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MG MGB GT V8 Factory Originals Technical - Tyre Pressures
|I'm currently using 32psi all round but lately I'm thinking this is a tad too high. The car jumps around quite a lot on rough roads. My tyres are 195/65-14. I notice the maint. manual for the MGB V8 recommends 26psi for the front & 32 for the rear. Anyone have any other thoughts on the subject ? Barrie E|
|32 seems high for the rear. You might get over steer. I've got it at about 22 rear and 28 front. Mind you I've got these awful (-ly cheap) tyres made in Eastern Europe somewhere. OK in dry conditions but in the wet so slippery that I'm going to replace them even though they are barely worn.|
|There always has to be a compromise between comfort, grip and tyre life. (195 x 15 x 60)|
I prefer 32 all around because it gives good grip and tyre life. However I am weakening a tad and lately have lowered the pressure 3 or 4 lbs.
|I'm no tire engineer but my experience says that with modern, belted radials the higher the pressure the better the grip. Some of the lower profile tires require pressures upward of 44psi to meet the load rating of the tire. The "correct" pressure would be a combination of the cars handling characteristics, % of required load rating and how you want the vehicle to feel as well as handle. My personal preference is to run 40psi front and rear. I sacrifice ride comfort a bit but the grip is exceptionally good. Since I'm not at the limit very often, I haven't biased my tire pressures to account for possible terminal oversteer.|
|As noted it's a compromise or balance, and can be shifted to meet your preferences. What you do greatly depends on tire size and contact area. The larger the contact patch the less pressure needed. This means that with a larger tire, pressure can go down and maintain roadholding but increase cushion. I run 265/50-14's all around at 22psi and they work extremely well. They do not fit under stock bodywork however.|
| Don't forget that the lower the pressure is in a tire the more it will flex. The more it flexes the more it heats up. The loss of power caused by the increased rolling resistance is turned into heat through internal friction of the tire. This is why Ford Exploders were killing people.(Fords fault not Firestones) An underinflated tire on a long high speed run can exceed the ability of the tire to dissapate heat. When they overheat they go bang. Never underinflate a tire on a long high speed trip it may give a better ride but it will lower your fuel milage and possibly cause the unneeded danger of tire failure. The speed rating of a tire is compromised by under inflation. Under inflated tires also tend to wear faster. A larger tire can safly be run with less pressure like Jim said. |
Safty Fast means more air not less.
|R J Brown|
The RV8 is 22F 24R
Basically same as std B, not surprising as basically same weight.
For high speed add 6 psi so 28F 30R is a useful all round setting.
The higher the tyre pressure the lower the slip angle. Adjusting the front rear split alters the handling balance. In general grip depends on compound being used in correct heat range.
|Thanks for the comments.I'll try Paul's suggestion of 28/30 for starters. Barrie E|
|I am on 195/55s V rating (now its 'winter) and find 25 -30 gives a positive 'feel' at speed - more and the car wanders - very little play on the kingpins (in case you are wondering) - on OE V8 wheels and 185/70 Dunlops it runs well at 24 -34|
This thread was discussed between 26/10/2005 and 27/10/2005
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