Tyre pressure Agilis 109T?

[Red Bicycle]

Hi

Just replaced my 215/65/16 Agilis 106T with a new set load rated at 109T. Old tyres had a max pressure of 54psi which I ran them at. New tyres have max pressure of 69psi!! Tyre centre pressured them to 50psi. Have about 150kg of load on a permanent basis - two occupants. Question is should I run them at 69 - good idea or not?

Cheers

Michael

[team_v]

I would hazard a guess that 50PSI is fine.

You don't want to run them on maximum incase they heat up and increase the pressure further.

[Red Bicycle]

Thanks V

The 69psi is a 'cold' max so I'm assuming that this takes into account heating while driving. That being said I agree that 50 psi is probably enough but I would like to know if there is any benefit (fuel economy??) of running them high.

Cheers

Michael

[Transporter]

See how they wear out. I would start with 60psi and if they would be wearing more in the middle, then I would drop the pressure down to 55psi or even 50psi.

[Red Bicycle]

Transporter - that is what I have done (60psi is the max the servo pump would go to). I was just surprised by the 15 psi difference between the 106T and 109T rating.

[Diesel_vert]

A tyre with higher load index on the same size usually requires a higher pressure to achieve the same load capacity, as well as to reach its maximum load capacity. For instance:

The maximum load capacity per axle for single fitment 215/65 R16C 102/100T tyres is 1700 kg @ 3.25 bar (47 psi).

The maximum load capacity per axle for single fitment 215/65 R16C 106/104T tyres is 1900 kg @ 3.75 bar (54 psi).

The maximum load capacity per axle for single fitment 215/65 R16C 109/107T tyres is 2060 kg @ 4.75 bar (69 psi).

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It therefore follows that 215/65 R16C 109/107T tyres have a load capacity (per axle) of:

1520 kg @ 3.25 bar (47 psi)

1705 kg @ 3.75 bar (55 psi)

1900 kg @ 4.30 bar (63 psi)

2060 kg @ 4.75 bar (69 psi)

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[Red Bicycle]

Very cool info DV

Let's take load out the equation - any benefit to fuel economy and handling with a higher pressure?

[Sunny43.5]

I'll just add a short one higher air pressure better economy rougher ride and possible wear irregularity , personal observation from years of seeing end results of high tyre pressures on car parts .

[Red Bicycle]

Sunny

Good info

Rougher ride but less 'float' if you know what I mean. Will watch wear.

Regards

Michael

[Diesel_vert]

Let's take load out the equation - any benefit to fuel economy and handling with a higher pressure?

Rolling resistance is mainly energy loss through internal friction of the tyre itself. An increase in inflation pressure will go some way in reducing RR, but that effect tends to decrease exponentially as you add more air. The choice of tyre (and how it's constructed) will have a bigger effect on RR more than anything.

In regards to roadholding, a higher inflation pressure tends to make the steering feel more crisp and responsive, but high inflation pressures can also reduce a tyre's contact patch, affecting outright grip.

As you can see, it's not easy to determine the "optimum" inflation pressure for one's own requirements, though the manufacturer's recommendations are a good place to start, who I'm sure went to some trouble trying to find an acceptable compromise.

[bobf]

had a similar problem working out pressure for my 215 60 R17 109s - 17 not 16 I know but same laod rating and sidewall max pressure = 70 psi. An old tyre techo told me that the max pressure is for the max load, and the way to work out the optimum pressure is to divide the actual tyre load by the tyre load rating and multiply by max pressure rating - seemed pretty close to the money. With an all up weight of 2800kg (campervan) the tyre placard said 60psi, by calc said 46. Adam Platte at Pink Roadhouse also said 46 which is good enough for me. I found that 50 was too rough and that 45 on bitumen is the best ride and grip - no noticeable difference in fuel economy at 45 or 50. Using a reliable TPMS I found that the psi increased 6-10 psi after an hours driving, depending on ambient temp and road surface, and that increase was the same for 35 on unsealed roads, and 45, 50 and 55 on sealed roads - I think that the heavier load rating tyres seem to build up pressure more than standard tyres.

[Red Bicycle]

Great info. Thanks bobf