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RDS wheel rim sizes and profiles for replacement

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  • RDS wheel rim sizes and profiles for replacement

    I intend to replace both my wheel rims and the front one looks original being a Dunlop WM1 2 ¼ x 18 while the back one is an Italian make. The “British 250 Racer” says the rims were Dunlop “H” section WM1 and WM2 so I’m guessing the rear wheel rim is slightly wider than the front – is that so? What are the correct wheel rims for an RDS please?

  • #2
    As far as I have been able to find, of the 250s ,only the RAS came with the WM2 rear rim and 3:00 tyre (until the Oulton). The RDS service notes do not quote a rim size but lists 2:75" Dunlop triangulars as the tyres fitted front and rear and I believe had WM1 rims front and rear.

    It depends on whether you want to make the bike completely original or a working race bike. I changed the rims on my RDS to WM2 (1.85") front and rear, originally fitted with Avon 80/90 front and 90/90 rear tyres but now using Heidenau 2.75 front and 3.00 rear tyres. Anything narrower that 1.85" and the tyre beads are pinched in and they don't profile correctly (identified by "chicken strips" on the edge of the treads). Probably the WM1s worked with the original triangulars we used in the 60s as they really were triangular and pointy!

    This is just my experience from racing my RDS continuously since 1982.

    Stan

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    • #3
      The Greeves parts book for the RDS lists the WM1 x 18 for the front and rear wheels. As Stan says though this may have been better with the older triangular tyres - perhaps these days something wider would be better.

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      • #4
        I believe Ian's right and the RDS came out of the factory with WM1 rims. By the time I bought my first RDS in 1972 the Dunlop rim on the rear had been changed for a Borrani WM2 rim and that's what I used all the time I was racing it. I kept the WM1 on the front and even fitted a Michelin 3.25 on it, which worked well. Of course, if you want originality I have a couple of sets of triangulars left which you can have. Hardly worn, should scrub in nicely

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        • #5
          No race scrutineer would allow Dunlop triangs out on the track these days as the rubber sets like porcelain- I had the loan of a Silverstone and had to get special permission to do one practise lap at Cadwell on the original tyres as we did not know if the gearbox would work, on the condition that the tyres would be changed immediately if the bike was OK, and that was about thirty years ago! Peter.

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          • #6
            Kevin, thanks for the offer but I'll give the triangulars a miss for now! My rear wheel is a Borrani as well and front is a Dunlop WM1. So do I stay original or go racier? My tyres are Avon Roadrider 90/90/18 AM 26 A49 (front) and Avon Roadrider 90/90/18 AM 26 633 (rear) which give good adhesion.

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            • #7
              Avon recommend a 2.15" rim for the 90/90 section tyres with alternative sizes of 1.85" minimum and 2.50" maximum. I would go for WM2 (1.85") on both ends, which is what I run. There is no doubt you could squeeze these tyres on 1.60" rims but if you are going to change the rims anyway and intend to ride the bike on the track, why not use the recommended sizes. As for originality, I try and keep my bike as close as possible to how it was raced in the 60s but the difference in size is hardly noticeable, except to a rivet counter.

              Stan

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              • #8
                Peter.....I think the joke was lost on you.

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                • #9
                  Oops!...................

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                  • #10
                    Ha...in fact I do have a couple of sets, I took them off the rims about a year ago, where they had been since the mid 70s. Blimey it was tough work muscling them off without damaging the rims though, the entire carcasses are like rock.

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                    • #11
                      Those triangulars could be valuable. Someone offered and paid silly money for an old 1930s speedway tyre I was about to throw away. He wanted it for a display bike. The price of originality.

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                      • #12
                        I've got a 1950's racing tyre, can't remember if its Avon or Dunlop but if you know anyone in need.........

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                        • #13
                          On the RBS I raced up until 2018 I ran WM1 front and WM2 rear with a 90/90 roadrider on the front and a 110/80 AM22 front on the rear.

                          I had several race and championship wins so it obviously worked.

                          On the 350 I have a WM2 front and a WM3 rear and run a 100/90 Continental Attack 2 CR on the front and a 110/80 Attack 3 CR on the rear. This is a far better setup but the 250 rolling chassis wasn't mine so I couldn't change the rims.

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                          • #14
                            Thanks Will and what a shame Pembrey is now cancelled. Let's hope for a better season in 2021! I think for tyres I will run 90/90-18 AM26 front and 110/80VB18 AM22 rear - my only remaining decision is should I go for WM1 & WM2 or WM2 & WM3 front/rear respectively? Cheers Rene

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                            • #15
                              My current thinking is to use Avon tyres: 90/90-18 AM26 front and 110/80VB18 AM22 rear and to match these the best rim choice appears to be: 1.85-18 (WM2) front and 2.15-18 (WM3) rear.

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