12-24-2006, 09:49 AM
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Is the appropriate tire pressure in a Spider just a matter of trial and error? Or, are there some good guidelines or generally accepted tire pressures, given types of driving, type of car and type of tire? For example, is it possible to find a good pressure starting point for driving an S4 with Centerline performance springs and Falken 195/65-14 tires and not-terribly-agressive driving? Or, should I throw a tire gauge and an air pump in the back and head out? Merci. And Merry Christmas, all.
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David
'91 Red Spider
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12-24-2006, 10:58 AM
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Location: Tempe, Arizona-US
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 Quote:
Originally Posted by DavidH
Is the appropriate tire pressure in a Spider just a matter of trial and error? Or, are there some good guidelines or generally accepted tire pressures, given types of driving, type of car and type of tire? For example, is it possible to find a good pressure starting point for driving an S4 with Centerline performance springs and Falken 195/65-14 tires and not-terribly-agressive driving? Or, should I throw a tire gauge and an air pump in the back and head out? Merci. And Merry Christmas, all.
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Just mess around to find what "YOU" like. Others have their specs and they may not suit you nor your set up.
OE specs I think are : 27.0 in the front and 28.4 in the rear. This is set up for stock 15" and suspension and setup for understeer.
You may want to keep the rear higher but go a bit lower in PSI, maybe 24/25-27
But if your more aggressive of a driver you may want to go opposite. But again with performance springs you have to factor the rates in front and rear, sway bars tire width and size, etc...
Ciao and Merry Christmas to all!
Last edited by Alfissimo Int.; 12-24-2006 at 11:04 AM.
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12-24-2006, 11:21 AM
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Location: sacramento,ca
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i think it might be the diff. tyre makers. a 205/50/16 from one brand might take diff. tyre pressures than another brand..
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12-24-2006, 11:36 AM
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Quote:
Originally Posted by Green Dragon
I assume your readings were taken at the track (WS?)
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[COLOR="Navy"]Dionisios di Fiflos
73 GTV - 81 GTV-6 *R.I.P.* - Jetta vr6 - Honda Hawk GT - Yamaha FZ6[/COLOR]
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12-24-2006, 12:29 PM
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In the Spiders' nest...
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Join Date: Jun 2005
Location: Nutley/NJ & Middletown/OH, USA
Posts: 4,861
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Quote:
Posted by DavidH
Is the appropriate tire pressure in a Spider just a matter of trial and error? Or, are there some good guidelines or generally accepted tire pressures, given types of driving, type of car and type of tire? For example, is it possible to find a good pressure starting point for driving an S4 with Centerline performance springs and Falken 195/65-14 tires and not-terribly-agressive driving? Or, should I throw a tire gauge and an air pump in the back and head out? Merci. And Merry Christmas, all.
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Yes, there are guidelines, and engineers did spend a lot of time devising these for our street Spiders. Your Spider should have a recommended tire pressure sticker in the glove box inside door panel. The settings are probably no more than 24 psi. These were recommended for tires that were available 15 years ago, taking into account the type of tires for that period, tread wear, the weight of the car, and safety while driving in a variety of wet and dry conditions. When one drives aggressively, such as in an autocross, tires are pumped up to avoid sidewall flex. If you autocross your Spider you would more than likely be advised to pump your tires to 40 psi, and start adjusting from there. If you don’t pump up your tires, and take a very hard corner, with a bit of a slide, the tire can and will come off the rim! Obviously, you are not asking about this type of driving, but I'm just giving you a point of reference. So why do we like running the cars with higher tire pressure? Simply, because at higher pressures the car rolls a little better (better mpg), corners a little better, and feels a little zippier. At the same time, the shape of a tire is different due to the higher pressure and the middle section wears much quicker than the rest of the tire. The nice advantage that we have today, however is that manufacturers have designed modern tires to be run at higher pressures, giving us the better handling, without sacrificing tread life. That doesn’t mean running at 40 psi, such as at an autocross, but it does mean that 30 psi is quite normal. Also, if you run any tire underinflated, it will wear much quicker, so you don't want to do that to a modern tire. That is why we don't follow the lower pressure recommendations of 15 years ago.
If you run the 195/65-14s around 28 - 30 psi, the car should feel just fine, and you should not have any issues in the rain. The 195/65-14s are just a Plus Zero upgrade (very much within spec) and the Centerlines springs certainly are a very streetable version, as I’m sure you can vouch for, since you have probably noticed that you have a better ride than with the stock springs, yet you didn’t sacrifice any comfort. If it's within your tire manufacturer's spec, you can try the original recommended psi, but you will probably notice that there is no advantage to this and that the car will feel better at 28 - 30 psi. For every day driving, you can also increase the tire pressure on a modern tire considerably above 30 psi, but you may find that it is too much for good handling in the rain.
If you increase the wheel size and go to a lower profile tire, such as bianchi1 has done (in this thread), the same principles apply, although the ride will feel different (stiffer) with lower profile tires. Your 14 inch rims may be fitted with 185/70-14s (original), 195/65-14s (most common today, especially due to better tire selection) or 205/60-14s (more performance oriented), and all are within the correct overall diameter and should give you excellent handling on dry or wet roads. Just note that tires are made for certain car weights, which is why you would never want to fit SUV tires on your much lighter Spider, and the manufacturer's specified psi allows for a wide range, which you can further use to suit your driving style.
Best regards and Happy Holidays!
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Enrique
Spider 74, 84 & 87
164 93L & 95Q
Milano 88 Verde
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12-24-2006, 12:47 PM
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Extraordinary advice, guys. Thanks, Enrique, Dion, Bianchi and Jason.
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David
'91 Red Spider
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04-03-2008, 09:51 PM
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i.am back
i have had my tires set at 29 front and 32 rear for a month now.. workes well. i might try 1 psi more in the front and rear to see how it go's...and keep increasing untill i do not like it...lets see what happans.
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04-03-2008, 11:14 PM
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Location: Thousand Oaks, CA
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Hi there all!
Had 205's on my Spider when bought it. Steering was tough and had to increase pressure. But then I just replaced them by 185's Pirelli P3000 and the tire shop put in a pressure of 32. The car was bouncing and steering was feeling way to easy  Reduced to 27 and got much better , even if steering at low speed is tougher, obviously.  |
04-04-2008, 12:17 AM
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Location: sacramento,ca
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hum... i have no problem at all with steering issuses.. even at slow speeds( my castor is set a 2*)camber at 1.5*( i do not have an adjust. upper contorl arm as yet)i do have to 'ride the ridges' on the local cali. highways thou..she is still nice and 'tossable' at any speed... 
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