Tyre sizes

[oldbmw]

Yesterday I fitted a new tyre to my Enfield. The old one was an Avon AM26 the new one an Avon SM rear. The AM26 when fitted to the wheel fits in the boot of my car, the SM does not. When I measured them I found the SM is 27mm taller ( bigger in diametre) than The AM26. I realise some of this is tread depth as the AM was worn out. but that is not all of the story, even though they are both listed as 3.50X19. I can actually notice it has moved my gear change speeds up a little.

[andrewaust]

Yes mate, had the same thing happen with the Dunlop tyre I purchased, the new tyre has a lot more roll-out, many wonder why I still use a 17tooth sprocket, that's the reason, the gearing is good for what I use the bike for, any higher in the gearing and the 10hp (a lot less in summer = 35-40C) and the engine would struggle.

Saves the hassle of re gearing the bike, not that I'm saying I'm a lazy bugger !!


A

[Diesel Dave]

Try some TT100's - they reduce rolling diameter quite a bit, equal to about 1/2 a tooth of gearing.

Dave

[Sphere]

Hrm. Altmann uses a 20t sprocket, and he also has a Yanclone (Kama I think). He doesn't report problems.

Yes mate, had the same thing happen with the Dunlop tyre I purchased, the new tyre has a lot more roll-out, many wonder why I still use a 17tooth sprocket, that's the reason, the gearing is good for what I use the bike for, any higher in the gearing and the 10hp (a lot less in summer = 35-40C) and the engine would struggle.

Saves the hassle of re gearing the bike, not that I'm saying I'm a lazy bugger !!


A

[andrewaust]

Hrm. Altmann uses a 20t sprocket, and he also has a Yanclone (Kama I think). He doesn't report problems.

Yeah I'm in contact with Charles on a regular basis, I think he might be using a 19T at the moment. Don't know how he squeezes enough HP out of the bike though, must be using lower roll out tyres then myself, plus geographic location helps. If I resided in Mildura or Broken Hill where it's flat I guess I could gear it up.

But! Maybe if I get this whizzy thing to work I will be able to anyway .

I have an 18 and a 19, so the 19 might get to go on next.



A

[TedV]

not to thread jack, but how did y'all like the Avon AM26? I just ordered a set for my CB250 Nighthawk. The rears were the small size 120/80-16 compared to the more commen listed as stock on the CB250, 120/90-16. About 3% change in roll out. Most other decent quality tires started at 130/90-16 for the rear and might not clear on the bike so thought it better to be a tad smaller and fit, than rub. I've been thinking of regearing to try some fuel economy stuff on it until I can get a diesel bike running. Already have the diesel daily driver and diesel autocross car

[coachgeo]

... Already have ... diesel autocross car

fun fun, A VW I assume? Solo II SCCA?

[coachgeo]

How can I check my tyres for wear problems?
cbr600f4 fairings

sPam Spam spAm

reported

[UAofE]

So you single cylinder yancloners are using 17-20 tooth sprockets?
Mine currently has a 20t on the front with (I believe) a 40t rear. With the Comet 94C/90D clutches and V-twin, should I put a larger drive sprocket or keep the 20t?