shopping for fat 18" sand mx tire

 

friggin' Michelin tire sizes, new metric sizing, old metric sizing...
everybody is on a different page. PITMFA

2001 GasGas xc300
there sure are a lot more choices for folks with 19"wheels.

120/90-18 michelin s12 would be the easy answer.

Depending on which conversion chart you use, perhaps this IRC M5B in a
140/80-18 would be just fine. That is not a cheap tire but looks nice
and dennis kirk has a nice price. Has anybody used one of these?

matching front either way...
I want fresh sneakers for Stimilon.

decisions, decisions...
I'd run Cheng Shin if they'd sponsor me LOL

 

Dean,
  If you use a michelin S-12, get the 140/80-18, but don't expect to
be breaking loose the rear wheel very much. (In "Dunlop-speak" this
would be a 120/100-18.  Dunlop uses "new Metric" sizing. Michelin uses
"old Metric" sizing. Pirelli may use either, depending on how old the
tire design/mold is.)

 If you want to go cheap; in deep sand, the old cheap Kenda K760
Trackmaster2 works very well.

  

 


Thanks Jim, will do. My riding style does not depend a lot on
wheelspin. Well, I have been known to say "spare the clutch, let the
tire do the slipping". Last year I was experiencing copious wheelspin
with the 120/90-18 s12.


Michelin is now also split using two systems S12xc, M12xc and Desert
use "non-standard" markings, the others use "Michelin Markings". This
could really make a Monty Python skit.

OK, so...
my GG Manual del usuario (Service Manual) specifies:

Front    80/100 x21
Rear     120/90 x18

is that new metric, old metric, Michelin marking, or "non-standard"
Michelin marking? LOL
This thing is as clear as mud:
http://www.michelinmotorcycle.com/mxsizing.html

is the 140/80-18 oversized? (that's OK for Southwick, I think)

A simple prefix on the sizes could be an easy fix. They wouldn't even
have to change the old tire molds, just add the prefixes to the
catalogs. <grumbles...>

Thanks again! You da man.
-Dean

 


**************************************************


 Considering the small size of the knobs on the 120/90-19 S-12, I can
easily believe that.  
 That is the "old metric" size for a 100/100-18 Dunlop.  
 The difference between "Old metric" and "new metric" is that Old
Metric measures the outside of the knobs for the tire width, and new
metric measures the width of the tire's carcass.  



  I think that the manual is using the New Metric sizing.
I know that many of the bikes I sold in the early '00s came with the
M-12 Michelins in a size equivalent to the Dunlop 100/100-18.
  I think that this was because Don Knight's riders, at least his sons
and Clay Boreing rode with a style which had the rear wheel going 35
mph when the front wheel was going only 20 mph.  The resulting gyro
effect would make the rear wheel pinball off stumps and tree trunks as
it flew down the trail, without upsetting the equilibrium of the bike.
(They would remain completely upright during the process.  I couldn't
ride like this, but my son Joshua occasionally achieved it.)

  OMT; The Michelin M-12 has almost identical knobs on the 120/90-18
as it does on the 140/80-18.  Not so the S-12. On the S-12, the knobs
on the largest sized tires are twice as large as the knobs on the
smallest, with the 130/80-18 somewhere in the middle.
This is the only tire that I know of which has such a pronounced
difference in the knob size in relation to the tire size.  


  Not as long as you aren't planning on steering the bike by spinning
the rear wheel.

BTW, Michelin tires with Old Metric sizing molded into the marking on
the carcass now come with a sticker (applied to the sidewall) which
states the size in New Metric.


You're welcome.

 I often run a 110/100-18 rear tire on my 300.  This is because the
Bridgestone tires that I run as a "everywhere, but especially the
mountains" tire don't come in the larger size. If I was running the
Kenda K760, it would be a 120/100-18 (unless I already had the
110/100-18 in my stock, paid for.).

Also:
  Deb is depending on you and Sean making it to BMMP next month. If
you two back out, please call and tell us.  That would keep me out of
trouble.  (I'll go anyway, but Deb may not.)

Jim

 



We will be there. I will let you know if something goes wrong.

speaking of going wrong...

Damn, I just had a triple-track storm window come down like a
guilotine across the knuckles on both hands - WHAM!. Only one knuckle
is bleeding. Frozen peas make a good ice pack. I was worried for a
minute there.

This is taking all the fun out of installing my new air conditioner.