150/65-18 Tyre on 3.50” Width Rim?

150/65-18 Tyre on 18x3.50” Rear Rim = unwise or do you think it’s okay?

I’m building a 1977 KZ650b with the stock rear drum hub and a Krüger&Junginger Box Swingarm capable of taking about 190 width tyres or less. I want to purchase an Excel 18x3.50” Rim laced to my rear drum hub with a Conti Road Attack 3 CR 150/65-18 Tyre. Why? Because this combo is available to me for roughly $400 cheaper than if I went with a 4.25” width Excel Rim + 160/60 or 150/65 Tyre.

The Continental Tyre manufacturer suggests rim widths of 4.0”, 4.25” or 4.50” for their 150/65 tyre, however a wheel lacing shop said a 3.50” should be fine.
ZukDave is running a 150/60 Shinko 006 Podium Tyre with an 18x3.50” Rear Rim on his 1980 KZ650 F1 (and similarly Shinko suggest 4”-4.5” width rims for that Tyre) so I would love to hear some feedback from you please zukdave? -> do you only use this set up for drag runs or is it a successful set up for the road?

If anyone has any advice regarding this combination I would greatly appreciate the feedback... thank you so much.

Cheers,
Nick

One thing you need to check first is the clearance between the chain and tire and chain and bike frame. You may find that if the chain is away from the tire far enough that it does not hit the tire it may then hit the frame. Ed

This bike has a 150/80/16 metzeler on a 3” rim. Road hard and never had a problem

Short profile tire and somewhat narrow rim may not play nice together??

I have a 140 on a 3.5" rim, no way Id go 150.

Ran a metzler 150 on my turbo years ago was never a problem . Since then im older and wiser and just run what kawasai recommends.

650ed - Thanks for the heads up regarding the chain & frame clearances. The Krüger&Junginger swingarm is specifically designed for the KZ650 77-83. It comes with a sprocket for use with wider tyres 170-200 width. 160 and below the spacer sprocket is not required as it clears naturally, but I have it in case I need it. No probs there.

My query is about running a 150/65 tyre on a 3.50” rim on basically any motorcycle. In particular how important it is to follow the manufacturers recommendations for their tyre width vs rim width combinations?

An example is the 150/70-18 Avon Roadrunner MK2 suggest a minimum rim width of 3.50” whereas the 150/65-18 Contiroadattack 3 suggest a minimum of 4.0”. I’m really keen to try out the highly reputable Contiroadattack 3’s on my KZ650 but if it’s not advisable or would get in the way of roadworthy certificate then I will stick with the Avon of the similar size.

Thanks for the responses so far... still keen to hear more please?


PHOTOS BELOW: KZ650 using my same K&J Swingarm - Front 18x3.50” Rim. Rear 18x5.75” Rim with 180/55-18 Tyre. With tyres this wide I imagine it feels like driving a bus... but yes it clears the chain and frame.

Forget about clearance, the narrow rim will deform the profile of the tire. I ride supermoto, this crap comes up all the time. Usually people wanting to run 150s on 4.25 rims, not 3.5!