Timeing Belt?

Lanny Chambers wrote:

> Lots of situations can go from "inconvenient" to "life threatening" in
> short order.
>

Yeah no doubt.

Something as simple as a flat tire would be worse in all of these situations.

But it's not really a mechanical safety risk ... not on the order of a
broken tie rod or a brake fluid leak or something like that. As "safety
risks" go, broken timing belt in a non-interference engine is pretty much
botom of the list. I guess by this definition, pretty much any mechanical
problem is counted as a safety risk if it requires you to make an unplanned
stop.

Lanny Chambers wrote:

> What if you're in the middle lane of an 8-lane freeway at the time?

That would be a bad one. Luckily I have never driven an 8-lane highway.
I have had a far less nimble car than the miata lose power for another
reason on a busy 4-lane freeway and had no problem pulling over, though
I agree it would have been much safer if I had been able to keep
applying power.

> What
> if it's 3 a.m. and you're in the worst part of town with a
> suspicious-looking car on your tail?

Besides looking for drug dealers or prostitutes, why would anyone be
cruising the worst part of town at 3 a.m.? Not that it has to be a bad
part of town or 3 a.m. to be dangerous. Breaking down almost anywhere
can be dangerous if the wrong person comes along.
Finally, the car doesn't have to be broken down anyway. My great-aunt
was murdered in the afternoon in a shopping mall parking lot by a
"person" who was looking for a working car to take.

What if you're drifting past the
> apex of a 35 mph onramp at 70 (trailing-throttle oversteer)?

An argument could be made that driving high speeds on public roadways is
irresponsibly dangerous and should be left for the track with a car
equipped with a rollbar or rollcage, safety harness and helmet for the
driver.
What if a tire blows out during this 35 mph onramp entrance at 70 mph?

> Lots of situations can go from "inconvenient" to "life threatening" in
> short order.

Agreed. Situations can even turn from "completely comfortable" to
"life-ending" in a split second.

Pat

In article <1126027082.14165@sj-nntpcache-3>, josh >
wrote:

> I guess by this definition, pretty much any mechanical
> problem is counted as a safety risk if it requires you to make an unplanned
> stop.

Most other serious mechanical failures offer warning signs to the
observant: bald tires are more likely to go flat, leaky brakes and
radiators leave puddles, etc. Timing belts typically fail without
warning (other than the odometer reading).

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

josh > wrote:

>Leon van Dommelen wrote:
>
>>
>> There have been reports here of them breaking somewhat over 100 kmi.
>> Of course, a belt breaking unexpectedly is a potential safety risk,
>> as well as an almost certain major inconvenience.
>
>Potential safety risk... ? well I guess the car dies and you have to park
>on the shoulder.

I assume you mostly drive in the right hand lane. I have had the engine
die quite a number of times on me on Interstates, and in each case I experienced
considerable risk getting to the right hand lane with aggressive drivers
passing me from the right while coasting down. Of course, you can just stop
in the middle of the interstate and other drivers behind you must "be able
to stop within the distance the road is visible and free of obstacles."
Personally, I will take considerable risk trying to reach the side of the road
before stopping in the middle of the Interstate anyway.

I also quite frequently cross roads and take left turns close enough to
approaching cars that an unexpected engine failure and an oncoming car
not paying enough attention to judge available distance correctly would mean
major trouble. It so happens that where I live, I do not think most
drivers are able to judge distance even if they were not on the cell
phone.

Nor can I say that parking on the shoulder is necessarily such a great idea.
The last time my engine died, I put it on the shoulder of the two lane
highway. It was close to rush hour then, and it then took about 2 hours
for the AAA to arrive. In those two hours, we had one of our bad Florida
thunderstorms, with about half an hour of absolute zero visibility for anyone
driving without Rain-X on their windshield. If someone who could not
see anything would have decided to put their car on the shoulder to wait
out the worst, I would have been toast. I can tell you that I spend
that half hour looking in my rearview mirrors. (I would still rather be
hit inside my car than outside it.)

>Well I have about 62K on my Miata, maybe I should think about changing the
>timing belt... and cams ... and cam pulleys ...

Personally, I assume that if Mazda does not tell me that the cams and
cam pulleys must be changed, that risk should be an acceptable one. But
if you are that afraid, maybe you should take the bus.

If you take very many different unnecessary risks, statistically one is
sure to catch up with you. But 100 times 0.000001 is still zero.
Especially since the chances of dying were rated at 100% the last time
I looked.

Leon
--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)

Leon van Dommelen wrote:

>
>>Well I have about 62K on my Miata, maybe I should think about changing the
>>timing belt... and cams ... and cam pulleys ...
>
>
> Personally, I assume that if Mazda does not tell me that the cams and
> cam pulleys must be changed, that risk should be an acceptable one. But
> if you are that afraid, maybe you should take the bus.
>

Ha ... my point was, while I have it all apart, I should do cams,
adjustable cam pulleys, etc.

In article <1126097848.985180@sj-nntpcache-3>, josh >
wrote:

> my point was, while I have it all apart, I should do cams,
> adjustable cam pulleys, etc.

If you're prepared to tune your car on a dyno, a few horsepower can be
found via adjustable pulleys. You'd be trading off low end for top end,
and possibly lose some drivability. Hotter cams aren't worth much
without serious headwork and a replacement ECU (and more dyno time to
tune it).

None of these things are nearly as cost effective as basic forced
induction. IMHO, a Miata owner's money is better spent on the
suspension, where it will add smiles to every mile you drive.

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

Lanny Chambers wrote:

> None of these things are nearly as cost effective as basic forced
> induction. IMHO, a Miata owner's money is better spent on the
> suspension, where it will add smiles to every mile you drive.


That would be great, if there was any easy way to pull it off without a
change in ride height. dangit. i don't like the feel of big swaybars on a
soft-sprung car, so without lowering the car, my only choices a shock
absorbers (unlikely to make a HUGE improvement by themselves), mystery
coil-over-kit that adjusts from stock (seems most adjust from topped-out at
something lower than stock, to extremely low), or get custom-rate springs made.

or just leave it alone

i thought i read somewhere that there's an intake cam that will improve
performance across the range... am i wrong?

wouldn't be the first time.

Timing belt observations:

First change on the 90 Miata (80K miles) - at first glance, upon removing
the timing belt covers, the belt looked like new. Then I noticed all the
"rubber dust" inside the timing belt cavity. Where do you think that stuff
came from?

97 Mazda Protégé (105K miles) - at first glance, upon removing the timing
belt covers, the belt looked like new. Then I noticed all the "rubber dust"
inside the timing belt cavity. Where do you think that stuff came from?
After removing the belt, I inspected the areas where the ribs meet the belt.
Clearly, the substrate material was visible in the "valleys". What this
means is that the only attachment point for each rib was the material at the
base of the rib. I suppose with continued use, the shear force would cause
failure at one rib and then the progression of slipping and shearing would
begin. This would cause stress and failure of adjacent ribs. Maybe this
would cause the belt to break or merely remove a bunch of ribs. In any
event: performance would suffer.

Conclusion: I think 60K is a bit conservative but would not want to go much
past 100K in these cars. Also: my 2000 Audi A4 (1.8T) has a 60K limit as
well. It also has an interference engine so I am less inclined to cheat.



"N93332" > wrote in message
...
> "Mal Osborne" > wrote in message
> ...
> > If you drop a trace of cocaine in the ashtray, and a copy of "Advanced
> > sacred dolphin channeling" in the glovebox, could you fool the car into
> > thinking it was in California?
>
> That's what I did so it would get 100k miles on the timing belt!
>
> ;-)
>
>

KWS wrote:

> Conclusion: I think 60K is a bit conservative but would not want to go much
> past 100K in these cars. Also: my 2000 Audi A4 (1.8T) has a 60K limit as
> well. It also has an interference engine so I am less inclined to cheat.
>
>

I have a bent valve here at my desk from a 16V VW Jetta GLI. It was my
constant reminder to be attentive to the timing belt changes in interference
engines.

Twice I have had timing belt failures while cars I was driving were running.
Both times it was "teeth" or "ribs" sheared off of the belt leaving a
smooth spot where the belt runs over the crank pulley. I haven't ever seen
one actually break.

In article <1126104077.466651@sj-nntpcache-5>, josh >
wrote:

> > IMHO, a Miata owner's money is better spent on the
> > suspension, where it will add smiles to every mile you drive.
>
>
> That would be great, if there was any easy way to pull it off without a
> change in ride height. dangit. i don't like the feel of big swaybars on a
> soft-sprung car, so without lowering the car, my only choices a shock
> absorbers (unlikely to make a HUGE improvement by themselves), mystery
> coil-over-kit that adjusts from stock (seems most adjust from topped-out at
> something lower than stock, to extremely low), or get custom-rate springs
> made.

You don't need to change springs to get major improvements. In fact,
lowering springs are 95% cosmetic, and in the real world their drawbacks
outweigh any handling gains, unless they're very stiff (stiff enough to
remove the swaybars altogether).

I agree, big sways are not appropriate for street use. But I think my
7/8" front, 5/8" rear FM bars are just right. They feel a lot better
with my Konis than they did with worn out OEM shocks (or with the
dreaded HPs). Konis are indeed a "HUGE" improvement. Don't underestimate
the benefits of reliable car control.

My advice was intended to include sticky tires (T1R, Azenis, S03, etc.).
Tie everything together with a precision alignment, and be amazed at the
usable improvement in handling. And it will delight you every day, not
just in drag races.

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html