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Tire decision for R90

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Jon Falabella
(@18676)
Posts: 3
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Topic starter
 

Has anybody tried running a 120/19 x 18 rear tire? Also, I see they are making radials specifically for bias ply bikes. I saw the Continental Classic Attack, for example. Any experience or advice would be greatly appreciated. 

 
Posted : 04/01/2025 05:42
James Strickland
(@8053)
Posts: 427
Reputable Member
 

If I can not get the OE spec, inch sized tires, (4.00x18 for the rear) I prefer run the slightly smaller 110 metric size to attempt to avoid rubbing. I used to own a 1988 R100RS that came to me with a 120 on the rear, and the edge of the tire rubbed ever so slightly on the driveshaft side of the rear swing arm. I have used 120 sized tires on my R75/5 and it did not rub.  The '88 RS was a rear mono shock model and that may have contributed to the interference.  The tire profile when mounted may have been part of the issue as well. 110 tires are slightly smaller than 4.00 tires and 120's are slightly larger when mounted and inflated. 

This post was modified 1 day ago 2 times by James Strickland

former Airmarshal, IL.

 
Posted : 04/01/2025 11:00
Jon Falabella
(@18676)
Posts: 3
Active Member
Topic starter
 

Thanks, James. My 1976 R90/6 has a stiffened San Jose aftermarket swingarm. I should probably just play it safe with the 110. It's not like the bike needs any more tire in terms of width. Thanks for your input.

 
Posted : 04/01/2025 11:52
Larry A. Chabira
(@2659)
Posts: 16
Active Member
 

there is NO benefit to running a bigger tire. some that big rub the swing arm. buy a good quality 400x18 , your not riding at Daytona

 
Posted : 04/01/2025 12:05
Jon Falabella
(@18676)
Posts: 3
Active Member
Topic starter
 

It is a bit challenging finding tires, in general. I am now looking for 110/90-18's for the street and also 110/90-18's for dual sport leaning towards dirt. I am helping a buddy with his 1983 R80ST which he will be riding on dirt roads and pavement up here in the VT NEK area. Any suggestions on tires would be much appreciated.

 
Posted : 04/02/2025 05:48
James Strickland
(@8053)
Posts: 427
Reputable Member
 

As Larry suggests, the 4.00 x18 is the O.E.M. tire size for your /6.

This post was modified 6 hours ago by James Strickland

former Airmarshal, IL.

 
Posted : 04/02/2025 10:54

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