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Author Topic: 350 18 rear tyre on 1980 R65?  (Read 323 times)

Offline rickloader

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350 18 rear tyre on 1980 R65?
« on: July 18, 2022, 09:38:38 AM »
Hi, is it possible to put a 350 18 in place of a 400 18? Any snags / safety concerns?
The reason is that my preferred Heidenau K34 /6 or Metzler ME77  400 18 don`t seem to be available at present in the UK. But I do have a new 350 18 K34 to match the new K34 325 18 already on the front.
I guess I could go for a metric width tyre, but the swinging arm clearance seems very tight.
I`m a sedate rider so  performance at speed is not a big concern.
Thanks, Rick
1980 R65 (January 81 registered)
1977 Norton Commando
1976 Moto Morini Strada
1960 Velocette Mss

Offline rickloader

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Re: 350 18 rear tyre on 1980 R65?
« Reply #1 on: July 18, 2022, 12:44:34 PM »
Sorry to answer my own question but  there is a 400 x 18 Avon Road Rider 2 available, to save the metric uncertainty. 87  inc carriage at BikespeedUK.com. Seems reasonable, and I`ve used the Roadrider before on other bikes, with good results
I looked at a lot of data and it looks like 350 might have been ok, but I will go with the 400
Thanks, Rick
1980 R65 (January 81 registered)
1977 Norton Commando
1976 Moto Morini Strada
1960 Velocette Mss

Offline Tony Smith

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Re: 350 18 rear tyre on 1980 R65?
« Reply #2 on: July 25, 2022, 06:37:13 PM »
A 110/90 rear will fit comfortably and most 120/90s will fit if you are prepared to make new spacers to move the wheel a could of millimetres away from the FD.

Fitting narrower tyres is not recommended due to reduction of the already marginal. Intact patch and the possibility of rolling the tyre off the bead
1978 R100RS| 1981 R100RS (JPS) | 1984 R65 | 1992 KLE500 | 2002 R1150GSA |

Offline rickloader

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Re: 350 18 rear tyre on 1980 R65?
« Reply #3 on: August 01, 2022, 10:18:00 AM »
Thanks Tony for your reply. I am only familiar with the WM series of rims, and I could not relate these to the BMW rim. Your info about the 350 is just what I need - thanks.
The Avon 400 x18 is a good fit, and it seems compatible with the 325 Heidenau on the front. The worn out ME77 rear white lined badly. Cured now
I would not be happy making non standard spacers.
Every time I find a tyre I like - Metzler, Heidenau , They discontinue it!
Rick
1980 R65 (January 81 registered)
1977 Norton Commando
1976 Moto Morini Strada
1960 Velocette Mss

Offline Tony Smith

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  • Posts: 2304
  • Graduate, Wallace and Gromit School of Engineering
Re: 350 18 rear tyre on 1980 R65?
« Reply #4 on: August 01, 2022, 06:30:01 PM »
Tell me about it. Pirelli used to make their "City Demon" tyres in BMW sizes. They were fantastic having a. Very soft compound, excellent water wipes and a lovely profile.

They didn't last long - around 6k kilometres but they made those kilometres very exciting.

I was very disappointed when they became unavailable.

There is nothing "dodgy" about playing with spacer lengths, back in the day you could buy them from BMW. These days the only contra- indication is that most of be splines will exhibit some gnificant wear which makes putting all the load on very short bits of splines a bit problematic.
1978 R100RS| 1981 R100RS (JPS) | 1984 R65 | 1992 KLE500 | 2002 R1150GSA |

Offline rickloader

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Re: 350 18 rear tyre on 1980 R65?
« Reply #5 on: August 03, 2022, 05:30:41 AM »
6k km is a rather short life. Even if affordable ( it wouldn`t be for me), frequent tyre changing sessions are a chore. My formative motorcycling was done on tyres with much less grip. Caution in the wet, extra braking distance is ingrained . I do not push tyres to the limit.
Thanks for the spacer info . My splines are good, but dry and red rusty, now moly lubed.
i spoke too soon saying the Avon is a good fit. Widthwise yes. But I have not seated it concentrically. A couple of attempts gives no improvement. I will try again with proper tyre soap. Maybe coerce the tyre with ratchet straps or g cramps. Any tips for correct tyre seating? This is my first bike with cast wheels. Not had this trouble with spoked rims.
Thanks, Rick
1980 R65 (January 81 registered)
1977 Norton Commando
1976 Moto Morini Strada
1960 Velocette Mss