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Discussion Starter · #1 · (Edited)
Internet said 150 tire fits in the swing arm without any mods. Got a Cognito Moto rear hub conversion, laced it up to 17" x 4.25" rim and got 150/60/17 tire. It turns out, in my situation, its just short by about 2mm on the side of the final drive.
IMG_8641.JPG

Plenty of room on the other side, about an inch or more.
Looks like I would have to 'notch' the swing arm to accommodate extra few mm. How much can I notch?

My other idea is to make a 3.5mm thick spacer and place it under that final drive gear flange (or what ever its called, see image bellow). That would move the wheel to the left just enough to clear the tire. Though it would leave only about 1 - 1.5mm of space between the tire and swing arm. Not sure if this option throws something off in the alignment and causes some issues down the road.

Not sure which way to go. Obviously there is another option that some of you might point out to is to get a smaller tire, but I've diced to stay with 150.

IMG_3413.JPG
 

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Discussion Starter · #2 ·
Not sure why the images are not showing up. In the post preview they did show up fine.
 

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There is a forum issue with photos, hopefully resolved soon.
 
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Any notching will weaken the arm.You might blow the bearings in the final drive if you put shims where they did not exist before and it would cock the tire enough to cause rapid wear, this is my opinion not necessarily a fact.
 

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the big issue you have to consider is when you provide "clearance " to fit the 150 tire to the cx swing arm it is a risky tight fit

if you ever get a flat at high speed the tire will bind to the swing arm and toss you on your ass possibly wrecking your bike

and hurting you

all the ways of doing what you want are poser for looks only

there is no safe engineered way of putting that big a tire on

that said we have don things we should not before so stay safe

and IF shim the driven gear do not go more then 1/8 inch and remember to make a new distance collar with the same

increased length

also you dont need to do a complicated "notch"

grind the inside of the swing arm where you want to add clearance

take a piece of 2 1/2 inch schedule 40 pipe about 4 inched long

or if you have it a piece of 2-2 /12 inch shaft

heat the inside of the swing arm red hot with a torch

when hot put the pipe round section up against the swing arm and pull it in with a big "c"clamp

a few heat applications and you will have a nice rounded indent that will give you more clearance and not get close

to the drive shaft if you watch what you are doing dont go to far
 

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Discussion Starter · #8 ·
Murray, thanks for the idea on heating and slightly bending the tube to add clearance, I like it more than my other ideas. Will have to get a torch now!
Maybe I can find a tube to do a practice run too.
 

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Discussion Starter · #9 ·
Missing o-ring groove

Noticed that Cognito Moto rear hub does not have a groove for the o- ring. Not sure how to fix this.

CognitoMoto hub:


Comstar hub:


Looks like uploaded forum images still not showing up, trying with Imgur
 

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Discussion Starter · #12 ·
Got the tire cleared

Here is the result after using torch and c clamp as Murray suggested. I got about 2 to 2.5mm clearance. Not too much but better than before, tire is not touching. Drive shaft can still be inserted and removed. During the process I left the drive shaft in the fork just in case I go too far and can't insert it afterwards. If I go further drive shaft would have to stay in there forever but that would give more clearance. Not sure if I should leave it as is or squeeze another mm or so.



If I had to do this all over again I prob would go with a smaller tire for safety reasons Murray mentioned above. I've heard all these discussions before here on the forum, but I chose to ignore them. Now, when I'm working on my own bike it kind of dawns on me that I'll be the one riding it!
 

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Is there room inside to make the part you squeezed longer? I'm thinking that would give more clearance by the sidewall and also more clearance if the next tire is a bit smaller.
 

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way to conservative heat that puppy up red hot and make a DIMPLE

and in a bigger radius towards the rear even if you have to reposition the pipe and heat it again

make the "notch" long enough to clear the side wall of the tire do it in stages

also i thought you were going to shim the driven gear and increase the length of the distance collar

a little more heating and dimpling and a 1/8 shift to the left and you got it

if i have time i will go through and find some pictures
 

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Discussion Starter · #17 ·
Thanks for the feedback, back to torch again! Murray, that would be great to see some pictures ( if you have time ).
 

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...If I had to do this all over again I prob would go with a smaller tire for safety reasons Murray mentioned above. I've heard all these discussions before here on the forum, but I chose to ignore them. Now, when I'm working on my own bike it kind of dawns on me that I'll be the one riding it!
No, don't give up now. You're almost there and you know it IS possible, so just complete the job. There's no question a bigger tyre looks better (and in terms of ultimate performance works better too), so go for it. Basically when the tyre spins it will get narrower. Just a little, but it certainly doesn't get fatter as I have seen claimed. You can ride a bike with the tyre rubbing slightly when stationary and afterwards it has not worn because the tyre fling has reduced the width a bit so it didn't rub and so no wear. Obviously that all depends on by how much it rubbed, but you get the drift.

With tubeless tyres there should be no problem even with a puncture. In the early days we had Dunlop demonstrate a CB750 fitted with the then new tubeless tyres, being ridden at over 70 mph with no tyre valve, i.e. zero pressure in the tyre. No problem at all. Not even any weave. Tubeless tyre rims are designed to hold the tyre in place even when pressure is low (or zero in this case). As long as it doesn't rub when just pushing the bike ('cos that makes it hard work) I wouldn't worry.

Note I said I wouldn't worry. What you do is up to you.
 

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I beg to differ. A normal tire that barely rubs the swingarm may fling out and shrink from side to side at speed but it is possible for a defective tire to become wider in use. I know because I've had it happen. I used to run Shinko 230 Tour Masters on my '83 GoldWing for several years, in the stock sizes as specified on the decal. The 3rd 230 rear I bought mounted normally and cleared the swingarm by about 5mm when first mounted but after a couple of hundred KM I started smelling rubber burning and when I looked for the source I discovered that the corner where the tread meets the sidewall had worn off all the way around where it was rubbing the swingarm. I contacted the dealer and they got me a replacement. That one started rubbing in less than 20 Km so the dealer asked me to bring it back still on the rim for them to check. They determined that nothing I did while mounting the tire could have caused that problem. Since I had previously mounted two of them and used them until worn out with no problems it was obvious that these ones were from a bad batch but at that point I didn't want to take another chance so when the dealer offered me a different tire in replacement for the second bad 230 I accepted it.
 
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