Correct tire pressures?

[Henrik]

I am geting ready to drive to Houston for the Open House. What is the correct tire pressures. I have stock tires.

Thanks,

[sean]

For Concours:
Front: 23 psi +- 2 psi
Rear: 30psi +- 2 psi
Spare: 60psi +- 5 psi

[mluder]

Generally it's printed on the wall of the tire.

[Henrik]

Thanks guys. I am about to make the 4 1/2 hr trek to Houston after a 4 year rebuild project. I am hoping I haven't forgotten to tighten anything, but I guess I am about to find out. To be safe, I am bringing every tool and spare I can think of. (No wonder my wife refused to come with me. :)

[sean]

Generally it's printed on the wall of the tire.

Tis true but I'm wondering if Henrik is competing and if he is he needs the above numbers. Last I saw 4 cars were in it this go around.


edit

Henrik beat me to it. Are you competing?

[Rad Dad]

It seems that almost everybody quotes the 23/30 numbers because that is what is in the owners manual. BUT, the owners manual also says that for higher speed highway driving (Interstate speed levels) 25 and even 27 is recommended for the front and 32 + for the rears. On cross country trips (I have made at least 30 trips of over 1000 miles each way) I always go with the 27/34 and have never had extraordinary wear problems and,of course, I get better gas mileage with those numbers.

Have a great trip.

Just my 2¢ after 200,000+ miles in a DeLorean.

[Farrar]

The tire pressures are on a sticker under the lid of my car's glovebox. Does every DeLorean have this or just the early ones?

Also, Henrik: I hope by "stock tires" you don't mean "1981 tires." ;-) Congrats on the restoration!

Farrar

[sean]

The tire pressures are on a sticker under the lid of my car's glovebox. Does every DeLorean have this or just the early ones?


Nope, they all should unless removed. I've seen more than a few that are no longer legible though do to warping/bubbling.

[jmettee]

Generally it's printed on the wall of the tire.

Really, I'm the first to reply "NO, INCORRECT" to this? (Sorry mluder, not attacking, just making things right)

The pressure on the TIRE is the MAX save pressure for that tire.

The pressure is specific to the car for ride comfort & proper traction based on weight. The correct tire pressure is in the owner's manual & also under the glove box door.

Proper pressures are:
23 Front / 30 Rear "normal"
27 Front / 32 Rear "high speed driving"

The print on the tires on my car read max 44 Front & max 35 Rear. Quite a bit different than what's recommended above, eh?

[David T]

The pressure on the wall of the tire is the maximum cold pressure to get the maximum weight carrying capacity that the tire is rated for. Under ordinary "normal" circumstances you should use the pressures recommended by the car manufacturer. On the Delorean they are in the owner's manual, Workshop Manual and the sticker on the underside of the glove box. For sustained high speed driving you can bump up the pressures if the tires are rated for the higher speeds. The higher pressures are mainly for the higher side loads encountered during cornering to keep the tire from rolling off the bead and suddenly losing all pressure. You will get better mileage but the ride will be harder and you will have a smaller contact patch with the road. For long road trips carry an empty container for gas or water, a bottle of water is useful, if you get thirsty or the car needs some. A spare belt is nice along with fuses and jumper wires and the paperwork so you know how to use them. A portable battery pack with a compressor is very handy. Rags, a large plastic bag for the tire and a bungee cord. The best thing is a AAA card and a cell phone and a credit card. You can never carry enough tools and spare parts to cover every contingency.
David Teitelbaum

[Henrik]

Henrik beat me to it. Are you competing?

Heck no, I am not competing. My car is in a a weird in between state with the rear including the motor being immaculate but the interior still in need of some TLC.


the owners manual also says that for higher speed highway driving (Interstate speed levels) 25 and even 27 is recommended for the front and 32 + for the rears.

That's excellent feedback. Thanks!!!


Also, Henrik: I hope by "stock tires" you don't mean "1981 tires." ;-) Congrats on the restoration!

Farrar

Well, I hope they don't back to '81... not sure. They are Yokohama AVS.


....empty container for gas or water, a bottle of water is useful, if you get thirsty or the car needs some. A spare belt is nice along with fuses and jumper wires and the paperwork so you know how to use them. A portable battery pack with a compressor is very handy. Rags, a large plastic bag for the tire and a bungee cord. The best thing is a AAA card and a cell phone and a credit card. You can never carry enough tools and spare parts to cover every contingency.
David Teitelbaum

Yep, I've GOT IT ALL, and then some - thanks. Now I know why my wife isn't coming with me: There is no space left!! :)

[TTait]

Well, I hope they don't back to '81... not sure. They are Yokohama AVS.


You should always know how old your tires are.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11

Its unlikely that you will run the tread down to nothing, so conventional wisdom says you replace the tires every 7 years.

Tom

[David T]

I was at Hershey this past weekend talking to tire vendors. I specifically asked about the 7 year thing. The general consensus is that is it NOT a hard and fast rule. If the tires are not cracked, dry rotted, or worn out you can go longer than 7 years. !0 is probably pushing it but you need to evaluate on an individual basis. If the car is lightly used and garaged so the tires are not exposed to a lot of sunlight you can go longer than if you use the car a lot and park it outside. If you have a 3 digit date code the tires are not for driving on anymore. If you have original NCT's use them just for show.
David Teitelbaum

[BTTF-1]

Excellent Tom

Thanks for your post.

Ed

[Mike C.]

Really, I'm the first to reply "NO, INCORRECT" to this? (Sorry mluder, not attacking, just making things right)

The pressure on the TIRE is the MAX save pressure for that tire.

The pressure is specific to the car for ride comfort & proper traction based on weight. The correct tire pressure is in the owner's manual & also under the glove box door.

Proper pressures are:
23 Front / 30 Rear "normal"
27 Front / 32 Rear "high speed driving"

The print on the tires on my car read max 44 Front & max 35 Rear. Quite a bit different than what's recommended above, eh?

:thumbup2:

[mluder]

Really, I'm the first to reply "NO, INCORRECT" to this? (Sorry mluder, not attacking, just making things right)

The pressure on the TIRE is the MAX save pressure for that tire.

The pressure is specific to the car for ride comfort & proper traction based on weight. The correct tire pressure is in the owner's manual & also under the glove box door.

Proper pressures are:
23 Front / 30 Rear "normal"
27 Front / 32 Rear "high speed driving"

The print on the tires on my car read max 44 Front & max 35 Rear. Quite a bit different than what's recommended above, eh?

No worries, Justin. I appreciate the save. I probably should have answered with a question mark at the end as I was only 75% sure...

Steve

[Jonathan]

And shoot for whatever pressure you're aiming for with COLD tires, i.e. first thing before you go driving around anywhere. If you keep it in the garage (cause the sunlight can heat up the air and raise the pressure too), try your air pressures there before heading out. That's what those numbers assume, that you measure it cold.

Here's the vehicle capacity/tire pressure label:

6006

[Ron]

Ahem...

6007
Page 40, Owners Manual

[jawn101]

Bringing back an old thread from the dead - do these recommended pressures change in the case of smaller rear tires? I am running the 225s in back. Should they still be aired up to the pressures indicated for 235s?

[David T]

That's a very good question. The only good way to find out is to go with the 30 psi and measure the tread wear every 1,000 miles. Measure in several points around the tire and in the middle and both sides of the tread. If you see you are wearing in the middle faster than the outsides you need a little less pressure and if the middle is not wearing as fast as the sides you need a little more pressure.
David Teitelbaum

[jawn101]

Fair enough. 30 it is then :)

[Rich W]

Fair enough. 30 it is then :)

I think you need to look at the Big Picture when making adjustments to the tire pressures, including whether or not you have a stock
or lowered suspension (including stock or lowered springs), stock or +1 or -1 tires (such as using 225/60/15 rear tires) or custom rims,
stock shocks or after-market shocks (and if they are soft or firm shocks), stock or upgraded engine (with extra HP) and trunk weight.

My latest tire pressure experiment has been with a friend's DeLorean, recently upgraded to a "used" Stage II engine before DCS 2012,
automatic, Grady front lowering springs, Marty Maier KYB shocks all around, and brand new 195/60/14 and 225/60/15 just before DCS.
4,000 miles in 4 months (Chicago to FL and back, Chicago to Detriot, MI and back), nearly all highway driving and fully packed bonnet.

Running 26psi in the 195/60/14's up front and 32psi in the 225/60/15's out back. Highway handling has been very good, wet or dry,
and there has been no unusual wear, so far. Fuel mileage has been better than expected, but I do not recall the MPG's, off hand,
but I do know that he has been running Premium gas for the Stage II engine.

Later,
Rich W.

[jawn101]

I think you need to look at the Big Picture when making adjustments to the tire pressures, including whether or not you have a stock
or lowered suspension (including stock or lowered springs), stock or +1 or -1 tires (such as using 225/60/15 rear tires) or custom rims,
stock shocks or after-market shocks (and if they are soft or firm shocks), stock or upgraded engine (with extra HP) and trunk weight.

My latest tire pressure experiment has been with a friend's DeLorean, recently upgraded to a "used" Stage II engine before DCS 2012,
automatic, Grady front lowering springs, Marty Maier KYB shocks all around, and brand new 195/60/14 and 225/60/15 just before DCS.
4,000 miles in 4 months (Chicago to FL and back, Chicago to Detriot, MI and back), nearly all highway driving and fully packed bonnet.

Running 26psi in the 195/60/14's up front and 32psi in the 225/60/15's out back. Highway handling has been very good, wet or dry,
and there has been no unusual wear, so far. Fuel mileage has been better than expected, but I do not recall the MPG's, off hand,
but I do know that he has been running Premium gas for the Stage II engine.

Later,
Rich W.

That's all pretty complicated for someone like me who just wants to go make sure the tires aren't too low... lol.

For what it's worth, my boot is typically empty. Engine is original. Shocks are original. Springs are lowered. Wheels are stock. Tires are the original size up front and 225's in the rear.

[dmc6960]

I've run the "high speed" pressures since I've owned my car.

29 Front, 34 Rear.

12+ years, 100,000+ miles. No abnormal pressure related wear. If anything the outside treads always wear out faster due to my consistently fast cornering.

[Rich W]

I've run the "high speed" pressures since I've owned my car.

29 Front, 34 Rear.

12+ years, 100,000+ miles. No abnormal pressure related wear. If anything the outside treads always wear out faster due to my consistently fast cornering.

Agreed.

I have always run 28 in front (with 195/60/14) and 34 in back (with 235/60/15) with no wear problems.

[David T]

The only way to do this is to measure with some kind of device to remove any subjectivity. You need an accurate tire pressure gauge, an accurate tread measuring tool and it is helpful to also check IR temps but I don't think that will tell you much. You need to repeat the measurements as consistently as you can, ie, at the same temperatures, in the same places, etc. As pointed out, if you have done things to the car to make it non-standard, it affects weight and balance and will change the way you wear the tires. Driving style will also affect the wear, especially the outsides of the front tires. As they say, "Your results may vary". When I weighed my car I was surprised at how easy it is to overload the car if you have 2 large people in it and then fill the trunk, put some stuff on the package shelf and there is still a luggage rack you can pile more stuff on! Depending on how much more you overload the car you may have to add tire pressure just for that! The increased tire pressures for sustained high speed driving are mostly to prevent you from rolling the tire off the bead of the rim due to the increased forces from cornering. For the majority of us we will not wear out the tires before they get too old to use. You will not be all that far off using the recommended pressures. If you do fill to the pressure on the sidewall the ride will be VERY harsh. On one car I saw at a tech event all of the tires had WAY too much pressure. The owner said the doors rattled and the car would go up into the air when it hit a pothole! Once I adjusted the pressures the owner commented the car drove COMPLETELY DIFFERENTLY!!!!!!! Imagine that! Tire pressure can make a LOT of difference! Going low can be a lot more dangerous than going higher. The tire is more susceptible to damage and you could roll the tire off the rim while turning and lose all pressure immediately. Imagine that in a hard turn. Probably a bad idea to go below 23 PSI front and 30 rear.
David Teitelbaum

[dmc6960]

Probably a bad idea to go below 23 PSI front and 30 rear.

I've always been an advocate to running the higher 29/34 pressures. David, you and me have actually bumped heads one of two times in the past advocating which one is better in general. I do believe you have just proved my justification though in running the higher pressures. A tire's pressure will drop over time, not rise*.

Plus going through 2+ sets of tires over 100,000+ miles in 12+ years is a heck of a road test.

*Temperature and atmospheric variation aside.

[Rich W]

I've always been an advocate to running the higher 29/34 pressures. David, you and me have actually bumped heads one of two times in the past advocating which one is better in general. I do believe you have just proved my justification though in running the higher pressures. A tire's pressure will drop over time, not rise*.

Plus going through 2+ sets of tires over 100,000+ miles in 12+ years is a heck of a road test.

*Temperature and atmospheric variation aside.

I agree with Jim again, for a number of reasons, especially the fact that tire technology and rubber compounds have changed significantly
over the past 30 years, and since most aluminum rims will drop pressure seasonally (more in colder climates), its best to run a little higher.

BTW: If someone does want to do some wear measurements, I happen to have the last 3 sets of tires (all still mounted) that have been run
on the same car since 96/97 (I use the old ones to store project cars). Yes, it comes in handy having several sets of spare rims available.
All these tires have been run at slightly higher tire pressures for their entire useful life (and at least minimum tire pressures as storage sets).
The first set (Yokahamas) were used for the first 10 years or so (garaged 90%), the second set for 5 years, the third set since this June.

Later,
Rich W.

[Tillsy]

My preferred style is firm, but not rock hard crash bang.

To that end, after many different combinations, I found my sweet spot today - 25psi front and 31psi rear.

Higher was too harsh and lower was too mushy (again strictly my personal opinion).

[jawn101]

I ended up doing 25/32 because the tires heated up on the way to the gas station to get air. My 12v pump won't plug into the lighter (of course) so I had no choice. I figured I'd add a little extra to account for the heat, then release some pressure the next morning after they cooled off.

[David T]

Tire pressure is a "moving target" so to speak. For every 10 degrees in temp the pressure will change approximately 1 LB. Tires can lose around 1 LB per month just sitting. Most will not notice a change in wear or performance for 1-2 psi. Higher is always better and safer. I recommend using the placarded pressures because you can't get into much trouble with them but they are not optimized for everyone's driving habits. As they say, "Your individual results may vary". At least some of you are watching your tire pressures! I have seen cars running on 50 psi and some on 5!!!!!! Higher pressures will improve gas mileage but can contribute to excessive wear in the middle, a harder ride and a smaller contact patch so handling and traction can be adversely affected. It is a big compromise. Some attributes can be improved by rubber compounds, tread pattern, etc. There is a whole science to this. BTW if you fill the trunk to capacity you probably need more pressure in the front tires. The placard does not have an "economy" pressure and a max load carrying pressure like many cars now have.
David Teitelbaum