1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

P11 Fenders/mudguards

Discussion in 'Norton P11 Motorcycles' started by Junglebiker, Feb 20, 2019.

  1. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    Pretty sure I know where I am going to get my fenders from, but the supplier offers them in several different diameters. Anyway, any chance that somebody could give me some idea what the (theoretical) diameter of the rear fender on a P11 is? Available diameters are 26.5", 27.5" and 28.5"

    Available widths are 4.5", 5", and 6". How wide is the original rear fender on a P11?
     
  2. p400

    p400 VIP MEMBER

    Joined:
    Jul 14, 2014
    I think Walridge can supply 03-3138 rear alloy P11 fender.
    Guessing and settling for an alternate may not add the ultimate value to your time and project.
    Here are approximate length measures.
    Make sure the rear fender leading edge overlaps the seat bottom by at least ½".


    P11AlloyRearFenderLenght1.jpg P11AlloyRearFenderLength2.jpg
     
  3. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    Hmmmmm. Thanks for that P400. I still would like to know the estimated diameter, if nobody can figure it out, I'll just guess, which I'd rather not do.

    What about width? Surely the width of a P11 rear fender is easy to measure?
     
  4. Ron L

    Ron L VIP MEMBER

    Joined:
    Feb 27, 2004
    My '67 fenders measure 4" wide front, 5" wide rear. Front measures about 15 1/2 inches from center of axle to top of fender at fender brace, so about 31 inches in diameter? I have no idea how to measure the diameter of the rear at only about 18" long.
     
  5. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    Does fender diameter pertain to the actual diameter of the fender, or to the tire diameter the fender is to cover?

    The values 26.5, 27.5, and 28.5 inches that JungleBiker states in his post, seem to be more the tire diameter. Tire diameter is easy to measure.

    Specifying diameter as that of the tire, eliminates the quandary of where on the fender to measure the diameter ..... that is to the fender edge (rim), or the maximum outermost curvature.

    Slick
     
    Last edited: Feb 26, 2019
  6. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018

    Excellent! Thank you, Ron L! 5 inches is what I needed to know.
     
  7. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    I am wanting to copy Mike Patrick's 4.50 x 18 front and rear tire fitment and the total diameter of that wheel/tire assembly should be around 27", so I'm thinking that even if I went with the largest diameter (28.5") I should be alright, especially as the rear is only 18" long (and I may go a little shorter than that). On top of that, I rather suspect that as long as the fender is an inch or so larger in diameter than the wheel assembly, then it will look okay, especially on a bike like the P11, where the fenders live (relatively) close to the wheel. I'm thinking to use the same width fender on the front (I'm using a wider than standard front end) and to mount the front fender so that it has a good inch of clearance between the tire tread and the inside of the fender. The rear fender will of course be mounted in the usual place.
     
    jerrykap likes this.
  8. jerrykap

    jerrykap VIP MEMBER

    Joined:
    Jul 23, 2014
    Unfortunately I had to replace the rotted tire carcass on the front of the Patrick racer. It was a 4.50" X 19" Dunlop trials type. They have not been made for a very long time. I couldn't even find a decent used one from any of the ex desert racers. All I could find at the time was a Goodyear grasshopper in the required 4.50" X 19" size. The tread pattern will never look right to me but at least the size was correct. I think if I had to do it over I would have settled for an easily available trials tire in the 4.00 X 19" size. The rear 4.50 X 18" offered many more suitable choices. Good luck with your tire choices. This is how Mike's racer looked when I brought it home in 2002. C-ya, Jer


     

    Attached Files:

    Last edited: Feb 28, 2019
  9. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    !! I could have sworn that I read somewhere that Mike's P11 race bike had a 4.50 x 18 on the front. Oh well, I'm committed now, already got heavy duty stainless spokes from Buchanan's to fit an 18" rim. It'll be cool, anyway.

    I liked the look of the Goodyear Grasshopper on that bike--enough I did some checking to see if anybody was making a replica of it, but nobody is. I think I'm going to end up going with IRC Battle Rally tires. DOT approved and FIM approved in case I feel like entering the ISDE. :)
     
    jerrykap likes this.
  10. jerrykap

    jerrykap VIP MEMBER

    Joined:
    Jul 23, 2014
    How she stands now. Oct., 2018 at the Barber Museum.
     

    Attached Files:

  11. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    Okay, the guy I'm getting my fenders from says that he can make them any diameter I want. Based on what Ron L says, I think I'll tell him 31" diameter on the front. That leaves just the rear. Let me try asking this question: can anybody tell me what the distance is between the top of the rear tire and the inside of the rear fender? I'm wondering if maybe I can use that info to come up with a theoretical diameter for the rear fender.
     
  12. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    The question isn't just about diameter, length and width, but of section type as well. I believe the early P11 and P11A used a C section, while the P11A Ranger and P11 Ranger 750 used D sections at the rear.

    P11A Ranger rear mudguard apex has approx. 37.25in diameter based on photographic measurements of the factory PR pictures.

    -Knut
     
    Last edited: Apr 24, 2019
  13. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    Thank Knut, I was guesstimating it to be somewhere between 35" and 37", just based on photos. If I screw up and get the wrong size, I'll use the fender on some other project.
     
  14. motorson

    motorson VIP MEMBER

    Joined:
    Nov 29, 2011
    That picture with Jerrykap sure looks like an 18" front tire.
     
  15. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    I've noticed that in a few other P11 pictures, too--the front tire looks like it is the same size as the rear, but I'm not sure that it is. Certainly they came with a 19 on the front as far as I can tell.
     
  16. jerrykap

    jerrykap VIP MEMBER

    Joined:
    Jul 23, 2014
    Optical illusion? Definitely 19" wheel on the front.

     
  17. Junglebiker

    Junglebiker

    Joined:
    May 16, 2018
    I wonder if my 18" front wheel is going to look too small now? We'll see. I can always switch to a 19 later.
     

Share This Page