The increased number of convoy attacks in Iraq has exposed serious problems with the armored HMMWVs. The ton or more of additional weight of the armor added to hummers has caused premature wear on the suspension systems. The models of the hummer that had armor installed at the factory, like the M1114, had the suspension beefed up as well. But the standard suspension turned out to develop problems after a few thousand kilometers of travel with the added weight. The army won't say how many hummers have been sidelined for repairs because of this problem, but it appears to be causing some real strain on the maintenance resources in Iraq and Kuwait.
Moreover, the weight of the armor has limited the amount of weapons you can then load into the vehicle. On top of that, the armored hummers do not protect their crews as well as do vehicles designed as armored vehicles. So the army is looking for more armored vehicles for convoy escort duty. M-2 Bradleys are the preferred vehicle, but the tracks on the Bradley wear out (and have to be replaced) after 1200 kilometers of travel. In effect, Bradley's cost about $18 per kilometers traveled because of this.
The expense of replacing tracks is less of a problem than is the shortage of new tracks. The shortage was created last year when the march on Baghdad wore out more tracks than were available in the army's world wide inventory. The Stryker armored vehicle could be used, but there are fewer of them available. Since the attacks on convoys will become less of a problem (soon) as the Iraqi gangs are hunted down and killed, there will probably be an attempt to just bring in more M-2s and Strykers.