Rim size vs tire size and /5 SWB fitting??

jjwithers · 06-13-2012, 07:37 PM

I'm going to lace some Akront rims to some BMW hubs (for two SWB bikes).

I have two different size rear rims and the same 2 fronts.

My front rims are 19 x 1.85 (same as a stock BMW).
I know a typical front tire size is 100 / 90 -19.

I have two rear rims,
one is the stock size 18 x 2.15

and the other is 18 x 2.50

I currently have a 120/90-18 tire on the rear wheel of a stock rim.
Will that same size tire fit on the 2.50 rim?

Does anybody have any ideas how wide of a tire is possible before it starts getting too close to the swingarm?
Does anybody run a 130 sized tire on their rear wheel?

And what about different aspect ratio sizes? 90 seems like it is the maximum size for both the front and rear tire availability. Is it just stupid to run a tire that has a lower profile?

supershaft · 06-13-2012, 09:42 PM

1.85's are too narrow for anything but 90/90's which are by most accounts the correct metric size. I would run a 2.15 up front or maybe a 2.5 but I don't like 19" front wheels so I am just guessing about the 2.5.

Unless it's a BT45 130's will rub the swingarm. 130's will fit on Mono's but that's a different story. I run 80 and sometimes 70 aspect ratio tires. It probably is stupid. I run them that size because that's the size the sticky tires come in.

jjwithers · 06-14-2012, 06:05 PM

Do you happen to have a photo of your lower profile tires on a 70's BMW?

supershaft · 06-14-2012, 09:33 PM

Sorry. Personally, I like them up to '55 and would and have owned them up to '69. After that I skip the seventies and go to '81 and later models. I do have some pictures of my LS and my Mono with 70 and 80 series tires but I don't have a scanner. I think the only 70's I have run were 130/70's on the back of my Mono. I was only running them because I use to run 110/80's up front on that same bike because those 110/80/18 AM22's were by far the best front street tire I have ever run. I sure wish they didn't stop making them!

06-13-2012, 07:37 PM	#1
jjwithers ^OP Adventurer Joined: Apr 2011 Location: So-Cal Oddometer: 44	Rim size vs tire size and /5 SWB fitting?? I'm going to lace some Akront rims to some BMW hubs (for two SWB bikes). I have two different size rear rims and the same 2 fronts. My front rims are 19 x 1.85 (same as a stock BMW). I know a typical front tire size is 100 / 90 -19. I have two rear rims, one is the stock size 18 x 2.15 and the other is 18 x 2.50 I currently have a 120/90-18 tire on the rear wheel of a stock rim. Will that same size tire fit on the 2.50 rim? Does anybody have any ideas how wide of a tire is possible before it starts getting too close to the swingarm? Does anybody run a 130 sized tire on their rear wheel? And what about different aspect ratio sizes? 90 seems like it is the maximum size for both the front and rear tire availability. Is it just stupid to run a tire that has a lower profile? __________________ www.beemersandbits.com www.joshuawithers.com/r100s www.joshwithers.com/slash5 jjwithers screwed with this post 06-14-2012 at 06:04 PM

06-14-2012, 06:05 PM	#3
jjwithers ^OP Adventurer Joined: Apr 2011 Location: So-Cal Oddometer: 44	Do you happen to have a photo of your lower profile tires on a 70's BMW? __________________ www.beemersandbits.com www.joshuawithers.com/r100s www.joshwithers.com/slash5

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06-13-2012, 09:42 PM	#2
supershaft because I can Joined: Sep 2010 Location: San Francisco Bay area Oddometer: 6,056	1.85's are too narrow for anything but 90/90's which are by most accounts the correct metric size. I would run a 2.15 up front or maybe a 2.5 but I don't like 19" front wheels so I am just guessing about the 2.5. Unless it's a BT45 130's will rub the swingarm. 130's will fit on Mono's but that's a different story. I run 80 and sometimes 70 aspect ratio tires. It probably is stupid. I run them that size because that's the size the sticky tires come in.

06-14-2012, 09:33 PM	#4
supershaft because I can Joined: Sep 2010 Location: San Francisco Bay area Oddometer: 6,056	Sorry. Personally, I like them up to '55 and would and have owned them up to '69. After that I skip the seventies and go to '81 and later models. I do have some pictures of my LS and my Mono with 70 and 80 series tires but I don't have a scanner. I think the only 70's I have run were 130/70's on the back of my Mono. I was only running them because I use to run 110/80's up front on that same bike because those 110/80/18 AM22's were by far the best front street tire I have ever run. I sure wish they didn't stop making them!