littlejim Posted April 2, 2012 Report Share Posted April 2, 2012 I"m hoping to make the 4A handle bit better by playing around with the tyre pressures. The recommendations I've found so far should be shown below (if the attachment process works):* Currently using the "book" pressures but no likum. Think I'll try Stuart's next, but open to suggestions. * Photobucket is giving me the cold shoulder - won't take any more pictures on board. Might have to change my brand of toothpaste. Quote Link to post Share on other sites
graeme Posted April 2, 2012 Report Share Posted April 2, 2012 Hi Littlejim, Marx numbers will be OK on the track, I use the same as Stuart after much trial and error. What I found the most important was the difference between front and rear, between 2 and 4 PSI seems to work well. Once over 30PSI I find the car seems very light and skitty, similar to driving on a slippy surface, although I have used it on the track and it seems OK. I guess the surface of a track is different, probably more abrasive than road surface. Cheers Quote Link to post Share on other sites
John Morrison Posted April 2, 2012 Report Share Posted April 2, 2012 Little jim, Stuart is very close to the mark, 24Fr 28 Rr seems to suit most road applications, personally I would NOT go below 22 Fr, You are getting close to the possibility running the tyre off the rim in decent cornering. You can also up the rears to 30 for a full boot load or sustained high speed motoring. John. Quote Link to post Share on other sites
RogerH Posted April 2, 2012 Report Share Posted April 2, 2012 Hi LittleJim, your table makes interesting reading. They all show (for the 4A) lower pressure at the front. I would have thought it would have been better to have lower at the rear. The front end is heavier than the back 'cos of the engine etc. With the lower tyre pressure this would give a much greater foot print than the rear with the higher pressure. This gives the benefit of the rear breaking away before the front. Silly question time - Would it not be better to have the higher pressure at the front and have apprx equal sized foot prints. Roger Quote Link to post Share on other sites
manray1 Posted April 2, 2012 Report Share Posted April 2, 2012 I have vredestein 165/15x80 classics on my 4a with Fr : 28 psi and Rr : 26 psi Quote Link to post Share on other sites
littlejim Posted April 2, 2012 Author Report Share Posted April 2, 2012 Thanks to all! Wouldn't have thought of some of those variations with my limited imagination. look forward to trying them out over a period of time. Will have to select a decent circuit with a few bends to get your money's worth. Quote Link to post Share on other sites
John Morrison Posted April 2, 2012 Report Share Posted April 2, 2012 No Roger! weight the tyre is carrying is not the only criteria. If you look at any tyre pressure chart from the period of the sixties and seventies you will see almost always lower tyre pressures at the front than the rears. they are set this way to ensure smaller slip angles at the rear, because higher slip angles at the back compared to the front would open the possibility of unpridictable oversteer. This applies to our cars.and not front wheel drive which is a whole diffent ball game, ansd why SWMBO's Peugeot is harder at the front. John. Quote Link to post Share on other sites
Guest ntc Posted April 2, 2012 Report Share Posted April 2, 2012 Unless you are going backward's all the time Roger Quote Link to post Share on other sites
Badfrog Posted April 2, 2012 Report Share Posted April 2, 2012 (edited) If you look at any tyre pressure chart from the period of the sixties and seventies you will see almost always lower tyre pressures at the front than the rears. they are set this way to ensure smaller slip angles at the rear, because higher slip angles at the back compared to the front would open the possibility of unpridictable oversteer. John. John, After many years following this rule, I was told by a vintage racer to be harder (28 psi, 2 kg/cm2) in the front for precise track and cornering and softer in the rear (26psi, 1.8 kg/cm2) for better grip and motricity. I found this to change the car behaviour in a tremendous way. if you drive fast, these are the good figures. If not, use whatever. Roger may have a silly hat but he makes a lot of sense, even forward-wise. Over, Badfrog Edited April 2, 2012 by Badfrog Quote Link to post Share on other sites
Guest ntc Posted April 2, 2012 Report Share Posted April 2, 2012 Yep for track use Jf but not for road Quote Link to post Share on other sites
Badfrog Posted April 2, 2012 Report Share Posted April 2, 2012 Yep for track use Jf but not for road Sure Neil, the problem is I'm constantly confusing both. Another of my senior moments at the wheel. Badfrog PS: It's great to overspeed again .... Quote Link to post Share on other sites
RogerH Posted April 2, 2012 Report Share Posted April 2, 2012 Hi Neil/John, I think I will have to adjust the pressures as racing around London is not on. Roger Quote Link to post Share on other sites
BrianC Posted April 2, 2012 Report Share Posted April 2, 2012 Without proferring any advice, I'd just point out that tyre pressures and front/rear differences are somewhat different for IRS cars than for the earlier live-axle TR2-4 (and non-IRS 4As). Best option is to start from the original recommended pressures and make small adustments at either end until you get the right balance for your own car and driving style. Quote Link to post Share on other sites
Quentin Posted April 2, 2012 Report Share Posted April 2, 2012 I know mine is a 6, but I find the 24 front/26 rear to work really well for me (vredestein T-Trac 165s). It seems much more pointy but in a good way. It gives me more confidence. In fact it seem amazing how a little extra psi here or there makes such a big difference. Q Quote Link to post Share on other sites
dbug Posted April 13, 2012 Report Share Posted April 13, 2012 TR4A - used 28psi front, 26psi rear - over a number of years Quote Link to post Share on other sites
Mark1965TR4aBRG Posted April 13, 2012 Report Share Posted April 13, 2012 dbug - you might like to try the 24fr and 26r as I did recently and have stuck with them as my 4a feels 'better'.. Track day next week and I'll increase the front to 28psi as badfrog suggests. Quote Link to post Share on other sites
dbug Posted April 13, 2012 Report Share Posted April 13, 2012 dbug - you might like to try the 24fr and 26r as I did recently and have stuck with them as my 4a feels 'better'.. Track day next week and I'll increase the front to 28psi as badfrog suggests. I would if it was still on the road mate - currently laid up in my garage Quote Link to post Share on other sites
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