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mcummo

2000 Rav 4 - 226,000 Mi.

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Hi All;

Original suspension on my Rav 4 and want to re-do it. Would like to get a more comfortable ride as I do not travel off road at all - mostly highway driving. What can I do with parts and/or suspension that could give me a smooth ride but still handle my motorcycle toe.

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Leave it as it is?

Dave

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I'm with Dave, too. Leave as is - the ride should already be good.

If dampers (shock absorbers) are past their best, then by all means replace these. (You can do a simple test by unbolting the lower end of a damper, and pulling it out to its maximum length. You should feel steady resistance when you pull, and similarly when you collapse it - steady 'thick oily' resistance all the way. Any loose spots, or hiccups, then replace the units - and do all four together.)

Also, remember that the tyres are the most critical item in the suspension chain. They absorb all the sudden bumps/ridges/potholes. If tyres are ancient, replace.

Also, avoid over-inflating tyres, even by 1-2 psi. An over-inflated tyre can wreck comfort. Always check pressure when tyre is cold (i.e. first thing in the morning).

If car has tendency to 'wander', or be imprecise on the steering/cornering, check out the rubber suspension-pivot bearings. If back end flails about when the steering wheel is waggled, suspect under-inflated rear tyres.

Buy decent tyres - eg Bridgestone, Michelin or whatever. Avoid all budget stuff.

Chris

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So if I overinflate my tyres by 2psi, Chris, which is 6%, you think there would be a perceptible difference...? I shall desist forthwith and fifth without......

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So if I overinflate my tyres by 2psi, Chris, which is 6%, you think there would be a perceptible difference...? I shall desist forthwith and fifth without......

On my cars, I've always over-inflated slightly (2 psi or so) to allow for leakages, temp changes, etc. On my bikes I tend to go the other way to keep temp up.

This degree of difference is neither here nor there , IMHO and most gauges are not 100% accurate anyway. the big problems occur when the inflation difference gets to 20% or more on a consistent basis. then you risk excessive wear (over-inflated) or carcase failure/tread delamination if consitently under-inflated.

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How you feel about the way a car drives - suspension comfort and handling - is obviously a very subjective area, and not everyone will agree. If most driving is done on good tarmac, free from potholes, then slight over-inflation can produce some improvement in mpg, by reducing rolling resistance. The downside is reduced rubber-to-road contact - something you wouldn't want in the wet.

Vehicle manufacturers frequently specify higher inflation pressures for both full or heavy loads, for laden estate cars, and sometimes for towing. The reduced tyre footprint, in these cases, is essentially cancelled out by the increased weight on the tyre. All vehicle manufacturers advise against both under- and over-inflation.

Personally, I've driven dozens of vehicles (and been a passenger in others) where, on damaged or uneven road surfaces, the ride in the vehicle can only be described as harsh. We've lost count of the number of hire-cars we've been handed, where the car has crashed and bumped its way along the road, only to find - too often - that the tyres have been over-inflated by as much as 1 bar (15psi) ! For Hertz and co to do this is unforgivable. Restoring the correct pressures has transformed the way Fords, Peugeots and Kias have driven.

I can usually tell if tyres are too soft (poor handling) or too hard (crashy suspension), and can detect this down to a couple of psi. Sometimes the tyres have just been inflated/checked at a less than a helpful time of day.

And forget garage forecourt and tyre-dealer pressure gauges - carry your own. A Sykes-Pickavent from Halfords does nicely.

Chris

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Tyre pressures have always interested me. If you were racing round a track, you want to take your pressure reading as 'dynamic' after a few hard laps.

If you check road tyres cold and set 32psi after running around France (where i am now) the air temp is 27 so road temp will be higher, what would the dynamic pressure be?

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Tyre pressures have always interested me. If you were racing round a track, you want to take your pressure reading as 'dynamic' after a few hard laps.

If you check road tyres cold and set 32psi after running around France (where i am now) the air temp is 27 so road temp will be higher, what would the dynamic pressure be?

Is this a quiz?

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I once followed a salesmans advice and dropped the pressure in the new Duellers on my 1st RAV. It cost me 2 new tyres after 18k due to excessive shoulder wear. Not sure how good at detecting a 2psi difference in pressure my central nervous system is but I am quite sure it will produce easily measurable differences in tyre wear and fuel consumption.

Dom

If a 5 ton truck was carrying 10 tons of budgies and they all took off at the same time, what would the truck weigh?

Is static tyre pressure different than dynamic pressure?

Is wine still cheap over there as I will be coming for a RAV load later in the year?

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Comment longue est une piece de string.....? Reponse sur un postcard, DP.....?

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Good tires and balanced tire pressure - all OK.

After 226,000/mi and 13 years, do you think that the rough ride can be contributed to suspension (struts and shocks)?
And if so, any consideration to quality and brand?

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What i meant was...

If racing you'd take your tyre pressure reading after a few hard laps when the tyre was warm. When a tyre warms, air inside warms and pressure increases.

Why then do we take road car pressures cold?

Also....

A general rule of thumb. For every 10 faranheight change in temp, expect a 1psi decrease/increase in tyre pressure. I left the Uk on Thurs. The ambient temp was 59 degrees on Thurs when i set 32psi. Today its 80.6 ambient and my tyres are in direct sunlight. I would say my pressures are going to be 2-3psi higher now than when i set them in the UK.

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Tyre pressures are usually specified "cold" (20degC), simply because it's a reasonably easy standard to apply, and a common-ish temperature for cars to be after an overnight parkup, and (optimistically) when diligent drivers were (once upon a golden time) thought most likely to check out their steeds before a day's "motoring".

You're right about racing. If tyre pressure is critical at a much higher temperature, then that's the temperature at which they should be checked. If you live in the tropics, or arctic wastes, then checking at 20degC doesn't make much sense, so I suppose locals will have another figure to check out.

There are graphs on the net which give a reading of pressure against tyre temperature, but (i) most folk can't be bothered, and (ii) half-way through a journey, how would you measure tyre temperature anyway?

The 20degC figure is good enough for a lot of geographical locations, and takes into account the rising pressure that will take place during a journey. Just don't try to aim for that pressure at a brief motorway stop, otherwise the pressures will look somewhat low the next morning!

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My TPMS system gives me info on each tyre for both Temp and Pressure in real time (well, 15 sec time slices anyway :) ) , and I have seen over the years that the principle of setting tyres pressure to the recommended pressure when the tyre is "cold" is a little flawed, as "cold" is meaningless really, and what is really meant by cold is really "ambient".

And as the ambient temp can vary tremendously, by the time the tyres have warmed upto normal operating temperature - which for the RAV4 tends to mean an internal air temp of around 32 degrees C, the PSI of the tyre could have increased anywhere from 2 PSI upto over 10 PSI compared to the "cold" setting, depending on time of year, if the sun was shining and warming up one side of the car and its tyres, etc.

It also really depends on what kind of driving you do .... If you are driving long distances, then your tyres will be upto temp for most of the journey, if you drive the car 2 miles to the station, then, just like the engine, the tyres will never reaching normal operating temp and the pressure will not increase to any significant degree.

So IMO, the pressure you set should bear all these factors in mind, with the target being for the pressures to be at the recommended level for as much of the driving time as possible - which may mean in the winter having the pressures slightly lower then normal if checking first thing in the morning so they are not going too high after an extended journey, and maybe if a short-distance driver, having the pressures a little higher then recommended as the tyres never really heat up.

I have also noticed that the as the tyres warm up, the pressures and temp of each tyre vary, with the right side being slightly greater then the left, and the fronts being higher then the rears - and that is the same pattern over quite a few years for three different vehicles I've had these TPMS systems on.

Note: these are just my own observations and are not a recommendation for anyone to do anything! I set customers tyre pressure to whatever the book says before handing them back (and tell them to check them themselves anyway).

As far as "up here" goes, and prob all of UK, the chance of having the 'cold' temp of 20c in the morning is most unlikely first thing in the morning at any time of year :D

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Its a subjectof greater intetest than it first appears (for me anyway).

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DominicPriestly - Who would have thought?

I am now looking into the (original) shocks and struts to see if they need replacing. Something has to account for the very rough ride. Seems like every crack and bump in the road is magnified. Tires are good and corectly psi'd.

To be continued.

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I have just replaced 4 shocks on my 59 plate Rav. The ride had become choppy and seriously bumpy. The change in ride quality is huge. Wasnt too bad a job. A 1h30 for the fronts and a 1hr45 for the rears.

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Thanks. I'll keep you posted.

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