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Discussion Starter · #1 ·
Hello all! New to the forum and CX ownership. When I decided to customize a bike instead of restoring them like I normally do, I chose the CX because of the way cool engine design. Now I am trying to put on a larger tire in the rear. The current rear tire/rim is a 130/90-18 and I had a second set of rims with a 16" rim so I bought a 150/80-16 online. Got the tire in the mail today and it looks pretty fat. I would prefer not to remove the rear wheel at this stage just to check clearance. Can anyone tell me from experience if this tire will fit? Thanks in advance for your help.
 

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It might fit but I don't think it will spin. The biggest manageable tire is 140/90 and that's only because between the brands some 130's are really 120 and some are 140.



The only way to make it fit and spin is probably going to be to cut down the swing arm and weld in a new flat section as long as that doesn't get in the way of the drive shaft.
 

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Discussion Starter · #3 ·
Thanks for the info. Looked at it a long time last night and it is going to be close. But I already decided that I would rather cut back the swing arm support a bit instead of downsizing. Any smaller tire would ruin the look I am going for in this build. Will let y'all know how it turns out.
 

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Most 150/80-16 tyres are normally close to their top allowable limit on width so are liable to be around 160mm when fitted on the correct rim size. So this will present a problem on a standard Cx application. Even if you could notch out the swing arm sufficiently to allow a relaxed tyre to spin ( once the carcass relaxes it will be wider than when new, the rear rim is too narrow for this tyre, at 2.75 when the minimum is 3.00. This means the tyre will be larger in diameter than normal and narrower, but not in a good way.

Probably best to move that tyre on and fit a good 130. Its far better to have a skinny 130 that works well as opposed to a wider 150 that doesn't
 

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What you are going to try to do is dangerous.



You have exceeded the maximum "tire to rim fitment" for the wheel.

Even if you manage to squeeze the tire on the rim, even if you manage to fit the wheel into the swingarm, and even if the wheel actually manages to spin without load, the carcass of the tire will be so warped that your handling characteristics will be unpredictable.

Worse, as soon as you put a load on it, IE. take a turn, the carcass is likely to hit the swingarm.



This is a whole lot of really bad idea.
 

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I like to watch disasters on youtube but not hear about them withing the group.
When using bias belted tires it is especially important to fit the correct tire to rim width. Too narrow of a rim will signifantly change the tire profile. I ordered the next size up and ended up returning them at my expence because they were wrong. I used a profile guage to measure width versus profile and it was way off. sorry for the bad news.

Cheers, 50gary
 

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You can get a 140 on there, but, have to let the air out to remove the wheel !!



Not recommended.
 

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Discussion Starter · #9 ·
I appreciate all the info and the concerns. But let me approach this a different way. If you wanted to run a 150 tire (because with all due respect, that 130 is just wimpy and y'all haven't seen how cool that 150 wide whitewall tire looks), how would you all go about doing it? It sounds like I need a different rim, right? Then as long as I could get it to spin, the aspect ratio wouldn't be a problem? Sorry if I am oversimplifying things and really do appreciate any insight.



P.S. Alternatively, do y'all think the 140 would be as "Jackass" dangerous?
 

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I appreciate all the info and the concerns. But let me approach this a different way. If you wanted to run a 150 tire (because with all due respect, that 130 is just wimpy and y'all haven't seen how cool that 150 wide whitewall tire looks), how would you all go about doing it? It sounds like I need a different rim, right? Then as long as I could get it to spin, the aspect ratio wouldn't be a problem? Sorry if I am oversimplifying things and really do appreciate any insight.



P.S. Alternatively, do y'all think the 140 would be as "Jackass" dangerous?




If you want to use that tire then you will need a larger rim and have to modify the swing arm. Probably a lot more mods just to get it to fit. 140 might fit but 150 is a waste of time. I think the 140 my brother runs is a Maxis and starts with a C name. Any bit deflated and it will rub the swing arm.
 

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You will have that rubbing issue, whether you change rim or not. The swingarm is closer on one side than the other. I have widened my swingarm to take a 180 rear tyre, but it involves a lot of work. You have to cut the frame and widen it also. Ground up rebuild.

 

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Discussion Starter · #12 ·
he frame and swing arm mods aren't so bad because I already had some plans to so some others. As to the rims, though, it must have been a low blood sugar day because I hadn't looked at the rim width before y'all mentioned it here. The 16" rim is a 2.5"! Not sure about the 18" I have because I haven't looked at it. Went and checked Avon's tire width recommendations and they are way larger like 4" and above. Not sure what to do at this point except punt.



Followup: Talked to the folks at Motorcycletire.com and told them my big brothers wouldn't let me ride the 150 and they are taking it back in exchange for the 130. Much love to the folks at motorcycletire.com and to y'all for talking me down from the ledge.
 

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You will have that rubbing issue, whether you change rim or not. The swingarm is closer on one side than the other. I have widened my swingarm to take a 180 rear tyre, but it involves a lot of work. You have to cut the frame and widen it also. Ground up rebuild.



How did you handle the location of the output shaft?
 

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Tim,



Offset engine 25mm to the right, by altering the hangers. (Total width increase is 50mm)
 

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Hi,



it is possible to mount a 170/16 tyre on a 3,5" spoke rim by modifying the swing arm that way (0,5 MB PDF):



changed swing arm



(sorry - everyting is described in german, but I`m sure you`ll understand by having a look to the pictures.)

Hope you`ll enjoy it.



Matze
 

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Just a word of warning for anyone attemping to put a 170/60 tyre size on a 3.50 rim width. This is only permissable for a bias play tyre and a radial will require a much wider rim. If its a 17" tyre then ideally a 4.50, or 5.00 rim width is better although older radials were formulated to fit and work optimally on 5.50 rim widths as an alternative to 180/55-17 tyres
 

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Inwelding we trust I beg to differ bias belt tires are MORE sensitive to tire/rim width ratios. Radials have very flexible sidwalls and although it's never recommended to have too narrow rims for a given tire size the radial will be more forgiving. The radial belted tread will be stiffer to resist the change of profile to a degree at least. The stiffer bias sidewalls will heat up more and also distort the designed profile of the tire by pinching the bead inward and thus making a crown on the tread area. Two cents.

Cheers, 50qary
 

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Actually, you are completely wrong. Under tyre constructon and usage guidelines laid down under ETRTO, JATMA, and Tire & Rim, bias tyres fit on a wider range of rims than bias belted or radial. I did not say they would work in the same manner on all rims, merely that it was permissable

A radial or bias belted tyre has far less material in the make up of the sidewall ( at least half in fact) and has therefore much less vertical strength properties than a bias tyre

Of the three tyre types, bias tyres have stronger sidewalls, heavier treads and therefore resist torque distortion of the carcass induced by rim fitment more than any other type. Crown strength however is not high

Bias belted tyres have lower strength sidewalls but higher crown stiffness. However the belt pack is not anchored properly so when the crown is worn they generate far more instability than either bias or radial tyres as a bias belted tyre is not so much a radial as a stripped down bias tyre

Radials, like bias belt have low strength sidewalls that distort easily altering and even affecting the crown strength of the tyre so must neccessarily fit on a lower range of rim widths. Crown strength is high so handling feels generally superior, particularly if its a monospiral as opposed to cut belt radial

If your tyre code is blah-16 its bias, blah B16, its bias belted, and of course blah R16 is radial
 

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I said bias 'belted' and I think I meant bias. I yield to higher authority (no sarcasm intended) Interesting topic.

Cheers, 50gary
 
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