60 Series on R1100R

["Tom Brown" <tbrown@xxxxxxxxxxx>]

Liang:

>I have a '95 r1100r that currently has a Metzler Z4 120/70-17 front tire.
>I'm thinking about replacing it with a Metzler Z4 120/60-17.  Has anybody
>ever done this before?  Does a lower profile change the handling
>significantly?  The rear tire will remain 160/60-18 Z4s.


I've gone from a 70 series to a 65 series before on an Aprilia.   It lowers 
the front a bit and makes the bike turn in easier.   It's a bit like raising 
the fork tubes in a standard fork-suspended bike.   The soft rims on an R 
bike are a consideration here.

Bottom line?   If you already have a brand new 60 series tire that you want 
to try and it won't cost a lot of money, then try it.  Make sure you keep at 
least 36 psi cold pressure in the front tire.   More if you're a heavy guy 
or riding double or packing the bike with luggage.

If you are considering buy a 60 series tire instead of a 70, I wouldn't do 
it.   65 series tires are available in many tire brands.  That would be a 
better compromise.   Staying with 70 series is probably best.   If Metzler 
doesn't make a Z4 in 65 series, I would not go to a different tire on the 
front without also changing the rear.

Consider that your speedometer error will be even more than it is now. 
With a smaller diameter, the front  wheel will turn faster for the distance 
travelled.   Speedometer drive is on the front wheel.

If you're having trouble with the bike not wanting to turn in, your rear 
suspension preload may be set too low or your rear tire may be squared. 
Usually replacing the rear tire makes a huge improvement in the turn-in.

There are folks around who've actually succeeded in peeling down the corners 
of their rear tires to make them handle like new tires again.   I bought a 
litttle rasp type tool at the hardware store for this, but never tried it. 
I have a feeling I'd hurt myself.


Z4's are particularly fussy about having a round profile on the rear tire. 
This is why I switched to Bridgestone BT020...They're fun until the end of 
their life.  I've since tried the new Roadtec Z6 and I'm quite smitten with 
it, but Bridgestone is coming out with a new 020 called 020N (N is for new). 
Read a European report that it's a significant improvement.

- -TB 

------------------------------