The tire presure I chose was chosen for its looks or sidewall
appearance. It was however chosen for it's stability and handling on a
curvey down hill road near by. When I buoght the tires they were at 28
lbs front and rear. It handled better than it did with the previous
bias ply tires, but they still squeeled and rolled way to much in medium
to hard cornering (2 X Posted speed limit through turn). It had
exsesive roll and had a great deal of under steer. I played with
presures until I found what gave me the correct handling for a car with
the Alpines weight distribution which as I remember was 51/49. At the
presures I mentioned, it gave me very predicatable steering with the
bias easily controlable by throtle position. Drifting through a turn
was a choice and was fun instead of being scary. I haven't had a car
since that I could balance as well.
It wasn't the presure that made these tires bad in the wet.
They wre AWFUL in the wet regardless of presure. That's why they
changed the design a couple of years later. Back then the two
performance tires were the BFG Radial T/A's and the Goodyear GT Radials
with the Kevlar belts. Things have changed just a bit since then
Rich
> ----------
> From: GDWF22A(at)prodigy.com[SMTP:GDWF22A(at)prodigy.com]
> Reply To: GDWF22A(at)prodigy.com
> Sent: Wednesday, September 10, 1997 5:00 PM
> To: alpines(at)autox.team.net
> Subject: Reply to Steve, Rich and Jarrid
>
> Steve; the Alpine does have a nice X member frame as well as rails
> forward
> of the firewall to which the cross member is bolted.
> Jacking points were mentioned to you a day ago and this is all
> correct.
> Also, you can floor jack this car and also position support stands
> under
> any portion of the lower cross member, lower A frames, side frame
> members ,
> rear axle housing and rear springs themselves. This car is light and
> those
> various places can handle the weight without deforming or bending.
> Avoid jacking under the thin wall portion of the rocker panels or
> other
> actual body sheet metal.
> I see NO reason not to trust four properly placed stands or supports.
> use of drive-on ramps is OK and certainly are solid but they encroach
> too
> much around the front car area and hamper certain work areas.
> ------------------
> Rich; you mentioned using BR60x13 tires with 42 and 45 psi front and
> 40
> psi rear. No wonder you slide around a lot !
> These are radial tires and as we know, they look somewhat bulged or
> underinflated when set at recommended psi.
> The idea of the radial (which makes it so much better than a bias ply
> tire)
> is that when a radial is inflated PROPERLY, it will not lift it's
> trear off
> the ground in a hard corner and will instead just keep it's tread hard
> on
> the ground and allow the side wall to flex over to one side.
> A bias ply tire in a hard corner, keeps its sidewall rather straight
> but
> lifts the tread off the road.
> To get a better handle on this, stand up with your shoes a few inches
> apart
> and just lean your body to one side. The shoes remain flat on the
> floor but
> if you had ridgid ankles, you would have tipped up or lifted up the
> outside
> edge of your shoes, like tilting a statue off it's base.
> Now....when you air up a radial way too high, you make it act like a
> bias
> ply tire. It cannot flex and keep it's "footprint" on the ground
> properly.
> Also, whenusing too much air, the front-rear length of foot print is
> shortened a lot . The result of all this is as you alreadu found ! No
> grip
> and lots of skidding.
> By law, tires are marked on the side with their MAXIMUM load carrying
> capacity when aired up to a certain MAXIMUM pressure. This marking is
> misunderstood by far too many people in the tire and garage business.
> The marking represents a max pressure you "could" use if you had to
> carry a
> max weight on that tire.
> A typical text may read: " Max allowable weight 1020 lbs (at) 35 psi
> inflation". This sidewall pressure marking is NOT the pressure you
> would
> normally inflate the tire to for road use!!!
> By law, cars sold here after approx 1972 (?) must display a sticker
> telling
> the tire pressures (cold temps.) for normal driving and normal loads.
> If
> the mfr. wants some increase in pressure for heavy loads or high speed
> driving, this must also be on the sticker !
> Your BR60x13 certainly won't have normal footprint size nor flexible
> side
> wall action at the pressures you have used.
> I am rusty on this subject but will guess you need around 24 psi front
> and
> 22 psi rear (cold setting) to obtain proper "radial tire grip".
> Perhaps
> some reader with current data or tire industry technical book can
> reply
> here and supply the actual correct data if I am off a bit.
> Also be aware....different brand tires as well as different
> construction
> variations makes for different psi requirements (2 ply, vs. 4 ply ,
> steel
> vs nylon or rayon cord belts etc. etc.).
> ----------------------
> Jarrid; your interesting comments re. lifters require me to offer the
> following comments .
> When you state that regrinding the lifter base to obtain the "concave"
> affect, this is not correct. Due to being positoned off-center from
> the
> cam lobe, the lifter is expected to be rotated by the cam lobe. This
> results in the lifter receiving equal wear all around it's base but
> also
> gives the lifter a "concave" wear pattern which we would NOT want to
> intentionally put back onto the lifter.
> The cam lobe is ground dead flat (not rounded in any way) and we need
> a
> dead flat lifter to carry the extreme pressures present all the way
> across
> the cam lobe evenly. After long use, the lifter and lobe will of
> course
> have worn into a slightly curved shape but they MUST start out flat
> when
> new .
> I found it also interesting that you "never saw Alpine lifters without
> pits". Well of course we all have seen pits but I would say that most
> lifters I have seen were without pits and could be refaced and made
> serviceable again. Hmmm...wonder where all the badly pitted Alpine
> lifters
> have gone to?
> Now for the last point you raised (and it is one I failed to comment
> upon).
> This matter of the internal cup shape base in the lifter and the
> bottom of
> the push rod which rides in it.
> The radius machined on the push rod bottom is NOT designed to match
> the cup
> radius in the lifter. This intentional difference is done to create an
> "interference angle" which in turn gives "line contact" between the
> parts.
> In my opinion, the burr or ridge you may have seen in a few cases on
> the
> push rod is of no importance and does not result in any change in
> valve gap
> after the engine has miles on it.
> Due to where this exists it would not be seen by the eye but by the
> use of
> some machinists "blueing" called Prussian Blue paste, we can apply the
> blue
> to degreased parts, assemble them and note the area of contact.
> When I have been concerned over a slight little ridge worn on the rod
> base
> I did check out a few rods by this method and found the ridge was not
> making contact at all and that only a nice polished spherical ball
> area on
> the push rod base was in contact with the lifter . Result... no wear
> expected nor found later and no early readjustment of valve gap
> required.
>
> Re. the cost of case hardening lifter base if major regrind was done
> and
> too much metal had to be removed....The lifter is cast iron, not steel
> and
> all that needs to be done is to buy some gunsmiths hardening powder
> and the
> one I use is called Casinet from Brownells catalog.
> The lifter base is simply heated to a red glow with a torch and the
> powder
> applied . It provides a high carbon case hardening of unknown depth
> but
> then we don't need more than a few thou. So I feel this is so cheap
> that
> anyone could afford a couple bucks for the powder and this makes
> rehardening lifter bases not as costly, as you suggested.
> Dick T.
>
> As we both know....there can be exceptions to just about everything
> which
> we write about or try to share with others. There is rarely a clear
> black/white condition. Our various opinions are the results of our
> own
> experiences, tests, investigations, and mistakes. Readers don't have
> to
> accept anything we say but are at least benefited by having seen the
> comments and they in turn are then alerted to conditions they may not
> have
> even considered. They can then check out their own cars to see if what
> they
> have read here applies to their own situation.
>
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