Ion-row does not have width 100%

Hi,
I don’t know why the ion-row does not have width 100%. This is the code

<ion-grid>
  <ion-row>
    <ion-col>This column will take 1</ion-col>
    <ion-col>This column will take 1</ion-col>
    <ion-col>This column will take 1</ion-col>
    <ion-col>This column will take 1</ion-col>
  </ion-row>
</ion-grid>

Instead the same code done with

<div class=row>
  <div class="col">.col</div>
  <div class="col">.col</div>
  <div class="col">.col</div>
  <div class="col">.col</div>
</div>

does have width 100%.
Any helps? Thanks.