Results 1 to 15 of 15

Thread: Metric tire size for R90?

  1. #1
    Registered User
    Join Date
    May 2005
    Location
    Chardon, Oh
    Posts
    66

    Metric tire size for R90?

    I have a 1975 R90 and need a new tire. When I ask for a 4.00X18 at the local bike shops they act like I asked for dozer treads. They go to a conversion chart for a metric size. I lack confidence in these sizes. Does anyone have any experience in an alternate tire size to the stock 4.00X18.
    Thanks,
    Marty

  2. #2
    Focused kbasa's Avatar
    Join Date
    Mar 2003
    Location
    Marin By God County, California
    Posts
    11,664
    I think you get a 120/18 instead.
    Dave Swider
    Marin County, CA

    Some bikes. Some with motors, some without.

  3. #3
    dlearl476
    Guest
    Quote Originally Posted by KBasa
    I think you get a 120/18 instead.
    Actually Dave, it's a
    110/90-18 Whether you can find a tire in that size or not, who knows.
    FWIW, Southwest Moto tire has Michelin Mac 50/50E in the old sizes. I love them on my /5 and I think they'd be great on your S as well.
    (Scroll down to the bottom of the Mac 50 page, IIRC the front and rear BMW sized tires are the last two listed).

  4. #4
    '99 '03 '06 National Co-Rally Chair Friedle's Avatar
    Join Date
    Mar 2003
    Location
    Poughkeepsie, NY
    Posts
    1,708

    Metric sizes

    Hello Dave,

    Actually it depends on the brand and model of tire.

    Some 120 section 18 inch rear tires will rub against the swingarm. You might need to install a 110 section 18 inch rear instead.

    Marty, why don't you go to the www.Airheads.org site and do a little research where you will soon find way more than you ever wished to know about rear tires for an airhead BMW. Lots of different "favorites" and "bests" in a couple of different sizes.

    As the Airheads say, "Keep it simple". Find what works and fits for you, and then just keep using it. Trying to convince everyone else that it is the only viable choice is optional.

    Friedle
    Airheads Beemer Club Board of Directors
    BMW MOA Board of Directors
    I like OLD bikes!
    Ride fast safely

  5. #5
    Minnesota Nice! braddog's Avatar
    Join Date
    Jun 2003
    Location
    Twin Cities - MN
    Posts
    1,953

    My experience...

    I've got a '77 R100RS. I had to replace both my fronts and rears. It had Metzler ME77's, so had the 4.00X18 on the rear and 3.25X19 on the front.

    They were replaced by a ME88 120X18 on the rear, and a ME880 110X19 on the front (it may be a 100X19). Both tires are a bit wider than the ME77's they replaced, but no issues at all with crowding any parts.

    I chose these because I had it done at a dealer, and their prices were quite good for both the tires and the mounting. The dealer had these on hand and available, so I took 'em. I've been pleased so far. I know there are lots of other options out there, this is just my experience.
    -----------------------------------------
    Brad D. - Member #105766
    '77 R100RS - Black Beauty (big pipe, baby!)
    '94 R1100RS - Sylvia

  6. #6
    Blocking the slow lane
    Join Date
    Mar 2003
    Location
    Edwardsville, IL
    Posts
    1,852
    SWMotoTires can get a Bridgestone BT45 in the 110 width. We have one on my wife's R90S.
    Jon Diaz
    BMW K75/K12GT
    BMWMOA Ambassador

  7. #7
    bmwmick
    Guest
    Here's another vote for the Michelin Mac50E/Mac50 in the proper sizes. 3.25X19 front and 4.00X18 rear. SW Moto always seems to have a good stock.

  8. #8
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Location
    Albuquerque, NM
    Posts
    6,223
    Quote Originally Posted by bmwmick
    Here's another vote for the Michelin Mac50E/Mac50 in the proper sizes. 3.25X19 front and 4.00X18 rear. SW Moto always seems to have a good stock.
    Ditto.

    BTW, there ARE NO metric equivalents to 3.25X19 and 4.00X18.

    If there were, the latter would have likely disappeared.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  9. #9
    Registered User
    Join Date
    May 2005
    Location
    Chardon, Oh
    Posts
    66

    Thanks for all the input

    Well I settled on a Metzeler 120-90-18. I mounted and balanced it. It fit without any interferances. It feels good on the freeway, rides nice and smooth. I will see how it peforms when I ride it to the rally in Lima later this week.

    Thanks to you all for in inputs.
    Marty

  10. #10
    leave my monkey alone LORAZEPAM's Avatar
    Join Date
    Jun 2003
    Location
    West Salem, OH
    Posts
    2,888
    Quote Originally Posted by lkchris
    Ditto.

    BTW, there ARE NO metric equivalents to 3.25X19 and 4.00X18.

    If there were, the latter would have likely disappeared.
    I believe that in their infinite wisdom, the germans require that you put the original equipment tire on the bike, so those sizes will be available for some time to come.
    Gale Smith
    2009 Versys
    1999 R1100RT

  11. #11
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Location
    Albuquerque, NM
    Posts
    6,223
    Quote Originally Posted by lorazepam
    I believe that in their infinite wisdom, the germans require that you put the original equipment tire on the bike, so those sizes will be available for some time to come.
    That's correct.

    The bike was tested and certified with certain tires.

    Use of anything else is "outside the type certificate."

    Would you fly an airliner with "parts that fit?"
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  12. #12
    James.A
    Guest
    I wouldn't fly on an airliner, period.
    I do possess the means and patience to find tires that fit.

  13. #13
    On the Road 115290's Avatar
    Join Date
    Oct 2004
    Location
    Auburn, CA
    Posts
    29
    I'm about to change out a set of Dunlop D404's on my R90/6, and they have about 8,300 miles on them. I've always run Michelin Mac 50's before, but they've been discontinued. The Dunlops have been quite a suprise. They work well, hold the road in the rain, and have lasted far longer than I ever expected. The best part is that a set of Michelins runs almost double the Dunlop price, so the value is high. Mine are 100/90-19 F, 120/90-18 R, and I've had no clearance issues. Let us know what you choose.

  14. #14
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Location
    Albuquerque, NM
    Posts
    6,223
    Macadams still shown available at Michelin Web site.

    Have just installed some.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  15. #15
    On the Road 115290's Avatar
    Join Date
    Oct 2004
    Location
    Auburn, CA
    Posts
    29
    Quote Originally Posted by lkchris
    Macadams still shown available at Michelin Web site.

    Have just installed some.
    Michelin has a habit of listing items until they run low on stock. I've worked for a Michelin dealer for the last 16 years, and this business tactic has caused us no end of headaches. If I only had a dime for every time I've heard "but it's listed online", then I could probably quit working. I used the Mac 50's on my BMW for AHRMA racing, and on my Kawasaki GPZ750 for club racing, and I can't say enough good things about the way that they work and wear. Fantastic tires.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •