Suitable tyres for a P4, 95

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Suitable tyres for a P4, 95

Postby Robert Tucker » Wed Apr 06, 2011 10:20 pm

First and foremost, any P4 will require a 3.5 ratio differential from an early Range Rover, a Mk3 3 litre or a P5b. This will equip it with a reasonable compromise between ability to move away up a hill and cruise silently at 110 kms/hr. The nicest compromise in tyres is 175/15 Michelin MX, (made for an early 1970s VW of some sort) The best I have ever had, by a long margin, was the 185/15 Michelin XVS (made for Citreon DS23) and the nicest looking was a Michelin XMUR 205/15 (made for the American market)
The 3.5 diff. makes both freewheel and overdrive un-necessary and an added advantage is sure-footed reversing as both freewheel and overdrive develop problems in these departments with the onset of age. One more nicety is to add an MG B non return valve into the suction line between the inlet manifold nipple and the vacuum reservoir to make sure that suction is not lost. Happy Rovering, Robert.
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Re: Suitable tyres for a P4, 95

Postby deckell » Fri Jan 31, 2014 3:56 am

Robert would this information regarding the diff be also applicable to a p3 75. is this just a diff center replacement.regards Derrick.Smith
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Re: Suitable tyres for a P4, 95

Postby jefflee » Fri Jan 31, 2014 9:21 am

Hi deckell,
Just pull out the half shafts and swop the diff I've done this with P2s using various ratio upgrades,
This is well worth doing more economy less revs much longer legged for modem motoring.
All rover diffs. seam interchangeable after the war from 1946 to early land/range rover.
Rover Car diffs are ok they must be 10 spline, but some 4x4 diffs need to be drilled and tapped
for plug as there is no filler/oil level in the diff. (this is in the axle).
There is a great range of ratios your 75 should be ok with 3.54 I have several 3.54 diffs
but I am looking for a 3.9 as 3.54 is too much for my 16hp,
Diff gaskets cheep are from land rover garage or eBay.
hope this helps.
cheers Jeff.
1937-20 SS _ 1938-20 SS _ 1946-16 SS _ 1947-16 saloon
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Re: Suitable tyres for a P4, 95

Postby deckell » Fri Jan 31, 2014 12:21 pm

Thank you jefflee for your guidance and words of wisdom, all i have to do is find a diff. thanks again regards Derrick.Smith
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Re: Suitable tyres for a P4, 95

Postby djm16 » Sun Feb 12, 2017 2:46 am

Am I the only dissenting voice?

205 is way wider than the original 6" tyres. IMHO they look vulgar on a P4 or other classic in the way that the wide-boy low profiles on a BMW X5 look vulgar.

Second, if at cruising speeds on a standard diff your engine is sounding strained, then it is worth checking
1) the timing (static and / or idle timing is not an accurate way to method of setting full advance) which may include a complete distributor
rebuild +- electronic triggering (ie Pertronix).
2) the mixture
3) the balance - in particular the clutch if it has been renewed, and the harmonic balancer - the rubbers are usually hardened and contributing nothing.
4) play in the prop shaft.
5) persistent use of oil with low ZDDP will lead to a noisy engine too.

If there is a problem with any of the above, then labouring the engine instead by over-gearing is not going to improve things even though it might be easier on the ear.

The IOE 6 should be smooth and sweet and capable of sustained 4,000 rpm.

COI, 1955 90, standard diff, freewheel, fine at highway speeds and more economical (much more) than a 110 with overdrive and high ratio diff that I had for a year. It is at least as fast too.
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