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Thread: 110 or 120 rear tire on a R75/5?

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    Registered User j_withers's Avatar
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    Question 110 or 120 rear tire on a R75/5?

    Forgive me if this has been discussed before...
    But i have two local mechanics that both gave me a thumbs up on my tire choice (Battleaxe BT45) but they have different opinions on sizing.

    One says go with a 110 rear and and a 100/80 front.
    The other says 120 rear and 100/90 front.

    I've always thought that wider would be better (more surface contact) but it seems that many 'purists' say that the bike was designed with the thinner tires in mind and they are better for our old airheads.

    I'd love to know if skinny is actually better and why? Or is it just a matter of opinion?

    The bike is going to be a dry street only, cafe style R75/5. The bike is currently being built but it is time to mount some rubber on the rims. I'll want tires that will compliment the cafe/street fighter/ canyon carver riding style.

    I have the wider sets on my current bikes but I don't know any different.

    -J

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    Administrator 20774's Avatar
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    I'd be cautious about a 100 in front...it might not clear the fender brace. A 120 on the rear is going to be a real bear to get on/off past the shock mount and brake housing. Remember the front was designed for a 3.25 inch and a 4.0 inch tire...you do the math for metric. Plus, just because someone says a tire is 100/110/120 metric doesn't really mean it will be those actual sizes...they vary between manufacturer.
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    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    fatter is not necessarily better. yeah, more potential tire to road traction, but they will also be more resistant to turning. and, as Kurt pointed out- since the rims (and swingarm) were designed to handle inch size tires, any metric tire will be a bit of a compromise. if you decide to go metric instead of 3.25" and 4.00" (yes, they are available), then get closest to original size that you can. that would not be a 120 rear, and probably not a 100 front.
    Ride Safe, Ride Lots

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    Registered User j_withers's Avatar
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    I've been there with different tire 'actual' widths.

    For example, a spitfire S11 120 is actually wider then a BT45 120 tire. I found our real quick when it was rubbing the swingarm and not spinning freely.
    And usually i have to let the air out of the tire to squeeze it past the brake shoes and then inflate it when it is seated properly.

    I currently have 100's on the front of both of my bikes and there are no issues. It is a tight clearance when mounting a fender with the tire on though.

    Out of curiosity, who sells non-metric tires? All i can find are metric sizes in the Avon, Bridgestone brands. I'm not going to bother with Metzlers for this bike.

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    Administrator 20774's Avatar
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    As a matter of fact Avon sells inch-sized tires...the RoadRider series. I have a Michelin Pilot Activ (inch-sized) on the front of my /7. There are other off-brands that sell retro looking tires for the vintage crowd...I have some IRC tires on my R69S. Lots of people sell non-metric tires.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by brewmeister View Post
    I heard this past weekend that avon (tires) is out of business,please someone chime in if this is true?
    where'd you hear that rumor? anyone with a shred of reliability?

    it sure looks like they are in business. http://www.avon-tyres.co.uk/about-avon fwiw- Avon is owned by Cooper Tires, and tehy seem to be doing fine as well.
    Ride Safe, Ride Lots

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    Quote Originally Posted by j_withers View Post
    I've been there with different tire 'actual' widths.

    Out of curiosity, who sells non-metric tires? All i can find are metric sizes in the Avon, Bridgestone brands. I'm not going to bother with Metzlers for this bike.
    I just ordered for my R75\5

    Continental Twins-Classic Tires
    Tire Size: 3.25H19 Front
    Tire Size: 4.00H18 Rear
    Thanks
    01 R1150GS
    75 R75/5 Toaster LWB Red
    Al Navecky Jr

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    Actually cafe' bikes

    I was always of the belief that Cafe' or canyon carver bikes of vintage design were supposed to have the same width tire and if possible the same diameter tire front and rear. I understand that it makes for a quicker handling and leaning of the bike. Its just something that I heard out and about but there is some logic to it as many European only bikes of that time have the same width tire front and rear

    Another interesting thing I have found are there are more than just a few /5 rear rims out there that are the same narrow width as the front rim. I'm told by a few so called gurus that those narrow rear rims were for early /5 and very rare. I have one on my two owner 701/2 and one on may three owner 9,000 mile 73 /5. So just how rare are they?

    Anybody out there know anything about that or why BMW would put such a narrow rear rim on a bike that should have a 400 tire mounted on it.

    I would love to find a 350 / 19 for the front and a 350 / 18 for the rear that would be a nice vintage look matching set for both bikes. Has anybody got a source for those tires.

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    Registered User j_withers's Avatar
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    Quote Originally Posted by gnavecky View Post
    I just ordered for my R75\5

    Continental Twins-Classic Tires
    Tire Size: 3.25H19 Front
    Tire Size: 4.00H18 Rear

    I've been real curious about those tires since i read the article on them. What is the tread pattern like? Do you have any photos?

  10. #10
    Registered User Bob_M's Avatar
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    82 rs

    I have 3 weeks on Avon INCH sized tires, both front and rear. These originally specified size tires don't look small or wimpy, but fill up the space nicely. They look good but handle better than they look

  11. #11
    RPG
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    Avon RoadRider 3.25 x19 and 4.00 x 18 are all the tire you'll need for that bike. They will fit and the bike will handle wet and dry just fine.

    have them on my R90s. Did a 2000 mile Blue Ridge Parkway trip in the spring, followed up by a May Track Day. Three days on the BRP was in pouring rain and had zero issues. And at the track, the bike was pushed pretty hard with no issues either.

    Actually thought of wider tires too, but I was so impressed with the performance, that I'm leaving well enough alone.

    RPG

  12. #12
    Registered User rapz's Avatar
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    I put Metzler stock OEM size on my '79 and I look over at my brother's RT and wonder about it every now and then, but I have no problems with my riding style.
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    Current Bike 1979 BMW 100RT; 2013 BMW R1200RT 90th Anniversary Edition; 2008 Harley Davidson Ultra Classic 105th Anniversary Edition

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