Tires: 1992 CB750 Nighthawk

Im got new rear rubber for my bike, and have yet to get it put on. The
tire was worn out and dry rotted. I had heard once that it is best to
replace both tires on a bike at once, and use matching tires (same
series, age, condition). The front tire does not really look bad
though. It is not dry cracking, and has enough tread left on it. Should
I replace it anyway?
Thanks for your thoughts.
Dan

 

So both tires were the same age? Give us more information.

There's plenty of folks here who mix tire models, brands, ages,
whatever. Of course, there's people here who say all sorts of crazy
things. If your front and rear tires were the same age, and on the bike
the same time, and you replaced the rear because of dry rot and
cracking, why wouldn't you replace the front as well?

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

I dont know if/when the front was replaced. The bike has 10.5K mi on
it. I got it in may with 7.5k on it. How long to tires typically last,
and can you explain more about the curing process and its effects?
The front has much less severe wear than the rear, so I assume it
either has been replaced. I really dont know though.

 

Sure?

 

Not really. No point in replacing a tyre that's still fine.

To a degree. Some tyres are designed to work in matched pairs, yes, but
see above.

No again. If it's in good condition, use it.

 

Replace both, thats me. I look at it this way, my life is worth more than a
tire. Why play the odds. If one of my bikes need one tire, it gets both. Or
it dont move. 20 years of riding and like to see more. Even new ones are a
chance on two wheels. Its the only thing keeping you on the road. Dont
gamble, be sure and safe.

 

Original equipment Japanese motorcycle tires used to be made with cheap
natural rubber and I remember how the Inoue rear tire of my first 750cc
machine only lasted about 6000 miles.

That annoyed me. I went out looking at tires and saw how expensive they
were and realized that riding a motorcycle for transportation was going
to be a very expensive proposition if I couldn't find cheaper tires.

A BMW rider told me about some hard rubber Cheng Shin tires made in
Taiwan that he swore would last for 15000 to 20000 miles in cross
country touring service. I tried those tires and found that it was true
that I could get lots of mileage, but I didn't have a lot of traction.
It was the same thing with Nitto tires.

I don't think Nitto makes motorcycle tires anymore, and Cheng Shin has
adopted the new name Maxxis to enhance sales amongst motorcyclists who
may have heard bad things about Cheng Shins and how hard they were.

And, I talked to performance riders who demanded lots of traction for
cornering. They used and English brand made under license in various
countries, including the USA, England, Japan, and Ireland. The Irish
tires had lots of traction, but only lasted 3000 miles.

The general perception was that Japanese tires were no good at all,
they were just "rim protectors". The guys who knew motorcycles said to
buy Metzeler or Pirelli tires. They are made by the same company in the
same factory. Dunlop, which was originally an
English company makes quality tires in the USA.

Bridgestone makes their BattleAx tires for any model of motorcycle you
can imagine.
I have generally despised Bridgestones every time I've tried them since
their Spitfire series came out in the early 1980's. Bridgestone is
*still* using the same tread pattern 25 years later,

But you may find that the only easily available tires you can get for
your Nighthawk are the BT-45H and BT-45V BattleAx donuts. I don't like
them much, I find them to be squirmy, but others will protest that they
are great. Triumph even selected BT-45V's for original equipment on
some models according to one old time rider that I have known forever.

Original equipment Dunlop tires made in Japan are probably available
too. They may be made with mostly natural rubber to keep costs down.
The Japanese motorcycle engineers have been know for designing
fantastic motorcycles and then choosing really crappy tires because
they could save a nickel per tire.

But they have gotten smarter now that the Japanese companies are
blending synthetic rubber with the natural rubber. I got about 8000
miles on an original equipment Japanese Dunlop rear tire on a 1000cc
machine. The really soft original equipment Japanese Dunlop lasted less
than 2000 miles in extreme service sport riding through canyons.

So, I started using Metzeler tires. I routinely got 12000 miles out of
a Metzeler front tire, before I decided to try Bridgestone BattleAX
BT-020's. The BT-020 front tire sucks, big time. It wiggles and
shimmies over rain grooves and bumps due to its tread pattern, and the
profile makes the steering very vague at highway speeds.

Front tires usually do last longer than rear tires because they have
less weight on them and they are not transmitting power to the road.
It's very possible to get 12000 miles on a front tire.

As far as "curing" is concerned, tires will have more traction and be
more "compliant", i.e., they will absorb small bumps better when they
are new and the rubber is softer and more elastic. The rubber will turn
the energy imparted into them by small bumps into heat. You'll notice
that new tires get noticeably warm from absorbing energy from the bumps
and changing them to heat.

But, after only a few thousand miles, this heat has fully "cured" the
rubber, it is no longer as elastic as it was, it does not absorb the
road shocks as well and the ride quality and traction decrease.

So, when your tires stop heating up when you ride, the rubber is
"dead". The tire may look OK, but it's not working as well as a new
tire, even if it still has a lot of tread depth and the case isn't
cracked.

 

1. What tires are on your bike now? What tires did you buy to replace
them?

It's incredibly difficult to say anything about "typical" mileage
without knowing what sort of tires you have. Hard-riding sportbikes can
run through a tire in less than 6000 miles. I've heard claims of
15-20000 miles on touring tires combined with easier riding. Currently,
I've got 12k on a set of Avon AV45/6, and there's more tread left in
them.

Differential tire wear has been explained to me in the following ways:
a) front wears first on sportsbikes because of high cornering loads.
b) rear wears first on sportsbikes because of high power output.
I suspect that these explanations (so far as they're valid at all) work
for all bikes. Differences in riding style, weight distribution, road
surface, all affect wear rates (and affect front and rear differently).
Again, some people like to replace tires as a set (for various reasons),
while others will replace whichever one is worn out (again, for various
reasons).

Knowing as little as I do about your situation, it's hard to make any
recommendation about whether or not to change your front tire. You need
to consider the changes in grip over the lifetime of a tire, the effects
of environmental exposure even when the motorcycle is not ridden, your
use of the motorcycle, and a number of other factors (some of which I've
mentioned here). I'll lay out two scenarios for consideration:

1. the conservative: replace both tires. You don't know the condition of
the front tire, and the rear is shot. Replacing both removes any
uncertainty about the age and condition of the tires, allowing more
confident operation of the motorcycle; you've put the bike into a known
state. It's more expensive, but arguably safer, particularly if one is
new to motorcycles, new to a particular bike, or wishes to minimize
uncertainty in their riding.

2. The expert: replace only the rear tire. You're familiar enough with
your bike, the roads, and motorcycling that you can adjust your riding
style. You are sensitive to tire feedback, allowing you to determine the
condition of the tire during riding, and are able to determine when it
is finally unsuitable for riding.

Now then, these scenarios are not intended to be advice based on your
capabilities (after all, I don't know them. They are intended to
highlight some, and only some, of the considerations that are involved.
While we're happy to help out, ultimately it's your decision.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

Me: if it needs one tyre, it gets one.

And 30 years of riding ;-)

 

<snip the rest of one of the most misleading and ill-informed posts it's
even been my privilege to witness>

 

I like to play it safe. I didnt mean anything about the years, just want to
see more. lol
Anyways, he should change both of them. He dont no how long they been on
there. Then go from there, the next tire need. that he knows: when, how
long, where tires come from and so on. Thats just my opinion. To what its
worth?