Is a 4.25 rear tyre too big?

[SteveW]

Just getting my CB550 ready for its MOT, noticed that the previous owner has put a 4.25 wide rear tyre on it.

Seems fit ok, haven't ridden the bike yet due to knackered carbs, electrics etc etc.

Is 4.25 too wide?, I will probably be changing tyres soon, should i go for a 4.0?

[SteveD CB500K0]

Always had 425/85 Tyres on my 500s.


Sent from my iPhone using Tapatalk

[hairygit]

Fitting a 4.25 tyre on the rear was a popular choice back in the day. Don't recall anyone having issues with it, and it raises the gearing very slightly and makes the bike fractionally taller, but it won't be a problem unless you're a shortarse like Mrs Hairy, or a certain member on here with a green 750!

Sent from my X6pro using Tapatalk

[SteveW]

Thanks guys 

[Johnwebley]

I fit a 4.00
That is already 2 sizes bigger than the 3.50 standard for the 500

Sent from my SM-G361F using Tapatalk

[Bryanj]

4.00 x 18 is English size and 4,25/85 x 18 Metrisish and both sizes are really the same (550 came with 400 x 18)

[matthewmosse]

I think the widest tyre I had was a 500/15 that I picked up on a custom rim, that just about fitted cold but rubbed the torque arm sometimes on the move. I suspect going that wide on a stock rim would bunch the tyre up and not be safe....

[Moorey]

4.00 x 18 is English size and 4,25/85 x 18 Metrisish and both sizes are really the same (550 came with 400 x 18)

Where is the Metrisish bit, isn't 4.25 = 4.1/4 inch 85 is tyre wall size as a % of tyre width and 18 the wheel diameter in inches.  So isn't  a 4.25 wider than a 4.00 .  Sometimes another 1/4" can make all the difference or am I wrong.

[MrDavo]

The early CB750 I had in the 70's came with an oversize back tyre, 4.25 TT100 I think, coupled with Girling shocks that may have been on the long side (I didn't know any better to find out / go back to standard) it snaked like a pig (if pigs can snake) at high speeds, I got rid after a couple of near terminal experiences, it put me off big Hondas for years.

The K1 I have now has bog stock tyre and shock sizes, and doesn't wobble at all.

[K2-K6]

Isn't 4.25  decimal expression of inches, so a sort of hybrid rather than fractions of an inch as would be usual?

So decimal being base ten does make it metrinch-ish by combining the two 

It's a real hotchpotch even now with tyres all still having imperial sized rim diameter, plus metric width,  plus % aspect ratio as moorey states.

[Seabeowner]

Yes and the rim is 1.85" wide just add to the mix.
Always used 4.25/85 in years of old. The 85% profile coincidentally means the gearing is virtually unchanged,
Standard tyre was 3.50 on 500, 3.75 on 550.

[Tomb]

I use a 120/90 rear on my 500, it works really well - if you want to go totally metric.

Its close but clear of the torque arm though I am using a Dresda box section arm if that makes any difference.

[peterengland]

No, it's fine

[Green1]

Just to let you know I have a 400x18 on my 550 and 750 and can reach the floor easily even though I am a wee bit shorter then you freakishly tall people.
Super Moto boots help a little on the 750 

[SteveD CB500K0]

Do these “super” boots have high heels then?


Sent from my iPhone using Tapatalk