Auckland firefighters have been warned not to drive faster than 100km/h to emergencies because their truck tyres are "not fit-for-purpose".

Fire and Emergency NZ's own policies allow for firefighters to drive their appliances at up to 105km/h to emergencies, leading the firefighters' union to express concern about the use of tyres which are not rated to travel at that speed.

The Auckland Local Committee of the New Zealand Professional Firefighters Union alerted members to the tyre issues as well as potential defects in fire appliances that had not been repaired during servicing in a memo on the union website.

The committee said it had "serious concerns" around particular tyres being used on some of the Auckland fleet trucks.

"A tyre with a J-rating has a maximum speed rating of 100kmh, as opposed to M-rated tyres, which are what would have been fitted to both Scania and MAN appliances at the factory."

M-rated tyres can be operated up to 130kmh, the memo said.

"As the FENZ Response Driving Policy allows for speeds up to 105kmh, J-rated tyres are not fit-for-purpose when fitted to a fire appliance.

"A driver involved in a crash at over 100kmh, if they survived, would have no defence if the vehicle was exceeding the speed rating of the tyre."

The memo went on to instruct members to examine the tyres on their appliance and return to workshops to have M-rated tyres fitted if necessary.

However Fire and Emergency New Zealand fire region 1 manager Kerry Gregory said the tyres were safe at the open road speed limit and firefighters were not expected to drive faster than 100kmh.

Given he didn't expect appliances to travel faster than that, he believed they were safe for use.

Gregory said he met with union representatives in Auckland to hear their concerns about the tyres.

"The advice we have received from both the tyre manufacturer and the supplier is that the J-rated GiTi tyres are safe for use on our appliances."

He said the safety of the tyre related not just to the speed vehicles were driven, but to a combination of speed, axle weights and duration the vehicle was driven at a speed.

"However, we want our personnel to feel safe, as well as to be safe.

"Therefore I have issued a notice informing staff that there are no circumstances in which I expect our appliances to be driven at speeds greater than 100kmh should drivers feel unsure about safety.

"That is a speed at which no one disputes the safety of the tyres."

Gregory agreed with union representatives that no more of the tyres would be put on the appliances "until we have had further discussions with them about the performance suitability of these tyres for our vehicles".

Meanwhile in the same memo the union committee said it had been informed by some members that appliance defects were not being repaired during servicing.

"That is, members are being called to uplift an appliance from workshops following servicing and not all noted defects have been corrected.

"In this regard, the Local instructs members to verify whether noted defects have been corrected.

"If a defect has not been addressed, then do not uplift an appliance until such time as the defect(s) have been fixed."