Hi ,

doubts about tires' pressure

bought these goodyear eagle GT+4 255/60/15 . OK , there's better stuff on the market, but the availability of tires with white letters here is quite difficult ( and price was fair for my tires)

can't find any spec about correct pressure ( nothing written on the tire itself and nothing on the Goodyear website). So I'm referring to my car's specs on the door. But I suppose that I'm making mistakes with the pressure choice.
Help please

Aldo

local://upfiles/6949/3AA7BE8DFC8F461F8486868DE516516E.jpg

local://upfiles/6949/CAF5521F0498445DAAED74B1AC5BDE0A.jpg

32 or 34 psi is pretty much a standard pressure. :)

Aldo,
I usually keep my tires at 35 psiwhich is the max pressureon most of our size tires and is also listed on the placard on our driver side door.
When I had the Firehawks on my 'Vette, I would run 30 to 32 psi in them, unless Iwas going for a long trip on the highway, as those tires rode very hard, something I supposeshould be expectedfromsome performance tires. The lower pressure didn't cause any premature or abnormal wear, butI gotjust alittle smoother ride. With the "Good Year Integritys" I have now, a middle of the road touring tire that performs just fine for the kind of driving I do, my 'Vette ridesVERY smooth running them at 35 psi.and creates no new rattles in the process.
In the GM manual for my '81 'Vette, they mention that for driving at 75 to 85 mph you should increase the tire pressure by 4 psi if that 4 psi doesn't cause you to over-inflate the tire,max being35 psi..So it sounds like 31 psi. is OK according to the manual.
Personally, I like to beable to run my tires at max pressure as they're ready tobe pushed to the limitand at which time I'll getthe most out of them.Especially with the 'Vette, why not? If you have tires that ride alittle hard, I don't feel that it's bad to run them alittle soft as long as it's not to the point where you'll getabnormal or premature wear, which from underinflation would be excessive wear at the outer edges of the tire. (Over inflation would cause excessive wear in the center of the tire. Although for you "foot-stompin' 'Vette owners, the excessive wear in the center ofyour tires, only on the rear,is fromopening the secondaries every time you take off from a dead stop. LOL)
I called"Shine Brothers"today which isa local Good Year dealerwho does good front end work. I've gotten afew alignments there and (I watched the guy and the car drove perfectly afterward) they did a good job. The guy told me that 31 or 32 psi. wouldn't hurt that Eagle plus4 you have, Aldo,and that 35 was the appropriate max psi. for it.
One thing that is very important is to make darn sure that you have a good quality gauge andthat it's"ACCURATE." I have afew gauges and even acouple of the good ones vary a pound ortwo in either direction. A friend of mine who used to have a Matco Tool business checksmy torque wrench andmy besttire gauge for me every now and then and I keep them both in a padded metal box. I've seen tire gauges that are four to six pounds off right off the shelf. The kind at the check out counter in a big bucket at your local ie;Auto Zone are like "pot luck." You can get a good one or one that's way off.
I've also been told by more than one reputable tire person that using that tire shineor tire dressing will dry your tires out prematurely. Supposedly, it's notharmful if you use it in moderation, like anything else.
As I said in another post, I also found the selection oflettered tires for our 'Vettes isgoing away due to all the bigger rims and low profile tires that are made now days. If we want to stay with our stocksize rims, we'll just have to settle for what's available.
I hope I helped you alittle, Aldo. I know that you and DeeVee will be takingyour new treads to the limit. Just becareful andkeep you 'Vettes "rece-worthy" in the process.

***If anyone knows anything else about the tire pressures for that Good Year plus4 oranything that conflicts with what I was told by the local Good Year dealer here, please post it so we all"get it right."

DeeVee, Nice jobon the rims. I like the black as it blends in with the car and with the exception of the white letters on the tires,the car has a really cool plain look, which I like in a car.

Hi Texas Jim,

thanks so much. Now I'm running my tires less inflated than what you say. I will readjust the pressure. My pressure gauge is quite precise ( checked with a pro one).
Same pressure for front and rear tires? Or more on rear, like GM says?

I like the more comfort of " softer tires" ( I'm going also to replace the old oil shocks with gas Bilsteins which will make my ride "harder") but I want safety and performance when I decide to ride "strong". So I think I will set the pressure at an intermediate point : let's say 33-34 psi. What do you think?

I'm restoring my Corvette and my first thought is "safety" : I want to be sure that my car will remain stable in the turns and when riding a bit faster ( not very fast at all . I have dicovered that I have a 3.55:1 rear end gear ratio). So I'm going to replace :
-Front coil springs
-swaybar links and bushings
-rear spring links
-4 shocks ( all bilstein)
-power steering control valve ( I have a play on the steering wheel in the central position and it's "quite light" , not tight as I would like: I don't feel safe...)

my brakes seems really OK , instead. No leakage at calipers, pads seems OK. Brakes are strong and balanced.

referring to the old spark plugs matter...
Got a set of NGK UR4 and going to fit them on my engine ( replacing a set of 20 years old AC delco with lot of rust).
I want to file back the neg contact , but how? which tool do I need? It's not easy with a file ( I risk to "file" the pos contact too).
I was thinkingthat could be easierto move back the neg contact with tweezers , readjusting the gap to specs. please tell me about

thanks
Aldo

I gently pry the neg electrode upward, say about 1/8". ( I use my pocket knife blade to do that. I have a tool for that, but since I don't use it very often, I can't always find it. :D) Now using a small flat file, round the end of the contact.

ORIGINAL: aldous
-power steering control valve ( I have a play on the steering wheel in the central position and it's "quite light" , not tight as I would like: I don't feel safe...)


Sounds more like your steering gear box is loose and needs to be adjusted per the service manual. The control valve just controls which direction the assist goes.

Hi 73Shark,

I have already checked the steering box and it seems that there's no play there ( but i'm possibly wrong). Anyway the control valve is leaking a lot of oil ( look at pic) so I'll replace it first, then I'll see what happens



local://upfiles/6949/6AD4A561402440C799A401C5AD079D69.jpg

Aldo,
Jack the car up, with both front wheels off the ground, and push and pull on the tires, left and right, top and bottom. Your play may be in the tie rod ends.
Per Spark Plugs: Cover the positive electrode with a small piece of sheet metal then use a file to file the negative electrode back to where it is half way across thepositive electrode.The filed edge of the negative electrode cuts the circle of the positive electrode in half. Where I used to use a file, I now use a Dremel tool as it can cut the negative electrode back quickly, clean the burr from the cut edge and there's no need to use the piece of sheet metal to protect the positive electrode. After cutting the negative electrode back, check the gap and install them.
Back and front tires should be at the same psi.. And yes, Aldo, you should run youir tires at the max pressure, 35 psi.. With the roads being the way they are in your part of the world, your tires should be at max psi.
You're right. With a file, it's not the easiest job to cut the negative electrodes back. I did the job with a file for many years, but now I use a Dremel, as it's quicker and easier. Do not try to "move" the negative electrode.
If you're not sure how to cut these electrodes back, just send me your address and I'll buy some, file them back and send them to you, ready to go. Just let me know.

ThanksTexas Jim,

I have completed the spark plugs' job right now... look at pics : before and after. I have filed the neg electrode not exhactly to the mid of pos one , but enough in my opinion to have good performances. I can't wait to have the new sparks fitted on my Corvette . those I'm running now are more than old.
tomorrow morning I expect to replace spark plugs , check the compression ratio on at least 1-2 cylinders, go to my tires shop and set tires to proper pressure ( needless to say : my pressure gauge is not correct...)Ok , max pressure front and rear. I don't understand why GM says on my door's label less pressure on front tires in respect to rear...

power steering : I already lift the car at my mech to check everything underside. I checked also my rear end gear ratio by turning by hands the shaft and checking how many turns for 1 wheel turn. 3.55:1
My mech has checked the power steering and tie rod ends are OK. I have probably to check better the steering box , but it seems to me that no play is there. Instead I hear a strange vacuum noise from the control valvewhen I turn the steering wheel in the position where it has play ( with engine OFF). If I turn more the steering wheel , in the no play position , no noise anymore.



local://upfiles/6949/31CF7B17607A41E893EA5726C8E0C288.jpg

local://upfiles/6949/56B93AE5449A42D396496A71CA15E794.jpg

Plug looks good, Aldo. You're right, they don't have to be perfect. The old guy who taught me that said that being pretty close was all it took. I would try to take the little burr off if possible.
With the power steering, when you turn the steering wheelas far as you can in one direction, it does make a hissing noise. If this is the noise that you're explaining.

Hey, on my '81 I have a little play when the steering wheel is in the central position, like you gotta crank it maybe a 1/4" in either direction before the car moves that way. I check the rag joint, and all the tie rods, drag link, idler arm, ball joints, they are all nice and tight. Any help on where I can get a service manual to check the gear box?

Hi Texas Jim,

yesterday my mechanic put in place the new spark plugs. The old sparks were OK , the problem was : 2-3 were slightly loose ( those that are more difficult to reach ). Infact I supposed that something was wrong with sparks.

Oh my god , what a difference with new sparks! Above all at low-mid rpm. now my engine runs so smooth...It desn't smoke anymore and I'm sure that the gas consumption will be improved ( good). less noise too. Instead I don't see a great difference at high RPM : but I must probably go for a larger air cleaner ( now mine is 10"), to have more air flow when the carb demands .

before replacing the last spark plug , my mech measured the compression ratio. He had some difficulties in keeping firmly the meter in the spark's hole ( due to high pressure) so we supposed that the actual compression ratio is slightly more than the value measured : we have measured 9:1 . But we think it should be about 9,2:1 . Does this value tell something to you about my engine HP?

power steering . I hear a hissing noise in the play position ( with engine OFF) coming from the control valve. No noise if I go over the play position.
I have checked the gear box watching it through the engine bay( from above): I see the shafts and levers moving without any play there

Set all the 4 tires at high pressure too

thanks
Aldo

Curious as to how you can measure compression ratio with a gauge?

ORIGINAL: 73shark

Curious as to how you can measure compression ratio with a gauge?


Me too....:eek:
The compression ratio is the TDC cylinder volume vs the BDC cylinder volume. I can't see how a gauge is goin' to measure that. [&:]
The gauge only measures the psi per cylinder, whichgives no indication of the cylinder volume.:)If your mech knows something I don't, please fillme in on his method. ;)

Plus if he's really just measuring compression, then he should have all of the plugs out and carb at WOT.

73 shark,
yes you are right. Also my mech told me that to make a correct measure we should remove all the spark plugs...but no time for this now.
So we have made the measure on 1 cylinder only , with all the spark plugs in place, distributor off , carb at full power ( open ).Running the engine with starter only for about 10 sec until we got the measure
I think that at the end the measure has been substantially correct...

The gauge used is a quite usual tool here ( it seems to me), but can't tell you more... If I go to the shop soon , I'll take a pic of this gauge

Aldo

That would be nice to see a picture. Can always use a new tool/gauge. :)

One method I heard of for measuring the ratio and CID,..... is to fill the cyl with liquid at BDC, turn the engine over by hand to TDC, and measure the differance in the volume of fluid removed to the volume of fluid used to fill the cyl at BDC. This method is generally done with the engine out of the car and on a stand. It can be done while the engine is still in the car though. I've never used this method, but they used to do it at the race track to verify CID, when there was dispute over an engine's displacement. Some classes limited the CID.( it was done on the compression stroke so that the valves were closed ) This was done with a hose and fitting that would screw into the spark plug hole.

Yes, yes, I know....there is a point where there is a lap over of a valve still remaining patially open during the comp stroke. Especially in a soupedup engine. I don't fully understand how they would get an accurate measurement since it seems to me that there would be a fluid loss out the open valve, but that's what they did at the track. Maybe they would measure the fluid remaining in the cyl by sucking it out and measuring it's volume. :eek:

That sounds possible but pretty sloppy and fraught with error. You could eliminate the valve overlap problem by backing off the rockers on that cylinder.

I know when youare checking CRout of the car, you need a piece of plexiglass to put over the combustion chamber and sealed with grease and then fill it with a measured amount of liquid to get the cc volume and do the same thing with the piston @ TDC. You also need to know the pop-up volume and valve reliefs. You can calculate the swept volume from stroke and bore dia. Lot of math. [:'(]

Well, like I said, I heard of them doin' that, but never saw it done.
The only thing I've ever done is to mic the cyliders before installing the heads. Bore X stroke.

[sm=icon_cheers.gif]ORIGINAL: aldous

Hi ,

doubts about tires' pressure

bought these goodyear eagle GT+4 255/60/15 . OK , there's better stuff on the market, but the availability of tires with white letters here is quite difficult ( and price was fair for my tires)

can't find any spec about correct pressure ( nothing written on the tire itself and nothing on the Goodyear website). So I'm referring to my car's specs on the door. But I suppose that I'm making mistakes with the pressure choice.
Help please

Aldo

local://upfiles/6949/3AA7BE8DFC8F461F8486868DE516516E.jpg

local://upfiles/6949/CAF5521F0498445DAAED74B1AC5BDE0A.jpg




44 PSI






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225/55VR16
Load Index 94 = 1477lbs (670kg) per tire
Speed Rating “V” = 149mph (240kph) 94V (http://www.tirerack.com/tires/Spec.jsp?make=Goodyear&model=Eagle+GT%2B4&tirePage LocQty=#) SL
Treadwear: 240
Traction: A
Temperature: A240 A A (http://www.tirerack.com/tires/Spec.jsp?make=Goodyear&model=Eagle+GT%2B4&tirePage LocQty=#)

1477 lbs.

44 psi

11/32"

24 lbs.
6-9"

7"

9.2"

8.2"

25.8"

807





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ORIGINAL: aldous

Hi Texas Jim,

yesterday my mechanic put in place the new spark plugs. The old sparks were OK , the problem was : 2-3 were slightly loose ( those that are more difficult to reach ). Infact I supposed that something was wrong with sparks.

Oh my god , what a difference with new sparks! Above all at low-mid rpm. now my engine runs so smooth...It desn't smoke anymore and I'm sure that the gas consumption will be improved ( good). less noise too. Instead I don't see a great difference at high RPM : but I must probably go for a larger air cleaner ( now mine is 10"), to have more air flow when the carb demands .

before replacing the last spark plug , my mech measured the compression ratio. He had some difficulties in keeping firmly the meter in the spark's hole ( due to high pressure) so we supposed that the actual compression ratio is slightly more than the value measured : we have measured 9:1 . But we think it should be about 9,2:1 . Does this value tell something to you about my engine HP?

power steering . I hear a hissing noise in the play position ( with engine OFF) coming from the control valve. No noise if I go over the play position.
I have checked the gear box watching it through the engine bay( from above): I see the shafts and levers moving without any play there

Set all the 4 tires at high pressure too

thanks
Aldo



383 Crate motor - origin unknown - I think it is safe to assume a 9.5:1 compression ratio, that's pretty standard for a crate 383 that runs on pump gas.

[sm=icon_cheers.gif]

44 psi is the max pressure rating for the tire.

So, DV8. Ya got any tire info? :D
Great post. :)

All I did was cut and paste....

Glad to help!

[sm=icon_cheers.gif]

DeeVee,
Is the Max pressure for the GTplus4 44psi for the 225/55VR16 only or for all GTplus4s reguardless of the size?
If it's 44psi for the 60/15, I'll be calling Shine Bros. and blowing out the guy who gave me the "wack" info.
I went to "Tire Rack" which I'm familiar with but only see the 225/55VR16, like you posted. When I clicked on "specs" I got only the one size. Aldo's tire is a 255/60/15.

My Goodyear GT II's were 44 PSI as are my Firestone Firehawk Indy 500's - both are 255/60/15's. I agree withTexas Jim'scomment on that being the only size posted on Tire Rack, so I did make an "assumption" based on that information as well as my experience with my own tires.

Now I fully expect that you guys will give me the Benny Hill version of what an assumption is.....

[sm=icon_cheers.gif]

DeeVee,
Where did you get the info for 44psi for the 15s? Or is the 44psi the assumption you made? I'm not doubting your info, just wanted to know where you got it. Like I had said in another post, I had Firehawks before the Good Years I have now and they were 35psi.

Nah, that's too easy. ;) Didn't know that it originated w/ Benny Hill tho. Learn something new everyday. :)

BTW, my old original Eagle GTs (early 80s)state 35 psi max on the sidewall.

Can you clear this up for me?
I have 235-70-15 on the front and
255-60-15 on the rear and I have 26 psi cold in all, do I need more than that? PG.

Depends on several things. Even tire wear, comfort, lower friction, handling. My door sticker says 20 psi for the original GR70-15s. I ran about 28-30 in them and got even wear and decent mpg. For autoX, I ran low 40s to keep the tread on the ground.

I usually run about 32-34 psi. what i find funny isthe door sticker says to run 20/26 for fuel economy.

Hi Phill,
my sticker says 30 psi frontand 35 psi rearfor fuel economy. you have a 79 Corvette. what does your door sticker says?
after all the infos on this topic, I'm running my tires at 34-35psi. 44 psi as DV8 says seems so high to me ...
I have seen anywaythat there'snothing sure about our Corvette tires' pressure... so please everybody continue on this topic , so we can reach "akindtruth" about.
To have the proper pressure is a matter of safety too

I'll have to check tonight, but it should be the same. i was noting the optional pressure on your sticker 20/26 seems low by todays standards.

After reading all the replies under this topic, and all the different tire pressures on door stickers, I'm wondering why all the different answers. Would the different pressures on the doors have anything to do with where the vehicle is being shipped to, geographical location? That doesn't make perfect sense to me either seeing where everyone is from and considering the psi they've posted. And Aldo w/ two different pressuresfor the front and back, WTF?
I run a tire at max psi as I buy the tire for whatthe tire isabout. I want it to do what it's supposed to if I decide to beat on it, so I want the pressure to be up. I've run race compound tires at a low psi in the past for better "off the line" traction knowing that it's not great for the side walls. I like a hard tire, psi-wise, as theyfeel better all around. I don't like over-inflating a tire as it's hard on the belts and I don't want to slip a belt long before the tire is worn out, even if it didn't prematurely wear the tire in the center. Those Firehawks rode hard and I did run them alittle soft, but not less than 30psi.
If running a tire very soft or very hard didn't kill the tire prematurely, then I see no reason why a person shouldn't do what they want.
Still don't know what the reason for so many different door sticker pressures.

How about we make a post to list; 1. the year of your 'Vette 2. the door sticker tire psi recommendation 3. the original shipping destination of your 'Vette.

Maybe we can figure outwhat the differences in psi info on the door has todo with; local, year, ora combination of both, or something else entirely different. ***Unless someone has this thing figured out or no one gives a crap. LOL I, for one, would like to know.