2.15-2.75 inch rim, but a 4.00x18 on the stock wheel will probably work Okay. But you're probably going to sacrifice some handling for the "look" you're after. Generally, stock sizes handle the best.

- Mark

crazypj · « **Reply #8 on:** April 21, 2009, 11:33:04 PM »

It really needs a 2.15 rim to actually work. tyre wear WILL be excessive on narrow rim even if you don't have any other problems. ( as low as one third normal mileage)
Get a CB350/360 twin wheel and try that in there first, I'm pretty sure they are the same ( or at least close enough) I've got 350F and CB360 but cant check for at least two weeks. Fit wider rim to 360 wheel and then fit wider tyre, that way you can revert to stock if you need to.
Personally, I'm saving up for some flanged 2.15x18" rims from Mikes XS (@ $89.95 each)
PJ

many408 · « **Reply #9 on:** April 22, 2009, 04:13:59 PM »

I ran a 5.10x16 on a 350f frame; was tight, but it fit.

71CB500chris · « **Reply #10 on:** April 22, 2009, 04:37:32 PM »

I have a CB750 rim laced to my CB500 hub with a 4.00 x 18 tire
this combo looks and handles great
Chris

kslrr · « **Reply #11 on:** April 22, 2009, 06:06:47 PM »

On my '72 CB350F, I have a Dunlap Sport Elite 120/80/18 on the rear which messures 4.75 in. across. This is a wide tire made for what was considered standard width rims back in the '80's. The bead and side walls are constructed in such a way that the tire retains it's proper shape and grips the rim tighter. No interference with the chain, the bike corners nicely and is stable at 100mph, without a steering damper.

333 · « **Reply #12 on:** April 22, 2009, 06:27:34 PM »

A 350F that does 100? Brand new, and bone stock, all the magazines of the day have them topping out at around 86. Must be heavily worked on.

Despite my feeling that goes along with what some have said here already, to get a decent tire, I have had to go up in size to the 4.00 rear. I am using the stock rim, and have not experienced any ill behaviour.

crazypj · « **Reply #13 on:** April 22, 2009, 10:20:52 PM »

Quote from: kslrr on April 22, 2009, 06:06:47 PM

On my '72 CB350F, I have a Dunlap Sport Elite 120/80/18 on the rear which messures 4.75 in. across. This is a wide tire made for what was considered standard width rims back in the '80's. The bead and side walls are constructed in such a way that the tire retains it's proper shape and grips the rim tighter. No interference with the chain, the bike corners nicely and is stable at 100mph, without a steering damper.

From your pics the 80 series tyre looks well over a 100 series on that rim.
It also looks like you have at least inch and a quarter unused either side (aka, chicken strips)
Whats the overall height of tyre when fitted?
It should be about 24.5 inches or less on correct rim.
I have a 110/80x18 on WM3 rim for CB360 and that measures about twenty four and a quarter inches high which is pretty close to the 24" stock tyre/stock rim.
Pic is my Katana front with only 10mm oversize tyre, (120 instead of 110) cant get to edge although I have managed to get as far as the direction arrow since pic was taken
Not best angle as it makes tyre look flat when its really extra tall, second pic gives better idea of what it really looks like, its a long way over to get there
PJ

aussie · « **Reply #14 on:** April 23, 2009, 12:41:16 AM »

Quote from: kslrr on April 22, 2009, 06:06:47 PM

On my '72 CB350F, I have a Dunlap Sport Elite 120/80/18 on the rear which messures 4.75 in. across. This is a wide tire made for what was considered standard width rims back in the '80's. The bead and side walls are constructed in such a way that the tire retains it's proper shape and grips the rim tighter. No interference with the chain, the bike corners nicely and is stable at 100mph, without a steering damper.

Dont mean to be rude, but that tire looks like its never seen a corner and lives on straight roads.Im guessing youre idea of handling isnt one to go by

Taymar, to answer your question, if your not worried about optimal handling. ( and i say that with a smirk on my face

,we are talking about a 30 year old bike thats handling capability are fairly average). Put the biggest tyre that you can get to fit on there, it will still work and will get the looks your after.Just be a little cautious next time your out scraping your knee around the corner

333 · « **Reply #15 on:** April 23, 2009, 06:17:47 AM »

The chicken strips can be explained by explaining tire sizing.

With metric sizing, the first number is the width, in millimeters. The second number is the height, and is a percentage of the first number. So, on Ksirr's bike, the tire is 120 cm wide, and 96 cm tall, as 96 is 80% of 120. Because the tire is squeezed on a rim made to fit a smaller tire, the tire is squeezed on so that the tire actually sits taller than the dictated height. So when he takes it into a turn, the bike never goes over far enough to scuff the outer edge of the tire. This is what happens when you put an almost 4 3/4 inch wide tire on a rim made for a 3 1/2 inch tire.

And while we're on the subject, when you bump up the size of a front tire, you screw up the accuracy of your speedo, as the outside diameter is different.

kslrr · « **Reply #16 on:** April 23, 2009, 08:41:09 AM »

In response to the "chicken strips", I haven't had the chance over the last 20 years to use the bike to it's full potential. I didn't ride, nor continue to work on the bike for the 12 years of my first marrage. One reason she's my ex.

crazypj · « **Reply #17 on:** April 23, 2009, 09:22:48 AM »

Quote from: 333 on April 23, 2009, 06:17:47 AM

And while we're on the subject, when you bump up the size of a front tire, you screw up the accuracy of your speedo, as the outside diameter is different.

Yep, it makes speedo run slightly slower with a larger rolling radius (which isn't the same as the actual radius due to fact tyre 'flattens' slightly where it touches road) You can work out difference by marking tyre and moving one full revolution then work out theoretical circumference and noting difference
PJ

taymoor · « **Reply #18 on:** April 23, 2009, 12:55:13 PM »

Quote from: kslrr on April 22, 2009, 06:06:47 PM

On my '72 CB350F, I have a Dunlap Sport Elite 120/80/18 on the rear which messures 4.75 in. across. This is a wide tire made for what was considered standard width rims back in the '80's. The bead and side walls are constructed in such a way that the tire retains it's proper shape and grips the rim tighter. No interference with the chain, the bike corners nicely and is stable at 100mph, without a steering damper.

so... what mods have you done to the engine? and where can I get them?

crazypj · « **Reply #19 on:** April 24, 2009, 05:47:30 AM »

Looks like an open Jardine? and no air box to me.
With correct jetting that will give a bit more power.
Forgot to mention in last reply (about speedo being inaccurate with oversize tyre) Iys probably closer to correct now, Its always cheaper to make a fast speedo than a fast bike.
I think most people who have checked (using GPS or similar) find speedo is 'out' by 5~10 mph on the fast side (ie, reading 70, really doing 60~65)
PJ

kslrr · « **Reply #20 on:** April 24, 2009, 08:39:49 AM »

Quote from: crazypj on April 24, 2009, 05:47:30 AM

Looks like an open Jardine? and no air box to me.
With correct jetting that will give a bit more power.....

If your refering to my pipes, these were custom made by the previous owner back in the late '70's. They were originally Black Crome.

taymoor · « **Reply #21 on:** April 24, 2009, 08:51:05 AM »

how do you custom make pipes? I need to do that because I can't afford 250 dollar aftermarket pipes.

crazypj · « **Reply #22 on:** April 24, 2009, 10:51:02 PM »

Quote from: taymoor on April 24, 2009, 08:51:05 AM

how do you custom make pipes? I need to do that because I can't afford 250 dollar aftermarket pipes.

Buy a bunch of U bends, cut them up, weld them together.
If you don't have a welder and flanges, by the time your done, $250.00 doesn't seem so bad.

PJ

themotoworks · « **Reply #23 on:** April 25, 2009, 05:38:11 AM »

i think what you might want to look at is actually a lower profile tire, that is if you're looking for something more aggressive... also, you can find a lot of used rims on egay, and as long as they're 40 spoke rims, they'll basically work with your rear hub, buchanan spokes can cut spokes for x rim to y hub for about $106, and they're very nice. so, maybe it would be possible to find a 3.5x18 rim out there and fit maybe a 140/70 to it...

taymoor · « **Reply #24 on:** April 25, 2009, 08:09:54 AM »

that does sound pretty awesome. A lo-pro is a wicked look for a cafe. I can't wait to get pics up of my project. I'm still awaiting the battery for my camera from ebay.

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Author Topic: 350f fatter rear tire. (Read 7406 times)

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