Friday, Apr 30, 2010 at 20:52
A year ago an engineer from Bridgestone was kind enough to send me the following information.
As to how noisy?
I can't tell the difference from the previous Cooper ATRs and depends what type of vehicle you drive.
I'm due for new tyres and I will be putting LT 694s on again.
Below text is from Bridgestone, the Table has got out of alignment, but you should be able to work it out. The tyre manufacturers don't recommend the low pressures most bush travellers use. However most bush travellers should not be driving at high speeds either, so probably explains how we get away with it.
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Inflation pressure will really depend on the weight each tyre has to support. I have included the table below for your reference:
LT265/65R17 116S
Size, load index, speed symbol
36Psi
44Psi
51Psi
54Psi
58Psi
65Psi
8PR
820kg
930kg
1030kg
1085kg
1140kg
1250kg
The table shows the minimum cold inflation pressure for the relevant load in kilograms per wheel. Please note that 36 Psi is the minimum inflation pressure for this tyre and Bridgestone does not recommend using a pressure lower than this even if the weight is lower than the weight listed above.
I would suggest using the relevant cold inflation pressure for each wheel according to weight for each tyre as a starting point and if required (changing dynamics e.g. sidewall flex, high speed etc) increasing in 1 -2 Psi increments but not exceeding 65Psi.
The damage that can result from running tyres below minimum recommendation is mainly heat related. When the tyres flex or over deflect past design limits the excess flex/deflection causes excess friction and heat which can break down the rubber components– but also causes stress to internal construction (steel belts and body ply) which can in a worse case fracture and break. Over flexing and over deflection can also cause damage to the bead area through heat and excess movement.
In some cases people may be using pressures 20 – 25% above the minimum cold inflation pressure required to carry the specific load – this can sometimes cause confusion. Due to heavier construction LT tyres generate more heat than a “passenger construction” tyre. Hence, for a given load LT tyres require more inflation pressure than a “passenger construction” tyre. For example:
The LT265/65R17 116S requires a minimum cold inflation pressure of 36 Psi to support 820kg per tyre.
The “passenger construction” 265/65R17 112S requires a minimum cold inflation pressure of 24Psi to support 825kg per tyre. 24 Psi being the minimum for the “passenger construction” 265/65R17 112S.
The main areas of Puncture resistance can be seen as:
The tyres construction strength – e.g. tread depth, under tread gauge, heavy steel belts, nylon cap layer. The D694 LT has heavy steel belts, Nylon cap layer, thick under tread and relatively deep tread depth (when new)
The other being the tyres ability to envelope the object as much as possible without the object penetrating through.
Altering driving to the conditions E.G. lowering speed on sharp rocks etc.
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Follow Up By: JohnnyTasman - Friday, Apr 30, 2010 at 22:46
Friday, Apr 30, 2010 at 22:46
many thanks Mark. Very helpful.
johnny
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Follow Up By: Muntoo - Saturday, May 01, 2010 at 00:04
Saturday, May 01, 2010 at 00:04
Roger, so on my car (BT50), which has a recommended pressure of 32psi allround unloaded, if i was to fit these tyres i would have to run them at 36psi as a minimum. Damn that would make for a bit of a harsh ride around town.
I didnt think that LTs needed more pressure for the same weight compared to passenger tyres.
I remember a Coopers tyre guru telling me that with LT tyres you need less pressure and thats why there better for 4wding because they can handle lower pressures better.
Goes to show never believe a salesman. Not that i was interested in his products though.
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