Topic: Quick tire question

[AlekStooge]

I'm rebuilding my wheels. 1978 CB 550K, stock size rim 1.85 front and rear. I found front tire 3.25/100-19 for the back I could do 100/90-18 or save $20 and do 4.00/100-18. The width difference is minuet, I'm thinking of the aspect ratio should I match it to the front or just save the $?

https://www.denniskirk.com/avon/am26-roadrider-tire.pfp543162.prdf

Thanks

[Bankerdanny]

The 4.00 is too wide. The 750 that tire fits has a 2.15 rear rim. Spend the extra $20 and get the 100/90, it is slightly wider that stock, but will fit the rim fine.

[AlekStooge]

It's a 1.6mm difference between the 4.00 and 100? The cost is less for the 100/90...

[Stev-o]

I put a 4.00 on my 550F....no issue for me. 

[flatlander]

#me too

[brewsky]

Me 3....'78 550K
Match front and back....either inch or metric for both
3.25-19 and 4.00-18 handle perfectly

[TwoTired]

I've been using 3.25 19 fronts and 4.00 18 rears on my 550s for 30 years.  No regrets. I did try metrics out a while back.  But, went back to inch sizes.

I think the stock rear was 3.75, 18  which isn't easy to find these days.  (Or necessary, imo.) 

The inch sizes are more apt to have the aspect ratio profile (100%) that was used in the suspension design, rather than metric sizes which use, at best, a 90% ratio.  But, tire manufacturer do take liberties.

I've been happiest with Metzelers, so far.

Cheers,