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Triumph TR6 - Tyre pessures

I recently have had 4 pirelli P6000 195/65 R15 tyres fitted to my TR6, the tyres were fitted on to standard wheels ,the tyre supplier said to keep the tyre pressures as standard (22psi front 26psi rear) but I am not so sure any advice apreciated in advance.
simon

Unfortunately you went a bit small (in diameter) on your new tires and will have lots of open space between the tires and the fenders. I am not sure what the standard tire size for the European version (165R15??) of the TR6 but here is North America it was 185 R 15 (which had an odd 78% aspect ratio). In order to keep the same overall diameter you should have gone to 205/70 R 15 or 195/75 R 15.

Anyhow that was an aside, over 'ere in North America the correct pressures are 20 front and 24 rear in psi. This reading from the decal originally mounted on the glove box door. Perhaps go with the North American standard as you are running larger tires.
steven

I run at a higher psi, I'm running low end goodyear that came with the car. 30 psi
tom mcewen

If you are using modern tires then pressures in the range of 20 psi may not be appropriate - remember the tire pressure suggested at the time the Tr6 was produced were for altogether different tires (bias ply with tubes etc) than are used today. Check the sidewall for the correct pressure range. Also see the web sites that deal with suspension tuning or handling improvements which have much info on tire pressure and its effects on handling etc.
M. McLaughlin

M. McLaughlin of Calgary, you are quite wrong in suggesting that the TR6 where produced in a time prior to radials. The radial tire was developed in 1948 by Michelin, it was only here in North America that it took time to catch on with most domestic cars only starting to use radials in the mid 1970's. In europe radials were the rage at least a decade earlier.

The TR6 came with radials right from the start either Michelin X redwall or Goodyear G600 redwall, some were running Michelin XAS (non-symetrical treads)

With too much pressure in the rear b/c of the inhierent negative camber you will find the inside tread will wear down very quickly and having a lower pressure will allow the tire to run more evenly

As a footnote take the pressure of the most tecnological tires of the day, those running on F1 teams and you will find that the pressure is around 18psi or less
steven

I too went with 195-65 r 15 tires, in a now out of production Dunlop D40 M2. I personally like the look of the tire and Panasport wheel combination, and think the 205-70 tires too wide on the sidewall. Oh well, different strokes as they say. As to the tire being smaller in diameter, that is true. The 195's are 1 1/2 inches smaller in diameter which places me 3/4 inch closer to the ground. It helps when I fall out when exiting! As to the error on the speedometer, ha! We don't need no stinking speedometer! I drive on tach speed anyway. 3000-3200 on the highway. (no O.D.)
dennis costello

Steven,
Thanks for the correction. See and how we are on the topic of corrections I would like to state that you are still quite wrong in suggesting that low tire pressures are correct. I still suggest that you should review the many available web sites for suspension, handlng and tire pressure info. I also suggest that tire pressure is not a means of correcting a tired suspension - if your car sags to much fix it and then run the correct tire pressures. Low tire pressure on F1 cars is completely irrelevant to this discussion and for your information race tire design, construction and intended purpose have almost nothing in common with the tires you or I use except that they are tires. Also I like the look of my 195 65 15s too - Dennis said it right -who cares about the speedo - I bet you my TR corners better than yours.
M. McLaughlin

The wider the tyre (eg 205 versus 175 section) the larger the area of its footprint and the lower the pressure needed to support the weight of the car.I find 22 psi about right for 205 section tyres on standard steel rims. The physics is the same for fomula 1 too ( but I bet 4psi is nearer their pressure!). Racers use tyre temperature gauges to measure the heat across the width of the tread following a fast run.
Peter Cobbold

Hi,

I ride my car with Pirelli P600 215-70x15 at 28 lbs front and 32 lbs rear for many years and it performs well. Compare to my old XAS michelin newer generation of tires require higher pressure.
Cheers, JGC
Jean G. Catford

I'm curently running 195/75 R15's and when doing 60m.p.h. rev at approx 3000rpm, am I actualy going 60 mph or slower?
Ted
T. Grant

My decision to run at 22psi was based on hillclimb experiences. At 25/27 F/R I was getting significant understeer into sharp corners. Dropping the pressure to 22 made a marked improvement on the next run. Repeating the changes convinced me that the lower pressure helps adhesion. The change would probably not be noticeable in normal road-driving where behaving like a hooligan is frowned upon. If tyres squeal in corners that is an indication of running pressure too low- and at 22 psi I get no squeal. The speedo does read fast, but as I'm on third speedometer, third diff and second gearbox there are other causes to consider other as well as tyre rolling radius.
Peter Cobbold

Peter

This certainly became a topic with lots of opinions! You mentioned that you find 22psi works best but you never mentioned what size tires you use and the aspect ratio. Also do you run 22psi all way around?

Another trick I heard is to chalk the tires and take a short drive and then see how much of the chalk is worn on the edge of the tread and part of the sidewall. If chalk is still noticeable on the outer edges of the tread = too high a pressure; chalk worn away on the top of the sidewall = too low pressure. Have you heard of this before?

While we are on the subject of tires and wheels, have you done any tricks to the alignment of the wheels. Visually my fronts carry a degree of positive camber and the rears pretty well normal (used to be lots of neg camber until I changed the worn-out bushings in the rear.
steven

Steve,
Tyres are Yokohama A-509 205/60/R15.
I have not heard of the chalk method. I would guess that suspension roll stiffness could influence the results. Or is the test done with straight line driving?- in which case the camber angle would be a factor to consider too.
I have set front wheels to about half degree negative camber. Rears are similar. This helps cornering greatly , but has no adverse effect on wear or straight line stability. The suspension is greatly stiffened with loss of ride comfort, and a distinct susceptibilty to rear end breakaway in bumps in mid-corner. But smooth-track road-holding and braking are much better. Having said that one of the most effective hill climbers here has really soft supension, allowing him to throw the car into a corner so that the roll allows the rear to break way into an oversteer which he controls with opposite lock!
Fred Puhn's book is a gold mine of how-to information. He describes the turning-circle method for setting up tyres and suspension. First find a large area of flat smooth tarmac........
Peter Cobbold

This thread was discussed between 02/06/2001 and 08/06/2001

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