what is the meaning of"let ur tyres down?"

[Lindt]

today i watched a show and there's sth i couldn't understand,here i'll expalin the context:
a woman comes to dinner with her bf and she expected that he would purpose,but instead he broke up with her.and then when she calmed down ,she went to her bf's(maybe wanted a talk)but found a bag of lady's underwears(her bf had seen someone,obviously)so she said "i won't let your tyres down"and left.her face looked quite disappointed
waiting for ur answer,thank!!

 

[bhaisahab]

Today I watched a show and there's something I couldn't understand, I'll explain the context:
A woman comes to dinner with her boyfriend? and she expected that he would propose but instead he broke up with her and then when she calmed down, she went to her bf's(maybe wanted a talk)but found a bag of ladies underwear (her bf had seen someone,obviously) so she said "I won't let your tyres down" and left, her face looked quite disappointed
waiting for your answer, thanks!!

Please don't use text-speak, do use capital letters where appropriate, and respect spaces between words and after punctuation marks.
She was saying that she wouldn't let down the tyres on his car in revenge.

 

[emsr2d2]

In case you are still not clear on "let down" in this context, it means to allow the air to escape. To deflate the tyres.

 

[Lindt]

Please don't use text-speak, do use capital letters where appropriate, and respect spaces between words and after punctuation marks.
She was saying that she wouldn't let down the tyres on his car in revenge.

Well, I thought there might be implications of her words, and I know the phrase means to deflate the car's tyres.