• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

  • Beginning April 1st, and running through April 30th, there is a new 2024 BMW MOA Election discussion area within The Club section of the forum. Within this forum area is also a sticky post that provides the ground rules for participating in the Election forum area. Also, the candidates statements are provided. Please read before joining the conversation, because the rules are very specific to maintain civility.

    The Election forum is here: Election Forum

Tires on 83 R100 size help please

R

robbie9999

New member
Hi Guys

Have a 1983 BMW R100 I am not sure the original sizes on the bike for tires, this is what it said (what does the numbers mean ? )

Rear original size 18 inch 4.00 - 18 Front original size 19 inch 3.25-19

Want the bike to sit even, can you please suggest tire sizes, I am getting the nice small white wall look tires want the height across linear to ensure the bike is sitting even
These are the tires I am going for ....

https://www.ridersdomain.com/motorc...niversal-tire-p?0&c=2343&idd1=60839&idd2=4954

Check out the pic attached, the look I am going
 

Attachments

  • unnamed.jpg
    unnamed.jpg
    36.1 KB · Views: 163
And here's another where you can find the specs for most if not all BMW models.

http://www.bmbikes.co.uk/bmwmodels.htm

Your sizes should be:
Wheel Rims, Front 2.15 B 19
Wheel Rims, Rear 2.50 B 18
Tyres, Front 3.25 H 19
Tyres, Rear 4.00 H 18


Yer on yer own on where to find whitewalls! No idea whatsoever on those. :scratch
 
robbie9999 said:
Hi Guys

Have a 1983 BMW R100 I am not sure the original sizes on the bike for tires, this is what it said (what does the numbers mean ? )

Rear original size 18 inch 4.00 - 18 Front original size 19 inch 3.25-19

Want the bike to sit even, can you please suggest tire sizes, I am getting the nice small white wall look tires want the height across linear to ensure the bike is sitting even
These are the tires I am going for ....

https://www.ridersdomain.com/motorc...niversal-tire-p?0&c=2343&idd1=60839&idd2=4954

Check out the pic attached, the look I am going
Click to expand...
The tires you are looking at are for 16" rims..You need something to fit the rims on the bike. Search for vintage or classic style tires in the correct size you need.
 
I take from OP’s comment that the bike in the attached photo is not his bike, but has the appearance he’s trying to achieve. OP: The original tire size info you have means that 1. Your bike’s original rear tire was for a wheel that was 18” in diameter, and the tire was 4” wide at its widest point, and 2. Your bike’s original front tire was for a wheel that was 19” in diameter, and that tire was 3.25” wide. It was typical, back in the day, (and remains so today) for motorcycle manufacturers to put different size wheels on the front and rear of the motorcycles (the front and rear wheels perform different specific functions), recognizing that this may not be the preferred aesthetic choice for today’s cafe’d rides. If your bike still has its original wheels on it, those sizes still remain the best choice for best handling. If you’ve changed the wheels on the bike to achieve some preferred aesthetic, you’ll need to find tires that fit those wheels’ diameters. I don’t know of any whitewall options available for the original 18” and 19” wheels, but they may be out there.
 
tires sizes

Hi Gentlemen,

The pic posted is not my bike, but my goal to build, been doing some research , originally and whats on the wheel is Front 19 - 3.25 Rear 18 - 4.00

I have reached out to tires shops and the best we can come up that come in WHITE WALL are :
Front 19 - 3.25 Dunlop D401 front tire 100 /90 / 19 in modern tire size
Rear 18 - 4.50 Dunlop K177 front tire 120 / 90/ 18 in modern tire size

1. Having two front tires is it a big deal ?

2. Rear would be half inch bigger would this be safe and good to work, and have no issues ? Can I get away with it ?

Thank you
 
pic of tires

robbie9999 said:
Hi Gentlemen,

The pic posted is not my bike, but my goal to build, been doing some research , originally and whats on the wheel is Front 19 - 3.25 Rear 18 - 4.00

I have reached out to tires shops and the best we can come up that come in WHITE WALL are :
Front 19 - 3.25 Dunlop D401 front tire 100 /90 / 19 in modern tire size
Rear 18 - 4.50 Dunlop K177 front tire 120 / 90/ 18 in modern tire size

1. Having two front tires is it a big deal ?

2. Rear would be half inch bigger would this be safe and good to work, and have no issues ? Can I get away with it ?

Thank you
Click to expand...



Here is a pic of the tires that may or may not work ?
 

Attachments

  • tires.jpg
    tires.jpg
    83 KB · Views: 114
I'm not sure why you're so intent on having both tires to be the same size. To me, if you're going to use the mag style wheels shown will be extremely difficult. The rear wheel has the final drive which is completely different than the simple hub of the front wheel. I'm not sure how I see how a rear wheel could be used in front or how a front wheel could be used in the rear. Now if you were going to use spokes, you probably could remove the spokes from the hubs and relace them accordingly. Even then, I'm not sure about the offset needed on the hubs and if a rear wheel hub will fit between the forks of the front.

Seems like a lot of work. Just put on the white wall tires you're interested in on the correct front/rear rims and know that your geometry, handling, etc., won't be compromised.
 
Assuming that your bike still has its OEM "snowflake" cast wheels, a 120/90-18 will be a tight fit on your rear wheel, if it will fit at all. The fit issue is at the swingarm; this size may well rub on the inside of the driveshaft side of the swingarm. That being said, I have used 120/90-18 rear tires (Metzerler ME-88s, I think), on my long-ago R90/6 and R90Ses. I believe that there was an official spacer recommended for the wheel hub that moved the rear wheel just enough to the left to provide adequate swingarm clearance for this non-OE tire size. I don't know whether this spacer is still available or not. The other complicating factor is that tires from different manufacturers that share the same nominal sizes, don't all fit precisely the same when they get mounted on a wheel and bike. Overall real-world inflated widths can vary a little, and there isn't much room between the rear tire's sidewall and the swingarm to begin with, so it can be a bit of a gamble when trying to fit something other than a 4.00 x 18. Tom Cutter, the proprietor of Rubber Chicken Racing, would likely know which tires are most likely to fit, and can fill you in on the spacer solution, if it's still available. Both of your candidate whitewall tires are intended for front wheel use; I don't know what the implications might be for using a designed front tire in a rear wheel application.
 
20774 said:
I'm not sure why you're so intent on having both tires to be the same size. To me, if you're going to use the mag style wheels shown will be extremely difficult. The rear wheel has the final drive which is completely different than the simple hub of the front wheel. I'm not sure how I see how a rear wheel could be used in front or how a front wheel could be used in the rear. Now if you were going to use spokes, you probably could remove the spokes from the hubs and relace them accordingly. Even then, I'm not sure about the offset needed on the hubs and if a rear wheel hub will fit between the forks of the front.

Seems like a lot of work. Just put on the white wall tires you're interested in on the correct front/rear rims and know that your geometry, handling, etc., won't be compromised.
Click to expand...

Sorry I am not replacing any rims keeping the stock ones, just looking at the tires is all sir
 
tires sizes

khittner1 said:
Assuming that your bike still has its OEM "snowflake" cast wheels, a 120/90-18 will be a tight fit on your rear wheel, if it will fit at all. The fit issue is at the swingarm; this size may well rub on the inside of the driveshaft side of the swingarm. That being said, I have used 120/90-18 rear tires (Metzerler ME-88s, I think), on my long-ago R90/6 and R90Ses. I believe that there was an official spacer recommended for the wheel hub that moved the rear wheel just enough to the left to provide adequate swingarm clearance for this non-OE tire size. I don't know whether this spacer is still available or not. The other complicating factor is that tires from different manufacturers that share the same nominal sizes, don't all fit precisely the same when they get mounted on a wheel and bike. Overall real-world inflated widths can vary a little, and there isn't much room between the rear tire's sidewall and the swingarm to begin with, so it can be a bit of a gamble when trying to fit something other than a 4.00 x 18. Tom Cutter, the proprietor of Rubber Chicken Racing, would likely know which tires are most likely to fit, and can fill you in on the spacer solution, if it's still available. Both of your candidate whitewall tires are intended for front wheel use; I don't know what the implications might be for using a designed front tire in a rear wheel application.
Click to expand...


Thank you Khitter for the information I will reach out to him now sir ... very kind of you I emailed him he was not impressed with the idea or the build lol
 
Last edited:
robbie9999 said:
Thank you Khitter for the information I will reach out to him now sir ... very kind of you I emailed him he was not impressed with the idea or the build lol
Click to expand...

Not surprising; Tom is a great airhead mechanic, but may not silently suffer "customization" much. Did you get any info on tire fit, or the 120/90 adaptor?
 
tire size

khittner1 said:
Not surprising; Tom is a great airhead mechanic, but may not silently suffer "customization" much. Did you get any info on tire fit, or the 120/90 adaptor?
Click to expand...


Sir I have been scouring, the two tires I have been looking at will work, the rear is coming out as either 4.25 or 4.50 half in max in either side, I do not have the bike as it is at a shop now, I will have to measure how much clearance is left between the swing arm and other side with the stock wheels on it now.

You mentioned and adapter sir ?

I want the aesthetics of white walls but NO I WILL NOT RISK SAFETY first.
 
Not sure what you're measuring, but the tire dimensions as in 4.00x18 are nominally 4 inches wide, but they can vary among manufacturers.

I suspect the reference to adapter is towards a spacer which will move the rear wheel over a little bit. Snowbum talks about it under paragraph 5 here:

http://bmwmotorcycletech.info/wheels.htm
 
Yes, thanks, Kurt---that's what I was referring to, but using the wrong term--it's a "spacer" or "thrust sleeve" that can be used to fit a 120/90-18 rear tire.
 
tire size

I believe I have found a company that makes the tires in the correct tire sizes


SHINKO CLASSIC 240 100/90 - 19

SHINKO SUPER CLASSIC 270 WHITE WALL 110 /90 - 18

I am going to look up there reviews now, as per this forum best to stick to original tire size !!!!
 
Be careful with the 100/90 up front. Depending on the fender being used, it might not clear the brace that is built into the fender. Typically a 90/90 is the preferred up front...on a stock setup. If you're going for the picture you posted, it doesn't appear it would be an issue. Note, though, that a wider tire up front can add some difficulty to the steering. You have a wider contact patch and it takes more to turn off of that patch due to the rack/trail setup for the bike.
 
robbie9999 said:
I believe I have found a company that makes the tires in the correct tire sizes


SHINKO CLASSIC 240 100/90 - 19

SHINKO SUPER CLASSIC 270 WHITE WALL 110 /90 - 18

I am going to look up there reviews now, as per this forum best to stick to original tire size !!!!
Click to expand...


Not to encourage your deviation from The True Path to Airhead Street Cred, or anything, but Shinko also lists their “Super Classic” as being available in 4.00 x 18. Not sure that I’d want to ride those on a rain-grooved highway, but maybe that’s not your plan, and maybe they’d be about the same as a set of Conti RB2/K112s anyway.
 
20774 said:
Be careful with the 100/90 up front. Depending on the fender being used, it might not clear the brace that is built into the fender. Typically a 90/90 is the preferred up front...on a stock setup. If you're going for the picture you posted, it doesn't appear it would be an issue. Note, though, that a wider tire up front can add some difficulty to the steering. You have a wider contact patch and it takes more to turn off of that patch due to the rack/trail setup for the bike.
Click to expand...

Thank you Kurt ! For the information, dully noted sir !! I do believe if my calculations are correct that the front is 9 - 3.25 which equals 100 90 -19 which equals out to 3.25- 3.50 its' a range given so I "should" be ok
 
You must log in or register to reply here.

Similar threads

D
'78 R100 Rear Tire Replacement
Replies
11
Views
886
arhd63
A
senseamidmadness
R850R: Tire size options for 18 inch spoked front?
Replies
3
Views
885
senseamidmadness
senseamidmadness
G
Adventure Tires - sizing on 1984 R100T
Replies
1
Views
737
20774
20774
Omega Man
Dealership Tales- You Can Order It? So Can I!
2
Replies
35
Views
3K
gsinnc
gsinnc
C
2004 R1100s rear tire size
Replies
7
Views
4K
carfont
C
Back
Top