Mobile Traffic Eating Your Budget? Portfolio Bidding, Max CPC and Value Rules

The target (CPA or ROAS) is not a volume knob. It expresses your economics: the acquisition cost your margin can pay, or the minimum return each euro must bring back. Lowering your target ROAS to « get more traffic » tells the algorithm you accept being less profitable, when all you wanted was more volume.

What Google says. To be fair: Google states that changing a target does not trigger a learning period (About Smart Bidding learning, FAQ Google). But Google also says that when you change targets, the bidder reacts immediately and needs one to two conversion cycles to hit the new target (About Target ROAS bidding, FAQ Google). Every tweak costs one or two cycles spent chasing a goal that just moved. An account whose target changes every week never converges.

The max CPC lever. In a portfolio Target CPA or Target ROAS strategy, Google lets you set a maximum (and minimum) bid limit, applied on the Search Network (About Target CPA bidding, FAQ Google; About Target ROAS bidding, FAQ Google). These limits are not available in standard strategies, which is a concrete reason to move to a portfolio.

Google does not recommend it, because limits restrict automated optimisation. Experience across accounts nonetheless calls for nuance: a CPC cap doesn’t replace the algorithm, it frames it. The target keeps your profitability intact; the cap limits exposure to the most expensive auctions (generic queries, competitive spikes) when you want to slow traffic down, and raising it step by step brings volume back without redefining your goal. Two rules make it work:

• Start from your actual CPC distribution, not a round number. A cap set too low starves the campaign, as Google itself warns (About Maximize clicks bidding, FAQ Google).
• Move the cap in steps and observe over one to two conversion cycles before drawing conclusions.

The August 2026 update and portfolio strategies

Since 17 August 2026 (rollout completed on 27 August), Target CPA and Target ROAS campaigns that are « Limited by budget » optimise consistently toward their target. Previously, a budget-constrained campaign could overperform its target; that is no longer the case. Google does not automatically adjust your budgets or your targets (Frequently asked questions about the changes to target-based bid strategies, FAQ Google).

The update explicitly applies to portfolio strategies and shared budgets:

• target adjustments are made at portfolio level (or shared-budget level), not campaign by campaign;
• in a portfolio with non-shared budgets, only budget-constrained campaigns are affected;
• with a constrained shared budget, the impact is distributed uniformly across all campaigns in the group.

In the same FAQ, Google states that Smart Bidding reacts to target changes in real time, even rapid ones, and that you can adjust targets to manage spend. Google also advises against adding bid limits solely in response to this update. A bid target adjustment tool has also been available since 6 July 2026 (About Target CPA bidding, FAQ Google).

Field observation suggests a complementary reading. Since the target is now followed faithfully, even when the budget is limited, it should reflect the business’s real profitability rather than serve as a volume dial. Volume is set by the budget and, in a portfolio, by the CPC cap.