My Civics normal pressures are 35F 33R
fully loaded it is 38F 33R
Towing its 35F 38R
Was going down to Bishops Stortford for a family wedding, fully loaded with 5 people and cases. The above pressures dont make logical sense to me, queried with Honda and they confirmed they were correct.
Explained that I thought it was maybe a typo and could they check with technical dept and they did and came back and said they are correct.
So why, when I fully load the car, should more pressure be put in the front and backs left unchanged?
And why, when you have a trailer on the towball, you put more pressure on the rear?
Surely 3 passengers in rear and boot full would put more weight on back of car than a trailer or caravan with an axle to take the weight?
Any logical explanations ?
|
I would guess its all about the load under braking.
A car when braked will put an increased load on the front tyres. A fully laden car will increase that load.
However when you brake with a trailer or caravan the weight of that trailer or 'van is transferred downward in part to the rear wheels of the car.
|
The trailer part is easy, you need 4%-7% of the trailer weight on the hitch, subject to the maximum for the car/towbar - probably on a scale of 50Kg for the Civic. In addition, the rear of the car being slightly stiffer in the lateral and vertical planes increases stability.
The increase in front pressures with no increase at the rear for increased loading is unusual as well as counter intuitive.
|
>>
>> The increase in front pressures with no increase at the rear for increased loading is
>> unusual as well as counter intuitive.
>>
Any car manual I have seen recommends increasing the rear pressures when loaded.
So it must be something peculiar to the design of this particular model.
|
|
The Civic has very little rear overhang, which may make a difference. Conversely, my LEC has a long overhang and the rear pressure rises from 33 to 44 for a full load.
|
|
Blimes. I'll have to check that properly when I load up for France. That's a big difference.
|
|
I run mine permanently at 34F / 40R. Too much faff to keep changing them as the car is some days full to the roof and others it isn't. I've found the handling and tyre wear are absolutely fine with that set up in all circumstances. Get about 50k miles out of a set.
|
|
That may account for the fact the Defender 90 I owned didn't change from 36 at the rear, towing or not, but the 110 I owned was I think, 48 towing.
|
>> The increase in front pressures with no increase at the rear for increased loading is
>> unusual as well as counter intuitive.
>>
There was a thread over at t'other place a few weeks ago on similar lines. My Honda CR-V is also unchanged rear pressures when fully loaded (35psi F, 33psi R), but the rear goes up to, I think, 36 with a trailer. It seems, from the discussion there, that it's not uncommon on SUV-type vehicles in particular for the rear pressures to be the same when loaded. My Saab, on low profile tyres, needed increased pressure when fully loaded. The Honda has 225/65 17" tyres, the Saab had 225/45 17".
I've driven long distances on the autobahns without increasing the pressures and it's never thrown up any problems, such as directional instability.
Last edited by: Mike H on Wed 22 Jun 16 at 14:11
|
I can't remember offhand what the recommended pressures are for my car, but I keep them at 35psi all round, higher than recommended. Means I don't have to faff around with the airline except at the start.
The car grips well, more sharply than with the recommended pressures, doesn't do anything untoward in ordinary brisk driving, and doesn't feel or sound harsh. It's probably marginally more economical too.
|
I can understand the towing settings, as FWD car often struggle for grip with a tonne or so of additional weight behind.
The settings for fully laden seem a bit strange.
My landcruiser is supposed to be 29 psi all round, for all conditions. But at that setting it wears the tyre edges. At 36 psi, the tyres wear perfectly evenly - and I've not noticed any ill effects on handling. The tyres have now done 45,000 miles and have 5mm of tread left.
|
My Landcruisers are 35 all round, all the time.
As you say, no undue wear, handling no more dodgy on tarmac than before, and no noticeable impact when its wearing chains or on mud.
|
>> Surely 3 passengers in rear and boot full would put more weight on back of car than a trailer or caravan with an axle to take the weight?
The trailer would probably be 50-75kg vertical load (depending how its loaded), a long way to the rear of the back axle. It tends to make the front wheels go 'light'
Last edited by: Tigger on Wed 22 Jun 16 at 17:31
|
Tyre pressures - CGNorwich
